Merge pull request #2147 from infogulch/lint-format

Resolve all lints and formating; split style checks into separate job

.git-blame-ignore-revs

@@ -0,0 +1,2 @@
+# Resolved all lints and formatted the codebase
+9444e62df9820d6bfd96dbd8849e177bc5cecc2e

.github/workflows/ci.yml

@@ -11,6 +11,47 @@ on:
   workflow_dispatch:
 
 jobs:
+  style:
+    runs-on: ubuntu-22.04
+    steps:
+      - uses: actions/checkout@v3
+      - uses: dtolnay/rust-toolchain@master
+        id: toolchain
+        with:
+          toolchain: nightly
+          targets: x86_64-unknown-linux-gnu
+          components: clippy, rustfmt
+      - run: cargo install cargo2junit --force
+      - uses: actions/cache@v3
+        with:
+          path: |
+            ~/.cargo/bin/
+            ~/.cargo/registry/index/
+            ~/.cargo/registry/cache/
+            ~/.cargo/git/db/
+            target/
+          key: style_rustc-${{ steps.toolchain.outputs.cachekey }}_cargo-${{ hashFiles('**/Cargo.lock') }}
+
+      - name: Check formatting
+        run: cargo fmt --check
+      - name: Check clippy
+        run: cargo clippy --no-deps --all-targets
+      - name: Test and report
+        run: |
+          RUSTC_BOOTSTRAP=1 cargo test --all -- -Z unstable-options --format json --report-time | cargo2junit > cargo_test_results.xml
+      - name: Publish cargo test results artifact
+        uses: actions/upload-artifact@v3
+        with:
+          name: cargo-test-results
+          path: cargo_test_results.xml
+      - name: Publish cargo test summary
+        uses: EnricoMi/publish-unit-test-result-action/composite@master
+        with:
+          check_name: Cargo test summary
+          files: cargo_test_results.xml
+          fail_on: nothing
+          comment_mode: off
+
   build-test:
     runs-on: ${{ matrix.os }}
     strategy:
@@ -18,13 +59,13 @@ jobs:
       matrix:
         include:
           # operating systems
-          - { os: windows-latest, rust-version: stable,  publish: true, target: 'x86_64-pc-windows-msvc'}
+          - { os: windows-latest, rust-version: stable,  target: 'x86_64-pc-windows-msvc',   publish: true }
-          - { os: macos-11,       rust-version: stable,  publish: true, target: 'x86_64-apple-darwin' }
+          - { os: macos-11,       rust-version: stable,  target: 'x86_64-apple-darwin',      publish: true }
-          - { os: ubuntu-20.04,   rust-version: stable,  publish: true, target: 'x86_64-unknown-linux-gnu' }
+          - { os: ubuntu-20.04,   rust-version: stable,  target: 'x86_64-unknown-linux-gnu', publish: true }
           # architectures
-          - { os: ubuntu-22.04,   rust-version: stable,  publish: true, target: 'x86_64-unknown-linux-gnu', extra: true }
+          - { os: ubuntu-22.04,   rust-version: stable,  target: 'x86_64-unknown-linux-gnu', publish: true }
-          - { os: ubuntu-22.04,   rust-version: stable,  publish: true, target: 'i686-unknown-linux-gnu' }
+          - { os: ubuntu-22.04,   rust-version: stable,  target: 'i686-unknown-linux-gnu',   publish: true }
-          - { os: ubuntu-22.04,   rust-version: nightly, publish: true, target: 'wasm32-unknown-unknown', args: '--no-default-features' }
+          - { os: ubuntu-22.04,   rust-version: nightly, target: 'wasm32-unknown-unknown',   publish: true, args: '--no-default-features' }
           # rust versions
           - { os: ubuntu-22.04,   rust-version: "1.70",  target: 'x86_64-unknown-linux-gnu'}
           - { os: ubuntu-22.04,   rust-version: beta,    target: 'x86_64-unknown-linux-gnu'}
@@ -39,7 +80,6 @@ jobs:
         with:
           toolchain: ${{ matrix.rust-version }}
           targets: ${{ matrix.target }}
-          components: clippy, rustfmt
       - name: Install i686 dependencies
         if: "contains(matrix.target,'i686')"
         run: |
@@ -62,36 +102,8 @@ jobs:
       - name: Build library
         run: cargo rustc --lib --target ${{ matrix.target }} ${{ matrix.args }} --verbose
       - name: Test
-        if: "!matrix.extra"
         run: cargo test --target ${{ matrix.target }} ${{ matrix.args }} --all --verbose || echo "::warning ::Tests failed"
 
-      # Extra steps only run once to avoid duplication, when matrix.extra is true
-      - name: Test and report
-        if: matrix.extra
-        run: |
-          cargo install cargo2junit --force
-          RUSTC_BOOTSTRAP=1 cargo test --all -- -Z unstable-options --format json --report-time | cargo2junit > cargo_test_results.xml
-      - name: Publish cargo test results artifact
-        if: matrix.extra
-        uses: actions/upload-artifact@v3
-        with:
-          name: cargo-test-results
-          path: cargo_test_results.xml
-      - name: Publish cargo test summary
-        if: matrix.extra
-        uses: EnricoMi/publish-unit-test-result-action/composite@master
-        with:
-          check_name: Cargo test summary
-          files: cargo_test_results.xml
-          fail_on: nothing
-          comment_mode: off
-      - name: Check formatting
-        if: matrix.extra
-        run: cargo fmt --check || echo "::warning ::cargo fmt found some formatting changes that may improve readability"
-      - name: Check clippy
-        if: matrix.extra
-        run: cargo clippy --no-deps || echo "::warning ::cargo clippy found some code style changes that may be more idiomatic"
-
       # On stable rust builds, build a binary and publish as a github actions
       # artifact. These binaries could be useful for testing the pipeline but
       # are only retained by github for 90 days.

Cargo.lock

@@ -2032,7 +2032,7 @@ checksum = "94143f37725109f92c262ed2cf5e59bce7498c01bcc1502d7b9afe439a4e9f49"
 
 [[package]]
 name = "scryer-prolog"
-version = "0.9.2"
+version = "0.9.3"
 dependencies = [
  "assert_cmd",
  "base64 0.12.3",

build/instructions_template.rs

@@ -31,6 +31,7 @@ struct Level;
 struct NextOrFail;
 struct RegType;
 
+#[allow(clippy::enum_variant_names)]
 #[allow(dead_code)]
 #[derive(ToDeriveInput, EnumDiscriminants)]
 #[strum_discriminants(derive(EnumProperty, EnumString))]
@@ -49,6 +50,7 @@ enum CompareNumber {
     NumberEqual(ArithmeticTerm, ArithmeticTerm),
 }
 
+#[allow(clippy::enum_variant_names)]
 #[allow(dead_code)]
 #[derive(ToDeriveInput, EnumDiscriminants)]
 #[strum_discriminants(derive(EnumProperty, EnumString))]
@@ -206,6 +208,7 @@ enum REPLCodePtr {
     AddNonCountedBacktracking,
 }
 
+#[allow(clippy::upper_case_acronyms)]
 #[allow(dead_code)]
 #[derive(ToDeriveInput, EnumDiscriminants)]
 #[strum_discriminants(derive(EnumProperty, EnumString))]
@@ -897,13 +900,13 @@ fn generate_instruction_preface() -> TokenStream {
         }
 
         impl ArithmeticTerm {
-            fn into_functor(&self, arena: &mut Arena) -> MachineStub {
+            fn into_functor(self, arena: &mut Arena) -> MachineStub {
                 match self {
-                    &ArithmeticTerm::Reg(r) => reg_type_into_functor(r),
+                    ArithmeticTerm::Reg(r) => reg_type_into_functor(r),
-                    &ArithmeticTerm::Interm(i) => {
+                    ArithmeticTerm::Interm(i) => {
                         functor!(atom!("intermediate"), [fixnum(i)])
                     }
-                    &ArithmeticTerm::Number(n) => {
+                    ArithmeticTerm::Number(n) => {
                         vec![HeapCellValue::from((n, arena))]
                     }
                 }
@@ -925,26 +928,17 @@ fn generate_instruction_preface() -> TokenStream {
         impl NextOrFail {
             #[inline]
             pub fn is_next(&self) -> bool {
-                if let NextOrFail::Next(_) = self {
+                matches!(self, NextOrFail::Next(_))
-                    true
-                } else {
-                    false
-                }
             }
         }
 
-        #[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
+        #[derive(Debug, Default, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
         pub enum Death {
             Finite(usize),
+            #[default]
             Infinity,
         }
 
-        impl Default for Death {
-            fn default() -> Self {
-                Death::Infinity
-            }
-        }
-
         #[derive(Clone, Copy, Debug)]
         pub enum IndexedChoiceInstruction {
             Retry(usize),
@@ -956,30 +950,30 @@ fn generate_instruction_preface() -> TokenStream {
 
         impl IndexedChoiceInstruction {
             pub(crate) fn offset(&self) -> usize {
-                match self {
+                match *self {
-                    &IndexedChoiceInstruction::Retry(offset) => offset,
+                    IndexedChoiceInstruction::Retry(offset) => offset,
-                    &IndexedChoiceInstruction::Trust(offset) => offset,
+                    IndexedChoiceInstruction::Trust(offset) => offset,
-                    &IndexedChoiceInstruction::Try(offset) => offset,
+                    IndexedChoiceInstruction::Try(offset) => offset,
-                    &IndexedChoiceInstruction::DefaultRetry(offset) => offset,
+                    IndexedChoiceInstruction::DefaultRetry(offset) => offset,
-                    &IndexedChoiceInstruction::DefaultTrust(offset) => offset,
+                    IndexedChoiceInstruction::DefaultTrust(offset) => offset,
                 }
             }
 
-            pub(crate) fn to_functor(&self) -> MachineStub {
+            pub(crate) fn to_functor(self) -> MachineStub {
                 match self {
-                    &IndexedChoiceInstruction::Try(offset) => {
+                    IndexedChoiceInstruction::Try(offset) => {
                         functor!(atom!("try"), [fixnum(offset)])
                     }
-                    &IndexedChoiceInstruction::Trust(offset) => {
+                    IndexedChoiceInstruction::Trust(offset) => {
                         functor!(atom!("trust"), [fixnum(offset)])
                     }
-                    &IndexedChoiceInstruction::Retry(offset) => {
+                    IndexedChoiceInstruction::Retry(offset) => {
                         functor!(atom!("retry"), [fixnum(offset)])
                     }
-                    &IndexedChoiceInstruction::DefaultTrust(offset) => {
+                    IndexedChoiceInstruction::DefaultTrust(offset) => {
                         functor!(atom!("default_trust"), [fixnum(offset)])
                     }
-                    &IndexedChoiceInstruction::DefaultRetry(offset) => {
+                    IndexedChoiceInstruction::DefaultRetry(offset) => {
                         functor!(atom!("default_retry"), [fixnum(offset)])
                     }
                 }
@@ -1038,7 +1032,7 @@ fn generate_instruction_preface() -> TokenStream {
                             ]
                         )
                     }
-                    &IndexingInstruction::SwitchOnConstant(ref constants) => {
+                    IndexingInstruction::SwitchOnConstant(constants) => {
                         let mut key_value_list_stub = vec![];
                         let orig_h = h;
 
@@ -1066,7 +1060,7 @@ fn generate_instruction_preface() -> TokenStream {
                             [key_value_list_stub]
                         )
                     }
-                    &IndexingInstruction::SwitchOnStructure(ref structures) => {
+                    IndexingInstruction::SwitchOnStructure(structures) => {
                         let mut key_value_list_stub = vec![];
                         let orig_h = h;
 
@@ -1177,7 +1171,7 @@ fn generate_instruction_preface() -> TokenStream {
 
             #[inline]
             pub fn is_head_instr(&self) -> bool {
-                match self {
+                matches!(self,
                     Instruction::Deallocate |
                     Instruction::GetConstant(..) |
                     Instruction::GetList(..) |
@@ -1201,9 +1195,7 @@ fn generate_instruction_preface() -> TokenStream {
                     Instruction::SetLocalValue(..) |
                     Instruction::SetVariable(..) |
                     Instruction::SetValue(..) |
-                    Instruction::SetVoid(..) => true,
+                    Instruction::SetVoid(..))
-                    _ => false,
-                }
             }
 
             pub fn enqueue_functors(
@@ -1213,7 +1205,7 @@ fn generate_instruction_preface() -> TokenStream {
                 functors: &mut Vec<MachineStub>,
             ) {
                 match self {
-                    &Instruction::IndexingCode(ref indexing_instrs) => {
+                    Instruction::IndexingCode(indexing_instrs) => {
                         for indexing_instr in indexing_instrs {
                             match indexing_instr {
                                 IndexingLine::Indexing(indexing_instr) => {
@@ -2331,7 +2323,7 @@ pub fn generate_instructions_rs() -> TokenStream {
     let mut is_inlined_arms = vec![];
 
     is_inbuilt_arms.push(quote! {
-        (atom!(":-"), 1 | 2) => true
+        (atom!(":-"), 1 | 2)
     });
 
     for (name, arity, variant) in instr_data.compare_number_variants {
@@ -2388,11 +2380,11 @@ pub fn generate_instructions_rs() -> TokenStream {
         });
 
         is_inbuilt_arms.push(quote! {
-            (atom!(#name), #arity) => true
+            (atom!(#name), #arity)
         });
 
         is_inlined_arms.push(quote! {
-            (atom!(#name), #arity) => true
+            (atom!(#name), #arity)
         });
     }
 
@@ -2421,7 +2413,7 @@ pub fn generate_instructions_rs() -> TokenStream {
         });
 
         is_inbuilt_arms.push(quote! {
-            (atom!(#name), #arity) => true
+            (atom!(#name), #arity)
         });
     }
 
@@ -2487,7 +2479,7 @@ pub fn generate_instructions_rs() -> TokenStream {
         });
 
         is_inbuilt_arms.push(quote! {
-            (atom!(#name), #arity) => true
+            (atom!(#name), #arity)
         });
     }
 
@@ -2549,16 +2541,17 @@ pub fn generate_instructions_rs() -> TokenStream {
         });
 
         is_inbuilt_arms.push(quote! {
-            (atom!(#name), #arity) => true
+            (atom!(#name), #arity)
         });
 
         is_inlined_arms.push(quote! {
-            (atom!(#name), #arity) => true
+            (atom!(#name), #arity)
         });
     }
 
     for (name, arity, variant) in instr_data.system_clause_type_variants {
         let ident = variant.ident.clone();
+        let ident_s = ident.to_string();
 
         let variant_fields: Vec<_> = variant
             .fields
@@ -2574,19 +2567,13 @@ pub fn generate_instructions_rs() -> TokenStream {
             .collect();
 
         clause_type_from_name_and_arity_arms.push(if !variant_fields.is_empty() {
-            if ident.to_string() == "SetCutPoint" {
+            if ident_s == "SetCutPoint" || ident_s == "SetCutPointByDefault" {
                 quote! {
                     (atom!(#name), #arity) => ClauseType::System(
                         SystemClauseType::#ident(temp_v!(1))
                     )
                 }
-            } else if ident.to_string() == "SetCutPointByDefault" {
+            } else if ident_s == "InlineCallN" {
-                quote! {
-                    (atom!(#name), #arity) => ClauseType::System(
-                        SystemClauseType::#ident(temp_v!(1))
-                    )
-                }
-            } else if ident.to_string() == "InlineCallN" {
                 quote! {
                     (atom!(#name), arity) => ClauseType::System(
                         SystemClauseType::#ident(arity)
@@ -2649,11 +2636,11 @@ pub fn generate_instructions_rs() -> TokenStream {
 
         is_inbuilt_arms.push(if let Arity::Ident("arity") = &arity {
             quote! {
-                (atom!(#name), _arity) => true
+                (atom!(#name), _)
             }
         } else {
             quote! {
-                (atom!(#name), #arity) => true
+                (atom!(#name), #arity)
             }
         });
     }
@@ -2724,7 +2711,7 @@ pub fn generate_instructions_rs() -> TokenStream {
         });
 
         is_inbuilt_arms.push(quote! {
-            (atom!(#name), #arity) => true
+            (atom!(#name), #arity)
         });
     }
 
@@ -2798,7 +2785,7 @@ pub fn generate_instructions_rs() -> TokenStream {
         });
 
         is_inbuilt_arms.push(quote! {
-            (atom!(#name), _arity) => true
+            (atom!(#name), _)
         });
     }
 
@@ -2819,8 +2806,8 @@ pub fn generate_instructions_rs() -> TokenStream {
             let placeholder_ids: Vec<_> =
                 (0..enum_arity).map(|n| format_ident!("f_{}", n)).collect();
 
-            if variant_string.starts_with("Call") {
+            if let Some(variant_suffix) = variant_string.strip_prefix("Call") {
-                let execute_ident = format_ident!("Execute{}", variant_string["Call".len()..]);
+                let execute_ident = format_ident!("Execute{}", variant_suffix);
 
                 Some(if enum_arity == 0 {
                     quote! {
@@ -2833,9 +2820,8 @@ pub fn generate_instructions_rs() -> TokenStream {
                             Instruction::#execute_ident(#(#placeholder_ids),*)
                     }
                 })
-            } else if variant_string.starts_with("DefaultCall") {
+            } else if let Some(variant_suffix) = variant_string.strip_prefix("DefaultCall") {
-                let execute_ident =
+                let execute_ident = format_ident!("DefaultExecute{}", variant_suffix);
-                    format_ident!("DefaultExecute{}", variant_string["DefaultCall".len()..]);
 
                 Some(if enum_arity == 0 {
                     quote! {
@@ -2868,29 +2854,20 @@ pub fn generate_instructions_rs() -> TokenStream {
                 0
             };
 
-            if variant_string.starts_with("Execute") {
+            if variant_string.starts_with("Execute") || variant_string.starts_with("DefaultExecute")
+            {
                 Some(if enum_arity == 0 {
                     quote! {
-                        Instruction::#variant_ident => true
+                        Instruction::#variant_ident
                     }
                 } else {
                     quote! {
-                        Instruction::#variant_ident(..) => true
+                        Instruction::#variant_ident(..)
-                    }
-                })
-            } else if variant_string.starts_with("DefaultExecute") {
-                Some(if enum_arity == 0 {
-                    quote! {
-                        Instruction::#variant_ident => true
-                    }
-                } else {
-                    quote! {
-                        Instruction::#variant_ident(..) => true
                     }
                 })
             } else if variant_string == "JmpByExecute" {
                 Some(quote! {
-                    Instruction::#variant_ident(..) => true
+                    Instruction::#variant_ident(..)
                 })
             } else {
                 None
@@ -2955,11 +2932,11 @@ pub fn generate_instructions_rs() -> TokenStream {
 
             Some(if enum_arity == 0 {
                 quote! {
-                    Instruction::#variant_ident => true
+                    Instruction::#variant_ident
                 }
             } else {
                 quote! {
-                    Instruction::#variant_ident(..) => true
+                    Instruction::#variant_ident(..)
                 }
             })
         })
@@ -2970,7 +2947,7 @@ pub fn generate_instructions_rs() -> TokenStream {
         .iter()
         .rev() // produce default, execute & default & execute cases first.
         .cloned()
-        .filter_map(|(name, arity, _, variant)| {
+        .map(|(name, arity, _, variant)| {
             let variant_ident = variant.ident.clone();
             let variant_string = variant.ident.to_string();
             let arity = match arity {
@@ -2978,6 +2955,7 @@ pub fn generate_instructions_rs() -> TokenStream {
                 _ => 1,
             };
 
+            #[allow(clippy::collapsible_else_if)]
             Some(if variant_string.starts_with("Execute") {
                 if arity == 0 {
                     quote! {
@@ -3066,10 +3044,10 @@ pub fn generate_instructions_rs() -> TokenStream {
 
             match arity {
                 Arity::Static(_) if enum_arity == 0 => {
-                    quote! { &Instruction::#ident => (atom!(#name), #arity) }
+                    quote! { Instruction::#ident => (atom!(#name), #arity) }
                 }
                 Arity::Static(_) => {
-                    quote! { &Instruction::#ident(..) => (atom!(#name), #arity) }
+                    quote! { Instruction::#ident(..) => (atom!(#name), #arity) }
                 }
                 Arity::Ident(_) if enum_arity == 0 => {
                     quote! { &Instruction::#ident(#arity) => (atom!(#name), #arity) }
@@ -3169,12 +3147,9 @@ pub fn generate_instructions_rs() -> TokenStream {
             }
 
             pub fn is_inbuilt(name: Atom, arity: usize) -> bool {
-                match (name, arity) {
+                matches!((name, arity),
-                    #(
+                    #(#is_inbuilt_arms)|*
-                        #is_inbuilt_arms,
+                )
-                    )*
-                    _ => false,
-                }
             }
 
             pub fn name(&self) -> Atom {
@@ -3186,12 +3161,9 @@ pub fn generate_instructions_rs() -> TokenStream {
             }
 
             pub fn is_inlined(name: Atom, arity: usize) -> bool {
-                match (name, arity) {
+                matches!((name, arity),
-                    #(
+                    #(#is_inlined_arms)|*
-                        #is_inlined_arms,
+                )
-                    )*
-                    _ => false,
-                }
             }
         }
 
@@ -3230,29 +3202,23 @@ pub fn generate_instructions_rs() -> TokenStream {
             }
 
             pub fn is_execute(&self) -> bool {
-                match self {
+                matches!(self,
-                    #(
+                    #(#is_execute_arms)|*
-                        #is_execute_arms,
+                )
-                    )*
-                    _ => false,
-                }
             }
 
             pub fn is_ctrl_instr(&self) -> bool {
-                match self {
+                matches!(self,
-                    &Instruction::Allocate(_) |
+                    Instruction::Allocate(_) |
-                    &Instruction::Deallocate |
+                    Instruction::Deallocate |
-                    &Instruction::Proceed |
+                    Instruction::Proceed |
-                    &Instruction::RevJmpBy(_) => true,
+                    Instruction::RevJmpBy(_) |
-                    #(
+                    #(#control_flow_arms)|*
-                        #control_flow_arms,
+                )
-                    )*
-                    _ => false,
-                }
             }
 
             pub fn is_query_instr(&self) -> bool {
-                match self {
+                matches!(self,
                     &Instruction::GetVariable(..) |
                     &Instruction::PutConstant(..) |
                     &Instruction::PutList(..) |
@@ -3265,9 +3231,8 @@ pub fn generate_instructions_rs() -> TokenStream {
                     &Instruction::SetLocalValue(..) |
                     &Instruction::SetVariable(..) |
                     &Instruction::SetValue(..) |
-                    &Instruction::SetVoid(..) => true,
+                    &Instruction::SetVoid(..)
-                    _ => false,
+                )
-                }
             }
         }
 
@@ -3335,7 +3300,8 @@ enum Arity {
 
 impl From<&'static str> for Arity {
     fn from(arity: &'static str) -> Self {
-        usize::from_str_radix(&arity, 10)
+        arity
+            .parse::<usize>()
             .map(Arity::Static)
             .unwrap_or_else(|_| Arity::Ident(arity))
     }
@@ -3442,13 +3408,12 @@ impl InstructionData {
             panic!("type ID is: {}", id);
         };
 
-        let v_string = variant.ident.to_string();
+        let v_ident = variant
-
+            .ident
-        let v_ident = if v_string.starts_with("Call") {
+            .to_string()
-            format_ident!("{}", v_string["Call".len()..])
+            .strip_prefix("Call")
-        } else {
+            .map(|s| format_ident!("{}", s))
-            variant.ident.clone()
+            .unwrap_or_else(|| variant.ident.clone());
-        };
 
         let generated_variant =
             create_instr_variant(format_ident!("{}{}", prefix, v_ident), variant.clone());

build/main.rs

@@ -55,7 +55,7 @@ fn main() {
     let out_dir = env::var("OUT_DIR").unwrap();
     let dest_path = Path::new(&out_dir).join("libraries.rs");
 
-    let mut libraries = File::create(&dest_path).unwrap();
+    let mut libraries = File::create(dest_path).unwrap();
     let lib_path = Path::new("src/lib");
 
     libraries
@@ -66,7 +66,7 @@ fn main() {
         )
         .unwrap();
 
-    find_prolog_files(&mut libraries, "", &lib_path);
+    find_prolog_files(&mut libraries, "", lib_path);
     libraries.write_all(b"\n        m\n    };\n}\n").unwrap();
 
     let instructions_path = Path::new(&out_dir).join("instructions.rs");

build/static_string_indexing.rs

@@ -35,7 +35,7 @@ impl Parse for ReadHeapCellExprAndArms {
         arms.push(input.parse()?);
 
         while !input.is_empty() {
-            if let Ok(_) = input.parse::<Token![,]>() {}
+            let _ = input.parse::<Token![,]>();
             arms.push(input.parse()?);
         }
 
@@ -52,7 +52,7 @@ impl Parse for MacroFnArgs {
         }
 
         while !input.is_empty() {
-            if let Ok(_) = input.parse::<Token![,]>() {}
+            let _ = input.parse::<Token![,]>();
             args.push(input.parse()?);
         }
 
@@ -65,22 +65,20 @@ impl<'ast> Visit<'ast> for StaticStrVisitor {
         let Macro { path, .. } = m;
 
         if path.is_ident("atom") {
-            if let Some(Lit::Str(string)) = m.parse_body::<Lit>().ok() {
+            if let Ok(Lit::Str(string)) = m.parse_body::<Lit>() {
                 self.static_strs.insert(string.value());
             }
         } else if path.is_ident("read_heap_cell") || path.is_ident("match_untyped_arena_ptr") {
-            if let Some(m) = m.parse_body::<ReadHeapCellExprAndArms>().ok() {
+            if let Ok(m) = m.parse_body::<ReadHeapCellExprAndArms>() {
                 self.visit_expr(&m.expr);
 
                 for e in m.arms {
                     self.visit_arm(&e);
                 }
             }
-        } else {
+        } else if let Ok(m) = m.parse_body::<MacroFnArgs>() {
-            if let Some(m) = m.parse_body::<MacroFnArgs>().ok() {
+            for e in m.args {
-                for e in m.args {
+                self.visit_expr(&e);
-                    self.visit_expr(&e);
-                }
             }
         }
     }
@@ -147,9 +145,8 @@ pub fn index_static_strings(instruction_rs_path: &std::path::Path) -> TokenStrea
         visitor.visit_file(&syntax);
     }
 
-    match process_filepath(instruction_rs_path) {
+    if let Ok(syntax) = process_filepath(instruction_rs_path) {
-        Ok(syntax) => visitor.visit_file(&syntax),
+        visitor.visit_file(&syntax)
-        Err(_) => {}
     }
 
     let indices = (0..visitor.static_strs.len()).map(|i| (i << 3) as u64);
@@ -161,7 +158,7 @@ pub fn index_static_strings(instruction_rs_path: &std::path::Path) -> TokenStrea
     quote! {
         use phf;
 
-        static STRINGS: [&'static str; #static_strs_len] = [
+        static STRINGS: [&str; #static_strs_len] = [
             #(
                 #static_strs,
             )*

src/allocator.rs

@@ -24,6 +24,7 @@ pub(crate) trait Allocator {
         code: &mut CodeDeque,
     );
 
+    #[allow(clippy::too_many_arguments)]
     fn mark_reserved_var<'a, Target: CompilationTarget<'a>>(
         &mut self,
         var_num: usize,
@@ -48,7 +49,7 @@ pub(crate) trait Allocator {
 
     fn reset(&mut self);
     fn reset_arg(&mut self, arg_num: usize);
-    fn reset_at_head(&mut self, args: &Vec<Term>);
+    fn reset_at_head(&mut self, args: &[Term]);
     fn reset_contents(&mut self);
 
     fn advance_arg(&mut self);

src/arena.rs

@@ -91,14 +91,14 @@ pub fn lookup_float(
 ) -> RcuRef<RawBlock<F64Table>, UnsafeCell<OrderedFloat<f64>>> {
     let f64table = global_f64table()
         .read()
-	.unwrap()
+        .unwrap()
         .upgrade()
         .expect("We should only be looking up floats while there is a float table");
 
     RcuRef::try_map(f64table.block.active_epoch(), |raw_block| unsafe {
         raw_block
             .base
-            .offset(offset.0 as isize)
+            .add(offset.0)
             .cast_mut()
             .cast::<UnsafeCell<OrderedFloat<f64>>>()
             .as_ref()
@@ -129,6 +129,7 @@ impl F64Table {
         }
     }
 
+    #[allow(clippy::missing_safety_doc)]
     pub unsafe fn build_with(&self, value: f64) -> F64Offset {
         let update_guard = self.update.lock();
 
@@ -152,9 +153,7 @@ impl F64Table {
 
         ptr::write(ptr as *mut OrderedFloat<f64>, OrderedFloat(value));
 
-        let float = F64Offset {
+        let float = F64Offset(ptr as usize - block_epoch.base as usize);
-            0: ptr as usize - block_epoch.base as usize,
-        };
 
         // atometable would have to update the index table at this point
 
@@ -230,7 +229,7 @@ impl<T: ?Sized + PartialOrd> PartialOrd for TypedArenaPtr<T> {
 
 impl<T: ?Sized + PartialEq> PartialEq for TypedArenaPtr<T> {
     fn eq(&self, other: &TypedArenaPtr<T>) -> bool {
-        self.0 == other.0 || &**self == &**other
+        self.0 == other.0 || **self == **other
     }
 }
 
@@ -245,13 +244,13 @@ impl<T: ?Sized + Ord> Ord for TypedArenaPtr<T> {
 impl<T: ?Sized + Hash> Hash for TypedArenaPtr<T> {
     #[inline(always)]
     fn hash<H: Hasher>(&self, hasher: &mut H) {
-        (&*self as &T).hash(hasher)
+        (self as &T).hash(hasher)
     }
 }
 
 impl<T: ?Sized> Clone for TypedArenaPtr<T> {
     fn clone(&self) -> Self {
-        TypedArenaPtr(self.0)
+        *self
     }
 }
 
@@ -279,10 +278,10 @@ impl<T: fmt::Display> fmt::Display for TypedArenaPtr<T> {
 
 impl<T: ?Sized + ArenaAllocated> TypedArenaPtr<T> {
     // data must be allocated in the arena already.
+    #[allow(clippy::not_unsafe_ptr_arg_deref)]
     #[inline]
     pub const fn new(data: *mut T) -> Self {
-        let result = unsafe { TypedArenaPtr(ptr::NonNull::new_unchecked(data)) };
+        unsafe { TypedArenaPtr(ptr::NonNull::new_unchecked(data)) }
-        result
     }
 
     #[inline]
@@ -347,6 +346,7 @@ pub trait ArenaAllocated: Sized {
         mem::size_of::<ArenaHeader>()
     }
 
+    #[allow(clippy::missing_safety_doc)]
     unsafe fn alloc(arena: &mut Arena, value: Self) -> Self::PtrToAllocated {
         let size = value.size() + mem::size_of::<AllocSlab>();
 
@@ -363,7 +363,7 @@ pub trait ArenaAllocated: Sized {
         (*slab).header = ArenaHeader::build_with(value.size() as u64, Self::tag());
 
         let offset = (*slab).payload_offset();
-        let result = value.copy_to_arena(offset as *mut Self);
+        let result = value.copy_to_arena(offset);
 
         arena.base = slab;
 
@@ -390,7 +390,7 @@ impl Eq for F64Ptr {}
 
 impl PartialOrd for F64Ptr {
     fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
-        (**self).partial_cmp(&**other)
+        Some(self.cmp(other))
     }
 }
 
@@ -403,13 +403,13 @@ impl Ord for F64Ptr {
 impl Hash for F64Ptr {
     #[inline(always)]
     fn hash<H: Hasher>(&self, hasher: &mut H) {
-        (&*self as &OrderedFloat<f64>).hash(hasher)
+        (self as &OrderedFloat<f64>).hash(hasher)
     }
 }
 
 impl fmt::Display for F64Ptr {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(f, "{}", *self)
+        write!(f, "{}", self as &OrderedFloat<f64>)
     }
 }
 
@@ -418,7 +418,7 @@ impl Deref for F64Ptr {
 
     #[inline]
     fn deref(&self) -> &Self::Target {
-        unsafe { &*self.0.get().as_ref().unwrap() }
+        unsafe { self.0.get().as_ref().unwrap() }
     }
 }
 
@@ -478,7 +478,7 @@ impl Eq for F64Offset {}
 impl PartialOrd for F64Offset {
     #[inline(always)]
     fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
-        self.as_ptr().partial_cmp(&other.as_ptr())
+        Some(self.cmp(other))
     }
 }
 
@@ -515,11 +515,12 @@ impl ArenaAllocated for Integer {
         mem::size_of::<Self>()
     }
 
+    #[allow(clippy::not_unsafe_ptr_arg_deref)]
     #[inline]
     fn copy_to_arena(self, dst: *mut Self) -> Self::PtrToAllocated {
         unsafe {
             ptr::write(dst, self);
-            TypedArenaPtr::new(dst as *mut Self)
+            TypedArenaPtr::new(dst)
         }
     }
 }
@@ -537,11 +538,12 @@ impl ArenaAllocated for Rational {
         mem::size_of::<Self>()
     }
 
+    #[allow(clippy::not_unsafe_ptr_arg_deref)]
     #[inline]
     fn copy_to_arena(self, dst: *mut Self) -> Self::PtrToAllocated {
         unsafe {
             ptr::write(dst, self);
-            TypedArenaPtr::new(dst as *mut Self)
+            TypedArenaPtr::new(dst)
         }
     }
 }
@@ -559,11 +561,12 @@ impl ArenaAllocated for LiveLoadState {
         mem::size_of::<Self>()
     }
 
+    #[allow(clippy::not_unsafe_ptr_arg_deref)]
     #[inline]
     fn copy_to_arena(self, dst: *mut Self) -> Self::PtrToAllocated {
         unsafe {
             ptr::write(dst, self);
-            TypedArenaPtr::new(dst as *mut Self)
+            TypedArenaPtr::new(dst)
         }
     }
 }
@@ -581,11 +584,12 @@ impl ArenaAllocated for TcpListener {
         mem::size_of::<Self>()
     }
 
+    #[allow(clippy::not_unsafe_ptr_arg_deref)]
     #[inline]
     fn copy_to_arena(self, dst: *mut Self) -> Self::PtrToAllocated {
         unsafe {
             ptr::write(dst, self);
-            TypedArenaPtr::new(dst as *mut Self)
+            TypedArenaPtr::new(dst)
         }
     }
 }
@@ -604,11 +608,12 @@ impl ArenaAllocated for HttpListener {
         mem::size_of::<Self>()
     }
 
+    #[allow(clippy::not_unsafe_ptr_arg_deref)]
     #[inline]
     fn copy_to_arena(self, dst: *mut Self) -> Self::PtrToAllocated {
         unsafe {
             ptr::write(dst, self);
-            TypedArenaPtr::new(dst as *mut Self)
+            TypedArenaPtr::new(dst)
         }
     }
 }
@@ -627,11 +632,12 @@ impl ArenaAllocated for HttpResponse {
         mem::size_of::<Self>()
     }
 
+    #[allow(clippy::not_unsafe_ptr_arg_deref)]
     #[inline]
     fn copy_to_arena(self, dst: *mut Self) -> Self::PtrToAllocated {
         unsafe {
             ptr::write(dst, self);
-            TypedArenaPtr::new(dst as *mut Self)
+            TypedArenaPtr::new(dst)
         }
     }
 }
@@ -649,11 +655,12 @@ impl ArenaAllocated for IndexPtr {
         mem::size_of::<Self>()
     }
 
+    #[allow(clippy::not_unsafe_ptr_arg_deref)]
     #[inline]
     fn copy_to_arena(self, dst: *mut Self) -> Self::PtrToAllocated {
         unsafe {
             ptr::write(dst, self);
-            TypedArenaPtr::new(dst as *mut Self)
+            TypedArenaPtr::new(dst)
         }
     }
 
@@ -672,7 +679,10 @@ impl ArenaAllocated for IndexPtr {
 
         (*slab).next = arena.base;
 
-        let result = value.copy_to_arena(mem::transmute::<_, *mut IndexPtr>(&(*slab).header));
+        let result = value.copy_to_arena(
+            &(*slab).header as *const crate::arena::ArenaHeader
+                as *mut crate::machine::machine_indices::IndexPtr,
+        );
         arena.base = slab;
 
         result
@@ -697,6 +707,7 @@ pub struct Arena {
 unsafe impl Send for Arena {}
 unsafe impl Sync for Arena {}
 
+#[allow(clippy::new_without_default)]
 impl Arena {
     #[inline]
     pub fn new() -> Self {
@@ -837,12 +848,12 @@ mod tests {
         let mut cell = HeapCellValue::from(fp.clone());
 
         assert_eq!(cell.get_tag(), HeapCellValueTag::F64);
-        assert_eq!(cell.get_mark_bit(), false);
+        assert!(!cell.get_mark_bit());
         assert_eq!(fp.deref(), &OrderedFloat(f));
 
         cell.set_mark_bit(true);
 
-        assert_eq!(cell.get_mark_bit(), true);
+        assert!(cell.get_mark_bit());
 
         read_heap_cell!(cell,
             (HeapCellValueTag::F64, ptr) => {
@@ -874,7 +885,7 @@ mod tests {
                 );
             }
             None => {
-                assert!(false);
+                unreachable!();
             }
         }
 
@@ -890,7 +901,7 @@ mod tests {
                 );
             }
             None => {
-                assert!(false);
+                unreachable!();
             }
         }
     }
@@ -912,7 +923,6 @@ mod tests {
         let untyped_arena_ptr = match cell.to_untyped_arena_ptr() {
             Some(ptr) => ptr,
             None => {
-                assert!(false);
                 unreachable!()
             }
         };
@@ -954,7 +964,7 @@ mod tests {
                 );
             }
             None => {
-                assert!(false); // we fail.
+                unreachable!();
             }
         }
 
@@ -991,7 +1001,7 @@ mod tests {
                 assert_eq!(&*atom.as_str(), "f");
             }
             None => {
-                assert!(false);
+                unreachable!();
             }
         }
 
@@ -1026,7 +1036,7 @@ mod tests {
                 assert_eq!(&*pstr.as_str_from(0), "ronan");
             }
             None => {
-                assert!(false);
+                unreachable!();
             }
         }
 
@@ -1046,7 +1056,7 @@ mod tests {
 
         match fixnum_cell.to_fixnum() {
             Some(n) => assert_eq!(n.get_num(), 3),
-            None => assert!(false),
+            None => unreachable!(),
         }
 
         read_heap_cell!(fixnum_cell,
@@ -1062,52 +1072,48 @@ mod tests {
 
         match fixnum_b_cell.to_fixnum() {
             Some(n) => assert_eq!(n.get_num(), 1 << 54),
-            None => assert!(false),
+            None => unreachable!(),
         }
 
-        match Fixnum::build_with_checked(1 << 56) {
+        if Fixnum::build_with_checked(1 << 56).is_ok() {
-            Ok(_) => assert!(false),
+            unreachable!()
-            _ => assert!(true),
         }
 
-        match Fixnum::build_with_checked(i64::MAX) {
+        if Fixnum::build_with_checked(i64::MAX).is_ok() {
-            Ok(_) => assert!(false),
+            unreachable!()
-            _ => assert!(true),
         }
 
-        match Fixnum::build_with_checked(i64::MIN) {
+        if Fixnum::build_with_checked(i64::MIN).is_ok() {
-            Ok(_) => assert!(false),
+            unreachable!()
-            _ => assert!(true),
         }
 
         match Fixnum::build_with_checked(-1) {
             Ok(n) => assert_eq!(n.get_num(), -1),
-            _ => assert!(false),
+            _ => unreachable!(),
         }
 
         match Fixnum::build_with_checked((1 << 55) - 1) {
             Ok(n) => assert_eq!(n.get_num(), (1 << 55) - 1),
-            _ => assert!(false),
+            _ => unreachable!(),
         }
 
         match Fixnum::build_with_checked(-(1 << 55)) {
             Ok(n) => assert_eq!(n.get_num(), -(1 << 55)),
-            _ => assert!(false),
+            _ => unreachable!(),
         }
 
-        match Fixnum::build_with_checked(-(1 << 55) - 1) {
+        if Fixnum::build_with_checked(-(1 << 55) - 1).is_ok() {
-            Ok(_n) => assert!(false),
+            unreachable!()
-            _ => assert!(true),
         }
 
         match Fixnum::build_with_checked(-1) {
             Ok(n) => assert_eq!(-n, Fixnum::build_with(1)),
-            _ => assert!(false),
+            _ => unreachable!(),
         }
 
         // float
 
-        let float = 3.1415926f64;
+        let float = std::f64::consts::PI;
         let float_ptr = float_alloc!(float, wam.machine_st.arena);
         let cell = HeapCellValue::from(float_ptr);
 

src/arithmetic.rs

@@ -268,7 +268,7 @@ impl<'a> ArithmeticEvaluator<'a> {
                 let ninterm = if a1.interm_or(0) == 0 {
                     self.incr_interm()
                 } else {
-                    self.interm.push(a1.clone());
+                    self.interm.push(a1);
                     a1.interm_or(0)
                 };
 
@@ -312,9 +312,8 @@ impl<'a> ArithmeticEvaluator<'a> {
         arg: usize,
     ) -> Result<ArithCont, ArithmeticError> {
         let mut code = CodeDeque::new();
-        let mut iter = src.iter()?;
 
-        while let Some(term_ref) = iter.next() {
+        for term_ref in src.iter()? {
             match term_ref? {
                 ArithTermRef::Literal(c) => push_literal(&mut self.interm, c)?,
                 ArithTermRef::Var(lvl, cell, name) => {
@@ -353,17 +352,17 @@ impl<'a> ArithmeticEvaluator<'a> {
 }
 
 // integer division rounding function -- 9.1.3.1.
-pub(crate) fn rnd_i<'a>(n: &'a Number, arena: &mut Arena) -> Number {
+pub(crate) fn rnd_i(n: &'_ Number, arena: &mut Arena) -> Number {
     match n {
         &Number::Integer(i) => {
             let result = (&*i).try_into();
-            if let Ok(value) = result{
+            if let Ok(value) = result {
                 fixnum!(Number, value, arena)
             } else {
                 *n
             }
         }
-        &Number::Fixnum(_) => *n,
+        Number::Fixnum(_) => *n,
         &Number::Float(f) => {
             let f = f.floor();
 
@@ -376,7 +375,7 @@ pub(crate) fn rnd_i<'a>(n: &'a Number, arena: &mut Arena) -> Number {
                 Number::Integer(arena_alloc!(Integer::from(f.0 as i64), arena))
             }
         }
-        &Number::Rational(ref r) => {
+        Number::Rational(ref r) => {
             let (_, floor) = (r.fract(), r.floor());
 
             if let Ok(value) = (&floor).try_into() {
@@ -399,9 +398,9 @@ impl From<Fixnum> for Integer {
 pub(crate) fn rnd_f(n: &Number) -> f64 {
     match n {
         &Number::Fixnum(n) => n.get_num() as f64,
-        &Number::Integer(ref n) => n.to_f64().value(),
+        Number::Integer(ref n) => n.to_f64().value(),
         &Number::Float(OrderedFloat(f)) => f,
-        &Number::Rational(ref r) => r.to_f64().value(),
+        Number::Rational(ref r) => r.to_f64().value(),
     }
 }
 
@@ -529,47 +528,51 @@ impl PartialEq for Number {
     fn eq(&self, rhs: &Self) -> bool {
         match (self, rhs) {
             (&Number::Fixnum(n1), &Number::Fixnum(n2)) => n1.eq(&n2),
-            (&Number::Fixnum(n1), &Number::Integer(ref n2)) => n1.get_num().num_eq(&**n2),
+            (&Number::Fixnum(n1), Number::Integer(ref n2)) => n1.get_num().num_eq(&**n2),
-            (&Number::Integer(ref n1), &Number::Fixnum(n2)) => (&**n1).num_eq(&n2.get_num()),
+            (Number::Integer(ref n1), &Number::Fixnum(n2)) => n1.num_eq(&n2.get_num()),
-            (&Number::Fixnum(n1), &Number::Rational(ref n2)) => Integer::from(n1.get_num()).num_eq(&**n2),
+            (&Number::Fixnum(n1), Number::Rational(ref n2)) => {
-            (&Number::Rational(ref n1), &Number::Fixnum(n2)) => (&**n1).num_eq(&Integer::from(n2.get_num())),
+                Integer::from(n1.get_num()).num_eq(&**n2)
+            }
+            (Number::Rational(ref n1), &Number::Fixnum(n2)) => {
+                n1.num_eq(&Integer::from(n2.get_num()))
+            }
             (&Number::Fixnum(n1), &Number::Float(n2)) => OrderedFloat(n1.get_num() as f64).eq(&n2),
             (&Number::Float(n1), &Number::Fixnum(n2)) => n1.eq(&OrderedFloat(n2.get_num() as f64)),
-            (&Number::Integer(ref n1), &Number::Integer(ref n2)) => n1.eq(n2),
+            (Number::Integer(ref n1), Number::Integer(ref n2)) => n1.eq(n2),
-            (&Number::Integer(ref n1), Number::Float(n2)) => {
+            (Number::Integer(ref n1), Number::Float(n2)) => {
                 OrderedFloat(n1.to_f64().value()).eq(n2)
             }
-            (&Number::Float(n1), &Number::Integer(ref n2)) => {
+            (&Number::Float(n1), Number::Integer(ref n2)) => {
                 n1.eq(&OrderedFloat(n2.to_f64().value()))
             }
-            (&Number::Integer(ref n1), &Number::Rational(ref n2)) => {
+            (Number::Integer(ref n1), Number::Rational(ref n2)) => {
                 #[cfg(feature = "num")]
                 {
                     &Rational::from(&**n1) == &**n2
                 }
                 #[cfg(not(feature = "num"))]
                 {
-                    (&**n1).num_eq(&**n2)
+                    n1.num_eq(&**n2)
                 }
             }
-            (&Number::Rational(ref n1), &Number::Integer(ref n2)) => {
+            (Number::Rational(ref n1), Number::Integer(ref n2)) => {
                 #[cfg(feature = "num")]
                 {
-                    &**n1 == &Rational::from(&**n2)
+                    n1 == &Rational::from(&**n2)
                 }
                 #[cfg(not(feature = "num"))]
                 {
-                    (&**n1).num_eq(&**n2)
+                    n1.num_eq(&**n2)
                 }
             }
-            (&Number::Rational(ref n1), &Number::Float(n2)) => {
+            (Number::Rational(ref n1), &Number::Float(n2)) => {
                 OrderedFloat(n1.to_f64().value()).eq(&n2)
             }
-            (&Number::Float(n1), &Number::Rational(ref n2)) => {
+            (&Number::Float(n1), Number::Rational(ref n2)) => {
                 n1.eq(&OrderedFloat(n2.to_f64().value()))
             }
             (&Number::Float(f1), &Number::Float(f2)) => f1.eq(&f2),
-            (&Number::Rational(ref r1), &Number::Rational(ref r2)) => r1.eq(&r2),
+            (Number::Rational(ref r1), Number::Rational(ref r2)) => r1.eq(r2),
         }
     }
 }
@@ -589,8 +592,8 @@ impl PartialOrd<usize> for Number {
                     (n as usize).partial_cmp(rhs)
                 }
             }
-            Number::Integer(n) => Some((&**n).num_cmp(rhs)),
+            Number::Integer(n) => Some((n).num_cmp(rhs)),
-            Number::Rational(r) => Some((&**r).num_cmp(&Integer::from(*rhs))),
+            Number::Rational(r) => Some((r).num_cmp(&Integer::from(*rhs))),
             Number::Float(f) => f.partial_cmp(&OrderedFloat(*rhs as f64)),
         }
     }
@@ -609,8 +612,8 @@ impl PartialEq<usize> for Number {
                     (n as usize).eq(rhs)
                 }
             }
-            Number::Integer(n) => (&**n).num_eq(rhs),
+            Number::Integer(n) => (n).num_eq(rhs),
-            Number::Rational(r) => (&**r).num_eq(&Integer::from(*rhs)),
+            Number::Rational(r) => (r).num_eq(&Integer::from(*rhs)),
             Number::Float(f) => f.eq(&OrderedFloat(*rhs as f64)),
         }
     }
@@ -626,17 +629,17 @@ impl Ord for Number {
     fn cmp(&self, rhs: &Number) -> Ordering {
         match (self, rhs) {
             (&Number::Fixnum(n1), &Number::Fixnum(n2)) => n1.get_num().cmp(&n2.get_num()),
-            (&Number::Fixnum(n1), Number::Integer(n2)) => Integer::from(n1.get_num()).cmp(&*n2),
+            (&Number::Fixnum(n1), Number::Integer(n2)) => Integer::from(n1.get_num()).cmp(n2),
-            (Number::Integer(n1), &Number::Fixnum(n2)) => (&**n1).cmp(&Integer::from(n2.get_num())),
+            (Number::Integer(n1), &Number::Fixnum(n2)) => (**n1).cmp(&Integer::from(n2.get_num())),
-            (&Number::Fixnum(n1), Number::Rational(n2)) => Rational::from(n1.get_num()).cmp(&*n2),
+            (&Number::Fixnum(n1), Number::Rational(n2)) => Rational::from(n1.get_num()).cmp(n2),
             (Number::Rational(n1), &Number::Fixnum(n2)) => {
-                (&**n1).cmp(&Rational::from(n2.get_num()))
+                (**n1).cmp(&Rational::from(n2.get_num()))
             }
             (&Number::Fixnum(n1), &Number::Float(n2)) => OrderedFloat(n1.get_num() as f64).cmp(&n2),
             (&Number::Float(n1), &Number::Fixnum(n2)) => n1.cmp(&OrderedFloat(n2.get_num() as f64)),
             (&Number::Integer(n1), &Number::Integer(n2)) => (*n1).cmp(&*n2),
             (&Number::Integer(n1), Number::Float(n2)) => OrderedFloat(n1.to_f64().value()).cmp(n2),
-            (&Number::Float(n1), &Number::Integer(ref n2)) => {
+            (&Number::Float(n1), Number::Integer(ref n2)) => {
                 n1.cmp(&OrderedFloat(n2.to_f64().value()))
             }
             (&Number::Integer(n1), &Number::Rational(n2)) => {
@@ -646,7 +649,7 @@ impl Ord for Number {
                 }
                 #[cfg(not(feature = "num"))]
                 {
-                    (&*n1).num_partial_cmp(&*n2).unwrap_or(Ordering::Less)
+                    (*n1).num_partial_cmp(&*n2).unwrap_or(Ordering::Less)
                 }
             }
             (&Number::Rational(n1), &Number::Integer(n2)) => {
@@ -656,7 +659,7 @@ impl Ord for Number {
                 }
                 #[cfg(not(feature = "num"))]
                 {
-                    (&*n1).num_partial_cmp(&*n2).unwrap_or(Ordering::Less)
+                    (*n1).num_partial_cmp(&*n2).unwrap_or(Ordering::Less)
                 }
             }
             (&Number::Rational(n1), &Number::Float(n2)) => {

src/atom_table.rs

@@ -186,7 +186,7 @@ impl Atom {
             unsafe {
                 AtomTableRef::try_map(atom_table.buf(), |buf| {
                     (buf as *const u8)
-                        .offset(((self.index as usize) - (STRINGS.len() << 3)) as isize)
+                        .add((self.index as usize) - (STRINGS.len() << 3))
                         .as_ref()
                 })
             }
@@ -209,9 +209,13 @@ impl Atom {
         }
     }
 
+    pub fn is_empty(self) -> bool {
+        self.len() == 0
+    }
+
     #[inline(always)]
     pub fn flat_index(self) -> u64 {
-        (self.index >> 3) as u64
+        self.index >> 3
     }
 
     pub fn as_char(self) -> Option<char> {
@@ -232,20 +236,17 @@ impl Atom {
     pub fn as_str(&self) -> AtomString<'static> {
         if self.is_static() {
             AtomString::Static(STRINGS[(self.index >> 3) as usize])
-        } else {
+        } else if let Some(ptr) = self.as_ptr() {
-            if let Some(ptr) = self.as_ptr() {
+            AtomString::Dynamic(AtomTableRef::map(ptr, |ptr| {
-                AtomString::Dynamic(AtomTableRef::map(ptr, |ptr| {
+                let header =
-                    let header =
+                    unsafe { ptr::read::<AtomHeader>(ptr as *const u8 as *const AtomHeader) };
-                        unsafe { ptr::read::<AtomHeader>(ptr as *const u8 as *const AtomHeader) };
+                let len = header.len() as usize;
-                    let len = header.len() as usize;
+                let buf = unsafe { (ptr as *const u8).add(mem::size_of::<AtomHeader>()) };
-                    let buf =
-                        unsafe { (ptr as *const u8).offset(mem::size_of::<AtomHeader>() as isize) };
 
-                    unsafe { str::from_utf8_unchecked(slice::from_raw_parts(buf, len)) }
+                unsafe { str::from_utf8_unchecked(slice::from_raw_parts(buf, len)) }
-                }))
+            }))
-            } else {
+        } else {
-                AtomString::Static(&STRINGS[(self.index >> 3) as usize])
+            AtomString::Static(STRINGS[(self.index >> 3) as usize])
-            }
         }
     }
 
@@ -258,14 +259,14 @@ impl Atom {
             return *self;
         };
 
-        AtomTable::build_with(&atom_tbl, &sub_str)
+        AtomTable::build_with(atom_tbl, sub_str)
     }
 }
 
 unsafe fn write_to_ptr(string: &str, ptr: *mut u8) {
     ptr::write(ptr as *mut _, AtomHeader::build_with(string.len() as u64));
     let str_ptr = (ptr as usize + mem::size_of::<AtomHeader>()) as *mut u8;
-    ptr::copy_nonoverlapping(string.as_ptr(), str_ptr as *mut u8, string.len());
+    ptr::copy_nonoverlapping(string.as_ptr(), str_ptr, string.len());
 }
 
 impl PartialOrd for Atom {

src/bin/scryer-prolog.rs

@@ -1,6 +1,6 @@
 fn main() -> std::process::ExitCode {
-    use scryer_prolog::*;
     use scryer_prolog::atom_table::Atom;
+    use scryer_prolog::*;
     use std::sync::atomic::Ordering;
 
     #[cfg(feature = "repl")]

src/codegen.rs

@@ -111,7 +111,7 @@ impl BranchCodeStack {
                     jump_span -= code.len() + 1;
                 } else {
                     jump_span -= code.len() + 1;
-                    code.push_back(instr!("jmp_by_call", jump_span as usize));
+                    code.push_back(instr!("jmp_by_call", jump_span));
 
                     jump_span -= 1;
                 }
@@ -124,9 +124,9 @@ impl BranchCodeStack {
 
         for mut branch_arm in self.stack.drain(self.stack.len() - depth..).rev() {
             let num_branch_arms = branch_arm.len();
-            branch_arm
+            if let Some(code) = branch_arm.last_mut() {
-                .last_mut()
+                code.extend(combined_code.drain(..))
-                .map(|code| code.extend(combined_code.drain(..)));
+            }
 
             for (idx, code) in branch_arm.into_iter().enumerate() {
                 combined_code.push_back(if idx == 0 {
@@ -376,7 +376,7 @@ impl<'b> CodeGenerator<'b> {
         Target: crate::targets::CompilationTarget<'a>,
     {
         if let Some(ref mut instr) = target.back_mut() {
-            if Target::is_void_instr(&*instr) {
+            if Target::is_void_instr(instr) {
                 Target::incr_void_instr(instr);
                 return;
             }
@@ -418,10 +418,10 @@ impl<'b> CodeGenerator<'b> {
                     .mark_non_var::<Target>(Level::Deep, term_loc, cell, target);
                 target.push_back(Target::clause_arg_to_instr(cell.get()));
             }
-            &Term::Literal(_, ref constant) => {
+            Term::Literal(_, ref constant) => {
-                target.push_back(Target::constant_subterm(constant.clone()));
+                target.push_back(Target::constant_subterm(*constant));
             }
-            &Term::Var(ref cell, ref var_ptr) => {
+            Term::Var(ref cell, ref var_ptr) => {
                 self.deep_var_instr::<Target>(
                     cell,
                     var_ptr.to_var_num().unwrap(),
@@ -509,7 +509,7 @@ impl<'b> CodeGenerator<'b> {
                 TermRef::PartialString(lvl, cell, string, tail) => {
                     self.marker
                         .mark_non_var::<Target>(lvl, term_loc, cell, &mut target);
-                    let atom = AtomTable::build_with(&self.atom_tbl, &string);
+                    let atom = AtomTable::build_with(self.atom_tbl, string);
 
                     target.push_back(Target::to_pstr(lvl, atom, cell.get(), true));
                     self.subterm_to_instr::<Target>(tail, term_loc, &mut target);
@@ -558,10 +558,10 @@ impl<'b> CodeGenerator<'b> {
         }
     }
 
-    fn compile_inlined<'a>(
+    fn compile_inlined(
         &mut self,
         ct: &InlinedClauseType,
-        terms: &'a Vec<Term>,
+        terms: &'_ [Term],
         term_loc: GenContext,
         code: &mut CodeDeque,
     ) -> Result<(), CompilationError> {
@@ -585,13 +585,13 @@ impl<'b> CodeGenerator<'b> {
 
                 compare_number_instr!(cmp, at_1, at_2)
             }
-            &InlinedClauseType::IsAtom(..) => match &terms[0] {
+            InlinedClauseType::IsAtom(..) => match &terms[0] {
-                &Term::Literal(_, Literal::Char(_))
+                Term::Literal(_, Literal::Char(_))
-                | &Term::Literal(_, Literal::Atom(atom!("[]")))
+                | Term::Literal(_, Literal::Atom(atom!("[]")))
-                | &Term::Literal(_, Literal::Atom(..)) => {
+                | Term::Literal(_, Literal::Atom(..)) => {
                     instr!("$succeed")
                 }
-                &Term::Var(ref vr, ref name) => {
+                Term::Var(ref vr, ref name) => {
                     self.marker.reset_arg(1);
 
                     let r = self.marker.mark_non_callable(
@@ -608,21 +608,21 @@ impl<'b> CodeGenerator<'b> {
                     instr!("$fail")
                 }
             },
-            &InlinedClauseType::IsAtomic(..) => match &terms[0] {
+            InlinedClauseType::IsAtomic(..) => match &terms[0] {
-                &Term::AnonVar
+                Term::AnonVar
-                | &Term::Clause(..)
+                | Term::Clause(..)
-                | &Term::Cons(..)
+                | Term::Cons(..)
-                | &Term::PartialString(..)
+                | Term::PartialString(..)
-                | &Term::CompleteString(..) => {
+                | Term::CompleteString(..) => {
                     instr!("$fail")
                 }
-                &Term::Literal(_, Literal::String(_)) => {
+                Term::Literal(_, Literal::String(_)) => {
                     instr!("$fail")
                 }
-                &Term::Literal(..) => {
+                Term::Literal(..) => {
                     instr!("$succeed")
                 }
-                &Term::Var(ref vr, ref name) => {
+                Term::Var(ref vr, ref name) => {
                     self.marker.reset_arg(1);
 
                     let r = self.marker.mark_non_callable(
@@ -636,15 +636,15 @@ impl<'b> CodeGenerator<'b> {
                     instr!("atomic", r)
                 }
             },
-            &InlinedClauseType::IsCompound(..) => match &terms[0] {
+            InlinedClauseType::IsCompound(..) => match &terms[0] {
-                &Term::Clause(..)
+                Term::Clause(..)
-                | &Term::Cons(..)
+                | Term::Cons(..)
-                | &Term::PartialString(..)
+                | Term::PartialString(..)
-                | &Term::CompleteString(..)
+                | Term::CompleteString(..)
-                | &Term::Literal(_, Literal::String(..)) => {
+                | Term::Literal(_, Literal::String(..)) => {
                     instr!("$succeed")
                 }
-                &Term::Var(ref vr, ref name) => {
+                Term::Var(ref vr, ref name) => {
                     self.marker.reset_arg(1);
 
                     let r = self.marker.mark_non_callable(
@@ -661,11 +661,11 @@ impl<'b> CodeGenerator<'b> {
                     instr!("$fail")
                 }
             },
-            &InlinedClauseType::IsRational(..) => match &terms[0] {
+            InlinedClauseType::IsRational(..) => match terms[0] {
-                &Term::Literal(_, Literal::Rational(_)) => {
+                Term::Literal(_, Literal::Rational(_)) => {
                     instr!("$succeed")
                 }
-                &Term::Var(ref vr, ref name) => {
+                Term::Var(ref vr, ref name) => {
                     self.marker.reset_arg(1);
                     let r = self.marker.mark_non_callable(
                         name.to_var_num().unwrap(),
@@ -680,11 +680,11 @@ impl<'b> CodeGenerator<'b> {
                     instr!("$fail")
                 }
             },
-            &InlinedClauseType::IsFloat(..) => match &terms[0] {
+            InlinedClauseType::IsFloat(..) => match terms[0] {
-                &Term::Literal(_, Literal::Float(_)) => {
+                Term::Literal(_, Literal::Float(_)) => {
                     instr!("$succeed")
                 }
-                &Term::Var(ref vr, ref name) => {
+                Term::Var(ref vr, ref name) => {
                     self.marker.reset_arg(1);
 
                     let r = self.marker.mark_non_callable(
@@ -701,14 +701,14 @@ impl<'b> CodeGenerator<'b> {
                     instr!("$fail")
                 }
             },
-            &InlinedClauseType::IsNumber(..) => match &terms[0] {
+            InlinedClauseType::IsNumber(..) => match terms[0] {
-                &Term::Literal(_, Literal::Float(_))
+                Term::Literal(_, Literal::Float(_))
-                | &Term::Literal(_, Literal::Rational(_))
+                | Term::Literal(_, Literal::Rational(_))
-                | &Term::Literal(_, Literal::Integer(_))
+                | Term::Literal(_, Literal::Integer(_))
-                | &Term::Literal(_, Literal::Fixnum(_)) => {
+                | Term::Literal(_, Literal::Fixnum(_)) => {
                     instr!("$succeed")
                 }
-                &Term::Var(ref vr, ref name) => {
+                Term::Var(ref vr, ref name) => {
                     self.marker.reset_arg(1);
 
                     let r = self.marker.mark_non_callable(
@@ -725,11 +725,11 @@ impl<'b> CodeGenerator<'b> {
                     instr!("$fail")
                 }
             },
-            &InlinedClauseType::IsNonVar(..) => match &terms[0] {
+            InlinedClauseType::IsNonVar(..) => match terms[0] {
-                &Term::AnonVar => {
+                Term::AnonVar => {
                     instr!("$fail")
                 }
-                &Term::Var(ref vr, ref name) => {
+                Term::Var(ref vr, ref name) => {
                     self.marker.reset_arg(1);
 
                     let r = self.marker.mark_non_callable(
@@ -746,11 +746,11 @@ impl<'b> CodeGenerator<'b> {
                     instr!("$succeed")
                 }
             },
-            &InlinedClauseType::IsInteger(..) => match &terms[0] {
+            InlinedClauseType::IsInteger(..) => match &terms[0] {
-                &Term::Literal(_, Literal::Integer(_)) | &Term::Literal(_, Literal::Fixnum(_)) => {
+                Term::Literal(_, Literal::Integer(_)) | Term::Literal(_, Literal::Fixnum(_)) => {
                     instr!("$succeed")
                 }
-                &Term::Var(ref vr, ref name) => {
+                Term::Var(ref vr, name) => {
                     self.marker.reset_arg(1);
 
                     let r = self.marker.mark_non_callable(
@@ -767,18 +767,18 @@ impl<'b> CodeGenerator<'b> {
                     instr!("$fail")
                 }
             },
-            &InlinedClauseType::IsVar(..) => match &terms[0] {
+            InlinedClauseType::IsVar(..) => match terms[0] {
-                &Term::Literal(..)
+                Term::Literal(..)
-                | &Term::Clause(..)
+                | Term::Clause(..)
-                | &Term::Cons(..)
+                | Term::Cons(..)
-                | &Term::PartialString(..)
+                | Term::PartialString(..)
-                | &Term::CompleteString(..) => {
+                | Term::CompleteString(..) => {
                     instr!("$fail")
                 }
-                &Term::AnonVar => {
+                Term::AnonVar => {
                     instr!("$succeed")
                 }
-                &Term::Var(ref vr, ref name) => {
+                Term::Var(ref vr, ref name) => {
                     self.marker.reset_arg(1);
 
                     let r = self.marker.mark_non_callable(
@@ -813,7 +813,7 @@ impl<'b> CodeGenerator<'b> {
 
     fn compile_is_call(
         &mut self,
-        terms: &Vec<Term>,
+        terms: &[Term],
         code: &mut CodeDeque,
         term_loc: GenContext,
         call_policy: CallPolicy,
@@ -828,8 +828,8 @@ impl<'b> CodeGenerator<'b> {
 
         self.marker.reset_arg(2);
 
-        let at = match &terms[0] {
+        let at = match terms[0] {
-            &Term::Var(ref vr, ref name) => {
+            Term::Var(ref vr, ref name) => {
                 let var_num = name.to_var_num().unwrap();
 
                 if self.marker.var_data.records[var_num].num_occurrences > 1 {
@@ -871,7 +871,7 @@ impl<'b> CodeGenerator<'b> {
                     compile_expr!(self, &terms[1], term_loc, code)
                 }
             }
-            &Term::Literal(
+            Term::Literal(
                 _,
                 c @ Literal::Integer(_)
                 | c @ Literal::Float(_)
@@ -896,7 +896,7 @@ impl<'b> CodeGenerator<'b> {
         Ok(())
     }
 
-    fn compile_seq<'a>(
+    fn compile_seq(
         &mut self,
         clauses: &ChunkedTermVec,
         code: &mut CodeDeque,
@@ -1066,7 +1066,7 @@ impl<'b> CodeGenerator<'b> {
 
         self.marker.reset_at_head(args);
 
-        let iter = FactIterator::from_rule_head_clause(&args);
+        let iter = FactIterator::from_rule_head_clause(args);
         let fact = self.compile_target::<FactInstruction, _>(iter, GenContext::Head);
 
         if self.marker.max_reg_allocated() > MAX_ARITY {
@@ -1074,7 +1074,7 @@ impl<'b> CodeGenerator<'b> {
         }
 
         self.marker.reset_free_list();
-        code.extend(fact.into_iter());
+        code.extend(fact);
 
         self.compile_seq(clauses, &mut code)?;
 
@@ -1099,7 +1099,7 @@ impl<'b> CodeGenerator<'b> {
                 return Err(CompilationError::ExceededMaxArity);
             }
 
-            code.extend(compiled_fact.into_iter());
+            code.extend(compiled_fact);
         }
 
         code.push(instr!("proceed"));
@@ -1112,7 +1112,7 @@ impl<'b> CodeGenerator<'b> {
         let iter = QueryIterator::new(term);
         let query = self.compile_target::<QueryInstruction, _>(iter, term_loc);
 
-        code.extend(query.into_iter());
+        code.extend(query);
 
         match term {
             &QueryTerm::Clause(_, ref ct, _, call_policy) => {
@@ -1204,12 +1204,12 @@ impl<'b> CodeGenerator<'b> {
 
             let clause_code = match clause {
                 PredicateClause::Fact(fact, var_data) => {
-                    let var_data = std::mem::replace(var_data, VarData::default());
+                    let var_data = std::mem::take(var_data);
-                    self.compile_fact(&fact, var_data)?
+                    self.compile_fact(fact, var_data)?
                 }
                 PredicateClause::Rule(rule, var_data) => {
-                    let var_data = std::mem::replace(var_data, VarData::default());
+                    let var_data = std::mem::take(var_data);
-                    self.compile_rule(&rule, var_data)?
+                    self.compile_rule(rule, var_data)?
                 }
             };
 
@@ -1237,9 +1237,7 @@ impl<'b> CodeGenerator<'b> {
                 skip_stub_try_me_else = !self.settings.is_dynamic();
             }
 
-            let arg = clause
+            let arg = clause.args().and_then(|args| args.get(optimal_index));
-                .args()
-                .and_then(|args| args.iter().nth(optimal_index));
 
             if let Some(arg) = arg {
                 let index = code.len();

src/debray_allocator.rs

@@ -295,11 +295,9 @@ impl DebrayAllocator {
                 let mut result = 0;
 
                 for reg in self.temp_lb.. {
-                    if !self.is_in_use(reg) {
+                    if !self.is_in_use(reg) && !temp_var_data.no_use_set.contains(reg) {
-                        if !temp_var_data.no_use_set.contains(reg) {
+                        result = reg;
-                            result = reg;
+                        break;
-                            break;
-                        }
                     }
                 }
 
@@ -321,13 +319,12 @@ impl DebrayAllocator {
                 let mut result = 0;
 
                 for reg in self.temp_lb.. {
-                    if !self.is_in_use(reg) {
+                    if !self.is_in_use(reg)
-                        if !temp_var_data.no_use_set.contains(reg) {
+                        && !temp_var_data.no_use_set.contains(reg)
-                            if !temp_var_data.conflict_set.contains(reg) {
+                        && !temp_var_data.conflict_set.contains(reg)
-                                result = reg;
+                    {
-                                break;
+                        result = reg;
-                            }
+                        break;
-                        }
                     }
                 }
 
@@ -349,16 +346,15 @@ impl DebrayAllocator {
                 // consider its use set. T == par_k iff
                 // (GenContext::Last(_), k) is in t_var.use_set.
 
-                match &self.var_data.records[t_var].allocation {
+                if let VarAlloc::Temp { temp_var_data, .. } =
-                    VarAlloc::Temp { temp_var_data, .. } => {
+                    &self.var_data.records[t_var].allocation
-                        if !temp_var_data
+                {
-                            .use_set
+                    if !temp_var_data
-                            .contains(&(GenContext::Last(chunk_num), k))
+                        .use_set
-                        {
+                        .contains(&(GenContext::Last(chunk_num), k))
-                            return Some((t_var, self.alloc_with_ca(t_var)));
+                    {
-                        }
+                        return Some((t_var, self.alloc_with_ca(t_var)));
                     }
-                    _ => {}
                 }
 
                 None
@@ -372,25 +368,22 @@ impl DebrayAllocator {
         chunk_num: usize,
         code: &mut CodeDeque,
     ) {
-        match self.alloc_in_last_goal_hint(chunk_num) {
+        if let Some((var_num, r)) = self.alloc_in_last_goal_hint(chunk_num) {
-            Some((var_num, r)) => {
+            let k = self.arg_c;
-                let k = self.arg_c;
 
-                if r != k {
+            if r != k {
-                    let r = RegType::Temp(r);
+                let r = RegType::Temp(r);
 
-                    code.push_back(Target::move_to_register(r, k));
+                code.push_back(Target::move_to_register(r, k));
 
-                    self.shallow_temp_mappings.swap_remove(&k);
+                self.shallow_temp_mappings.swap_remove(&k);
-                    self.shallow_temp_mappings.insert(r.reg_num(), var_num);
+                self.shallow_temp_mappings.insert(r.reg_num(), var_num);
 
-                    self.var_data.records[var_num]
+                self.var_data.records[var_num]
-                        .allocation
+                    .allocation
-                        .set_register(r.reg_num());
+                    .set_register(r.reg_num());
-                    self.in_use.insert(r.reg_num());
+                self.in_use.insert(r.reg_num());
-                }
             }
-            _ => {}
         };
     }
 
@@ -493,11 +486,8 @@ impl DebrayAllocator {
     }
 
     fn add_perm_to_free_list(&mut self, chunk_num: usize, var_num: usize) {
-        match &self.var_data.records[var_num].allocation {
+        if let VarAlloc::Perm(..) = &self.var_data.records[var_num].allocation {
-            VarAlloc::Perm(..) => {
+            self.perm_free_list.push_back((chunk_num, var_num));
-                self.perm_free_list.push_back((chunk_num, var_num));
-            }
-            _ => {}
         }
     }
 
@@ -521,12 +511,9 @@ impl DebrayAllocator {
     }
 
     pub(crate) fn free_var(&mut self, chunk_num: usize, var_num: usize) {
-        match &mut self.var_data.records[var_num].allocation {
+        if let VarAlloc::Perm(_, allocation) = &mut self.var_data.records[var_num].allocation {
-            VarAlloc::Perm(_, allocation) => {
+            *allocation = PermVarAllocation::Pending;
-                *allocation = PermVarAllocation::Pending;
+            self.add_perm_to_free_list(chunk_num, var_num);
-                self.add_perm_to_free_list(chunk_num, var_num);
-            }
-            _ => {}
         }
     }
 
@@ -570,18 +557,15 @@ impl DebrayAllocator {
                     *shallow_safety = VarSafetyStatus::unneeded(branch_designator);
                 } else if term_loc == GenContext::Head {
                     *shallow_safety = VarSafetyStatus::GloballyUnneeded;
-                } else {
+                } else if let Some(&temp_var_num) = self.shallow_temp_mappings.get(&self.arg_c) {
-                    if let Some(temp_var_num) = self.shallow_temp_mappings.get(&self.arg_c).cloned()
+                    match &mut self.var_data.records[temp_var_num].allocation {
-                    {
+                        VarAlloc::Temp {
-                        match &mut self.var_data.records[temp_var_num].allocation {
+                            ref mut to_perm_var_num,
-                            VarAlloc::Temp {
+                            ..
-                                ref mut to_perm_var_num,
+                        } => {
-                                ..
+                            *to_perm_var_num = Some(var_num);
-                            } => {
-                                *to_perm_var_num = Some(var_num);
-                            }
-                            _ => unreachable!(),
                         }
+                        _ => unreachable!(),
                     }
                 }
             }
@@ -886,12 +870,12 @@ impl Allocator for DebrayAllocator {
         self.arg_c += 1;
     }
 
-    fn reset_at_head(&mut self, args: &Vec<Term>) {
+    fn reset_at_head(&mut self, args: &[Term]) {
         self.reset_arg(args.len());
         self.arity = args.len();
 
         for (idx, arg) in args.iter().enumerate() {
-            if let &Term::Var(_, ref var) = arg {
+            if let Term::Var(_, ref var) = arg {
                 let var_num = var.to_var_num().unwrap();
                 let r = self.get_binding(var_num);
 

src/ffi.rs

@@ -28,7 +28,8 @@ use std::convert::TryFrom;
 use std::error::Error;
 use std::ffi::{c_void, CString};
 
-use libffi::low::{ffi_abi_FFI_DEFAULT_ABI, ffi_cif, ffi_type, prep_cif, type_tag, types, CodePtr};
+use libffi::low::type_tag::STRUCT;
+use libffi::low::{ffi_abi_FFI_DEFAULT_ABI, ffi_cif, ffi_type, prep_cif, types, CodePtr};
 use libloading::{Library, Symbol};
 
 pub struct FunctionDefinition {
@@ -69,11 +70,13 @@ impl ForeignFunctionTable {
     }
 
     pub fn define_struct(&mut self, name: &str, atom_fields: Vec<Atom>) {
-        let mut fields: Vec<_> = atom_fields.iter().map(|x| self.map_type_ffi(&x)).collect();
+        let mut fields: Vec<_> = atom_fields.iter().map(|x| self.map_type_ffi(x)).collect();
         fields.push(std::ptr::null_mut::<ffi_type>());
-        let mut struct_type: ffi_type = Default::default();
+        let struct_type = ffi_type {
-        struct_type.type_ = type_tag::STRUCT;
+            type_: STRUCT,
-        struct_type.elements = fields.as_mut_ptr();
+            elements: fields.as_mut_ptr(),
+            ..Default::default()
+        };
         self.structs.insert(
             name.to_string(),
             StructImpl {
@@ -121,11 +124,7 @@ impl ForeignFunctionTable {
                 let symbol_name: CString = CString::new(function.name.clone())?;
                 let code_ptr: Symbol<*mut c_void> =
                     library.get(&symbol_name.into_bytes_with_nul())?;
-                let mut args: Vec<_> = function
+                let mut args: Vec<_> = function.args.iter().map(|x| self.map_type_ffi(x)).collect();
-                    .args
-                    .iter()
-                    .map(|x| self.map_type_ffi(&x))
-                    .collect();
                 let mut cif: ffi_cif = Default::default();
                 prep_cif(
                     &mut cif,
@@ -163,7 +162,7 @@ impl ForeignFunctionTable {
 
     fn build_pointer_args(
         args: &mut Vec<Value>,
-        type_args: &Vec<*mut ffi_type>,
+        type_args: &[*mut ffi_type],
         structs_table: &mut HashMap<String, StructImpl>,
     ) -> Result<PointerArgs, FFIError> {
         let mut pointers = Vec::with_capacity(args.len());
@@ -237,6 +236,7 @@ impl ForeignFunctionTable {
                         let ptr = alloc(layout) as *mut c_void;
                         let mut field_ptr = ptr;
 
+                        #[allow(clippy::needless_range_loop)]
                         for i in 0..(struct_type.fields.len() - 1) {
                             macro_rules! try_write_int {
                                 ($type:ty) => {{
@@ -283,7 +283,7 @@ impl ForeignFunctionTable {
 
                                     std::ptr::copy(
                                         &*struct_ptr as *const _ as *const c_void,
-                                        field_ptr as *mut c_void,
+                                        field_ptr,
                                         struct_size,
                                     );
                                     field_ptr = field_ptr.add(struct_size);
@@ -293,12 +293,13 @@ impl ForeignFunctionTable {
                                 }
                             }
                         }
-                        return Ok((Box::from_raw(ptr), size, align));
+                        #[allow(clippy::from_raw_with_void_ptr)]
+                        Ok((Box::from_raw(ptr), size, align))
                     } else {
-                        return Err(FFIError::InvalidStructName);
+                        Err(FFIError::InvalidStructName)
                     }
                 }
-                _ => return Err(FFIError::ValueCast),
+                _ => Err(FFIError::ValueCast),
             }
         }
     }
@@ -336,7 +337,7 @@ impl ForeignFunctionTable {
                         &mut function_impl.cif,
                         Some(*function_impl.code_ptr.as_safe_fun()),
                         &mut *n as *mut _ as *mut c_void,
-                        pointer_args.pointers.as_mut_ptr() as *mut *mut c_void,
+                        pointer_args.pointers.as_mut_ptr(),
                     );
                     Ok(Value::Int(
                         i64::try_from(*n).map_err(|_| FFIError::ValueDontFit)?,
@@ -350,7 +351,7 @@ impl ForeignFunctionTable {
                         &mut function_impl.cif,
                         Some(*function_impl.code_ptr.as_safe_fun()),
                         &mut *n as *mut _ as *mut c_void,
-                        pointer_args.pointers.as_mut_ptr() as *mut *mut c_void,
+                        pointer_args.pointers.as_mut_ptr(),
                     );
                     Ok(Value::Float((*n).into()))
                 }
@@ -360,7 +361,7 @@ impl ForeignFunctionTable {
                         &mut function_impl.cif,
                         Some(*function_impl.code_ptr.as_safe_fun()),
                         &mut *n as *mut _ as *mut c_void,
-                        pointer_args.pointers.as_mut_ptr() as *mut *mut c_void,
+                        pointer_args.pointers.as_mut_ptr(),
                     );
                     Ok(Value::Float(*n))
                 }
@@ -380,10 +381,11 @@ impl ForeignFunctionTable {
                     libffi::raw::ffi_call(
                         &mut function_impl.cif,
                         Some(*function_impl.code_ptr.as_safe_fun()),
-                        &mut *ptr as *mut _ as *mut c_void,
+                        &mut *ptr as *mut _,
-                        pointer_args.pointers.as_mut_ptr() as *mut *mut c_void,
+                        pointer_args.pointers.as_mut_ptr(),
                     );
                     let struct_val = self.read_struct(ptr, name, struct_type);
+                    #[allow(clippy::from_raw_with_void_ptr)]
                     drop(Box::from_raw(ptr));
                     struct_val
                 }
@@ -441,7 +443,7 @@ impl ForeignFunctionTable {
                             .ok_or(FFIError::StructNotFound)?;
                         field_ptr = field_ptr
                             .add(field_ptr.align_offset(struct_type.ffi_type.alignment as usize));
-                        let struct_val = self.read_struct(field_ptr, &*substruct, struct_type);
+                        let struct_val = self.read_struct(field_ptr, &substruct, struct_type);
                         returns.push(struct_val?);
                         field_ptr = field_ptr.add(struct_type.ffi_type.size);
                     }

src/forms.rs

@@ -11,6 +11,7 @@ use crate::parser::dashu::{Integer, Rational};
 use crate::parser::parser::CompositeOpDesc;
 use crate::types::*;
 
+use dashu::base::Signed;
 use fxhash::FxBuildHasher;
 
 use indexmap::{IndexMap, IndexSet};
@@ -99,11 +100,7 @@ pub enum RootIterationPolicy {
 impl RootIterationPolicy {
     #[inline(always)]
     pub fn iterable(&self) -> bool {
-        if let RootIterationPolicy::Iterated = self {
+        matches!(self, RootIterationPolicy::Iterated)
-            true
-        } else {
-            false
-        }
     }
 }
 
@@ -151,6 +148,7 @@ impl DerefMut for ChunkedTermVec {
 }
 
 impl ChunkedTermVec {
+    #[allow(clippy::new_without_default)]
     #[inline]
     pub fn new() -> Self {
         Self {
@@ -202,8 +200,8 @@ pub enum QueryTerm {
     // register, clause type, subterms, clause call policy.
     Clause(Cell<RegType>, ClauseType, Vec<Term>, CallPolicy),
     Fail,
-    LocalCut { var_num: usize, cut_prev: bool },  // var_num
+    LocalCut { var_num: usize, cut_prev: bool }, // var_num
-    GlobalCut(usize), // var_num
+    GlobalCut(usize),                            // var_num
     GetCutPoint { var_num: usize, prev_b: bool },
     GetLevel(usize), // var_num
 }
@@ -211,7 +209,7 @@ pub enum QueryTerm {
 impl QueryTerm {
     pub(crate) fn arity(&self) -> usize {
         match self {
-            &QueryTerm::Clause(_, _, ref subterms, ..) => subterms.len(),
+            QueryTerm::Clause(_, _, subterms, ..) => subterms.len(),
             &QueryTerm::GetLevel(_) | &QueryTerm::GetCutPoint { .. } => 1,
             _ => 0,
         }
@@ -316,15 +314,15 @@ impl ClauseInfo for Rule {
 impl ClauseInfo for PredicateClause {
     fn name(&self) -> Option<Atom> {
         match self {
-            &PredicateClause::Fact(ref term, ..) => term.head.name(),
+            PredicateClause::Fact(ref term, ..) => term.head.name(),
-            &PredicateClause::Rule(ref rule, ..) => rule.name(),
+            PredicateClause::Rule(ref rule, ..) => rule.name(),
         }
     }
 
     fn arity(&self) -> usize {
         match self {
-            &PredicateClause::Fact(ref term, ..) => term.head.arity(),
+            PredicateClause::Fact(ref term, ..) => term.head.arity(),
-            &PredicateClause::Rule(ref rule, ..) => rule.arity(),
+            PredicateClause::Rule(ref rule, ..) => rule.arity(),
         }
     }
 }
@@ -339,7 +337,7 @@ impl PredicateClause {
     pub(crate) fn args(&self) -> Option<&[Term]> {
         match self {
             PredicateClause::Fact(term, ..) => match &term.head {
-                Term::Clause(_, _, args) => Some(&args),
+                Term::Clause(_, _, args) => Some(args),
                 _ => None,
             },
             PredicateClause::Rule(rule, ..) => {
@@ -433,13 +431,10 @@ impl OpDecl {
     pub(crate) fn insert_into_op_dir(&self, op_dir: &mut OpDir) -> Option<OpDesc> {
         let key = (self.name, fixity(self.op_desc.get_spec() as u32));
 
-        match op_dir.get_mut(&key) {
+        if let Some(cell) = op_dir.get_mut(&key) {
-            Some(cell) => {
+            let (old_prec, old_spec) = cell.get();
-                let (old_prec, old_spec) = cell.get();
+            cell.set(self.op_desc.get_prec(), self.op_desc.get_spec());
-                cell.set(self.op_desc.get_prec(), self.op_desc.get_spec());
+            return Some(OpDesc::build_with(old_prec, old_spec));
-                return Some(OpDesc::build_with(old_prec, old_spec));
-            }
-            None => {}
         }
 
         op_dir.insert(key, self.op_desc)
@@ -450,7 +445,7 @@ impl OpDecl {
         existing_desc: Option<CompositeOpDesc>,
         op_dir: &mut OpDir,
     ) -> Result<(), SessionError> {
-        let (spec, name) = (self.op_desc.get_spec(), self.name.clone());
+        let (spec, name) = (self.op_desc.get_spec(), self.name);
 
         if is_infix!(spec as u32) {
             if let Some(desc) = existing_desc {
@@ -484,7 +479,7 @@ impl AtomOrString {
     pub fn as_atom(&self, atom_tbl: &AtomTable) -> Atom {
         match self {
             &AtomOrString::Atom(atom) => atom,
-            AtomOrString::String(string) => AtomTable::build_with(atom_tbl, &string),
+            AtomOrString::String(string) => AtomTable::build_with(atom_tbl, string),
         }
     }
 
@@ -496,10 +491,11 @@ impl AtomOrString {
             AtomOrString::String(string) => AtomString::Static(string.as_str()),
         }
     }
+}
 
-    #[inline]
+impl From<AtomOrString> for String {
-    pub fn to_string(self) -> String {
+    fn from(val: AtomOrString) -> Self {
-        match self {
+        match val {
             AtomOrString::Atom(atom) => atom.as_str().to_owned(),
             AtomOrString::String(string) => string,
         }
@@ -543,7 +539,7 @@ pub(crate) fn fetch_op_spec(name: Atom, arity: usize, op_dir: &OpDir) -> Option<
             }
         }),
         1 => {
-            if let Some(op_desc) = op_dir.get(&(name.clone(), Fixity::Pre)) {
+            if let Some(op_desc) = op_dir.get(&(name, Fixity::Pre)) {
                 if op_desc.get_prec() > 0 {
                     return Some(*op_desc);
                 }
@@ -744,8 +740,8 @@ impl ArenaFrom<Number> for HeapCellValue {
 impl Number {
     pub(crate) fn sign(&self) -> Number {
         match self {
-            &Number::Float(f) if f == 0.0 => Number::Float(OrderedFloat(0f64)),
+            Number::Float(f) if *f == 0.0 => Number::Float(OrderedFloat(0f64)),
-            &Number::Float(f) => Number::Float(OrderedFloat(f.signum())),
+            Number::Float(f) => Number::Float(OrderedFloat(f.signum())),
             _ => {
                 if self.is_positive() {
                     Number::Fixnum(Fixnum::build_with(1))
@@ -761,39 +757,36 @@ impl Number {
     #[inline]
     pub(crate) fn is_positive(&self) -> bool {
         match self {
-            &Number::Fixnum(n) => n.get_num() > 0,
+            Number::Fixnum(n) => n.get_num() > 0,
-            &Number::Integer(ref n) => &**n > &Integer::from(0),
+            Number::Integer(ref n) => n.is_positive(),
-            &Number::Float(f) => f.is_sign_positive(),
+            Number::Float(f) => f.is_sign_positive(),
-            &Number::Rational(ref r) => &**r > &Rational::from(0),
+            Number::Rational(ref r) => r.is_positive(),
         }
     }
 
     #[inline]
     pub(crate) fn is_negative(&self) -> bool {
         match self {
-            &Number::Fixnum(n) => n.get_num() < 0,
+            Number::Fixnum(n) => n.get_num() < 0,
-            &Number::Integer(ref n) => &**n < &Integer::from(0),
+            Number::Integer(ref n) => n.is_negative(),
-            &Number::Float(OrderedFloat(f)) => f.is_sign_negative() && OrderedFloat(f) != -0f64,
+            &Number::Float(OrderedFloat(f)) => f.is_sign_negative() && f != -0f64,
-            &Number::Rational(ref r) => &**r < &Rational::from(0),
+            Number::Rational(ref r) => r.is_negative(),
         }
     }
 
     #[inline]
     pub(crate) fn is_zero(&self) -> bool {
         match self {
-            &Number::Fixnum(n) => n.get_num() == 0,
+            Number::Fixnum(n) => n.get_num() == 0,
-            &Number::Integer(ref n) => &**n == &Integer::from(0),
+            Number::Integer(ref n) => n.is_zero(),
-            &Number::Float(f) => f == OrderedFloat(0f64) || f == OrderedFloat(-0f64),
+            &Number::Float(OrderedFloat(f)) => f == 0.0 || f == -0.0,
-            &Number::Rational(ref r) => &**r == &Rational::from(0),
+            Number::Rational(ref r) => r.is_zero(),
         }
     }
 
     #[inline]
     pub(crate) fn is_integer(&self) -> bool {
-        match self {
+        matches!(self, Number::Fixnum(_) | Number::Integer(_))
-            Number::Fixnum(_) | Number::Integer(_) => true,
-            _ => false,
-        }
     }
 }
 
@@ -963,7 +956,7 @@ impl LocalPredicateSkeleton {
 
     #[inline]
     pub(crate) fn add_retracted_dynamic_clause_info(&mut self, clause_info: ClauseIndexInfo) {
-        debug_assert_eq!(self.is_dynamic, true);
+        debug_assert!(self.is_dynamic);
 
         if self.retracted_dynamic_clauses.is_none() {
             self.retracted_dynamic_clauses = Some(vec![]);
@@ -1008,7 +1001,7 @@ impl PredicateSkeleton {
     ) -> Option<usize> {
         let search_result = self.core.clause_clause_locs.make_contiguous()
             [0..self.core.clause_assert_margin]
-            .binary_search_by(|loc| clause_clause_loc.cmp(&loc));
+            .binary_search_by(|loc| clause_clause_loc.cmp(loc));
 
         match search_result {
             Ok(loc) => Some(loc),

src/heap_iter.rs

@@ -43,7 +43,7 @@ impl<'a> Drop for EagerStackfulPreOrderHeapIter<'a> {
         self.start_value.set_mark_bit(true);
         self.iter_stack.push(self.start_value);
 
-        while let Some(_) = self.follow() {}
+        while self.follow().is_some() {}
     }
 }
 
@@ -87,22 +87,22 @@ impl<'a> EagerStackfulPreOrderHeapIter<'a> {
                     let arity = cell_as_atom_cell!(self.heap[s]).get_arity();
 
                     for idx in (s + 1 .. s + arity + 1).rev() {
-			            if self.heap[idx].get_mark_bit() != self.mark_phase {
+                        if self.heap[idx].get_mark_bit() != self.mark_phase {
                             self.iter_stack.push(self.heap[idx]);
                             self.heap[idx].set_mark_bit(self.mark_phase);
-			            }
+                        }
                     }
                 }
                 (HeapCellValueTag::Lis, l) => {
-		            if self.heap[l+1].get_mark_bit() != self.mark_phase {
+                    if self.heap[l+1].get_mark_bit() != self.mark_phase {
-			            self.iter_stack.push(self.heap[l+1]);
+                        self.iter_stack.push(self.heap[l+1]);
-			            self.heap[l+1].set_mark_bit(self.mark_phase);
+                        self.heap[l+1].set_mark_bit(self.mark_phase);
-		            }
+                    }
 
-		            if self.heap[l].get_mark_bit() != self.mark_phase {
+                    if self.heap[l].get_mark_bit() != self.mark_phase {
-			            self.iter_stack.push(self.heap[l]);
+                        self.iter_stack.push(self.heap[l]);
-			            self.heap[l].set_mark_bit(self.mark_phase);
+                        self.heap[l].set_mark_bit(self.mark_phase);
-		            }
+                    }
                 }
                 (HeapCellValueTag::AttrVar | HeapCellValueTag::Var, h) => {
                     let var_value = self.heap[h];
@@ -270,7 +270,9 @@ pub trait FocusedHeapIter: Iterator<Item = HeapCellValue> {
     fn focus(&self) -> IterStackLoc;
 }
 
-impl<'a, ElideLists: ListElisionPolicy> FocusedHeapIter for StackfulPreOrderHeapIter<'a, ElideLists> {
+impl<'a, ElideLists: ListElisionPolicy> FocusedHeapIter
+    for StackfulPreOrderHeapIter<'a, ElideLists>
+{
     #[inline]
     fn focus(&self) -> IterStackLoc {
         self.h
@@ -506,10 +508,10 @@ impl<'a, ElideLists: ListElisionPolicy> Iterator for StackfulPreOrderHeapIter<'a
 }
 
 #[inline(always)]
-pub(crate) fn cycle_detecting_stackless_preorder_iter<'a>(
+pub(crate) fn cycle_detecting_stackless_preorder_iter(
-    heap: &'a mut [HeapCellValue],
+    heap: &'_ mut [HeapCellValue],
     start: usize,
-) -> CycleDetectingIter<'a, true> {
+) -> CycleDetectingIter<'_, true> {
     // const generics argument of true so that cycle discovery stops
     // the iterator.
     CycleDetectingIter::new(heap, start)
@@ -660,25 +662,25 @@ pub(crate) fn stackful_post_order_iter<'a, ElideLists: ListElisionPolicy>(
 #[cfg(test)]
 mod tests {
     use super::*;
+    use crate::machine::gc::IteratorUMP;
     use crate::machine::mock_wam::*;
-    use crate::machine::gc::{IteratorUMP};
 
     pub(crate) type RightistPostOrderHeapIter<'a> =
         PostOrderIterator<StacklessPreOrderHeapIter<'a, IteratorUMP>>;
 
     #[inline(always)]
     pub(crate) fn stackless_preorder_iter(
-        heap: &mut Vec<HeapCellValue>,
+        heap: &mut [HeapCellValue],
         start: usize,
     ) -> StacklessPreOrderHeapIter<IteratorUMP> {
         StacklessPreOrderHeapIter::<IteratorUMP>::new(heap, start)
     }
 
     #[inline]
-    pub(crate) fn stackless_post_order_iter<'a>(
+    pub(crate) fn stackless_post_order_iter(
-        heap: &'a mut Heap,
+        heap: &'_ mut Heap,
         start: usize,
-    ) -> RightistPostOrderHeapIter<'a> {
+    ) -> RightistPostOrderHeapIter {
         PostOrderIterator::new(stackless_preorder_iter(heap, start))
     }
 
@@ -954,7 +956,10 @@ mod tests {
             let pstr_offset_cell = pstr_offset_as_cell!(0);
 
             assert_eq!(unmark_cell_bits!(iter.next().unwrap()), pstr_offset_cell);
-            assert_eq!(unmark_cell_bits!(iter.next().unwrap()), fixnum_as_cell!(Fixnum::build_with(2)));
+            assert_eq!(
+                unmark_cell_bits!(iter.next().unwrap()),
+                fixnum_as_cell!(Fixnum::build_with(2))
+            );
             assert_eq!(unmark_cell_bits!(iter.next().unwrap()), pstr_cell);
             assert_eq!(unmark_cell_bits!(iter.next().unwrap()), pstr_second_cell);
 
@@ -999,11 +1004,17 @@ mod tests {
             let pstr_offset_cell = pstr_offset_as_cell!(0);
 
             assert_eq!(unmark_cell_bits!(iter.next().unwrap()), pstr_cell);
-            assert_eq!(unmark_cell_bits!(iter.next().unwrap()), pstr_loc_as_cell!(4));
+            assert_eq!(
+                unmark_cell_bits!(iter.next().unwrap()),
+                pstr_loc_as_cell!(4)
+            );
 
             assert_eq!(unmark_cell_bits!(iter.next().unwrap()), pstr_offset_cell);
             assert_eq!(unmark_cell_bits!(iter.next().unwrap()), pstr_offset_cell);
-            assert_eq!(unmark_cell_bits!(iter.next().unwrap()), fixnum_as_cell!(Fixnum::build_with(0)));
+            assert_eq!(
+                unmark_cell_bits!(iter.next().unwrap()),
+                fixnum_as_cell!(Fixnum::build_with(0))
+            );
 
             assert_eq!(iter.next(), None);
         }
@@ -1016,7 +1027,10 @@ mod tests {
             let mut iter = stackless_preorder_iter(&mut wam.machine_st.heap, 6);
 
             assert_eq!(unmark_cell_bits!(iter.next().unwrap()), pstr_cell);
-            assert_eq!(unmark_cell_bits!(iter.next().unwrap()), pstr_loc_as_cell!(4));
+            assert_eq!(
+                unmark_cell_bits!(iter.next().unwrap()),
+                pstr_loc_as_cell!(4)
+            );
 
             assert_eq!(
                 unmark_cell_bits!(iter.next().unwrap()),
@@ -1035,7 +1049,10 @@ mod tests {
         }
 
         assert_eq!(wam.machine_st.heap[4], pstr_offset_as_cell!(0));
-        assert_eq!(wam.machine_st.heap[5], fixnum_as_cell!(Fixnum::build_with(1i64)));
+        assert_eq!(
+            wam.machine_st.heap[5],
+            fixnum_as_cell!(Fixnum::build_with(1i64))
+        );
 
         all_cells_unmarked(&wam.machine_st.heap);
 
@@ -1501,7 +1518,9 @@ mod tests {
         wam.machine_st.heap.clear();
 
         {
-            wam.machine_st.heap.push(fixnum_as_cell!(Fixnum::build_with(0)));
+            wam.machine_st
+                .heap
+                .push(fixnum_as_cell!(Fixnum::build_with(0)));
 
             let mut iter = stackless_preorder_iter(&mut wam.machine_st.heap, 0);
 
@@ -1536,7 +1555,10 @@ mod tests {
                 atom_as_cell!(atom!("y"))
             );
 
-            assert_eq!(unmark_cell_bits!(iter.next().unwrap()), heap_loc_as_cell!(0));
+            assert_eq!(
+                unmark_cell_bits!(iter.next().unwrap()),
+                heap_loc_as_cell!(0)
+            );
 
             assert!(iter.next().is_none());
         }
@@ -1685,10 +1707,7 @@ mod tests {
         wam.machine_st.heap.push(heap_loc_as_cell!(0));
 
         {
-            let mut iter = stackless_preorder_iter(
+            let mut iter = stackless_preorder_iter(&mut wam.machine_st.heap, 9);
-                &mut wam.machine_st.heap,
-                9,
-            );
 
             /*
             while let Some(_) = iter.next() {
@@ -2889,8 +2908,7 @@ mod tests {
         {
             wam.machine_st.heap.push(heap_loc_as_cell!(0));
 
-            let mut iter =
+            let mut iter = stackless_post_order_iter(&mut wam.machine_st.heap, 0);
-                stackless_post_order_iter(&mut wam.machine_st.heap, 0);
 
             assert_eq!(
                 unmark_cell_bits!(iter.next().unwrap()),
@@ -2931,8 +2949,7 @@ mod tests {
         wam.machine_st.heap.push(empty_list_as_cell!());
 
         {
-            let mut iter =
+            let mut iter = stackless_post_order_iter(&mut wam.machine_st.heap, 0);
-                stackless_post_order_iter(&mut wam.machine_st.heap, 0);
 
             assert_eq!(
                 unmark_cell_bits!(iter.next().unwrap()),
@@ -2964,8 +2981,7 @@ mod tests {
         wam.machine_st.heap.push(heap_loc_as_cell!(0));
 
         {
-            let mut iter =
+            let mut iter = stackless_post_order_iter(&mut wam.machine_st.heap, 0);
-                stackless_post_order_iter(&mut wam.machine_st.heap, 0);
 
             // the cycle will be iterated twice before being detected.
             assert_eq!(
@@ -2993,8 +3009,7 @@ mod tests {
         }
 
         {
-            let mut iter =
+            let mut iter = stackless_post_order_iter(&mut wam.machine_st.heap, 0);
-                stackless_post_order_iter(&mut wam.machine_st.heap, 0);
 
             // cut the iteration short to check that all cells are
             // unmarked and unforwarded by the Drop instance of
@@ -3031,8 +3046,7 @@ mod tests {
         wam.machine_st.heap.push(pstr_loc_as_cell!(0));
 
         {
-            let mut iter =
+            let mut iter = stackless_post_order_iter(&mut wam.machine_st.heap, 2);
-                stackless_post_order_iter(&mut wam.machine_st.heap, 2);
 
             assert_eq!(
                 unmark_cell_bits!(iter.next().unwrap()),
@@ -3119,10 +3133,7 @@ mod tests {
                 unmark_cell_bits!(iter.next().unwrap()),
                 heap_loc_as_cell!(3)
             );
-            assert_eq!(
+            assert_eq!(unmark_cell_bits!(iter.next().unwrap()), pstr_second_cell);
-                unmark_cell_bits!(iter.next().unwrap()),
-                pstr_second_cell
-            );
             assert_eq!(unmark_cell_bits!(iter.next().unwrap()), pstr_cell);
             assert_eq!(iter.next(), None);
         }

src/heap_print.rs

@@ -1,9 +1,9 @@
 use crate::arena::*;
 use crate::atom_table::*;
 use crate::parser::ast::*;
-use crate::parser::dashu::{ibig, Integer, Rational};
 use crate::parser::dashu::base::RemEuclid;
 use crate::parser::dashu::integer::Sign;
+use crate::parser::dashu::{ibig, Integer, Rational};
 use crate::{
     alpha_numeric_char, capital_letter_char, cut_char, decimal_digit_char, graphic_token_char,
     is_fx, is_infix, is_postfix, is_prefix, is_xf, is_xfx, is_xfy, is_yfx, semicolon_char,
@@ -20,6 +20,7 @@ use crate::machine::stack::*;
 use crate::machine::streams::*;
 use crate::types::*;
 
+use dashu::base::Signed;
 use ordered_float::OrderedFloat;
 
 use indexmap::IndexMap;
@@ -258,9 +259,7 @@ pub(crate) fn requires_space(atom: &str, op: &str) -> bool {
                     oc == '(' || alpha_numeric_char!(oc)
                 } else if graphic_token_char!(ac) {
                     graphic_token_char!(oc)
-                } else if variable_indicator_char!(ac) {
+                } else if variable_indicator_char!(ac) || capital_letter_char!(ac) {
-                    alpha_numeric_char!(oc)
-                } else if capital_letter_char!(ac) {
                     alpha_numeric_char!(oc)
                 } else if sign_char!(ac) {
                     sign_char!(oc) || decimal_digit_char!(oc)
@@ -277,7 +276,7 @@ pub(crate) fn requires_space(atom: &str, op: &str) -> bool {
 
 fn non_quoted_graphic_token<Iter: Iterator<Item = char>>(mut iter: Iter, c: char) -> bool {
     if c == '/' {
-        return match iter.next() {
+        match iter.next() {
             None => true,
             Some('*') => false, // if we start with comment token, we must quote.
             Some(c) => {
@@ -287,9 +286,9 @@ fn non_quoted_graphic_token<Iter: Iterator<Item = char>>(mut iter: Iter, c: char
                     false
                 }
             }
-        };
+        }
     } else if c == '.' {
-        return match iter.next() {
+        match iter.next() {
             None => false,
             Some(c) => {
                 if graphic_token_char!(c) {
@@ -298,7 +297,7 @@ fn non_quoted_graphic_token<Iter: Iterator<Item = char>>(mut iter: Iter, c: char
                     false
                 }
             }
-        };
+        }
     } else {
         iter.all(|c| graphic_token_char!(c))
     }
@@ -310,9 +309,7 @@ pub(super) fn non_quoted_token<Iter: Iterator<Item = char>>(mut iter: Iter) -> b
             iter.all(|c| alpha_numeric_char!(c))
         } else if graphic_token_char!(c) {
             non_quoted_graphic_token(iter, c)
-        } else if semicolon_char!(c) {
+        } else if semicolon_char!(c) || cut_char!(c) {
-            iter.next().is_none()
-        } else if cut_char!(c) {
             iter.next().is_none()
         } else if c == '[' {
             iter.next() == Some(']') && iter.next().is_none()
@@ -328,6 +325,7 @@ pub(super) fn non_quoted_token<Iter: Iterator<Item = char>>(mut iter: Iter) -> b
     }
 }
 
+#[allow(clippy::len_without_is_empty)]
 pub trait HCValueOutputter {
     type Output;
 
@@ -370,7 +368,7 @@ impl HCValueOutputter for PrinterOutputter {
     }
 
     fn begin_new_var(&mut self) {
-        if self.contents.len() != 0 {
+        if !self.contents.is_empty() {
             self.contents += ", ";
         }
     }
@@ -415,9 +413,9 @@ fn negated_op_needs_bracketing(
         op.is_negative_sign()
             && iter.leftmost_leaf_has_property(op_dir, |addr| match Number::try_from(addr) {
                 Ok(Number::Fixnum(n)) => n.get_num() > 0,
-                Ok(Number::Float(f)) => f > OrderedFloat(0f64),
+                Ok(Number::Float(OrderedFloat(f))) => f > 0f64,
-                Ok(Number::Integer(n)) => &*n > &Integer::from(0),
+                Ok(Number::Integer(n)) => n.is_positive(),
-                Ok(Number::Rational(n)) => &*n > &Rational::from(0),
+                Ok(Number::Rational(n)) => n.is_positive(),
                 _ => false,
             })
     } else {
@@ -537,20 +535,10 @@ pub(crate) fn numbervar(offset: &Integer, addr: HeapCellValue) -> Option<String>
     }
 
     match Number::try_from(addr) {
-        Ok(Number::Fixnum(n)) => {
+        Ok(Number::Fixnum(n)) if n.get_num() >= 0 => {
-            if n.get_num() >= 0 {
+            Some(numbervar(offset + Integer::from(n.get_num())))
-                Some(numbervar(offset + Integer::from(n.get_num())))
-            } else {
-                None
-            }
-        }
-        Ok(Number::Integer(n)) => {
-            if &*n >= &Integer::from(0) {
-                Some(numbervar(Integer::from(offset + &*n)))
-            } else {
-                None
-            }
         }
+        Ok(Number::Integer(n)) if !n.is_negative() => Some(numbervar(Integer::from(offset + &*n))),
         _ => None,
     }
 }
@@ -640,12 +628,9 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
                 self.state_stack.push(TokenOrRedirect::Op(name, spec));
             }
         } else {
-            match &*name.as_str() {
+            if let "|" = &*name.as_str() {
-                "|" => {
+                self.format_bar_separator_op(max_depth, name, spec);
-                    self.format_bar_separator_op(max_depth, name, spec);
+                return;
-                    return;
-                }
-                _ => {}
             };
 
             if self.max_depth_exhausted(max_depth) {
@@ -657,22 +642,19 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
                 if is_xfy!(spec.get_spec()) {
                     let left_directed_op = DirectedOp::Left(name, spec);
 
-                    self.state_stack.push(TokenOrRedirect::CompositeRedirect(
+                    self.state_stack
-                        0,
+                        .push(TokenOrRedirect::CompositeRedirect(0, left_directed_op));
-                        left_directed_op,
-                    ));
 
                     self.state_stack.push(TokenOrRedirect::Op(name, spec));
                     self.state_stack.push(TokenOrRedirect::StackPop);
-                } else { // is_yfx!
+                } else {
+                    // is_yfx!
                     let right_directed_op = DirectedOp::Right(name, spec);
 
                     self.state_stack.push(TokenOrRedirect::StackPop);
                     self.state_stack.push(TokenOrRedirect::Op(name, spec));
-                    self.state_stack.push(TokenOrRedirect::CompositeRedirect(
+                    self.state_stack
-                        0,
+                        .push(TokenOrRedirect::CompositeRedirect(0, right_directed_op));
-                        right_directed_op,
-                    ));
                 }
             } else {
                 let left_directed_op = DirectedOp::Left(name, spec);
@@ -783,7 +765,7 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
         let h = self.iter.stack_last().unwrap();
 
         let cell = self.iter.read_cell(h);
-        let cell = heap_bound_store(&self.iter.heap, heap_bound_deref(&self.iter.heap, cell));
+        let cell = heap_bound_store(self.iter.heap, heap_bound_deref(self.iter.heap, cell));
 
         // 7.10.4
         if let Some(var) = numbervar(&self.numbervars_offset, cell) {
@@ -802,20 +784,16 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
         name: Atom,
         op_desc: Option<OpDesc>,
     ) -> bool {
-        if self.numbervars && is_numbered_var(name, arity) {
+        if self.numbervars && is_numbered_var(name, arity) && self.format_numbered_vars() {
-            if self.format_numbered_vars() {
+            return true;
-                return true;
-            }
         }
 
         let dot_atom = atom!(".");
 
         if let Some(spec) = op_desc {
-            if dot_atom == name && is_infix!(spec.get_spec()) {
+            if dot_atom == name && is_infix!(spec.get_spec()) && !self.ignore_ops {
-                if !self.ignore_ops {
+                self.push_list(max_depth);
-                    self.push_list(max_depth);
+                return true;
-                    return true;
-                }
             }
 
             if !self.ignore_ops && spec.get_prec() > 0 {
@@ -824,10 +802,10 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
             }
         }
 
-        return match (name, arity) {
+        match (name, arity) {
             (atom!("{}"), 1) if !self.ignore_ops => self.format_curly_braces(max_depth),
             _ => self.format_struct(max_depth, arity, name),
-        };
+        }
     }
 
     fn offset_as_string(&mut self, h: IterStackLoc) -> Option<String> {
@@ -866,7 +844,8 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
             loop {
                 let is_cyclic = orig_cell.get_forwarding_bit();
 
-                let cell = heap_bound_store(self.iter.heap, heap_bound_deref(self.iter.heap, orig_cell));
+                let cell =
+                    heap_bound_store(self.iter.heap, heap_bound_deref(self.iter.heap, orig_cell));
                 let cell = unmark_cell_bits!(cell);
 
                 match self.var_names.get(&cell).cloned() {
@@ -933,7 +912,10 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
                                         }
 
                                         let h = cell.get_value() as usize;
-                                        self.iter.push_stack(IterStackLoc::iterable_loc(h, HeapOrStackTag::Heap));
+                                        self.iter.push_stack(IterStackLoc::iterable_loc(
+                                            h,
+                                            HeapOrStackTag::Heap,
+                                        ));
 
                                         if let Some(cell) = self.iter.next() {
                                             orig_cell = cell;
@@ -951,13 +933,13 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
                 }
             }
         } else {
-            while let Some(_) = self.iter.pop_stack() {}
+            while self.iter.pop_stack().is_none() {}
             None
         }
     }
 
     fn print_impromptu_atom(&mut self, atom: Atom) {
-        let result = self.print_op_addendum(&*atom.as_str());
+        let result = self.print_op_addendum(&atom.as_str());
 
         push_space_if_amb!(self, result.as_str(), {
             append_str!(self, &result);
@@ -1145,8 +1127,6 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
                     self.state_stack.push(TokenOrRedirect::Open);
                     self.state_stack.push(TokenOrRedirect::Atom(rdiv_ct));
                 }
-
-                return;
             }
             _ => {
                 unreachable!()
@@ -1242,7 +1222,7 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
         let mut heap_pstr_iter = HeapPStrIter::new(self.iter.heap, focus.value() as usize);
 
         if heap_pstr_iter.next().is_some() {
-            while let Some(_) = heap_pstr_iter.next() {}
+            for _ in heap_pstr_iter.by_ref() {}
         } else {
             return self.push_list(max_depth);
         }
@@ -1258,11 +1238,9 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
 
         let at_cdr = self.outputter.ends_with("|");
 
-        if self.double_quotes {
+        if self.double_quotes && !self.ignore_ops && end_cell.is_string_terminator(self.iter.heap) {
-            if !self.ignore_ops && end_cell.is_string_terminator(&self.iter.heap) {
+            self.remove_list_children(focus.value() as usize);
-                self.remove_list_children(focus.value() as usize);
+            return self.print_proper_string(focus.value() as usize, max_depth);
-                return self.print_proper_string(focus.value() as usize, max_depth);
-            }
         }
 
         if self.ignore_ops {
@@ -1275,8 +1253,10 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
                         append_str!(self, "[]");
                     }
                 } else {
-                    self.state_stack.push(TokenOrRedirect::FunctorRedirect(max_depth));
+                    self.state_stack
-                    self.iter.push_stack(IterStackLoc::iterable_loc(end_h, HeapOrStackTag::Heap));
+                        .push(TokenOrRedirect::FunctorRedirect(max_depth));
+                    self.iter
+                        .push_stack(IterStackLoc::iterable_loc(end_h, HeapOrStackTag::Heap));
                 }
             }
         } else {
@@ -1287,7 +1267,7 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
 
             read_heap_cell!(value,
                 (HeapCellValueTag::Lis) => {
-                    return self.push_list(max_depth);
+                    self.push_list(max_depth)
                 }
                 _ => {
                     let switch = Rc::new(Cell::new((!at_cdr, 0)));
@@ -1386,13 +1366,16 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
 
         let switch = self.close_list(cell);
 
-        self.state_stack.push(TokenOrRedirect::FunctorRedirect(max_depth));
+        self.state_stack
+            .push(TokenOrRedirect::FunctorRedirect(max_depth));
         self.state_stack.push(TokenOrRedirect::HeadTailSeparator); // bar
-        self.state_stack.push(TokenOrRedirect::FunctorRedirect(max_depth + 1));
+        self.state_stack
+            .push(TokenOrRedirect::FunctorRedirect(max_depth + 1));
 
         self.open_list(switch);
     }
 
+    #[allow(clippy::too_many_arguments)]
     fn handle_op_as_struct(
         &mut self,
         name: Atom,
@@ -1448,7 +1431,7 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
                 for op in &[op, parent_op] {
                     if let Some(ref op) = &op {
                         if op.is_left()
-                            && (op.is_prefix() || requires_space(&*op.as_atom().as_str(), "("))
+                            && (op.is_prefix() || requires_space(&op.as_atom().as_str(), "("))
                         {
                             self.state_stack.push(TokenOrRedirect::Space);
                             return;
@@ -1463,7 +1446,7 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
 
     #[allow(dead_code)]
     fn print_tcp_listener(&mut self, tcp_listener: &TcpListener, max_depth: usize) {
-        let (ip, port) = if let Some(addr) = tcp_listener.local_addr().ok() {
+        let (ip, port) = if let Ok(addr) = tcp_listener.local_addr() {
             (addr.ip(), addr.port())
         } else {
             let disconnected_atom = atom!("$disconnected_tcp_listener");
@@ -1545,24 +1528,33 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
     }
 
     fn print_comma_separated_char_list(&mut self, char_list: CommaSeparatedCharList) {
-        let CommaSeparatedCharList { pstr, offset, max_depth, end_cell, end_h } = char_list;
+        let CommaSeparatedCharList {
+            pstr,
+            offset,
+            max_depth,
+            end_cell,
+            end_h,
+        } = char_list;
         let pstr_str = pstr.as_str_from(offset);
 
         if let Some(c) = pstr_str.chars().next() {
             let offset = offset + c.len_utf8();
 
             if !self.max_depth_exhausted(max_depth) {
-                self.state_stack.push(TokenOrRedirect::CommaSeparatedCharList(CommaSeparatedCharList {
+                self.state_stack
-                    pstr,
+                    .push(TokenOrRedirect::CommaSeparatedCharList(
-                    offset,
+                        CommaSeparatedCharList {
-                    max_depth: max_depth.saturating_sub(1),
+                            pstr,
-                    end_cell,
+                            offset,
-                    end_h,
+                            max_depth: max_depth.saturating_sub(1),
-                }));
+                            end_cell,
+                            end_h,
+                        },
+                    ));
 
                 let max_depth_allows = self.max_depth == 0 || max_depth > 1;
 
-                if max_depth_allows && pstr_str.chars().skip(1).next().is_some() {
+                if max_depth_allows && pstr_str.chars().nth(1).is_some() {
                     self.state_stack.push(TokenOrRedirect::Comma);
                 }
 
@@ -1576,10 +1568,12 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
             self.state_stack.push(TokenOrRedirect::HeadTailSeparator);
         } else if end_cell != empty_list_as_cell!() {
             if let Some(end_h) = end_h {
-                self.iter.push_stack(IterStackLoc::iterable_loc(end_h, HeapOrStackTag::Heap));
+                self.iter
+                    .push_stack(IterStackLoc::iterable_loc(end_h, HeapOrStackTag::Heap));
             }
 
-            self.state_stack.push(TokenOrRedirect::FunctorRedirect(max_depth + 1));
+            self.state_stack
+                .push(TokenOrRedirect::FunctorRedirect(max_depth + 1));
             self.state_stack.push(TokenOrRedirect::HeadTailSeparator);
         }
     }
@@ -1599,13 +1593,12 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
 
         let print_struct = |printer: &mut Self, name: Atom, arity: usize| {
             if name == atom!("[]") && arity == 0 {
-                match printer.state_stack.last() {
+                if let Some(TokenOrRedirect::CloseList(_) | TokenOrRedirect::ChildCloseList) =
-                    Some(TokenOrRedirect::CloseList(_) | TokenOrRedirect::ChildCloseList) => {
+                    printer.state_stack.last()
-                        if printer.at_cdr("") {
+                {
-                            return;
+                    if printer.at_cdr("") {
-                        }
+                        return;
                     }
-                    _ => {}
                 }
 
                 append_str!(printer, "[]");
@@ -1642,7 +1635,7 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
                     result.push('(');
                 }
 
-                result += &printer.print_op_addendum(&*name.as_str());
+                result += &printer.print_op_addendum(&name.as_str());
 
                 if op.is_some() {
                     result.push(')');
@@ -1652,14 +1645,14 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
                     append_str!(printer, &result);
                 });
             } else {
-                push_space_if_amb!(printer, &*name.as_str(), {
+                push_space_if_amb!(printer, &name.as_str(), {
                     printer.print_impromptu_atom(name);
                 });
             }
         };
 
         if !addr.is_var()
-            && !addr.is_compound(&self.iter.heap)
+            && !addr.is_compound(self.iter.heap)
             && self.max_depth_exhausted(max_depth)
         {
             if !(addr == atom_as_cell!(atom!("[]")) && self.at_cdr("")) {
@@ -1772,7 +1765,7 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
                 TokenOrRedirect::BarAsOp => append_str!(self, " | "),
                 TokenOrRedirect::Char(c) => print_char!(self, self.quoted, c),
                 TokenOrRedirect::Op(atom, op) => {
-                    self.print_op(&*atom.as_str());
+                    self.print_op(&atom.as_str());
 
                     if is_prefix!(op.get_spec()) {
                         self.set_parent_of_first_op(Some(DirectedOp::Left(atom, op)));

src/http.rs

@@ -1,5 +1,5 @@
-use std::sync::{Arc, Mutex, Condvar};
 use std::io::BufRead;
+use std::sync::{Arc, Condvar, Mutex};
 
 use warp::http;
 

src/indexing.rs

@@ -665,7 +665,7 @@ pub(crate) fn merge_clause_index(
 pub(crate) fn remove_constant_indices(
     constant: Literal,
     overlapping_constants: &[Literal],
-    indexing_code: &mut Vec<IndexingLine>,
+    indexing_code: &mut [IndexingLine],
     offset: usize,
 ) {
     let mut index = 0;
@@ -811,7 +811,7 @@ pub(crate) fn remove_constant_indices(
 pub(crate) fn remove_structure_index(
     name: Atom,
     arity: usize,
-    indexing_code: &mut Vec<IndexingLine>,
+    indexing_code: &mut [IndexingLine],
     offset: usize,
 ) {
     let mut index = 0;
@@ -843,10 +843,10 @@ pub(crate) fn remove_structure_index(
             IndexingLine::Indexing(IndexingInstruction::SwitchOnStructure(ref mut structures)) => {
                 structures_index = index;
 
-                match structures.get(&(name.clone(), arity)).cloned() {
+                match structures.get(&(name, arity)).cloned() {
                     Some(IndexingCodePtr::DynamicExternal(_))
                     | Some(IndexingCodePtr::External(_)) => {
-                        structures.remove(&(name.clone(), arity));
+                        structures.remove(&(name, arity));
                         break;
                     }
                     Some(IndexingCodePtr::Internal(o)) => {
@@ -877,7 +877,7 @@ pub(crate) fn remove_structure_index(
                             IndexingLine::Indexing(IndexingInstruction::SwitchOnStructure(
                                 ref mut structures,
                             )) => {
-                                structures.insert((name.clone(), arity), ext);
+                                structures.insert((name, arity), ext);
                             }
                             _ => {
                                 unreachable!()
@@ -908,7 +908,7 @@ pub(crate) fn remove_structure_index(
                             IndexingLine::Indexing(IndexingInstruction::SwitchOnStructure(
                                 ref mut structures,
                             )) => {
-                                structures.insert((name.clone(), arity), ext);
+                                structures.insert((name, arity), ext);
                             }
                             _ => {
                                 unreachable!()
@@ -948,7 +948,7 @@ pub(crate) fn remove_structure_index(
     }
 }
 
-pub(crate) fn remove_list_index(indexing_code: &mut Vec<IndexingLine>, offset: usize) {
+pub(crate) fn remove_list_index(indexing_code: &mut [IndexingLine], offset: usize) {
     let mut index = 0;
 
     match &mut indexing_code[index] {
@@ -1028,7 +1028,7 @@ pub(crate) fn remove_list_index(indexing_code: &mut Vec<IndexingLine>, offset: u
 
 pub(crate) fn remove_index(
     opt_arg_index_key: &OptArgIndexKey,
-    indexing_code: &mut Vec<IndexingLine>,
+    indexing_code: &mut [IndexingLine],
     clause_loc: usize,
 ) {
     match opt_arg_index_key {
@@ -1049,46 +1049,50 @@ pub(crate) fn remove_index(
 
 #[inline]
 fn cap_choice_seq(prelude: &mut [IndexedChoiceInstruction]) {
-    prelude.first_mut().map(|instr| {
+    if let Some(instr) = prelude.first_mut() {
         *instr = IndexedChoiceInstruction::Try(instr.offset());
-    });
+    }
 
     cap_choice_seq_with_trust(prelude);
 }
 
 #[inline]
 fn cap_choice_seq_with_trust(prelude: &mut [IndexedChoiceInstruction]) {
-    prelude.last_mut().map(|instr| match instr {
+    if let Some(instr) = prelude.last_mut() {
-        IndexedChoiceInstruction::Retry(i) => {
+        match instr {
-            *instr = IndexedChoiceInstruction::Trust(*i);
+            IndexedChoiceInstruction::Retry(i) => {
+                *instr = IndexedChoiceInstruction::Trust(*i);
+            }
+            IndexedChoiceInstruction::DefaultRetry(i) => {
+                *instr = IndexedChoiceInstruction::DefaultTrust(*i);
+            }
+            _ => {}
         }
-        IndexedChoiceInstruction::DefaultRetry(i) => {
+    }
-            *instr = IndexedChoiceInstruction::DefaultTrust(*i);
-        }
-        _ => {}
-    });
 }
 
 #[inline]
 fn uncap_choice_seq_with_trust(prelude: &mut [IndexedChoiceInstruction]) {
-    prelude.last_mut().map(|instr| match instr {
+    if let Some(instr) = prelude.last_mut() {
-        IndexedChoiceInstruction::Trust(i) => {
+        match instr {
-            *instr = IndexedChoiceInstruction::Retry(*i);
+            IndexedChoiceInstruction::Trust(i) => {
+                *instr = IndexedChoiceInstruction::Retry(*i);
+            }
+            IndexedChoiceInstruction::DefaultTrust(i) => {
+                *instr = IndexedChoiceInstruction::DefaultRetry(*i);
+            }
+            _ => {}
         }
-        IndexedChoiceInstruction::DefaultTrust(i) => {
+    }
-            *instr = IndexedChoiceInstruction::DefaultRetry(*i);
-        }
-        _ => {}
-    });
 }
 
 #[inline]
 fn uncap_choice_seq_with_try(prelude: &mut [IndexedChoiceInstruction]) {
-    prelude.first_mut().map(|instr| {
+    if let Some(instr) = prelude.first_mut() {
         if let IndexedChoiceInstruction::Try(i) = instr {
             *instr = IndexedChoiceInstruction::Retry(*i);
         }
-    });
+    }
 }
 
 pub(crate) fn constant_key_alternatives(
@@ -1105,7 +1109,7 @@ pub(crate) fn constant_key_alternatives(
             }
         }
         Literal::Char(c) => {
-            let atom = AtomTable::build_with(&atom_tbl, &c.to_string());
+            let atom = AtomTable::build_with(atom_tbl, &c.to_string());
             constants.push(Literal::Atom(atom));
         }
         /*
@@ -1124,9 +1128,11 @@ pub(crate) fn constant_key_alternatives(
         Literal::Integer(ref n) => {
             let result = (&**n).try_into();
             if let Ok(value) = result {
-                Fixnum::build_with_checked(value).map(|n| {
+                Fixnum::build_with_checked(value)
-                    constants.push(Literal::Fixnum(n));
+                    .map(|n| {
-                }).unwrap();
+                        constants.push(Literal::Fixnum(n));
+                    })
+                    .unwrap();
             }
         }
         _ => {}
@@ -1245,10 +1251,8 @@ impl Indexer for StaticCodeIndices {
                 index_locs.insert(key, IndexingCodePtr::Internal(prelude.len() + 1));
                 cap_choice_seq_with_trust(code.make_contiguous());
                 prelude.push_back(IndexingLine::from(code));
-            } else {
+            } else if let Some(i) = code.front() {
-                code.front().map(|i| {
+                index_locs.insert(key, IndexingCodePtr::External(i.offset()));
-                    index_locs.insert(key, IndexingCodePtr::External(i.offset()));
-                });
             }
         }
 
@@ -1285,7 +1289,7 @@ impl Indexer for StaticCodeIndices {
     ) -> IndexingCodePtr {
         if lists.len() > 1 {
             cap_choice_seq_with_trust(lists.make_contiguous());
-            let lists = mem::replace(lists, VecDeque::new());
+            let lists = std::mem::take(lists);
             prelude.push_back(IndexingLine::from(lists));
 
             IndexingCodePtr::Internal(1)
@@ -1361,10 +1365,8 @@ impl Indexer for DynamicCodeIndices {
                 prelude.push_back(IndexingLine::DynamicIndexedChoice(
                     code.into_iter().collect(),
                 ));
-            } else {
+            } else if let Some(i) = code.front() {
-                code.front().map(|i| {
+                index_locs.insert(key, IndexingCodePtr::DynamicExternal(*i));
-                    index_locs.insert(key, IndexingCodePtr::DynamicExternal(*i));
-                });
             }
         }
 
@@ -1400,7 +1402,7 @@ impl Indexer for DynamicCodeIndices {
         prelude: &mut VecDeque<IndexingLine>,
     ) -> IndexingCodePtr {
         if lists.len() > 1 {
-            let lists = mem::replace(lists, VecDeque::new());
+            let lists = std::mem::take(lists);
             prelude.push_back(IndexingLine::DynamicIndexedChoice(
                 lists.into_iter().collect(),
             ));
@@ -1458,11 +1460,7 @@ impl<I: Indexer> CodeOffsets<I> {
         index: usize,
     ) -> Vec<Literal> {
         let overlapping_constants = constant_key_alternatives(constant, atom_tbl);
-        let code = self
+        let code = self.indices.constants().entry(constant).or_default();
-            .indices
-            .constants()
-            .entry(constant)
-            .or_insert(VecDeque::new());
 
         let is_initial_index = code.is_empty();
         code.push_back(I::compute_index(
@@ -1472,11 +1470,7 @@ impl<I: Indexer> CodeOffsets<I> {
         ));
 
         for constant in &overlapping_constants {
-            let code = self
+            let code = self.indices.constants().entry(*constant).or_default();
-                .indices
-                .constants()
-                .entry(*constant)
-                .or_insert(VecDeque::new());
 
             let is_initial_index = code.is_empty();
             let index = I::compute_index(is_initial_index, index, self.non_counted_bt);
@@ -1488,11 +1482,7 @@ impl<I: Indexer> CodeOffsets<I> {
     }
 
     fn index_structure(&mut self, name: Atom, arity: usize, index: usize) -> usize {
-        let code = self
+        let code = self.indices.structures().entry((name, arity)).or_default();
-            .indices
-            .structures()
-            .entry((name.clone(), arity))
-            .or_insert(VecDeque::new());
 
         let code_len = code.len();
         let is_initial_index = code.is_empty();
@@ -1523,7 +1513,7 @@ impl<I: Indexer> CodeOffsets<I> {
             }
             &Term::Clause(_, name, ref terms) => {
                 clause_index_info.opt_arg_index_key =
-                    OptArgIndexKey::Structure(self.optimal_index, 0, name.clone(), terms.len());
+                    OptArgIndexKey::Structure(self.optimal_index, 0, name, terms.len());
 
                 self.index_structure(name, terms.len(), index);
             }
@@ -1575,20 +1565,14 @@ impl<I: Indexer> CodeOffsets<I> {
             &mut prelude,
         );
 
-        match &mut str_loc {
+        if let IndexingCodePtr::Internal(ref mut i) = &mut str_loc {
-            IndexingCodePtr::Internal(ref mut i) => {
+            *i += emitted_switch_on_constant as usize; // con_loc.is_internal() as usize;
-                *i += emitted_switch_on_constant as usize; // con_loc.is_internal() as usize;
+        }
-            }
-            _ => {}
-        };
 
-        match &mut lst_loc {
+        if let IndexingCodePtr::Internal(ref mut i) = &mut lst_loc {
-            IndexingCodePtr::Internal(ref mut i) => {
+            *i += emitted_switch_on_constant as usize; // con_loc.is_internal() as usize;
-                *i += emitted_switch_on_constant as usize; // con_loc.is_internal() as usize;
+            *i += emitted_switch_on_structure as usize; // str_loc.is_internal() as usize;
-                *i += emitted_switch_on_structure as usize; // str_loc.is_internal() as usize;
+        }
-            }
-            _ => {}
-        };
 
         let var_offset = 1 + skip_stub_try_me_else as usize;
 

src/iterators.rs

@@ -8,6 +8,7 @@ use std::collections::VecDeque;
 use std::iter::*;
 use std::vec::Vec;
 
+#[allow(clippy::borrowed_box)]
 #[derive(Debug, Clone)]
 pub(crate) enum TermRef<'a> {
     AnonVar(Level),
@@ -35,6 +36,7 @@ impl<'a> TermRef<'a> {
 }
 */
 
+#[allow(clippy::borrowed_box)]
 #[derive(Debug)]
 pub(crate) enum TermIterState<'a> {
     AnonVar(Level),
@@ -113,11 +115,11 @@ impl<'a> QueryIterator<'a> {
 
     fn extend_state(&mut self, lvl: Level, term: &'a QueryTerm) {
         match term {
-            &QueryTerm::Clause(ref cell, ClauseType::CallN(_), ref terms, _) => {
+            QueryTerm::Clause(ref cell, ClauseType::CallN(_), ref terms, _) => {
                 self.state_stack
                     .push(TermIterState::Clause(lvl, 1, cell, atom!("$call"), terms));
             }
-            &QueryTerm::Clause(ref cell, ref ct, ref terms, _) => {
+            QueryTerm::Clause(ref cell, ref ct, ref terms, _) => {
                 self.state_stack
                     .push(TermIterState::Clause(lvl, 0, cell, ct.name(), terms));
             }
@@ -214,7 +216,7 @@ impl<'a> FactIterator<'a> {
             .push_back(TermIterState::subterm_to_state(lvl, term));
     }
 
-    pub(crate) fn from_rule_head_clause(terms: &'a Vec<Term>) -> Self {
+    pub(crate) fn from_rule_head_clause(terms: &'a [Term]) -> Self {
         let state_queue = terms
             .iter()
             .map(|bt| TermIterState::subterm_to_state(Level::Shallow, bt))
@@ -312,14 +314,14 @@ impl<'a> Iterator for FactIterator<'a> {
     }
 }
 
-pub(crate) fn post_order_iter<'a>(term: &'a Term) -> QueryIterator<'a> {
+pub(crate) fn post_order_iter(term: &'_ Term) -> QueryIterator {
     QueryIterator::from_term(term)
 }
 
-pub(crate) fn breadth_first_iter<'a>(
+pub(crate) fn breadth_first_iter(
-    term: &'a Term,
+    term: &'_ Term,
     iterable_root: RootIterationPolicy,
-) -> FactIterator<'a> {
+) -> FactIterator {
     FactIterator::new(term, iterable_root)
 }
 
@@ -343,7 +345,7 @@ pub(crate) struct ClauseIterator<'a> {
     remaining_chunks_on_stack: usize,
 }
 
-fn state_from_chunked_terms<'a>(chunk_vec: &'a VecDeque<ChunkedTerms>) -> ClauseIteratorState<'a> {
+fn state_from_chunked_terms(chunk_vec: &'_ VecDeque<ChunkedTerms>) -> ClauseIteratorState {
     if chunk_vec.len() == 1 {
         if let Some(ChunkedTerms::Branch(ref branches)) = chunk_vec.front() {
             return ClauseIteratorState::RemainingBranches(branches, 0);
@@ -422,7 +424,7 @@ impl<'a> Iterator for ClauseIterator<'a> {
                     if focus < branches.len() =>
                 {
                     self.state_stack
-                        .push(ClauseIteratorState::RemainingBranches(&branches, focus + 1));
+                        .push(ClauseIteratorState::RemainingBranches(branches, focus + 1));
                     let state = state_from_chunked_terms(&branches[focus]);
 
                     if let ClauseIteratorState::RemainingChunks(..) = &state {

src/lib.rs

@@ -3,7 +3,8 @@
 #[macro_use]
 extern crate static_assertions;
 #[cfg(test)]
-#[macro_use] extern crate maplit;
+#[macro_use]
+extern crate maplit;
 
 #[macro_use]
 pub mod macros;
@@ -50,6 +51,7 @@ use wasm_bindgen::prelude::*;
 #[wasm_bindgen]
 pub fn eval_code(s: &str) -> String {
     use machine::mock_wam::*;
+    use web_sys::console;
 
     let mut wam = Machine::with_test_streams();
     let bytes = wam.test_load_string(s);

src/machine/args.rs

@@ -14,3 +14,9 @@ impl MachineArgs {
         }
     }
 }
+
+impl Default for MachineArgs {
+    fn default() -> Self {
+        Self::new()
+    }
+}

src/machine/arithmetic_ops.rs

@@ -1,6 +1,6 @@
 use dashu::base::{Abs, Gcd, Signed, UnsignedAbs};
-use dashu::integer::IBig;
 use dashu::integer::fast_div::ConstDivisor;
+use dashu::integer::IBig;
 use divrem::*;
 use num_order::NumOrd;
 
@@ -84,18 +84,18 @@ fn numerical_type_error(
 
 fn isize_gcd(n1: isize, n2: isize) -> Option<isize> {
     if n1 == 0 {
-        return n2.checked_abs().map(|n| n as isize);
+        return n2.checked_abs();
     }
 
     if n2 == 0 {
-        return n1.checked_abs().map(|n| n as isize);
+        return n1.checked_abs();
     }
 
     let n1 = n1.checked_abs();
     let n2 = n2.checked_abs();
 
-    let mut n1 = if let Some(n1) = n1 { n1 } else { return None };
+    let mut n1 = n1?;
-    let mut n2 = if let Some(n2) = n2 { n2 } else { return None };
+    let mut n2 = n2?;
 
     let mut shift = 0;
 
@@ -115,9 +115,7 @@ fn isize_gcd(n1: isize, n2: isize) -> Option<isize> {
         }
 
         if n1 > n2 {
-            let t = n2;
+            std::mem::swap(&mut n2, &mut n1);
-            n2 = n1;
-            n1 = t;
         }
 
         n2 -= n1;
@@ -350,22 +348,18 @@ pub(crate) fn int_pow(n1: Number, n2: Number, arena: &mut Arena) -> Result<Numbe
         (Number::Fixnum(n1), Number::Integer(n2)) => {
             let n1_i = n1.get_num();
 
-            if !(n1_i == 1 || n1_i == 0 || n1_i == -1) && &*n2 < &Integer::from(0) {
+            if !(n1_i == 1 || n1_i == 0 || n1_i == -1) && n2.is_zero() {
                 let n = Number::Fixnum(n1);
                 Err(numerical_type_error(ValidType::Float, n, stub_gen))
             } else {
                 let n1 = Integer::from(n1_i);
-                Ok(Number::arena_from(binary_pow(n1, &*n2), arena))
+                Ok(Number::arena_from(binary_pow(n1, &n2), arena))
             }
         }
         (Number::Integer(n1), Number::Fixnum(n2)) => {
             let n2_i = n2.get_num();
 
-            if !(&*n1 == &Integer::from(1)
+            if !(*n1 == Integer::from(1) || n1.is_zero() || *n1 == Integer::from(-1)) && n2_i < 0 {
-                || &*n1 == &Integer::from(0)
-                || &*n1 == &Integer::from(-1))
-                && n2_i < 0
-            {
                 let n = Number::Integer(n1);
                 Err(numerical_type_error(ValidType::Float, n, stub_gen))
             } else {
@@ -374,15 +368,13 @@ pub(crate) fn int_pow(n1: Number, n2: Number, arena: &mut Arena) -> Result<Numbe
             }
         }
         (Number::Integer(n1), Number::Integer(n2)) => {
-            if !(&*n1 == &Integer::from(1)
+            if !(*n1 == Integer::from(1) || n1.is_zero() || *n1 == Integer::from(-1))
-                || &*n1 == &Integer::from(0)
+                && n2.is_zero()
-                || &*n1 == &Integer::from(-1))
-                && &*n2 < &Integer::from(0)
             {
                 let n = Number::Integer(n1);
                 Err(numerical_type_error(ValidType::Float, n, stub_gen))
             } else {
-                Ok(Number::arena_from(binary_pow((*n1).clone(), &*n2), arena))
+                Ok(Number::arena_from(binary_pow((*n1).clone(), &n2), arena))
             }
         }
         (n1, Number::Integer(n2)) => {
@@ -455,14 +447,14 @@ pub(crate) fn max(n1: Number, n2: Number) -> Result<Number, MachineStubGen> {
             }
         }
         (Number::Fixnum(n1), Number::Integer(n2)) => {
-            if (&*n2).num_gt(&n1.get_num()) {
+            if (*n2).num_gt(&n1.get_num()) {
                 Ok(Number::Integer(n2))
             } else {
                 Ok(Number::Fixnum(n1))
             }
         }
         (Number::Integer(n1), Number::Fixnum(n2)) => {
-            if (&*n1).num_gt(&n2.get_num()) {
+            if (*n1).num_gt(&n2.get_num()) {
                 Ok(Number::Integer(n1))
             } else {
                 Ok(Number::Fixnum(n2))
@@ -499,14 +491,14 @@ pub(crate) fn min(n1: Number, n2: Number) -> Result<Number, MachineStubGen> {
             }
         }
         (Number::Fixnum(n1), Number::Integer(n2)) => {
-            if (&*n2).num_lt(&n1.get_num()) {
+            if (*n2).num_lt(&n1.get_num()) {
                 Ok(Number::Integer(n2))
             } else {
                 Ok(Number::Fixnum(n1))
             }
         }
         (Number::Integer(n1), Number::Fixnum(n2)) => {
-            if (&*n1).num_lt(&n2.get_num()) {
+            if (*n1).num_lt(&n2.get_num()) {
                 Ok(Number::Integer(n1))
             } else {
                 Ok(Number::Fixnum(n2))
@@ -583,15 +575,13 @@ pub(crate) fn idiv(n1: Number, n2: Number, arena: &mut Arena) -> Result<Number,
         (Number::Fixnum(n1), Number::Fixnum(n2)) => {
             if n2.get_num() == 0 {
                 Err(zero_divisor_eval_error(stub_gen))
+            } else if let Some(result) = n1.get_num().checked_div(n2.get_num()) {
+                Ok(Number::arena_from(result, arena))
             } else {
-                if let Some(result) = n1.get_num().checked_div(n2.get_num()) {
+                let n1 = Integer::from(n1.get_num());
-                    Ok(Number::arena_from(result, arena))
+                let n2 = Integer::from(n2.get_num());
-                } else {
-                    let n1 = Integer::from(n1.get_num());
-                    let n2 = Integer::from(n2.get_num());
 
-                    Ok(Number::arena_from(n1 / n2, arena))
+                Ok(Number::arena_from(n1 / n2, arena))
-                }
             }
         }
         (Number::Fixnum(n1), Number::Integer(n2)) => {
@@ -656,9 +646,9 @@ pub(crate) fn shr(n1: Number, n2: Number, arena: &mut Arena) -> Result<Number, M
             let n1 = Integer::from(n1_i);
 
             if let Ok(n2) = usize::try_from(n2_i) {
-                return Ok(Number::arena_from(n1 >> n2, arena));
+                Ok(Number::arena_from(n1 >> n2, arena))
             } else {
-                return Ok(Number::arena_from(n1 >> usize::max_value(), arena));
+                Ok(Number::arena_from(n1 >> usize::max_value(), arena))
             }
         }
         (Number::Fixnum(n1), Number::Integer(n2)) => {
@@ -667,12 +657,8 @@ pub(crate) fn shr(n1: Number, n2: Number, arena: &mut Arena) -> Result<Number, M
             let result: Result<usize, _> = (&*n2).try_into();
 
             match result {
-                Ok(n2) => {
+                Ok(n2) => Ok(Number::arena_from(n1 >> n2, arena)),
-                    Ok(Number::arena_from(n1 >> n2, arena))
+                Err(_) => Ok(Number::arena_from(n1 >> usize::max_value(), arena)),
-                }
-                Err(_) => {
-                    Ok(Number::arena_from(n1 >> usize::max_value(), arena))
-                }
             }
         }
         (Number::Integer(n1), Number::Fixnum(n2)) => match usize::try_from(n2.get_num()) {
@@ -686,14 +672,13 @@ pub(crate) fn shr(n1: Number, n2: Number, arena: &mut Arena) -> Result<Number, M
             let result: Result<usize, _> = (&*n2).try_into();
 
             match result {
-                Ok(n2) => {
+                Ok(n2) => Ok(Number::arena_from(Integer::from(&*n1 >> n2), arena)),
-                    Ok(Number::arena_from(Integer::from(&*n1 >> n2), arena))
+                Err(_) => Ok(Number::arena_from(
-                }
+                    Integer::from(&*n1 >> usize::max_value()),
-                Err(_) => {
+                    arena,
-                    Ok(Number::arena_from(Integer::from(&*n1 >> usize::max_value()), arena))
+                )),
-                }
             }
-        },
+        }
         (Number::Integer(_), n2) => Err(numerical_type_error(ValidType::Integer, n2, stub_gen)),
         (Number::Fixnum(_), n2) => Err(numerical_type_error(ValidType::Integer, n2, stub_gen)),
         (n1, _) => Err(numerical_type_error(ValidType::Integer, n1, stub_gen)),
@@ -718,9 +703,9 @@ pub(crate) fn shl(n1: Number, n2: Number, arena: &mut Arena) -> Result<Number, M
             let n1 = Integer::from(n1_i);
 
             if let Ok(n2) = usize::try_from(n2_i) {
-                return Ok(Number::arena_from(n1 << n2, arena));
+                Ok(Number::arena_from(n1 << n2, arena))
             } else {
-                return Ok(Number::arena_from(n1 << usize::max_value(), arena));
+                Ok(Number::arena_from(n1 << usize::max_value(), arena))
             }
         }
         (Number::Fixnum(n1), Number::Integer(n2)) => {
@@ -730,10 +715,8 @@ pub(crate) fn shl(n1: Number, n2: Number, arena: &mut Arena) -> Result<Number, M
                 Ok(n2) => {
                     let n1: u64 = n1.try_into().unwrap();
                     Ok(Number::arena_from(n1 << n2, arena))
-                },
+                }
-                _ => {
+                _ => Ok(Number::arena_from(n1 << usize::max_value(), arena)),
-			        Ok(Number::arena_from(n1 << usize::max_value(), arena))
-		        }
             }
         }
         (Number::Integer(n1), Number::Fixnum(n2)) => match usize::try_from(n2.get_num()) {
@@ -747,10 +730,11 @@ pub(crate) fn shl(n1: Number, n2: Number, arena: &mut Arena) -> Result<Number, M
             Ok(n2) => {
                 let n1: u64 = (&*n1).try_into().unwrap();
                 Ok(Number::arena_from(Integer::from(n1 << n2), arena))
-            },
+            }
-            _ => {
+            _ => Ok(Number::arena_from(
-		        Ok(Number::arena_from(Integer::from(&*n1 << usize::max_value()),arena))
+                Integer::from(&*n1 << usize::max_value()),
-	        }
+                arena,
+            )),
         },
         (Number::Integer(_), n2) => Err(numerical_type_error(ValidType::Integer, n2, stub_gen)),
         (Number::Fixnum(_), n2) => Err(numerical_type_error(ValidType::Integer, n2, stub_gen)),
@@ -882,7 +866,7 @@ pub(crate) fn modulus(x: Number, y: Number, arena: &mut Arena) -> Result<Number,
                 Err(zero_divisor_eval_error(stub_gen))
             } else {
                 let n1 = Integer::from(n1.get_num());
-                Ok(Number::arena_from(ibig_rem_floor(&n1, &*n2), arena))
+                Ok(Number::arena_from(ibig_rem_floor(&n1, &n2), arena))
             }
         }
         (Number::Integer(n1), Number::Fixnum(n2)) => {
@@ -892,14 +876,14 @@ pub(crate) fn modulus(x: Number, y: Number, arena: &mut Arena) -> Result<Number,
                 Err(zero_divisor_eval_error(stub_gen))
             } else {
                 let n2 = Integer::from(n2_i);
-                Ok(Number::arena_from(ibig_rem_floor(&*n1, &n2), arena))
+                Ok(Number::arena_from(ibig_rem_floor(&n1, &n2), arena))
             }
         }
         (Number::Integer(n1), Number::Integer(n2)) => {
             if n2.is_zero() {
                 Err(zero_divisor_eval_error(stub_gen))
             } else {
-                Ok(Number::arena_from(ibig_rem_floor(&*n1, &*n2), arena))
+                Ok(Number::arena_from(ibig_rem_floor(&n1, &n2), arena))
             }
         }
         (Number::Integer(_), n2) | (Number::Fixnum(_), n2) => {
@@ -1145,7 +1129,7 @@ impl MachineState {
                 &mut self.interms[i - 1],
                 Number::Fixnum(Fixnum::build_with(0)),
             )),
-            &ArithmeticTerm::Number(n) => Ok(n),
+            ArithmeticTerm::Number(n) => Ok(*n),
         }
     }
 
@@ -1167,8 +1151,8 @@ impl MachineState {
         value: HeapCellValue,
     ) -> Result<Number, MachineStub> {
         let stub_gen = || functor_stub(atom!("is"), 2);
-        let mut iter = stackful_post_order_iter::<NonListElider>
+        let mut iter =
-            (&mut self.heap, &mut self.stack, value);
+            stackful_post_order_iter::<NonListElider>(&mut self.heap, &mut self.stack, value);
 
         while let Some(value) = iter.next() {
             if value.get_forwarding_bit() {

src/machine/attributed_variables.rs

@@ -133,8 +133,8 @@ impl MachineState {
         let mut seen_set = IndexSet::new();
         let mut seen_vars = vec![];
 
-        let mut iter = stackful_preorder_iter::<NonListElider>
+        let mut iter =
-            (&mut self.heap, &mut self.stack, cell);
+            stackful_preorder_iter::<NonListElider>(&mut self.heap, &mut self.stack, cell);
 
         while let Some(value) = iter.next() {
             read_heap_cell!(value,

src/machine/compile.rs

@@ -282,28 +282,25 @@ fn merge_indexed_subsequences(
             .unwrap(),
     );
 
-    match &mut code[inner_try_me_else_loc] {
+    if let Instruction::TryMeElse(ref mut o) = &mut code[inner_try_me_else_loc] {
-        Instruction::TryMeElse(ref mut o) => {
+        retraction_info.push_record(RetractionRecord::ModifiedTryMeElse(
-            retraction_info.push_record(RetractionRecord::ModifiedTryMeElse(
+            inner_try_me_else_loc,
-                inner_try_me_else_loc,
+            *o,
-                *o,
+        ));
-            ));
 
-            match *o {
+        match *o {
-                0 => {
+            0 => {
-                    code[inner_try_me_else_loc] = Instruction::TrustMe(0);
+                code[inner_try_me_else_loc] = Instruction::TrustMe(0);
-                }
-                o => match &code[inner_try_me_else_loc + o] {
-                    Instruction::RevJmpBy(0) => {
-                        code[inner_try_me_else_loc] = Instruction::TrustMe(o);
-                    }
-                    _ => {
-                        code[inner_try_me_else_loc] = Instruction::RetryMeElse(o);
-                    }
-                },
             }
+            o => match &code[inner_try_me_else_loc + o] {
+                Instruction::RevJmpBy(0) => {
+                    code[inner_try_me_else_loc] = Instruction::TrustMe(o);
+                }
+                _ => {
+                    code[inner_try_me_else_loc] = Instruction::RetryMeElse(o);
+                }
+            },
         }
-        _ => {}
     }
 
     thread_choice_instr_at_to(
@@ -333,8 +330,8 @@ fn merge_indexed_subsequences(
                 retraction_info,
             );
         }
-        None => match &mut code[outer_threaded_choice_instr_loc] {
+        None => {
-            Instruction::TryMeElse(ref mut o) => {
+            if let Instruction::TryMeElse(ref mut o) = &mut code[outer_threaded_choice_instr_loc] {
                 retraction_info
                     .push_record(RetractionRecord::ModifiedTryMeElse(inner_trust_me_loc, *o));
 
@@ -342,8 +339,7 @@ fn merge_indexed_subsequences(
 
                 return Some(IndexPtr::index(outer_threaded_choice_instr_loc + 1));
             }
-            _ => {}
+        }
-        },
     }
 
     None
@@ -919,7 +915,7 @@ fn prepend_compiled_clause(
                     retraction_info,
                 );
 
-                code.extend(prepend_queue.into_iter());
+                code.extend(prepend_queue);
 
                 if skeleton.core.is_dynamic {
                     clause_loc
@@ -975,7 +971,7 @@ fn prepend_compiled_clause(
 
                 internalize_choice_instr_at(code, old_clause_start, retraction_info);
 
-                code.extend(prepend_queue.into_iter());
+                code.extend(prepend_queue);
 
                 clause_loc // + (outer_thread_choice_offset == 0 as usize)
             }
@@ -1004,7 +1000,7 @@ fn prepend_compiled_clause(
 
                 internalize_choice_instr_at(code, old_clause_start, retraction_info);
 
-                code.extend(prepend_queue.into_iter());
+                code.extend(prepend_queue);
 
                 // skeleton.clauses[0].opt_arg_index_key += clause_loc;
                 skeleton.clauses[0].clause_start = clause_loc;
@@ -1029,7 +1025,7 @@ fn prepend_compiled_clause(
 
                 internalize_choice_instr_at(code, old_clause_start, retraction_info);
 
-                code.extend(prepend_queue.into_iter());
+                code.extend(prepend_queue);
 
                 // skeleton.clauses[0].opt_arg_index_key += clause_loc;
                 skeleton.clauses[0].clause_start = clause_loc;
@@ -1134,21 +1130,18 @@ fn append_compiled_clause(
             skeleton.clauses[target_pos].opt_arg_index_key += clause_loc;
             code.extend(clause_code.drain(1..));
 
-            match skeleton.clauses[target_pos]
+            if let Some(index_loc) = skeleton.clauses[target_pos]
                 .opt_arg_index_key
                 .switch_on_term_loc()
             {
-                Some(index_loc) => {
+                // point to the inner-threaded TryMeElse(0) if target_pos is
-                    // point to the inner-threaded TryMeElse(0) if target_pos is
+                // indexed, and make switch_on_term point one line after it in
-                    // indexed, and make switch_on_term point one line after it in
+                // its variable offset.
-                    // its variable offset.
+                skeleton.clauses[target_pos].clause_start += 2;
-                    skeleton.clauses[target_pos].clause_start += 2;
 
-                    if !skeleton.core.is_dynamic {
+                if !skeleton.core.is_dynamic {
-                        set_switch_var_offset(code, index_loc, 2, retraction_info);
+                    set_switch_var_offset(code, index_loc, 2, retraction_info);
-                    }
                 }
-                None => {}
             }
 
             match skeleton.clauses[lower_bound]
@@ -1302,11 +1295,8 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                 clause_clause_locs.push_back(clause_index_info.clause_start);
             }
 
-            match &mut code[0] {
+            if let Instruction::TryMeElse(0) = &mut code[0] {
-                Instruction::TryMeElse(0) => {
+                code_ptr += 1;
-                    code_ptr += 1;
-                }
-                _ => {}
             }
 
             match self
@@ -1317,7 +1307,7 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                 Some(skeleton) => {
                     let skeleton_clause_len = skeleton.clauses.len();
 
-                    skeleton.clauses.extend(cg.skeleton.clauses.into_iter());
+                    skeleton.clauses.extend(cg.skeleton.clauses);
                     skeleton
                         .core
                         .clause_clause_locs
@@ -1371,7 +1361,7 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
             index_ptr,
         );
 
-        self.wam_prelude.code.extend(code.into_iter());
+        self.wam_prelude.code.extend(code);
         Ok(code_index)
     }
 
@@ -1563,7 +1553,7 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                 let global_clock = LS::machine_st(&mut self.payload).global_clock;
 
                 let result = append_compiled_clause(
-                    &mut self.wam_prelude.code,
+                    self.wam_prelude.code,
                     clause_code,
                     skeleton,
                     &mut self.payload.retraction_info,
@@ -1603,7 +1593,7 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                 let global_clock = LS::machine_st(&mut self.payload).global_clock;
 
                 let new_code_ptr = prepend_compiled_clause(
-                    &mut self.wam_prelude.code,
+                    self.wam_prelude.code,
                     compilation_target,
                     key,
                     clause_code,
@@ -1646,7 +1636,7 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
             .switch_on_term_loc()
         {
             Some(index_loc) => find_inner_choice_instr(
-                &self.wam_prelude.code,
+                self.wam_prelude.code,
                 skeleton.clauses[target_pos].clause_start,
                 index_loc,
             ),
@@ -1687,115 +1677,109 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
         if target_pos == 0 || (lower_bound + 1 == target_pos && lower_bound_is_unindexed) {
             // the clause preceding target_pos, if there is one, is of
             // key type OptArgIndexKey::None.
-            match skeleton.clauses[target_pos]
+            if let Some(index_loc) = skeleton.clauses[target_pos]
                 .opt_arg_index_key
                 .switch_on_term_loc()
             {
-                Some(index_loc) => {
+                let inner_clause_start = find_inner_choice_instr(
-                    let inner_clause_start = find_inner_choice_instr(
+                    code,
-                        code,
+                    skeleton.clauses[target_pos].clause_start,
-                        skeleton.clauses[target_pos].clause_start,
+                    index_loc,
-                        index_loc,
+                );
-                    );
 
-                    remove_index_from_subsequence(
+                remove_index_from_subsequence(
-                        code,
+                    code,
-                        &skeleton.clauses[target_pos].opt_arg_index_key,
+                    &skeleton.clauses[target_pos].opt_arg_index_key,
-                        inner_clause_start,
+                    inner_clause_start,
-                        &mut self.payload.retraction_info,
+                    &mut self.payload.retraction_info,
-                    );
+                );
 
-                    match derelictize_try_me_else(
+                match derelictize_try_me_else(
-                        code,
+                    code,
-                        inner_clause_start,
+                    inner_clause_start,
-                        &mut self.payload.retraction_info,
+                    &mut self.payload.retraction_info,
-                    ) {
+                ) {
-                        Some(offset) => {
+                    Some(offset) => {
-                            let instr_loc = find_inner_choice_instr(
+                        let instr_loc =
-                                code,
+                            find_inner_choice_instr(code, inner_clause_start + offset, index_loc);
-                                inner_clause_start + offset,
-                                index_loc,
-                            );
 
-                            let clause_loc = blunt_leading_choice_instr(
+                        let clause_loc = blunt_leading_choice_instr(
-                                code,
+                            code,
-                                instr_loc,
+                            instr_loc,
-                                &mut self.payload.retraction_info,
+                            &mut self.payload.retraction_info,
-                            );
+                        );
 
-                            set_switch_var_offset(
+                        set_switch_var_offset(
-                                code,
+                            code,
-                                index_loc,
+                            index_loc,
-                                clause_loc - index_loc,
+                            clause_loc - index_loc,
-                                &mut self.payload.retraction_info,
+                            &mut self.payload.retraction_info,
-                            );
+                        );
 
-                            self.payload.retraction_info.push_record(
+                        self.payload.retraction_info.push_record(
-                                RetractionRecord::SkeletonClauseStartReplaced(
+                            RetractionRecord::SkeletonClauseStartReplaced(
-                                    payload_compilation_target,
-                                    key,
-                                    target_pos + 1,
-                                    skeleton.clauses[target_pos + 1].clause_start,
-                                ),
-                            );
-
-                            skeleton.clauses[target_pos + 1].clause_start =
-                                skeleton.clauses[target_pos].clause_start;
-
-                            let update_code_index = target_pos == 0
-                                && skeleton.clauses[target_pos + 1]
-                                    .opt_arg_index_key
-                                    .switch_on_term_loc()
-                                    .is_none();
-
-                            let index_ptr_opt = if update_code_index {
-                                Some(IndexPtr::index(clause_loc))
-                            } else {
-                                None
-                            };
-
-                            return finalize_retract(
-                                key,
                                 payload_compilation_target,
-                                skeleton,
-                                code_index,
-                                target_pos,
-                                index_ptr_opt,
-                                &mut self.payload.retraction_info,
-                            );
-                        }
-                        None => {
-                            let index_ptr_opt = if target_pos > 0 {
-                                let preceding_choice_instr_loc =
-                                    skeleton.clauses[target_pos - 1].clause_start;
-
-                                remove_non_leading_clause(
-                                    code,
-                                    preceding_choice_instr_loc,
-                                    skeleton.clauses[target_pos].clause_start - 2,
-                                    &mut self.payload.retraction_info,
-                                )
-                            } else {
-                                remove_leading_unindexed_clause(
-                                    code,
-                                    skeleton.clauses[target_pos].clause_start - 2,
-                                    &mut self.payload.retraction_info,
-                                )
-                            };
-
-                            return finalize_retract(
                                 key,
-                                payload_compilation_target,
+                                target_pos + 1,
-                                skeleton,
+                                skeleton.clauses[target_pos + 1].clause_start,
-                                code_index,
+                            ),
-                                target_pos,
+                        );
-                                index_ptr_opt,
+
+                        skeleton.clauses[target_pos + 1].clause_start =
+                            skeleton.clauses[target_pos].clause_start;
+
+                        let update_code_index = target_pos == 0
+                            && skeleton.clauses[target_pos + 1]
+                                .opt_arg_index_key
+                                .switch_on_term_loc()
+                                .is_none();
+
+                        let index_ptr_opt = if update_code_index {
+                            Some(IndexPtr::index(clause_loc))
+                        } else {
+                            None
+                        };
+
+                        return finalize_retract(
+                            key,
+                            payload_compilation_target,
+                            skeleton,
+                            code_index,
+                            target_pos,
+                            index_ptr_opt,
+                            &mut self.payload.retraction_info,
+                        );
+                    }
+                    None => {
+                        let index_ptr_opt = if target_pos > 0 {
+                            let preceding_choice_instr_loc =
+                                skeleton.clauses[target_pos - 1].clause_start;
+
+                            remove_non_leading_clause(
+                                code,
+                                preceding_choice_instr_loc,
+                                skeleton.clauses[target_pos].clause_start - 2,
                                 &mut self.payload.retraction_info,
-                            );
+                            )
-                        }
+                        } else {
+                            remove_leading_unindexed_clause(
+                                code,
+                                skeleton.clauses[target_pos].clause_start - 2,
+                                &mut self.payload.retraction_info,
+                            )
+                        };
+
+                        return finalize_retract(
+                            key,
+                            payload_compilation_target,
+                            skeleton,
+                            code_index,
+                            target_pos,
+                            index_ptr_opt,
+                            &mut self.payload.retraction_info,
+                        );
                     }
                 }
-                None => {}
             }
         }
 
@@ -1824,16 +1808,13 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                             Instruction::RevJmpBy(target_indexing_loc - later_indexing_loc),
                         );
 
-                        match target_indexing_line {
+                        if let Instruction::IndexingCode(indexing_code) = target_indexing_line {
-                            Instruction::IndexingCode(indexing_code) => {
+                            self.payload.retraction_info.push_record(
-                                self.payload.retraction_info.push_record(
+                                RetractionRecord::ReplacedIndexingLine(
-                                    RetractionRecord::ReplacedIndexingLine(
+                                    target_indexing_loc,
-                                        target_indexing_loc,
+                                    indexing_code,
-                                        indexing_code,
+                                ),
-                                    ),
+                            );
-                                );
-                            }
-                            _ => {}
                         }
 
                         result = merge_indexed_subsequences(
@@ -1977,16 +1958,15 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                                         &mut self.payload.retraction_info,
                                     );
 
-                                    match &mut code[preceding_choice_instr_loc] {
+                                    if let Instruction::TryMeElse(0) =
-                                        Instruction::TryMeElse(0) => {
+                                        &mut code[preceding_choice_instr_loc]
-                                            set_switch_var_offset(
+                                    {
-                                                code,
+                                        set_switch_var_offset(
-                                                index_loc,
+                                            code,
-                                                preceding_choice_instr_loc + 1 - index_loc,
+                                            index_loc,
-                                                &mut self.payload.retraction_info,
+                                            preceding_choice_instr_loc + 1 - index_loc,
-                                            );
+                                            &mut self.payload.retraction_info,
-                                        }
+                                        );
-                                        _ => {}
                                     }
                                 }
                             }
@@ -2068,16 +2048,11 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
         {
             Some(skeleton) if append_or_prepend.is_append() => {
                 let tail_num = skeleton.core.clause_clause_locs.len() - num_clause_predicates;
-                skeleton.core.clause_clause_locs.make_contiguous()[tail_num..]
+                skeleton.core.clause_clause_locs.make_contiguous()[tail_num..].to_vec()
-                    .iter()
-                    .cloned()
-                    .collect()
             }
             Some(skeleton) => skeleton.core.clause_clause_locs.make_contiguous()
                 [0..num_clause_predicates]
-                .iter()
+                .to_vec(),
-                .cloned()
-                .collect(),
             None => {
                 unreachable!()
             }
@@ -2205,46 +2180,47 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                 )?;
             }
         } else {
-            if is_cross_module_clause {
+            if is_cross_module_clause && !local_predicate_info.is_extensible {
-                if !local_predicate_info.is_extensible {
+                if predicate_info.is_multifile {
-                    if predicate_info.is_multifile {
+                    println!(
-                        println!(
+                        "Warning: overwriting multifile predicate {}:{}/{} because \
-                            "Warning: overwriting multifile predicate {}:{}/{} because \
+                              it was not locally declared multifile.",
-                                  it was not locally declared multifile.",
+                        self.payload.predicates.compilation_target,
-                            self.payload.predicates.compilation_target,
+                        key.0.as_str(),
-                            key.0.as_str(),
+                        key.1
-                            key.1
+                    );
+                }
+
+                if let Some(skeleton) = self
+                    .wam_prelude
+                    .indices
+                    .remove_predicate_skeleton(&self.payload.predicates.compilation_target, &key)
+                {
+                    let compilation_target = self.payload.predicates.compilation_target;
+
+                    if predicate_info.is_dynamic {
+                        let clause_clause_compilation_target = match compilation_target {
+                            CompilationTarget::User => CompilationTarget::Module(atom!("builtins")),
+                            module => module,
+                        };
+
+                        self.retract_local_clauses_by_locs(
+                            clause_clause_compilation_target,
+                            (atom!("$clause"), 2),
+                            (0..skeleton.clauses.len()).map(Some).collect(),
+                            false, // the builtin M:'$clause'/2 is never dynamic.
                         );
+
+                        predicate_info.is_dynamic = false;
                     }
 
-                    if let Some(skeleton) = self.wam_prelude.indices.remove_predicate_skeleton(
+                    self.payload
-                        &self.payload.predicates.compilation_target,
+                        .retraction_info
-                        &key,
+                        .push_record(RetractionRecord::RemovedSkeleton(
-                    ) {
+                            compilation_target,
-                        let compilation_target = self.payload.predicates.compilation_target;
+                            key,
-
+                            skeleton,
-                        if predicate_info.is_dynamic {
+                        ));
-                            let clause_clause_compilation_target = match compilation_target {
-                                CompilationTarget::User => {
-                                    CompilationTarget::Module(atom!("builtins"))
-                                }
-                                module => module,
-                            };
-
-                            self.retract_local_clauses_by_locs(
-                                clause_clause_compilation_target,
-                                (atom!("$clause"), 2),
-                                (0..skeleton.clauses.len()).map(Some).collect(),
-                                false, // the builtin M:'$clause'/2 is never dynamic.
-                            );
-
-                            predicate_info.is_dynamic = false;
-                        }
-
-                        self.payload.retraction_info.push_record(
-                            RetractionRecord::RemovedSkeleton(compilation_target, key, skeleton),
-                        );
-                    }
                 }
             }
 
@@ -2262,20 +2238,17 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
             let code_index = self.compile(key, predicates, settings)?;
 
             if let Some(filename) = self.listing_src_file_name() {
-                match self.wam_prelude.indices.modules.get_mut(&filename) {
+                if let Some(ref mut module) = self.wam_prelude.indices.modules.get_mut(&filename) {
-                    Some(ref mut module) => {
+                    let index_ptr = code_index.get();
-                        let index_ptr = code_index.get();
+                    let code_index = *module.code_dir.entry(key).or_insert(code_index);
-                        let code_index = module.code_dir.entry(key).or_insert(code_index).clone();
 
-                        set_code_index(
+                    set_code_index(
-                            &mut self.payload.retraction_info,
+                        &mut self.payload.retraction_info,
-                            &CompilationTarget::Module(filename),
+                        &CompilationTarget::Module(filename),
-                            key,
+                        key,
-                            code_index,
+                        code_index,
-                            index_ptr,
+                        index_ptr,
-                        );
+                    );
-                    }
-                    None => {}
                 }
             }
         }
@@ -2344,7 +2317,7 @@ impl Machine {
         };
 
         let StandaloneCompileResult { clause_code, .. } = compile()?;
-        self.code.extend(clause_code.into_iter());
+        self.code.extend(clause_code);
 
         Ok(())
     }

src/machine/copier.rs

@@ -174,7 +174,7 @@ impl<T: CopierTarget> CopyTermState<T> {
 
     fn copy_attr_var_lists(&mut self) {
         while !self.attr_var_list_locs.is_empty() {
-            let iter = mem::replace(&mut self.attr_var_list_locs, vec![]);
+            let iter = std::mem::take(&mut self.attr_var_list_locs);
 
             for (threshold, list_loc) in iter {
                 self.target[threshold] = list_loc_as_cell!(self.target.threshold());

src/machine/cycle_detection.rs

@@ -73,7 +73,7 @@ impl<'a, const STOP_AT_CYCLES: bool> CycleDetectingIter<'a, STOP_AT_CYCLES> {
     fn traverse_subterm(&mut self, h: usize, arity: usize) -> Option<usize> {
         let mut last_cell_loc = h + arity - 1;
 
-        for idx in (h .. h + arity).rev() {
+        for idx in (h..h + arity).rev() {
             if self.heap[idx].get_forwarding_bit() {
                 if self.cycle_detection_active() {
                     self.cycle_found = true;
@@ -93,8 +93,8 @@ impl<'a, const STOP_AT_CYCLES: bool> CycleDetectingIter<'a, STOP_AT_CYCLES> {
 
     #[inline]
     fn continue_forwarding(&self) -> bool {
-        self.heap[self.current].get_mark_bit() != self.mark_phase ||
+        self.heap[self.current].get_mark_bit() != self.mark_phase
-            self.heap[self.current].get_forwarding_bit()
+            || self.heap[self.current].get_forwarding_bit()
     }
 
     fn forward(&mut self) -> Option<HeapCellValue> {
@@ -150,7 +150,7 @@ impl<'a, const STOP_AT_CYCLES: bool> CycleDetectingIter<'a, STOP_AT_CYCLES> {
                         }
 
                         if self.cycle_detection_active() {
-                            for idx in (h + 1 .. last_cell_loc).rev() {
+                            for idx in (h + 1..last_cell_loc).rev() {
                                 if self.heap[idx].get_forwarding_bit() {
                                     self.cycle_found = true;
                                     return None;
@@ -176,7 +176,7 @@ impl<'a, const STOP_AT_CYCLES: bool> CycleDetectingIter<'a, STOP_AT_CYCLES> {
                         };
 
                         if self.cycle_detection_active() {
-                            for idx in (self.next as usize .. last_cell_loc).rev() {
+                            for idx in (self.next as usize..last_cell_loc).rev() {
                                 if self.heap[idx].get_forwarding_bit() {
                                     self.cycle_found = true;
                                     return None;
@@ -309,19 +309,19 @@ impl<'a, const STOP_AT_CYCLES: bool> CycleDetectingIter<'a, STOP_AT_CYCLES> {
             HeapCellValueTag::Str => {
                 let mut new_str_back_link = self.current;
 
-                for idx in (0 .. self.current).rev() {
+                for idx in (0..self.current).rev() {
-                    if self.heap[idx].get_tag() == HeapCellValueTag::Atom {
+                    if self.heap[idx].get_tag() == HeapCellValueTag::Atom
-                        if cell_as_atom_cell!(self.heap[idx]).get_arity() > 0 {
+                        && cell_as_atom_cell!(self.heap[idx]).get_arity() > 0
-                            new_str_back_link = idx;
+                    {
-                            break;
+                        new_str_back_link = idx;
-                        }
+                        break;
                     }
 
-                    if self.heap[idx].get_mark_bit() != self.mark_phase {
+                    if self.heap[idx].get_mark_bit() != self.mark_phase
-                        if !self.heap[idx].get_forwarding_bit() {
+                        && !self.heap[idx].get_forwarding_bit()
-                            new_str_back_link = idx;
+                    {
-                            break;
+                        new_str_back_link = idx;
-                        }
+                        break;
                     }
                 }
 
@@ -402,7 +402,7 @@ impl<'a, const STOP_AT_CYCLES: bool> CycleDetectingIter<'a, STOP_AT_CYCLES> {
         self.next = self.heap[self.start].get_value();
         self.current = self.start;
 
-        while let Some(_) = self.forward() {}
+        while self.forward().is_some() {}
     }
 }
 
@@ -415,7 +415,6 @@ impl<'a, const STOP_AT_CYCLES: bool> Iterator for CycleDetectingIter<'a, STOP_AT
     }
 }
 
-
 impl<'a, const STOP_AT_CYCLES: bool> Drop for CycleDetectingIter<'a, STOP_AT_CYCLES> {
     fn drop(&mut self) {
         self.invert_marker();

src/machine/disjuncts.rs

@@ -226,7 +226,7 @@ fn merge_branch_seq(branches: impl Iterator<Item = BranchInfo>) -> BranchInfo {
 
     for mut branch in branches {
         branch_info.branch_num = branch.branch_num;
-        branch_info.chunks.extend(branch.chunks.drain(..));
+        branch_info.chunks.append(&mut branch.chunks);
     }
 
     branch_info.branch_num.delta = branch_info.branch_num.delta * Integer::from(2);
@@ -298,7 +298,7 @@ impl VariableClassifier {
 
     fn merge_branches(&mut self) {
         for branches in self.branch_map.values_mut() {
-            let mut old_branches = std::mem::replace(branches, vec![]);
+            let mut old_branches = std::mem::take(branches);
 
             while let Some(last_branch_num) = old_branches.last().map(|bi| &bi.branch_num) {
                 let mut old_branches_len = old_branches.len();
@@ -361,10 +361,7 @@ impl VariableClassifier {
             .current_chunk_type
             .to_gen_context(self.current_chunk_num);
 
-        let branch_info_v = self
+        let branch_info_v = self.branch_map.entry(var_info.var_ptr.clone()).or_default();
-            .branch_map
-            .entry(var_info.var_ptr.clone())
-            .or_insert_with(|| vec![]);
 
         let needs_new_branch = if let Some(last_bi) = branch_info_v.last() {
             !self.root_set.contains(&last_bi.branch_num)
@@ -420,56 +417,49 @@ impl VariableClassifier {
             arity: term.arity(),
         };
 
-        match term {
+        if let Term::Clause(_, _, terms) = term {
-            Term::Clause(_, _, terms) => {
+            for term in terms.iter() {
-                for term in terms.into_iter() {
+                for term_ref in breadth_first_iter(term, RootIterationPolicy::Iterated) {
-                    for term_ref in breadth_first_iter(term, RootIterationPolicy::Iterated) {
+                    if let TermRef::Var(lvl, _, var_ptr) = term_ref {
-                        if let TermRef::Var(lvl, _, var_ptr) = term_ref {
+                        // a body term, so we need the child level here.
-                            // a body term, so we need the child level here.
+                        let lvl = lvl.child_level();
-                            let lvl = lvl.child_level();
 
-                            // the body of the if let here is an inlined
+                        // the body of the if let here is an inlined
-                            // "probe_head_var". note the difference between it
+                        // "probe_head_var". note the difference between it
-                            // and "probe_body_var".
+                        // and "probe_body_var".
-                            let branch_info_v = self
+                        let branch_info_v = self.branch_map.entry(var_ptr.clone()).or_default();
-                                .branch_map
-                                .entry(var_ptr.clone())
-                                .or_insert_with(|| vec![]);
 
-                            let needs_new_branch = branch_info_v.is_empty();
+                        let needs_new_branch = branch_info_v.is_empty();
 
-                            if needs_new_branch {
+                        if needs_new_branch {
-                                branch_info_v
+                            branch_info_v.push(BranchInfo::new(self.current_branch_num.clone()));
-                                    .push(BranchInfo::new(self.current_branch_num.clone()));
-                            }
-
-                            let branch_info = branch_info_v.last_mut().unwrap();
-                            let needs_new_chunk = branch_info.chunks.is_empty();
-
-                            if needs_new_chunk {
-                                branch_info.chunks.push(ChunkInfo {
-                                    chunk_num: self.current_chunk_num,
-                                    term_loc: GenContext::Head,
-                                    vars: vec![],
-                                });
-                            }
-
-                            let chunk_info = branch_info.chunks.last_mut().unwrap();
-                            let var_info = VarInfo {
-                                var_ptr,
-                                classify_info,
-                                chunk_type: self.current_chunk_type,
-                                lvl,
-                            };
-
-                            chunk_info.vars.push(var_info);
                         }
-                    }
 
-                    classify_info.arg_c += 1;
+                        let branch_info = branch_info_v.last_mut().unwrap();
+                        let needs_new_chunk = branch_info.chunks.is_empty();
+
+                        if needs_new_chunk {
+                            branch_info.chunks.push(ChunkInfo {
+                                chunk_num: self.current_chunk_num,
+                                term_loc: GenContext::Head,
+                                vars: vec![],
+                            });
+                        }
+
+                        let chunk_info = branch_info.chunks.last_mut().unwrap();
+                        let var_info = VarInfo {
+                            var_ptr,
+                            classify_info,
+                            chunk_type: self.current_chunk_type,
+                            lvl,
+                        };
+
+                        chunk_info.vars.push(var_info);
+                    }
                 }
+
+                classify_info.arg_c += 1;
             }
-            _ => {}
         }
 
         Ok(())
@@ -538,7 +528,10 @@ impl VariableClassifier {
                     build_stack.push_chunk_term(if is_global {
                         QueryTerm::GlobalCut(var_num)
                     } else {
-                        QueryTerm::LocalCut { var_num, cut_prev: false }
+                        QueryTerm::LocalCut {
+                            var_num,
+                            cut_prev: false,
+                        }
                     });
                 }
                 TraversalState::CutPrev(var_num) => {
@@ -548,7 +541,10 @@ impl VariableClassifier {
 
                     self.probe_in_situ_var(var_num);
 
-                    build_stack.push_chunk_term(QueryTerm::LocalCut { var_num, cut_prev: true });
+                    build_stack.push_chunk_term(QueryTerm::LocalCut {
+                        var_num,
+                        cut_prev: true,
+                    });
                 }
                 TraversalState::Fail => {
                     build_stack.push_chunk_term(QueryTerm::Fail);
@@ -705,7 +701,9 @@ impl VariableClassifier {
                             state_stack.push(TraversalState::BuildDisjunct(build_stack_len));
                             state_stack.push(TraversalState::Fail);
                             state_stack.push(TraversalState::CutPrev(self.var_num));
-                            state_stack.push(TraversalState::ResetGlobalCutVarOverride(self.global_cut_var_num_override));
+                            state_stack.push(TraversalState::ResetGlobalCutVarOverride(
+                                self.global_cut_var_num_override,
+                            ));
                             state_stack.push(TraversalState::Term(not_term));
                             state_stack.push(TraversalState::OverrideGlobalCutVar(self.var_num));
                             state_stack.push(TraversalState::GetCutPoint {

src/machine/dispatch.rs

@@ -313,8 +313,8 @@ impl MachineState {
 impl Machine {
     pub(super) fn find_living_dynamic_else(&self, mut p: usize) -> Option<(usize, usize)> {
         loop {
-            match &self.code[p] {
+            match self.code[p] {
-                &Instruction::DynamicElse(birth, death, NextOrFail::Next(i)) => {
+                Instruction::DynamicElse(birth, death, NextOrFail::Next(i)) => {
                     if birth < self.machine_st.cc && Death::Finite(self.machine_st.cc) <= death {
                         return Some((p, i));
                     } else if i > 0 {
@@ -323,14 +323,14 @@ impl Machine {
                         return None;
                     }
                 }
-                &Instruction::DynamicElse(birth, death, NextOrFail::Fail(_)) => {
+                Instruction::DynamicElse(birth, death, NextOrFail::Fail(_)) => {
                     if birth < self.machine_st.cc && Death::Finite(self.machine_st.cc) <= death {
                         return Some((p, 0));
                     } else {
                         return None;
                     }
                 }
-                &Instruction::DynamicInternalElse(birth, death, NextOrFail::Next(i)) => {
+                Instruction::DynamicInternalElse(birth, death, NextOrFail::Next(i)) => {
                     if birth < self.machine_st.cc && Death::Finite(self.machine_st.cc) <= death {
                         return Some((p, i));
                     } else if i > 0 {
@@ -339,14 +339,14 @@ impl Machine {
                         return None;
                     }
                 }
-                &Instruction::DynamicInternalElse(birth, death, NextOrFail::Fail(_)) => {
+                Instruction::DynamicInternalElse(birth, death, NextOrFail::Fail(_)) => {
                     if birth < self.machine_st.cc && Death::Finite(self.machine_st.cc) <= death {
                         return Some((p, 0));
                     } else {
                         return None;
                     }
                 }
-                &Instruction::RevJmpBy(i) => {
+                Instruction::RevJmpBy(i) => {
                     p -= i;
                 }
                 _ => {
@@ -395,25 +395,14 @@ impl Machine {
     fn execute_switch_on_term(&mut self) {
         #[inline(always)]
         fn dynamic_external_of_clause_is_valid(machine: &mut Machine, p: usize) -> bool {
-            match &machine.code[p] {
+            if let Instruction::DynamicInternalElse(..) = machine.code[p] {
-                Instruction::DynamicInternalElse(..) => {
+                machine.machine_st.dynamic_mode = FirstOrNext::First;
-                    machine.machine_st.dynamic_mode = FirstOrNext::First;
+                return true;
-                    return true;
-                }
-                _ => {}
             }
 
-            match &machine.code[p - 1] {
+            if let Instruction::DynamicInternalElse(birth, death, _) = machine.code[p - 1] {
-                &Instruction::DynamicInternalElse(birth, death, _) => {
+                return birth < machine.machine_st.cc
-                    if birth < machine.machine_st.cc
+                    && Death::Finite(machine.machine_st.cc) <= death;
-                        && Death::Finite(machine.machine_st.cc) <= death
-                    {
-                        return true;
-                    } else {
-                        return false;
-                    }
-                }
-                _ => {}
             }
 
             true
@@ -1896,7 +1885,7 @@ impl Machine {
                             self.machine_st.backtrack();
                         }
                     }
-                    &Instruction::CallNumberLessThanOrEqual(ref at_1, ref at_2) => {
+                    Instruction::CallNumberLessThanOrEqual(ref at_1, ref at_2) => {
                         let n1 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_1));
                         let n2 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_2));
 
@@ -1910,7 +1899,7 @@ impl Machine {
                             }
                         }
                     }
-                    &Instruction::ExecuteNumberLessThanOrEqual(ref at_1, ref at_2) => {
+                    Instruction::ExecuteNumberLessThanOrEqual(ref at_1, ref at_2) => {
                         let n1 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_1));
                         let n2 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_2));
 
@@ -1924,7 +1913,7 @@ impl Machine {
                             }
                         }
                     }
-                    &Instruction::CallNumberEqual(ref at_1, ref at_2) => {
+                    Instruction::CallNumberEqual(ref at_1, ref at_2) => {
                         let n1 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_1));
                         let n2 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_2));
 
@@ -1938,7 +1927,7 @@ impl Machine {
                             }
                         }
                     }
-                    &Instruction::ExecuteNumberEqual(ref at_1, ref at_2) => {
+                    Instruction::ExecuteNumberEqual(ref at_1, ref at_2) => {
                         let n1 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_1));
                         let n2 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_2));
 
@@ -1952,7 +1941,7 @@ impl Machine {
                             }
                         }
                     }
-                    &Instruction::CallNumberNotEqual(ref at_1, ref at_2) => {
+                    Instruction::CallNumberNotEqual(ref at_1, ref at_2) => {
                         let n1 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_1));
                         let n2 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_2));
 
@@ -1966,7 +1955,7 @@ impl Machine {
                             }
                         }
                     }
-                    &Instruction::ExecuteNumberNotEqual(ref at_1, ref at_2) => {
+                    Instruction::ExecuteNumberNotEqual(ref at_1, ref at_2) => {
                         let n1 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_1));
                         let n2 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_2));
 
@@ -1980,7 +1969,7 @@ impl Machine {
                             }
                         }
                     }
-                    &Instruction::CallNumberGreaterThanOrEqual(ref at_1, ref at_2) => {
+                    Instruction::CallNumberGreaterThanOrEqual(ref at_1, ref at_2) => {
                         let n1 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_1));
                         let n2 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_2));
 
@@ -1994,7 +1983,7 @@ impl Machine {
                             }
                         }
                     }
-                    &Instruction::ExecuteNumberGreaterThanOrEqual(ref at_1, ref at_2) => {
+                    Instruction::ExecuteNumberGreaterThanOrEqual(ref at_1, ref at_2) => {
                         let n1 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_1));
                         let n2 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_2));
 
@@ -2008,7 +1997,7 @@ impl Machine {
                             }
                         }
                     }
-                    &Instruction::CallNumberGreaterThan(ref at_1, ref at_2) => {
+                    Instruction::CallNumberGreaterThan(ref at_1, ref at_2) => {
                         let n1 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_1));
                         let n2 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_2));
 
@@ -2022,7 +2011,7 @@ impl Machine {
                             }
                         }
                     }
-                    &Instruction::ExecuteNumberGreaterThan(ref at_1, ref at_2) => {
+                    Instruction::ExecuteNumberGreaterThan(ref at_1, ref at_2) => {
                         let n1 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_1));
                         let n2 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_2));
 
@@ -2036,7 +2025,7 @@ impl Machine {
                             }
                         }
                     }
-                    &Instruction::CallNumberLessThan(ref at_1, ref at_2) => {
+                    Instruction::CallNumberLessThan(ref at_1, ref at_2) => {
                         let n1 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_1));
                         let n2 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_2));
 
@@ -2050,7 +2039,7 @@ impl Machine {
                             }
                         }
                     }
-                    &Instruction::ExecuteNumberLessThan(ref at_1, ref at_2) => {
+                    Instruction::ExecuteNumberLessThan(ref at_1, ref at_2) => {
                         let n1 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_1));
                         let n2 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_2));
 
@@ -2064,7 +2053,7 @@ impl Machine {
                             }
                         }
                     }
-                    &Instruction::DefaultCallNumberLessThanOrEqual(ref at_1, ref at_2) => {
+                    Instruction::DefaultCallNumberLessThanOrEqual(ref at_1, ref at_2) => {
                         let n1 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_1));
                         let n2 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_2));
 
@@ -2077,7 +2066,7 @@ impl Machine {
                             }
                         }
                     }
-                    &Instruction::DefaultExecuteNumberLessThanOrEqual(ref at_1, ref at_2) => {
+                    Instruction::DefaultExecuteNumberLessThanOrEqual(ref at_1, ref at_2) => {
                         let n1 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_1));
                         let n2 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_2));
 
@@ -2090,7 +2079,7 @@ impl Machine {
                             }
                         }
                     }
-                    &Instruction::DefaultCallNumberNotEqual(ref at_1, ref at_2) => {
+                    Instruction::DefaultCallNumberNotEqual(ref at_1, ref at_2) => {
                         let n1 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_1));
                         let n2 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_2));
 
@@ -2103,7 +2092,7 @@ impl Machine {
                             }
                         }
                     }
-                    &Instruction::DefaultExecuteNumberNotEqual(ref at_1, ref at_2) => {
+                    Instruction::DefaultExecuteNumberNotEqual(ref at_1, ref at_2) => {
                         let n1 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_1));
                         let n2 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_2));
 
@@ -2116,7 +2105,7 @@ impl Machine {
                             }
                         }
                     }
-                    &Instruction::DefaultCallNumberEqual(ref at_1, ref at_2) => {
+                    Instruction::DefaultCallNumberEqual(ref at_1, ref at_2) => {
                         let n1 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_1));
                         let n2 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_2));
 
@@ -2129,7 +2118,7 @@ impl Machine {
                             }
                         }
                     }
-                    &Instruction::DefaultExecuteNumberEqual(ref at_1, ref at_2) => {
+                    Instruction::DefaultExecuteNumberEqual(ref at_1, ref at_2) => {
                         let n1 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_1));
                         let n2 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_2));
 
@@ -2142,7 +2131,7 @@ impl Machine {
                             }
                         }
                     }
-                    &Instruction::DefaultCallNumberGreaterThanOrEqual(ref at_1, ref at_2) => {
+                    Instruction::DefaultCallNumberGreaterThanOrEqual(ref at_1, ref at_2) => {
                         let n1 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_1));
                         let n2 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_2));
 
@@ -2155,7 +2144,7 @@ impl Machine {
                             }
                         }
                     }
-                    &Instruction::DefaultExecuteNumberGreaterThanOrEqual(ref at_1, ref at_2) => {
+                    Instruction::DefaultExecuteNumberGreaterThanOrEqual(ref at_1, ref at_2) => {
                         let n1 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_1));
                         let n2 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_2));
 
@@ -2168,7 +2157,7 @@ impl Machine {
                             }
                         }
                     }
-                    &Instruction::DefaultCallNumberGreaterThan(ref at_1, ref at_2) => {
+                    Instruction::DefaultCallNumberGreaterThan(ref at_1, ref at_2) => {
                         let n1 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_1));
                         let n2 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_2));
 
@@ -2181,7 +2170,7 @@ impl Machine {
                             }
                         }
                     }
-                    &Instruction::DefaultExecuteNumberGreaterThan(ref at_1, ref at_2) => {
+                    Instruction::DefaultExecuteNumberGreaterThan(ref at_1, ref at_2) => {
                         let n1 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_1));
                         let n2 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_2));
 
@@ -2194,7 +2183,7 @@ impl Machine {
                             }
                         }
                     }
-                    &Instruction::DefaultCallNumberLessThan(ref at_1, ref at_2) => {
+                    Instruction::DefaultCallNumberLessThan(ref at_1, ref at_2) => {
                         let n1 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_1));
                         let n2 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_2));
 
@@ -2207,7 +2196,7 @@ impl Machine {
                             }
                         }
                     }
-                    &Instruction::DefaultExecuteNumberLessThan(ref at_1, ref at_2) => {
+                    Instruction::DefaultExecuteNumberLessThan(ref at_1, ref at_2) => {
                         let n1 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_1));
                         let n2 = try_or_throw!(self.machine_st, self.machine_st.get_number(at_2));
 
@@ -2955,7 +2944,7 @@ impl Machine {
 
                         self.machine_st.p += 1;
                     }
-                    &Instruction::IndexingCode(ref indexing_lines) => {
+                    Instruction::IndexingCode(ref indexing_lines) => {
                         match &indexing_lines[self.machine_st.oip as usize] {
                             IndexingLine::Indexing(_) => {
                                 self.execute_switch_on_term();
@@ -2965,22 +2954,22 @@ impl Machine {
                                 }
                             }
                             IndexingLine::IndexedChoice(ref indexed_choice) => {
-                                match &indexed_choice[self.machine_st.iip as usize] {
+                                match indexed_choice[self.machine_st.iip as usize] {
-                                    &IndexedChoiceInstruction::Try(offset) => {
+                                    IndexedChoiceInstruction::Try(offset) => {
                                         self.indexed_try(offset);
                                     }
-                                    &IndexedChoiceInstruction::Retry(l) => {
+                                    IndexedChoiceInstruction::Retry(l) => {
                                         self.retry(l);
                                         increment_call_count!(self.machine_st);
                                     }
-                                    &IndexedChoiceInstruction::DefaultRetry(l) => {
+                                    IndexedChoiceInstruction::DefaultRetry(l) => {
                                         self.retry(l);
                                     }
-                                    &IndexedChoiceInstruction::Trust(l) => {
+                                    IndexedChoiceInstruction::Trust(l) => {
                                         self.trust(l);
                                         increment_call_count!(self.machine_st);
                                     }
-                                    &IndexedChoiceInstruction::DefaultTrust(l) => {
+                                    IndexedChoiceInstruction::DefaultTrust(l) => {
                                         self.trust(l);
                                     }
                                 }
@@ -5089,16 +5078,13 @@ impl Machine {
                             .get_predicate_skeleton_mut(&compilation_target, &key)
                             .unwrap();
 
-                        match skeleton.target_pos_of_clause_clause_loc(l) {
+                        if let Some(n) = skeleton.target_pos_of_clause_clause_loc(l) {
-                            Some(n) => {
+                            let r = self
-                                let r = self
+                                .machine_st
-                                    .machine_st
+                                .store(self.machine_st.deref(self.machine_st.registers[5]));
-                                    .store(self.machine_st.deref(self.machine_st.registers[5]));
 
-                                self.machine_st
+                            self.machine_st
-                                    .unify_fixnum(Fixnum::build_with(n as i64), r);
+                                .unify_fixnum(Fixnum::build_with(n as i64), r);
-                            }
-                            None => {}
                         }
 
                         self.machine_st.call_at_index(2, p);
@@ -5135,16 +5121,13 @@ impl Machine {
                             .get_predicate_skeleton_mut(&compilation_target, &key)
                             .unwrap();
 
-                        match skeleton.target_pos_of_clause_clause_loc(l) {
+                        if let Some(n) = skeleton.target_pos_of_clause_clause_loc(l) {
-                            Some(n) => {
+                            let r = self
-                                let r = self
+                                .machine_st
-                                    .machine_st
+                                .store(self.machine_st.deref(self.machine_st.registers[5]));
-                                    .store(self.machine_st.deref(self.machine_st.registers[5]));
 
-                                self.machine_st
+                            self.machine_st
-                                    .unify_fixnum(Fixnum::build_with(n as i64), r);
+                                .unify_fixnum(Fixnum::build_with(n as i64), r);
-                            }
-                            None => {}
                         }
 
                         self.machine_st.execute_at_index(2, p);
@@ -5226,7 +5209,7 @@ impl Machine {
                         // So we only have access to a runtime handle in here and can't shut it down.
                         // Since I'm not aware of the consequences of deactivating this new code which came in while PR 1880
                         // was not merged, I'm only deactivating it for now.
-                        
+
                         //#[cfg(not(target_arch = "wasm32"))]
                         //let runtime = tokio::runtime::Runtime::new().unwrap();
                         //#[cfg(target_arch = "wasm32")]

src/machine/gc.rs

@@ -9,14 +9,22 @@ pub(crate) trait UnmarkPolicy {
     fn forward_attr_var(iter: &mut StacklessPreOrderHeapIter<Self>) -> Option<HeapCellValue>
     where
         Self: Sized;
-    fn invert_marker(iter: &mut StacklessPreOrderHeapIter<Self>) where Self: Sized;
+    fn invert_marker(iter: &mut StacklessPreOrderHeapIter<Self>)
+    where
+        Self: Sized;
     fn mark_phase(&self) -> bool;
     #[inline]
-    fn report_var_link(iter: &StacklessPreOrderHeapIter<Self>) -> bool where Self: Sized {
+    fn report_var_link(iter: &StacklessPreOrderHeapIter<Self>) -> bool
+    where
+        Self: Sized,
+    {
         iter.heap[iter.next as usize].get_mark_bit() == iter.iter_state.mark_phase()
     }
     #[inline(always)]
-    fn record_focus(_iter: &mut StacklessPreOrderHeapIter<Self>) where Self: Sized {
+    fn record_focus(_iter: &mut StacklessPreOrderHeapIter<Self>)
+    where
+        Self: Sized,
+    {
     }
 }
 
@@ -34,7 +42,7 @@ fn invert_marker<UMP: UnmarkPolicy>(iter: &mut StacklessPreOrderHeapIter<UMP>) {
     iter.next = iter.heap[iter.start].get_value();
     iter.current = iter.start;
 
-    while let Some(_) = iter.forward() {}
+    while iter.forward().is_some() {}
 }
 
 impl UnmarkPolicy for IteratorUMP {
@@ -139,7 +147,7 @@ impl<'a> StacklessPreOrderHeapIter<'a, IteratorUMP> {
             start,
             current: start,
             next,
-            iter_state: IteratorUMP { mark_phase: true,},
+            iter_state: IteratorUMP { mark_phase: true },
         }
     }
 }
@@ -189,11 +197,9 @@ impl<'a, UMP: UnmarkPolicy> StacklessPreOrderHeapIter<'a, UMP> {
                             return Some(cell);
                         }
 
-                        if self.next < self.heap.len() as u64 {
+                        if self.next < self.heap.len() as u64 && UMP::report_var_link(self) {
-                            if UMP::report_var_link(self) {
+                            let tag = HeapCellValueTag::AttrVar;
-                                let tag = HeapCellValueTag::AttrVar;
+                            return Some(HeapCellValue::build_with(tag, next as u64));
-                                return Some(HeapCellValue::build_with(tag, next as u64));
-                            }
                         }
                     }
                     HeapCellValueTag::Var => {
@@ -203,11 +209,9 @@ impl<'a, UMP: UnmarkPolicy> StacklessPreOrderHeapIter<'a, UMP> {
                             return Some(cell);
                         }
 
-                        if self.next < self.heap.len() as u64 {
+                        if self.next < self.heap.len() as u64 && UMP::report_var_link(self) {
-                            if UMP::report_var_link(self) {
+                            let tag = HeapCellValueTag::Var;
-                                let tag = HeapCellValueTag::Var;
+                            return Some(HeapCellValue::build_with(tag, next as u64));
-                                return Some(HeapCellValue::build_with(tag, next as u64));
-                            }
                         }
                     }
                     HeapCellValueTag::Str => {
@@ -311,10 +315,8 @@ impl<'a, UMP: UnmarkPolicy> StacklessPreOrderHeapIter<'a, UMP> {
                         return Some(self.backward_and_return());
                     }
                 }
-            } else {
+            } else if self.backward() {
-                if self.backward() {
+                return None;
-                    return None;
-                }
             }
         }
     }
@@ -358,7 +360,7 @@ impl<'a, UMP: UnmarkPolicy> Iterator for StacklessPreOrderHeapIter<'a, UMP> {
 
 pub fn mark_cells(heap: &mut Heap, start: usize) {
     let mut iter = StacklessPreOrderHeapIter::<MarkerUMP>::new(heap, start);
-    while let Some(_) = iter.forward() {}
+    while iter.forward().is_some() {}
 }
 
 #[cfg(test)]
@@ -665,14 +667,18 @@ mod tests {
 
         wam.machine_st.heap.push(pstr_loc_as_cell!(1));
 
-        let pstr_var_cell = put_partial_string(&mut wam.machine_st.heap, "abc ", &wam.machine_st.atom_tbl);
+        let pstr_var_cell =
+            put_partial_string(&mut wam.machine_st.heap, "abc ", &wam.machine_st.atom_tbl);
         let pstr_cell = wam.machine_st.heap[pstr_var_cell.get_value() as usize];
 
         mark_cells(&mut wam.machine_st.heap, 0);
 
         all_cells_marked_and_unforwarded(&wam.machine_st.heap);
 
-        assert_eq!(unmark_cell_bits!(wam.machine_st.heap[0]), pstr_loc_as_cell!(1));
+        assert_eq!(
+            unmark_cell_bits!(wam.machine_st.heap[0]),
+            pstr_loc_as_cell!(1)
+        );
         assert_eq!(unmark_cell_bits!(wam.machine_st.heap[1]), pstr_cell);
         assert_eq!(
             unmark_cell_bits!(wam.machine_st.heap[2]),
@@ -720,7 +726,7 @@ mod tests {
 
         mark_cells(&mut wam.machine_st.heap, 7);
 
-        all_cells_marked_and_unforwarded(&wam.machine_st.heap[1 ..]);
+        all_cells_marked_and_unforwarded(&wam.machine_st.heap[1..]);
 
         assert_eq!(unmark_cell_bits!(wam.machine_st.heap[1]), pstr_cell);
         assert_eq!(
@@ -1536,10 +1542,10 @@ mod tests {
 
         mark_cells(&mut wam.machine_st.heap, 0);
 
-        all_cells_marked_and_unforwarded(&mut wam.machine_st.heap[0..24]);
+        all_cells_marked_and_unforwarded(&wam.machine_st.heap[0..24]);
 
         for cell in &wam.machine_st.heap[24..] {
-            assert_eq!(cell.get_mark_bit(), false);
+            assert!(!cell.get_mark_bit());
         }
 
         assert_eq!(

src/machine/heap.rs

@@ -169,7 +169,7 @@ pub(crate) fn allocate_pstr(heap: &mut Heap, mut src: &str, atom_tbl: &AtomTable
     let orig_h = heap.len();
 
     loop {
-        if src == "" {
+        if src.is_empty() {
             return if orig_h == heap.len() {
                 None
             } else {
@@ -199,7 +199,7 @@ pub(crate) fn allocate_pstr(heap: &mut Heap, mut src: &str, atom_tbl: &AtomTable
 
         heap.push(string_as_pstr_cell!(pstr));
 
-        if rest_src != "" {
+        if !rest_src.is_empty() {
             heap.push(pstr_loc_as_cell!(h + 2));
             src = rest_src;
         } else {
@@ -249,7 +249,7 @@ pub(crate) fn to_local_code_ptr(heap: &Heap, addr: HeapCellValue) -> Option<usiz
             Ok(Number::Integer(n)) => {
                 let value: usize = (&*n).try_into().unwrap();
                 Some(value)
-            },
+            }
             _ => None,
         }
     };

src/machine/lib_machine.rs

@@ -3,18 +3,17 @@ use std::sync::Arc;
 
 use crate::atom_table;
 use crate::heap_print::{HCPrinter, HCValueOutputter, PrinterOutputter};
-use crate::machine::{BREAK_FROM_DISPATCH_LOOP_LOC, LIB_QUERY_SUCCESS};
+use crate::machine::machine_indices::VarKey;
 use crate::machine::mock_wam::CompositeOpDir;
+use crate::machine::{BREAK_FROM_DISPATCH_LOOP_LOC, LIB_QUERY_SUCCESS};
+use crate::parser::ast::{Var, VarPtr};
 use crate::parser::parser::{Parser, Tokens};
 use crate::read::write_term_to_heap;
-use crate::machine::machine_indices::VarKey;
-use crate::parser::ast::{Var, VarPtr};
 use indexmap::IndexMap;
 
 use super::{
-    Machine, MachineConfig, QueryResult, QueryResolutionLine,
+    streams::Stream, Atom, AtomCell, HeapCellValue, HeapCellValueTag, Machine, MachineConfig,
-    Atom, AtomCell, HeapCellValue, HeapCellValueTag, Value, QueryResolution,
+    QueryResolution, QueryResolutionLine, QueryResult, Value,
-    streams::Stream
 };
 
 impl Machine {
@@ -30,7 +29,10 @@ impl Machine {
     pub fn consult_module_string(&mut self, module_name: &str, program: String) {
         let stream = Stream::from_owned_string(program, &mut self.machine_st.arena);
         self.machine_st.registers[1] = stream_as_cell!(stream);
-        self.machine_st.registers[2] = atom_as_cell!(&atom_table::AtomTable::build_with(&self.machine_st.atom_tbl, module_name));
+        self.machine_st.registers[2] = atom_as_cell!(&atom_table::AtomTable::build_with(
+            &self.machine_st.atom_tbl,
+            module_name
+        ));
 
         self.run_module_predicate(atom!("loader"), (atom!("consult_stream"), 2));
     }
@@ -62,21 +64,33 @@ impl Machine {
         // Parse the query so we can analyze and then call the term
         let mut parser = Parser::new(
             Stream::from_owned_string(query, &mut self.machine_st.arena),
-            &mut self.machine_st
+            &mut self.machine_st,
         );
         let op_dir = CompositeOpDir::new(&self.indices.op_dir, None);
-        let term = parser.read_term(&op_dir, Tokens::Default).expect("Failed to parse query");
+        let term = parser
+            .read_term(&op_dir, Tokens::Default)
+            .expect("Failed to parse query");
 
         // Write parsed term to heap
-        let term_write_result = write_term_to_heap(&term, &mut self.machine_st.heap, &mut self.machine_st.atom_tbl).expect("couldn't write term to heap");
+        let term_write_result =
+            write_term_to_heap(&term, &mut self.machine_st.heap, &self.machine_st.atom_tbl)
+                .expect("couldn't write term to heap");
 
         // Write term to heap
         self.machine_st.registers[1] = self.machine_st.heap[term_write_result.heap_loc];
 
         self.machine_st.cp = LIB_QUERY_SUCCESS; // BREAK_FROM_DISPATCH_LOOP_LOC;
-        self.machine_st.p = self.indices.code_dir.get(&(atom!("call"), 1)).expect("couldn't get code index").local().unwrap();
+        self.machine_st.p = self
+            .indices
+            .code_dir
+            .get(&(atom!("call"), 1))
+            .expect("couldn't get code index")
+            .local()
+            .unwrap();
 
-        let var_names: IndexMap<_, _> = term_write_result.var_dict.iter()
+        let var_names: IndexMap<_, _> = term_write_result
+            .var_dict
+            .iter()
             .map(|(var_key, cell)| match var_key {
                 // NOTE: not the intention behind Var::InSitu here but
                 // we can hijack it to store anonymous variables
@@ -99,27 +113,29 @@ impl Machine {
             //println!("stub_b: {}", stub_b);
             //println!("fail: {}", self.machine_st.fail);
 
-            if self.machine_st.ball.stub.len() != 0 {
+            if !self.machine_st.ball.stub.is_empty() {
                 // NOTE: this means an exception was thrown, at which
                 // point we backtracked to the stub choice point.
                 // this should halt the search for solutions as it
                 // does in the Scryer top-level. the exception term is
                 // contained in self.machine_st.ball.
-                let error_string = self.machine_st.ball.stub
+                let error_string = self
+                    .machine_st
+                    .ball
+                    .stub
                     .iter()
-                    .filter(|h| match h.get_tag() {
+                    .filter(|h| {
-                        HeapCellValueTag::Atom => true,
+                        matches!(
-                        HeapCellValueTag::Fixnum => true,
+                            h.get_tag(),
-                        _ => false,
+                            HeapCellValueTag::Atom | HeapCellValueTag::Fixnum
+                        )
                     })
                     .map(|h| match h.get_tag() {
                         HeapCellValueTag::Atom => {
                             let (name, _) = cell_as_atom_cell!(h).get_name_and_arity();
                             name.as_str().to_string()
                         }
-                        HeapCellValueTag::Fixnum => {
+                        HeapCellValueTag::Fixnum => h.get_value().clone().to_string(),
-                            h.get_value().clone().to_string()
-                        },
                         _ => unreachable!(),
                     })
                     .collect::<Vec<String>>()
@@ -154,7 +170,7 @@ impl Machine {
             let mut bindings: BTreeMap<String, Value> = BTreeMap::new();
 
             for (var_key, term_to_be_printed) in &term_write_result.var_dict {
-                if var_key.to_string().starts_with("_") {
+                if var_key.to_string().starts_with('_') {
                     continue;
                 }
                 let mut printer = HCPrinter::new(
@@ -210,7 +226,7 @@ mod tests {
     use ordered_float::OrderedFloat;
 
     use super::*;
-    use crate::machine::{QueryMatch, Value, QueryResolution};
+    use crate::machine::{QueryMatch, QueryResolution, Value};
 
     #[test]
     fn programatic_query() {
@@ -258,7 +274,9 @@ mod tests {
         let output = machine.run_query(query);
         assert_eq!(
             output,
-            Err(String::from("error existence_error procedure / triple 3 / triple 3"))
+            Err(String::from(
+                "error existence_error procedure / triple 3 / triple 3"
+            ))
         );
     }
 
@@ -278,26 +296,30 @@ mod tests {
                 constructor(xyz, '[{action: "addLink", source: "this", predicate: "recipe://title", target: "literal://string:Meta%20Muffins"}]').
             "#.to_string());
 
-        let result = machine.run_query(String::from("subject_class(\"Todo\", C), constructor(C, Actions)."));
+        let result = machine.run_query(String::from(
+            "subject_class(\"Todo\", C), constructor(C, Actions).",
+        ));
         assert_eq!(
             result,
-            Ok(QueryResolution::Matches(vec![
+            Ok(QueryResolution::Matches(vec![QueryMatch::from(
-                QueryMatch::from(btreemap! {
+                btreemap! {
                     "C" => Value::from("c"),
                     "Actions" => Value::from("[{action: \"addLink\", source: \"this\", predicate: \"todo://state\", target: \"todo://ready\"}]"),
-                }),
+                }
-            ]))
+            ),]))
         );
 
-        let result = machine.run_query(String::from("subject_class(\"Recipe\", C), constructor(C, Actions)."));
+        let result = machine.run_query(String::from(
+            "subject_class(\"Recipe\", C), constructor(C, Actions).",
+        ));
         assert_eq!(
             result,
-            Ok(QueryResolution::Matches(vec![
+            Ok(QueryResolution::Matches(vec![QueryMatch::from(
-                QueryMatch::from(btreemap! {
+                btreemap! {
                     "C" => Value::from("xyz"),
                     "Actions" => Value::from("[{action: \"addLink\", source: \"this\", predicate: \"recipe://title\", target: \"literal://string:Meta%20Muffins\"}]"),
-                }),
+                }
-            ]))
+            ),]))
         );
 
         let result = machine.run_query(String::from("subject_class(Class, _)."));
@@ -319,15 +341,17 @@ mod tests {
         let mut machine = Machine::new_lib();
         machine.load_module_string(
             "facts",
-                r#"
+            r#"
                 list([1,2,3]).
-            "#.to_string());
+            "#
+            .to_string(),
+        );
 
         let result = machine.run_query(String::from("list(X)."));
         assert_eq!(
             result,
-            Ok(QueryResolution::Matches(vec![
+            Ok(QueryResolution::Matches(vec![QueryMatch::from(
-                QueryMatch::from(btreemap! {
+                btreemap! {
                     "X" => Value::List(
                         Vec::from([
                             Value::Float(OrderedFloat::from(1.0)),
@@ -335,12 +359,11 @@ mod tests {
                             Value::Float(OrderedFloat::from(3.0))
                         ])
                     )
-                }),
+                }
-            ]))
+            ),]))
         );
     }
 
-
     #[test]
     fn consult() {
         let mut machine = Machine::new_lib();
@@ -397,7 +420,6 @@ mod tests {
             machine.run_query(String::from(r#"triple("a","new","b")."#)),
             Ok(QueryResolution::True)
         );
-
     }
 
     #[ignore = "fails on windows"]
@@ -462,12 +484,13 @@ mod tests {
             ),
         );
 
-        let query = String::from(r#"findall([Predicate, Target], triple(_,Predicate,Target), Result)."#);
+        let query =
+            String::from(r#"findall([Predicate, Target], triple(_,Predicate,Target), Result)."#);
         let output = machine.run_query(query);
         assert_eq!(
             output,
-            Ok(QueryResolution::Matches(vec![
+            Ok(QueryResolution::Matches(vec![QueryMatch::from(
-                QueryMatch::from(btreemap! {
+                btreemap! {
                     "Predicate" => Value::from("Predicate"),
                     "Result" => Value::List(
                         Vec::from([
@@ -476,9 +499,8 @@ mod tests {
                         ])
                     ),
                     "Target" => Value::from("Target"),
-                }),
+                }
-            ]))
+            ),]))
         );
-
     }
 }

src/machine/load_state.rs

@@ -137,10 +137,9 @@ pub(super) fn import_module_exports<'a, LS: LoadState<'a>>(
                 if let Some(src_code_index) = imported_module.code_dir.get(&key).cloned() {
                     let arena = &mut LS::machine_st(payload).arena;
 
-                    let target_code_index = code_dir
+                    let target_code_index = *code_dir
                         .entry(key)
-                        .or_insert_with(|| CodeIndex::default(arena))
+                        .or_insert_with(|| CodeIndex::default(arena));
-                        .clone();
 
                     set_code_index(
                         &mut payload.retraction_info,
@@ -189,16 +188,15 @@ fn import_module_exports_into_module<'a, LS: LoadState<'a>>(
                 let key = (*name, *arity);
 
                 if let Some(meta_specs) = imported_module.meta_predicates.get(&key) {
-                    meta_predicates.insert(key.clone(), meta_specs.clone());
+                    meta_predicates.insert(key, meta_specs.clone());
                 }
 
                 if let Some(src_code_index) = imported_module.code_dir.get(&key) {
                     let arena = &mut LS::machine_st(payload).arena;
 
-                    let target_code_index = code_dir
+                    let target_code_index = *code_dir
                         .entry(key)
-                        .or_insert_with(|| CodeIndex::default(arena))
+                        .or_insert_with(|| CodeIndex::default(arena));
-                        .clone();
 
                     set_code_index(
                         &mut payload.retraction_info,
@@ -209,7 +207,7 @@ fn import_module_exports_into_module<'a, LS: LoadState<'a>>(
                     );
                 } else {
                     return Err(SessionError::ModuleDoesNotContainExport(
-                        imported_module.module_decl.name.clone(),
+                        imported_module.module_decl.name,
                         (*name, *arity),
                     ));
                 }
@@ -243,18 +241,17 @@ fn import_qualified_module_exports<'a, LS: LoadState<'a>>(
                     wam_prelude
                         .indices
                         .meta_predicates
-                        .insert(key.clone(), meta_specs.clone());
+                        .insert(key, meta_specs.clone());
                 }
 
                 if let Some(src_code_index) = imported_module.code_dir.get(&key) {
                     let arena = &mut LS::machine_st(payload).arena;
 
-                    let target_code_index = wam_prelude
+                    let target_code_index = *wam_prelude
                         .indices
                         .code_dir
-                        .entry(key.clone())
+                        .entry(key)
-                        .or_insert_with(|| CodeIndex::new(IndexPtr::undefined(), arena))
+                        .or_insert_with(|| CodeIndex::new(IndexPtr::undefined(), arena));
-                        .clone();
 
                     set_code_index(
                         &mut payload.retraction_info,
@@ -265,7 +262,7 @@ fn import_qualified_module_exports<'a, LS: LoadState<'a>>(
                     );
                 } else {
                     return Err(SessionError::ModuleDoesNotContainExport(
-                        imported_module.module_decl.name.clone(),
+                        imported_module.module_decl.name,
                         (*name, *arity),
                     ));
                 }
@@ -311,10 +308,9 @@ fn import_qualified_module_exports_into_module<'a, LS: LoadState<'a>>(
                 if let Some(src_code_index) = imported_module.code_dir.get(&key) {
                     let arena = &mut LS::machine_st(payload).arena;
 
-                    let target_code_index = code_dir
+                    let target_code_index = *code_dir
                         .entry(key)
-                        .or_insert_with(|| CodeIndex::new(IndexPtr::undefined(), arena))
+                        .or_insert_with(|| CodeIndex::new(IndexPtr::undefined(), arena));
-                        .clone();
 
                     set_code_index(
                         &mut payload.retraction_info,
@@ -325,7 +321,7 @@ fn import_qualified_module_exports_into_module<'a, LS: LoadState<'a>>(
                     );
                 } else {
                     return Err(SessionError::ModuleDoesNotContainExport(
-                        imported_module.module_decl.name.clone(),
+                        imported_module.module_decl.name,
                         (*name, *arity),
                     ));
                 }
@@ -423,7 +419,7 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                         payload_compilation_target,
                         clause_clause_compilation_target,
                         key,
-                        mem::replace(&mut skeleton.clause_clause_locs, VecDeque::new()),
+                        std::mem::take(&mut skeleton.clause_clause_locs),
                     ),
                 );
 
@@ -436,7 +432,7 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
             }
         };
 
-        self.retract_local_clauses_impl(clause_clause_compilation_target, key, &clause_locs);
+        self.retract_local_clauses_impl(clause_clause_compilation_target, key, clause_locs);
     }
 
     pub(super) fn try_term_to_tl(
@@ -600,30 +596,22 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
         key: PredicateKey,
     ) -> CodeIndex {
         match self.wam_prelude.indices.modules.get_mut(&module_name) {
-            Some(ref mut module) => module
+            Some(ref mut module) => *module.code_dir.entry(key).or_insert_with(|| {
-                .code_dir
+                CodeIndex::new(
-                .entry(key)
+                    IndexPtr::undefined(),
-                .or_insert_with(|| {
+                    &mut LS::machine_st(&mut self.payload).arena,
-                    CodeIndex::new(
+                )
-                        IndexPtr::undefined(),
+            }),
-                        &mut LS::machine_st(&mut self.payload).arena,
-                    )
-                })
-                .clone(),
             None => {
                 self.add_dynamically_generated_module(module_name);
 
                 match self.wam_prelude.indices.modules.get_mut(&module_name) {
-                    Some(ref mut module) => module
+                    Some(ref mut module) => *module.code_dir.entry(key).or_insert_with(|| {
-                        .code_dir
+                        CodeIndex::new(
-                        .entry(key)
+                            IndexPtr::undefined(),
-                        .or_insert_with(|| {
+                            &mut LS::machine_st(&mut self.payload).arena,
-                            CodeIndex::new(
+                        )
-                                IndexPtr::undefined(),
+                    }),
-                                &mut LS::machine_st(&mut self.payload).arena,
-                            )
-                        })
-                        .clone(),
                     None => {
                         unreachable!()
                     }
@@ -640,13 +628,12 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
         let arena = &mut LS::machine_st(&mut self.payload).arena;
 
         match compilation_target {
-            CompilationTarget::User => self
+            CompilationTarget::User => *self
                 .wam_prelude
                 .indices
                 .code_dir
                 .entry(key)
-                .or_insert_with(|| CodeIndex::new(IndexPtr::undefined(), arena))
+                .or_insert_with(|| CodeIndex::new(IndexPtr::undefined(), arena)),
-                .clone(),
             CompilationTarget::Module(module_name) => {
                 self.get_or_insert_local_code_index(module_name, key)
             }
@@ -661,13 +648,12 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
         let arena = &mut LS::machine_st(&mut self.payload).arena;
 
         if module_name == atom!("user") {
-            return self
+            return *self
                 .wam_prelude
                 .indices
                 .code_dir
                 .entry(key)
-                .or_insert_with(|| CodeIndex::new(IndexPtr::undefined(), arena))
+                .or_insert_with(|| CodeIndex::new(IndexPtr::undefined(), arena));
-                .clone();
         } else {
             self.get_or_insert_local_code_index(module_name, key)
         }
@@ -694,7 +680,7 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
             }
             CompilationTarget::Module(module_name) => {
                 if let Some(module) = self.wam_prelude.indices.modules.get_mut(&module_name) {
-                    module.extensible_predicates.insert(key.clone(), skeleton);
+                    module.extensible_predicates.insert(key, skeleton);
 
                     let record = RetractionRecord::AddedExtensiblePredicate(
                         CompilationTarget::Module(module_name),
@@ -747,11 +733,10 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
         match payload_compilation_target {
             CompilationTarget::User => {
                 if let Some(filename) = listing_src_file_name {
-                    match self.wam_prelude.indices.modules.get_mut(&filename) {
+                    if let Some(ref mut module) =
-                        Some(ref mut module) => {
+                        self.wam_prelude.indices.modules.get_mut(&filename)
-                            op_decl.insert_into_op_dir(&mut module.op_dir);
+                    {
-                        }
+                        op_decl.insert_into_op_dir(&mut module.op_dir);
-                        None => {}
                     }
                 }
 
@@ -855,48 +840,43 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                     }
                 }
             }
-            _ => {
+            _ => match self.wam_prelude.indices.modules.get_mut(&module_name) {
-                match self.wam_prelude.indices.modules.get_mut(&module_name) {
+                Some(ref mut module) => match module.meta_predicates.insert(key, meta_specs) {
-                    Some(ref mut module) => {
+                    Some(old_meta_specs) => {
-                        match module.meta_predicates.insert(key.clone(), meta_specs) {
-                            Some(old_meta_specs) => {
-                                self.payload.retraction_info.push_record(
-                                    RetractionRecord::ReplacedMetaPredicate(
-                                        module_name,
-                                        key.0,
-                                        old_meta_specs,
-                                    ),
-                                );
-                            }
-                            None => {
-                                self.payload.retraction_info.push_record(
-                                    RetractionRecord::AddedMetaPredicate(module_name, key),
-                                );
-                            }
-                        }
-                    }
-                    None => {
-                        self.add_dynamically_generated_module(module_name);
-
-                        if let Some(module) = self.wam_prelude.indices.modules.get_mut(&module_name)
-                        {
-                            module.meta_predicates.insert(key.clone(), meta_specs);
-                        } else {
-                            unreachable!()
-                        }
-
                         self.payload.retraction_info.push_record(
-                            RetractionRecord::AddedMetaPredicate(module_name.clone(), key),
+                            RetractionRecord::ReplacedMetaPredicate(
+                                module_name,
+                                key.0,
+                                old_meta_specs,
+                            ),
                         );
                     }
+                    None => {
+                        self.payload
+                            .retraction_info
+                            .push_record(RetractionRecord::AddedMetaPredicate(module_name, key));
+                    }
+                },
+                None => {
+                    self.add_dynamically_generated_module(module_name);
+
+                    if let Some(module) = self.wam_prelude.indices.modules.get_mut(&module_name) {
+                        module.meta_predicates.insert(key, meta_specs);
+                    } else {
+                        unreachable!()
+                    }
+
+                    self.payload
+                        .retraction_info
+                        .push_record(RetractionRecord::AddedMetaPredicate(module_name, key));
                 }
-            }
+            },
         }
     }
 
     pub(super) fn add_dynamically_generated_module(&mut self, module_name: Atom) {
         let module_decl = ModuleDecl {
-            name: module_name.clone(),
+            name: module_name,
             exports: vec![],
         };
 
@@ -912,12 +892,9 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
 
         self.payload
             .retraction_info
-            .push_record(RetractionRecord::AddedModule(module_name.clone()));
+            .push_record(RetractionRecord::AddedModule(module_name));
 
-        self.wam_prelude
+        self.wam_prelude.indices.modules.insert(module_name, module);
-            .indices
-            .modules
-            .insert(module_name.clone(), module);
     }
 
     fn import_builtins_in_module(
@@ -956,51 +933,48 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
         self.remove_module_exports(module_name);
         self.remove_replaced_in_situ_module(module_name);
 
-        match self.wam_prelude.indices.modules.get_mut(&module_name) {
+        if let Some(module) = self.wam_prelude.indices.modules.get_mut(&module_name) {
-            Some(module) => {
+            let old_module_decl = mem::replace(&mut module.module_decl, module_decl.clone());
-                let old_module_decl = mem::replace(&mut module.module_decl, module_decl.clone());
 
-                let local_extensible_predicates = mem::replace(
+            let local_extensible_predicates = mem::replace(
-                    &mut module.local_extensible_predicates,
+                &mut module.local_extensible_predicates,
-                    LocalExtensiblePredicates::with_hasher(FxBuildHasher::default()),
+                LocalExtensiblePredicates::with_hasher(FxBuildHasher::default()),
+            );
+
+            for ((compilation_target, key), skeleton) in local_extensible_predicates.iter() {
+                self.retract_local_clauses_impl(
+                    *compilation_target,
+                    *key,
+                    &skeleton.clause_clause_locs,
                 );
 
-                for ((compilation_target, key), skeleton) in local_extensible_predicates.iter() {
+                let is_dynamic = self
-                    self.retract_local_clauses_impl(
+                    .wam_prelude
-                        *compilation_target,
+                    .indices
-                        *key,
+                    .get_predicate_skeleton(compilation_target, key)
+                    .map(|skeleton| skeleton.core.is_dynamic)
+                    .unwrap_or(false);
+
+                if is_dynamic {
+                    let clause_clause_compilation_target = match compilation_target {
+                        CompilationTarget::User => CompilationTarget::Module(atom!("builtins")),
+                        module => *module,
+                    };
+
+                    self.retract_local_clause_clauses(
+                        clause_clause_compilation_target,
                         &skeleton.clause_clause_locs,
                     );
-
-                    let is_dynamic = self
-                        .wam_prelude
-                        .indices
-                        .get_predicate_skeleton(compilation_target, key)
-                        .map(|skeleton| skeleton.core.is_dynamic)
-                        .unwrap_or(false);
-
-                    if is_dynamic {
-                        let clause_clause_compilation_target = match compilation_target {
-                            CompilationTarget::User => CompilationTarget::Module(atom!("builtins")),
-                            module => module.clone(),
-                        };
-
-                        self.retract_local_clause_clauses(
-                            clause_clause_compilation_target,
-                            &skeleton.clause_clause_locs,
-                        );
-                    }
                 }
-
-                self.payload
-                    .retraction_info
-                    .push_record(RetractionRecord::ReplacedModule(
-                        old_module_decl,
-                        listing_src.clone(),
-                        local_extensible_predicates,
-                    ));
             }
-            None => {}
+
+            self.payload
+                .retraction_info
+                .push_record(RetractionRecord::ReplacedModule(
+                    old_module_decl,
+                    listing_src.clone(),
+                    local_extensible_predicates,
+                ));
         }
     }
 
@@ -1180,11 +1154,11 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
             }
             ModuleSource::Library(library) => match LIBRARIES.borrow().get(&*library.as_str()) {
                 Some(code) => {
-                    if let Some(ref module) = self.wam_prelude.indices.modules.get(&library) {
+                    if let Some(module) = self.wam_prelude.indices.modules.get(&library) {
                         if let ListingSource::DynamicallyGenerated = &module.listing_src {
                             (
                                 Stream::from_static_string(
-                                    *code,
+                                    code,
                                     &mut LS::machine_st(&mut self.payload).arena,
                                 ),
                                 ListingSource::User,
@@ -1195,7 +1169,7 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                     } else {
                         (
                             Stream::from_static_string(
-                                *code,
+                                code,
                                 &mut LS::machine_st(&mut self.payload).arena,
                             ),
                             ListingSource::User,
@@ -1266,7 +1240,7 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                     } else {
                         (
                             Stream::from_static_string(
-                                *code,
+                                code,
                                 &mut LS::machine_st(&mut self.payload).arena,
                             ),
                             ListingSource::User,

src/machine/loader.rs

@@ -19,7 +19,6 @@ use std::cell::Cell;
 use std::collections::VecDeque;
 use std::convert::TryFrom;
 use std::fmt;
-use std::mem;
 use std::ops::{Deref, DerefMut};
 
 /*
@@ -136,7 +135,7 @@ impl RetractionInfo {
 
         Self {
             orig_code_extent,
-            records: mem::replace(&mut self.records, vec![]),
+            records: std::mem::take(&mut self.records),
         }
     }
 }
@@ -207,8 +206,8 @@ impl PredicateQueue {
     #[inline]
     pub(super) fn take(&mut self) -> Self {
         Self {
-            predicates: mem::replace(&mut self.predicates, vec![]),
+            predicates: std::mem::take(&mut self.predicates),
-            compilation_target: self.compilation_target.clone(),
+            compilation_target: self.compilation_target,
         }
     }
 
@@ -404,7 +403,7 @@ impl<'a> LoadState<'a> for BootstrappingLoadState<'a> {
 
     #[inline(always)]
     fn machine_st(loader: &mut Self::LoaderFieldType) -> &mut MachineState {
-        &mut loader.term_stream.parser.lexer.machine_st
+        loader.term_stream.parser.lexer.machine_st
     }
 
     #[inline(always)]
@@ -467,7 +466,7 @@ impl<'a> LoadState<'a> for InlineLoadState<'a> {
 
     #[inline(always)]
     fn machine_st(load_state: &mut Self::LoaderFieldType) -> &mut MachineState {
-        &mut load_state.machine_st
+        load_state.machine_st
     }
 
     #[inline(always)]
@@ -639,22 +638,19 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                 RetractionRecord::AddedDiscontiguousPredicate(compilation_target, key) => {
                     match compilation_target {
                         CompilationTarget::User => {
-                            self.wam_prelude
+                            if let Some(skeleton) =
-                                .indices
+                                self.wam_prelude.indices.extensible_predicates.get_mut(&key)
-                                .extensible_predicates
+                            {
-                                .get_mut(&key)
+                                skeleton.core.is_discontiguous = false;
-                                .map(|skeleton| {
+                            }
-                                    skeleton.core.is_discontiguous = false;
-                                });
                         }
                         CompilationTarget::Module(module_name) => {
-                            match self.wam_prelude.indices.modules.get_mut(&module_name) {
+                            if let Some(ref mut module) =
-                                Some(ref mut module) => {
+                                self.wam_prelude.indices.modules.get_mut(&module_name)
-                                    module.extensible_predicates.get_mut(&key).map(|skeleton| {
+                            {
-                                        skeleton.core.is_discontiguous = false;
+                                if let Some(skeleton) = module.extensible_predicates.get_mut(&key) {
-                                    });
+                                    skeleton.core.is_discontiguous = false;
                                 }
-                                None => {}
                             }
                         }
                     }
@@ -662,23 +658,20 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                 RetractionRecord::AddedDynamicPredicate(compilation_target, key) => {
                     match compilation_target {
                         CompilationTarget::User => {
-                            self.wam_prelude
+                            if let Some(skeleton) =
-                                .indices
+                                self.wam_prelude.indices.extensible_predicates.get_mut(&key)
-                                .extensible_predicates
+                            {
-                                .get_mut(&key)
+                                skeleton.core.is_dynamic = false;
-                                .map(|skeleton| {
+                            }
-                                    skeleton.core.is_dynamic = false;
-                                });
                         }
                         CompilationTarget::Module(module_name) => {
-                            match self.wam_prelude.indices.modules.get_mut(&module_name) {
+                            if let Some(ref mut module) =
-                                Some(ref mut module) => {
+                                self.wam_prelude.indices.modules.get_mut(&module_name)
-                                    module.extensible_predicates.get_mut(&key).map(|skeleton| {
+                            {
-                                        skeleton.core.is_dynamic = false;
+                                if let Some(skeleton) = module.extensible_predicates.get_mut(&key) {
-                                        skeleton.core.retracted_dynamic_clauses = None;
+                                    skeleton.core.is_dynamic = false;
-                                    });
+                                    skeleton.core.retracted_dynamic_clauses = None;
-                                }
+                                };
-                                None => {}
                             }
                         }
                     }
@@ -686,60 +679,52 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                 RetractionRecord::AddedMultifilePredicate(compilation_target, key) => {
                     match compilation_target {
                         CompilationTarget::User => {
-                            self.wam_prelude
+                            if let Some(skeleton) =
-                                .indices
+                                self.wam_prelude.indices.extensible_predicates.get_mut(&key)
-                                .extensible_predicates
+                            {
-                                .get_mut(&key)
+                                skeleton.core.is_multifile = false;
-                                .map(|skeleton| {
+                            }
-                                    skeleton.core.is_multifile = false;
-                                });
                         }
                         CompilationTarget::Module(module_name) => {
-                            match self.wam_prelude.indices.modules.get_mut(&module_name) {
+                            if let Some(ref mut module) =
-                                Some(ref mut module) => {
+                                self.wam_prelude.indices.modules.get_mut(&module_name)
-                                    module.extensible_predicates.get_mut(&key).map(|skeleton| {
+                            {
-                                        skeleton.core.is_multifile = false;
+                                if let Some(skeleton) = module.extensible_predicates.get_mut(&key) {
-                                    });
+                                    skeleton.core.is_multifile = false;
                                 }
-                                None => {}
                             }
                         }
                     }
                 }
                 RetractionRecord::AddedModuleOp(module_name, mut op_decl) => {
-                    match self.wam_prelude.indices.modules.get_mut(&module_name) {
+                    if let Some(ref mut module) =
-                        Some(ref mut module) => {
+                        self.wam_prelude.indices.modules.get_mut(&module_name)
-                            op_decl.remove(&mut module.op_dir);
+                    {
-                        }
+                        op_decl.remove(&mut module.op_dir);
-                        None => {}
                     }
                 }
                 RetractionRecord::ReplacedModuleOp(module_name, mut op_decl, op_desc) => {
-                    match self.wam_prelude.indices.modules.get_mut(&module_name) {
+                    if let Some(ref mut module) =
-                        Some(ref mut module) => {
+                        self.wam_prelude.indices.modules.get_mut(&module_name)
-                            op_decl.op_desc = op_desc;
+                    {
-                            op_decl.insert_into_op_dir(&mut module.op_dir);
+                        op_decl.op_desc = op_desc;
-                        }
+                        op_decl.insert_into_op_dir(&mut module.op_dir);
-                        None => {}
                     }
                 }
                 RetractionRecord::AddedModulePredicate(module_name, key) => {
-                    match self.wam_prelude.indices.modules.get_mut(&module_name) {
+                    if let Some(ref mut module) =
-                        Some(ref mut module) => {
+                        self.wam_prelude.indices.modules.get_mut(&module_name)
-                            module.code_dir.remove(&key);
+                    {
-                        }
+                        module.code_dir.remove(&key);
-                        None => {}
                     }
                 }
                 RetractionRecord::ReplacedModulePredicate(module_name, key, old_code_idx) => {
-                    match self.wam_prelude.indices.modules.get_mut(&module_name) {
+                    if let Some(ref mut module) =
-                        Some(ref mut module) => {
+                        self.wam_prelude.indices.modules.get_mut(&module_name)
-                            module
+                    {
-                                .code_dir
+                        if let Some(code_idx) = module.code_dir.get_mut(&key) {
-                                .get_mut(&key)
+                            code_idx.set(old_code_idx)
-                                .map(|code_idx| code_idx.set(old_code_idx));
                         }
-                        None => {}
                     }
                 }
                 RetractionRecord::AddedExtensiblePredicate(compilation_target, key) => {
@@ -758,11 +743,9 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                     self.wam_prelude.indices.code_dir.remove(&key);
                 }
                 RetractionRecord::ReplacedUserPredicate(key, old_code_idx) => {
-                    self.wam_prelude
+                    if let Some(code_idx) = self.wam_prelude.indices.code_dir.get_mut(&key) {
-                        .indices
+                        code_idx.set(old_code_idx)
-                        .code_dir
+                    }
-                        .get_mut(&key)
-                        .map(|code_idx| code_idx.set(old_code_idx));
                 }
                 RetractionRecord::AddedIndex(index_key, clause_loc) => {
                     if let Some(index_loc) = index_key.switch_on_term_loc() {
@@ -832,20 +815,17 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                     };
                 }
                 RetractionRecord::ReplacedSwitchOnTermVarIndex(index_loc, old_v) => {
-                    match self.wam_prelude.code[index_loc] {
+                    if let Instruction::IndexingCode(ref mut indexing_code) =
-                        Instruction::IndexingCode(ref mut indexing_code) => {
+                        self.wam_prelude.code[index_loc]
-                            match &mut indexing_code[0] {
+                    {
-                                IndexingLine::Indexing(IndexingInstruction::SwitchOnTerm(
+                        if let IndexingLine::Indexing(IndexingInstruction::SwitchOnTerm(
-                                    _,
+                            _,
-                                    ref mut v,
+                            ref mut v,
-                                    ..,
+                            ..,
-                                )) => {
+                        )) = &mut indexing_code[0]
-                                    *v = old_v;
+                        {
-                                }
+                            *v = old_v;
-                                _ => {}
-                            }
                         }
-                        _ => {}
                     }
                 }
                 RetractionRecord::ModifiedTryMeElse(instr_loc, o) => {
@@ -858,30 +838,24 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                     self.wam_prelude.code[instr_loc] = Instruction::RevJmpBy(o);
                 }
                 RetractionRecord::SkeletonClausePopBack(compilation_target, key) => {
-                    match self
+                    if let Some(skeleton) = self
                         .wam_prelude
                         .indices
                         .get_predicate_skeleton_mut(&compilation_target, &key)
                     {
-                        Some(skeleton) => {
+                        skeleton.clauses.pop_back();
-                            skeleton.clauses.pop_back();
+                        skeleton.core.clause_clause_locs.pop_back();
-                            skeleton.core.clause_clause_locs.pop_back();
-                        }
-                        None => {}
                     }
                 }
                 RetractionRecord::SkeletonClausePopFront(compilation_target, key) => {
-                    match self
+                    if let Some(skeleton) = self
                         .wam_prelude
                         .indices
                         .get_predicate_skeleton_mut(&compilation_target, &key)
                     {
-                        Some(skeleton) => {
+                        skeleton.clauses.pop_front();
-                            skeleton.clauses.pop_front();
+                        skeleton.core.clause_clause_locs.pop_front();
-                            skeleton.core.clause_clause_locs.pop_front();
+                        skeleton.core.clause_assert_margin -= 1;
-                            skeleton.core.clause_assert_margin -= 1;
-                        }
-                        None => {}
                     }
                 }
                 RetractionRecord::SkeletonLocalClauseClausePopFront(
@@ -891,16 +865,15 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                 ) => {
                     let listing_src_file_name = self.listing_src_file_name();
 
-                    match self.wam_prelude.indices.get_local_predicate_skeleton_mut(
+                    if let Some(skeleton) =
-                        src_compilation_target,
+                        self.wam_prelude.indices.get_local_predicate_skeleton_mut(
-                        local_compilation_target,
+                            src_compilation_target,
-                        listing_src_file_name,
+                            local_compilation_target,
-                        key,
+                            listing_src_file_name,
-                    ) {
+                            key,
-                        Some(skeleton) => {
+                        )
-                            skeleton.clause_clause_locs.pop_front();
+                    {
-                        }
+                        skeleton.clause_clause_locs.pop_front();
-                        None => {}
                     }
                 }
                 RetractionRecord::SkeletonLocalClauseClausePopBack(
@@ -910,16 +883,15 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                 ) => {
                     let listing_src_file_name = self.listing_src_file_name();
 
-                    match self.wam_prelude.indices.get_local_predicate_skeleton_mut(
+                    if let Some(skeleton) =
-                        src_compilation_target,
+                        self.wam_prelude.indices.get_local_predicate_skeleton_mut(
-                        local_compilation_target,
+                            src_compilation_target,
-                        listing_src_file_name,
+                            local_compilation_target,
-                        key,
+                            listing_src_file_name,
-                    ) {
+                            key,
-                        Some(skeleton) => {
+                        )
-                            skeleton.clause_clause_locs.pop_back();
+                    {
-                        }
+                        skeleton.clause_clause_locs.pop_back();
-                        None => {}
                     }
                 }
                 RetractionRecord::SkeletonLocalClauseTruncateBack(
@@ -930,29 +902,25 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                 ) => {
                     let listing_src_file_name = self.listing_src_file_name();
 
-                    match self.wam_prelude.indices.get_local_predicate_skeleton_mut(
+                    if let Some(skeleton) =
-                        src_compilation_target,
+                        self.wam_prelude.indices.get_local_predicate_skeleton_mut(
-                        local_compilation_target,
+                            src_compilation_target,
-                        listing_src_file_name,
+                            local_compilation_target,
-                        key,
+                            listing_src_file_name,
-                    ) {
+                            key,
-                        Some(skeleton) => {
+                        )
-                            skeleton.clause_clause_locs.truncate(len);
+                    {
-                        }
+                        skeleton.clause_clause_locs.truncate(len);
-                        None => {}
                     }
                 }
                 RetractionRecord::SkeletonClauseTruncateBack(compilation_target, key, len) => {
-                    match self
+                    if let Some(skeleton) = self
                         .wam_prelude
                         .indices
                         .get_predicate_skeleton_mut(&compilation_target, &key)
                     {
-                        Some(skeleton) => {
+                        skeleton.clauses.truncate(len);
-                            skeleton.clauses.truncate(len);
+                        skeleton.core.clause_clause_locs.truncate(len);
-                            skeleton.core.clause_clause_locs.truncate(len);
-                        }
-                        None => {}
                     }
                 }
                 RetractionRecord::SkeletonClauseStartReplaced(
@@ -961,15 +929,12 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                     target_pos,
                     clause_start,
                 ) => {
-                    match self
+                    if let Some(skeleton) = self
                         .wam_prelude
                         .indices
                         .get_predicate_skeleton_mut(&compilation_target, &key)
                     {
-                        Some(skeleton) => {
+                        skeleton.clauses[target_pos].clause_start = clause_start;
-                            skeleton.clauses[target_pos].clause_start = clause_start;
-                        }
-                        None => {}
                     }
                 }
                 RetractionRecord::RemovedDynamicSkeletonClause(
@@ -978,26 +943,22 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                     target_pos,
                     clause_clause_loc,
                 ) => {
-                    match self
+                    if let Some(skeleton) = self
                         .wam_prelude
                         .indices
                         .get_predicate_skeleton_mut(&compilation_target, &key)
                     {
-                        Some(skeleton) => {
+                        if let Some(removed_clauses) = &mut skeleton.core.retracted_dynamic_clauses
-                            if let Some(removed_clauses) =
+                        {
-                                &mut skeleton.core.retracted_dynamic_clauses
+                            let clause_index_info = removed_clauses.pop().unwrap();
-                            {
-                                let clause_index_info = removed_clauses.pop().unwrap();
 
-                                skeleton
+                            skeleton
-                                    .core
+                                .core
-                                    .clause_clause_locs
+                                .clause_clause_locs
-                                    .insert(target_pos, clause_clause_loc);
+                                .insert(target_pos, clause_clause_loc);
 
-                                skeleton.clauses.insert(target_pos, clause_index_info);
+                            skeleton.clauses.insert(target_pos, clause_index_info);
-                            }
                         }
-                        None => {}
                     }
                 }
                 RetractionRecord::RemovedSkeletonClause(
@@ -1007,19 +968,16 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                     clause_index_info,
                     clause_clause_loc,
                 ) => {
-                    match self
+                    if let Some(skeleton) = self
                         .wam_prelude
                         .indices
                         .get_predicate_skeleton_mut(&compilation_target, &key)
                     {
-                        Some(skeleton) => {
+                        skeleton
-                            skeleton
+                            .core
-                                .core
+                            .clause_clause_locs
-                                .clause_clause_locs
+                            .insert(target_pos, clause_clause_loc);
-                                .insert(target_pos, clause_clause_loc);
+                        skeleton.clauses.insert(target_pos, clause_index_info);
-                            skeleton.clauses.insert(target_pos, clause_index_info);
-                        }
-                        None => {}
                     }
                 }
                 RetractionRecord::ReplacedIndexingLine(index_loc, indexing_code) => {
@@ -1033,14 +991,15 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
                 ) => {
                     let listing_src_file_name = self.listing_src_file_name();
 
-                    match self.wam_prelude.indices.get_local_predicate_skeleton_mut(
+                    if let Some(skeleton) =
-                        compilation_target,
+                        self.wam_prelude.indices.get_local_predicate_skeleton_mut(
-                        local_compilation_target,
+                            compilation_target,
-                        listing_src_file_name,
+                            local_compilation_target,
-                        key,
+                            listing_src_file_name,
-                    ) {
+                            key,
-                        Some(skeleton) => skeleton.clause_clause_locs = clause_locs,
+                        )
-                        None => {}
+                    {
+                        skeleton.clause_clause_locs = clause_locs
                     }
                 }
                 RetractionRecord::RemovedSkeleton(compilation_target, key, skeleton) => {
@@ -1091,7 +1050,7 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
 
         let export_list = machine_st.read_term_from_heap(cell);
         let atom_tbl = &mut LS::machine_st(&mut self.payload).atom_tbl;
-        let export_list = setup_module_export_list(export_list, &atom_tbl)?;
+        let export_list = setup_module_export_list(export_list, atom_tbl)?;
 
         Ok(export_list.into_iter().collect())
     }
@@ -1363,7 +1322,7 @@ impl<'a, LS: LoadState<'a>> Loader<'a, LS> {
             *key,
         ) {
             Some(skeleton) if !skeleton.clause_clause_locs.is_empty() => {
-                mem::replace(&mut skeleton.clause_clause_locs, VecDeque::new())
+                std::mem::take(&mut skeleton.clause_clause_locs)
             }
             _ => return,
         };
@@ -1400,9 +1359,7 @@ impl<'a> MachinePreludeView<'a> {
             CompilationTarget::User => CompositeOpDir::new(&self.indices.op_dir, None),
             CompilationTarget::Module(ref module_name) => {
                 match self.indices.modules.get(module_name) {
-                    Some(ref module) => {
+                    Some(module) => CompositeOpDir::new(&self.indices.op_dir, Some(&module.op_dir)),
-                        CompositeOpDir::new(&self.indices.op_dir, Some(&module.op_dir))
-                    }
                     None => {
                         unreachable!()
                     }
@@ -1413,13 +1370,10 @@ impl<'a> MachinePreludeView<'a> {
 }
 
 impl MachineState {
-    pub(super) fn read_term_from_heap(
+    pub(super) fn read_term_from_heap(&mut self, term_addr: HeapCellValue) -> Term {
-        &mut self,
-        term_addr: HeapCellValue,
-    ) -> Term {
         let mut term_stack = vec![];
-        let mut iter = stackful_post_order_iter::<NonListElider>
+        let mut iter =
-            (&mut self.heap, &mut self.stack, term_addr);
+            stackful_post_order_iter::<NonListElider>(&mut self.heap, &mut self.stack, term_addr);
 
         while let Some(addr) = iter.next() {
             let addr = unmark_cell_bits!(addr);
@@ -1652,10 +1606,10 @@ impl Machine {
 
         let arity = self.deref_register(3);
         let arity = match Number::try_from(arity) {
-            Ok(Number::Integer(n)) if &*n >= &Integer::ZERO && &*n <= &Integer::from(MAX_ARITY) => {
+            Ok(Number::Integer(n)) if *n >= Integer::ZERO && *n <= Integer::from(MAX_ARITY) => {
                 let value: usize = (&*n).try_into().unwrap();
                 Ok(value)
-            },
+            }
             Ok(Number::Fixnum(n)) if n.get_num() >= 0 && n.get_num() <= MAX_ARITY as i64 => {
                 Ok(usize::try_from(n.get_num()).unwrap())
             }
@@ -1770,14 +1724,11 @@ impl Machine {
                         &ListingSource::DynamicallyGenerated,
                     );
 
-                    match loader.wam_prelude.indices.modules.get_mut(&module_name) {
+                    if let Some(module) = loader.wam_prelude.indices.modules.get_mut(&module_name) {
-                        Some(module) => {
+                        for (key, value) in module.op_dir.drain(0..) {
-                            for (key, value) in module.op_dir.drain(0..) {
+                            let mut op_decl = OpDecl::new(value, key.0);
-                                let mut op_decl = OpDecl::new(value, key.0);
+                            op_decl.remove(&mut loader.wam_prelude.indices.op_dir);
-                                op_decl.remove(&mut loader.wam_prelude.indices.op_dir);
-                            }
                         }
-                        None => {}
                     }
                 }
             }
@@ -1789,10 +1740,10 @@ impl Machine {
         self.restore_load_state_payload(result)
     }
 
-    pub(crate) fn loader_from_heap_evacuable<'a>(
+    pub(crate) fn loader_from_heap_evacuable(
-        &'a mut self,
+        &mut self,
         r: RegType,
-    ) -> Loader<'a, LiveLoadAndMachineState<'a>> {
+    ) -> Loader<'_, LiveLoadAndMachineState<'_>> {
         let mut load_state = cell_as_load_state_payload!(self
             .machine_st
             .store(self.machine_st.deref(self.machine_st[r])));
@@ -1868,7 +1819,7 @@ impl Machine {
         let path = cell_as_atom!(self.deref_register(2));
 
         self.load_contexts
-            .push(LoadContext::new(&*path.as_str(), stream));
+            .push(LoadContext::new(&path.as_str(), stream));
         Ok(())
     }
 
@@ -2021,8 +1972,8 @@ impl Machine {
 
             loader.payload.compilation_target = compilation_target;
 
-            let head = LiveLoadAndMachineState::machine_st(&mut loader.payload)
+            let head =
-                .read_term_from_heap(head);
+                LiveLoadAndMachineState::machine_st(&mut loader.payload).read_term_from_heap(head);
 
             let name = if let Some(name) = head.name() {
                 name
@@ -2218,7 +2169,7 @@ impl Machine {
             Ok(Number::Integer(n)) => {
                 let value: usize = (&*n).try_into().unwrap();
                 value
-            },
+            }
             Ok(Number::Fixnum(n)) => usize::try_from(n.get_num()).unwrap(),
             _ => unreachable!(),
         };
@@ -2520,7 +2471,7 @@ pub(super) fn load_module(
 
     import_module_exports::<LiveLoadAndMachineState>(
         &mut payload,
-        &compilation_target,
+        compilation_target,
         module,
         code_dir,
         op_dir,

src/machine/machine_errors.rs

@@ -80,7 +80,7 @@ impl ValidType {
 #[derive(Debug, Clone, Copy)]
 pub(crate) enum ResourceError {
     FiniteMemory(HeapCellValue),
-    OutOfFiles
+    OutOfFiles,
 }
 
 pub(crate) trait TypeError {
@@ -170,7 +170,11 @@ impl PermissionError for Atom {
     ) -> MachineError {
         let stub = functor!(
             atom!("permission_error"),
-            [atom(perm.as_atom()), atom(index_atom), cell(atom_as_cell!(self))]
+            [
+                atom(perm.as_atom()),
+                atom(index_atom),
+                cell(atom_as_cell!(self))
+            ]
         );
 
         MachineError {
@@ -319,10 +323,7 @@ impl MachineState {
                 )
             }
             ResourceError::OutOfFiles => {
-                functor!(
+                functor!(atom!("resource_error"), [atom(atom!("file_descriptors"))])
-                    atom!("resource_error"),
-                    [atom(atom!("file_descriptors"))]
-                )
             }
         };
 
@@ -355,13 +356,21 @@ impl MachineState {
                     from: ErrorProvenance::Received,
                 }
             }
-            ExistenceError::QualifiedProcedure { module_name, name, arity } => {
+            ExistenceError::QualifiedProcedure {
+                module_name,
+                name,
+                arity,
+            } => {
                 let h = self.heap.len();
 
                 let ind_stub = functor!(atom!("/"), [atom(name), fixnum(arity)]);
                 let res_stub = functor!(atom!(":"), [atom(module_name), str(h + 3, 0)], [ind_stub]);
 
-                let stub = functor!(atom!("existence_error"), [atom(atom!("procedure")), str(h, 0)], [res_stub]);
+                let stub = functor!(
+                    atom!("existence_error"),
+                    [atom(atom!("procedure")), str(h, 0)],
+                    [res_stub]
+                );
 
                 MachineError {
                     stub,
@@ -472,21 +481,15 @@ impl MachineState {
 
     pub(super) fn session_error(&mut self, err: SessionError) -> MachineError {
         match err {
-            SessionError::CannotOverwriteBuiltIn(key) => {
+            SessionError::CannotOverwriteBuiltIn(key) => self.permission_error(
-                self.permission_error(
+                Permission::Modify,
-                    Permission::Modify,
+                atom!("static_procedure"),
-                    atom!("static_procedure"),
+                functor_stub(key.0, key.1)
-                    functor_stub(key.0, key.1)
+                    .into_iter()
-                        .into_iter()
+                    .collect::<MachineStub>(),
-                        .collect::<MachineStub>(),
+            ),
-                )
-            }
             SessionError::CannotOverwriteBuiltInModule(module) => {
-                self.permission_error(
+                self.permission_error(Permission::Modify, atom!("static_module"), module)
-                    Permission::Modify,
-                    atom!("static_module"),
-                    module,
-                )
             }
             SessionError::ExistenceError(err) => self.existence_error(err),
             SessionError::ModuleDoesNotContainExport(..) => {
@@ -641,7 +644,7 @@ impl MachineState {
         self.ball.boundary = 0;
         self.ball.stub.truncate(0);
 
-        self.heap.extend(err.into_iter());
+        self.heap.extend(err);
 
         self.registers[1] = if err_len == 1 {
             heap_loc_as_cell!(h)
@@ -705,58 +708,58 @@ impl From<ParserError> for CompilationError {
 impl CompilationError {
     pub(crate) fn line_and_col_num(&self) -> Option<(usize, usize)> {
         match self {
-            &CompilationError::ParserError(ref err) => err.line_and_col_num(),
+            CompilationError::ParserError(err) => err.line_and_col_num(),
             _ => None,
         }
     }
 
     pub(crate) fn as_functor(&self) -> MachineStub {
         match self {
-            &CompilationError::Arithmetic(..) => {
+            CompilationError::Arithmetic(..) => {
                 functor!(atom!("arithmetic_error"))
             }
-            &CompilationError::CannotParseCyclicTerm => {
+            CompilationError::CannotParseCyclicTerm => {
                 functor!(atom!("cannot_parse_cyclic_term"))
             }
-            &CompilationError::ExceededMaxArity => {
+            CompilationError::ExceededMaxArity => {
                 functor!(atom!("exceeded_max_arity"))
             }
-            &CompilationError::ExpectedRel => {
+            CompilationError::ExpectedRel => {
                 functor!(atom!("expected_relation"))
             }
-            &CompilationError::InadmissibleFact => {
+            CompilationError::InadmissibleFact => {
                 // TODO: type_error(callable, _).
                 functor!(atom!("inadmissible_fact"))
             }
-            &CompilationError::InadmissibleQueryTerm => {
+            CompilationError::InadmissibleQueryTerm => {
                 // TODO: type_error(callable, _).
                 functor!(atom!("inadmissible_query_term"))
             }
-            &CompilationError::InconsistentEntry => {
+            CompilationError::InconsistentEntry => {
                 functor!(atom!("inconsistent_entry"))
             }
-            &CompilationError::InvalidMetaPredicateDecl => {
+            CompilationError::InvalidMetaPredicateDecl => {
                 functor!(atom!("invalid_meta_predicate_decl"))
             }
-            &CompilationError::InvalidModuleDecl => {
+            CompilationError::InvalidModuleDecl => {
                 functor!(atom!("invalid_module_declaration"))
             }
-            &CompilationError::InvalidModuleExport => {
+            CompilationError::InvalidModuleExport => {
                 functor!(atom!("invalid_module_export"))
             }
-            &CompilationError::InvalidModuleResolution(ref module_name) => {
+            CompilationError::InvalidModuleResolution(ref module_name) => {
                 functor!(atom!("no_such_module"), [atom(module_name)])
             }
-            &CompilationError::InvalidRuleHead => {
+            CompilationError::InvalidRuleHead => {
                 functor!(atom!("invalid_head_of_rule")) // TODO: type_error(callable, _).
             }
-            &CompilationError::InvalidUseModuleDecl => {
+            CompilationError::InvalidUseModuleDecl => {
                 functor!(atom!("invalid_use_module_declaration"))
             }
-            &CompilationError::ParserError(ref err) => {
+            CompilationError::ParserError(ref err) => {
                 functor!(err.as_atom())
             }
-            &CompilationError::UnreadableTerm => {
+            CompilationError::UnreadableTerm => {
                 functor!(atom!("unreadable_term"))
             }
         }
@@ -986,7 +989,11 @@ pub enum ExistenceError {
     Module(Atom),
     ModuleSource(ModuleSource),
     Procedure(Atom, usize),
-    QualifiedProcedure { module_name: Atom, name: Atom, arity: usize },
+    QualifiedProcedure {
+        module_name: Atom,
+        name: Atom,
+        arity: usize,
+    },
     SourceSink(HeapCellValue),
     Stream(HeapCellValue),
 }

src/machine/machine_indices.rs

@@ -118,18 +118,12 @@ impl IndexPtr {
 
     #[inline(always)]
     pub(crate) fn is_undefined(&self) -> bool {
-        match self.tag() {
+        matches!(self.tag(), IndexPtrTag::Undefined)
-            IndexPtrTag::Undefined => true,
-            _ => false,
-        }
     }
 
     #[inline(always)]
     pub(crate) fn is_dynamic_undefined(&self) -> bool {
-        match self.tag() {
+        matches!(self.tag(), IndexPtrTag::DynamicUndefined)
-            IndexPtrTag::DynamicUndefined => true,
-            _ => false,
-        }
     }
 }
 
@@ -231,6 +225,7 @@ pub enum VarKey {
 }
 
 impl VarKey {
+    #[allow(clippy::inherent_to_string)]
     #[inline]
     pub(crate) fn to_string(&self) -> String {
         match self {
@@ -241,11 +236,7 @@ impl VarKey {
 
     #[inline(always)]
     pub(crate) fn is_anon(&self) -> bool {
-        if let VarKey::AnonVar(_) = self {
+        matches!(self, VarKey::AnonVar(_))
-            true
-        } else {
-            false
-        }
     }
 }
 
@@ -429,9 +420,9 @@ impl IndexStore {
         match compilation_target {
             CompilationTarget::User => self.meta_predicates.get(&(name, arity)),
             CompilationTarget::Module(ref module_name) => match self.modules.get(module_name) {
-                Some(ref module) => module
+                Some(module) => module
                     .meta_predicates
-                    .get(&(name.clone(), arity))
+                    .get(&(name, arity))
                     .or_else(|| self.meta_predicates.get(&(name, arity))),
                 None => self.meta_predicates.get(&(name, arity)),
             },
@@ -446,7 +437,7 @@ impl IndexStore {
                 .map(|skeleton| skeleton.core.is_dynamic)
                 .unwrap_or(false),
             _ => match self.modules.get(&module_name) {
-                Some(ref module) => module
+                Some(module) => module
                     .extensible_predicates
                     .get(&key)
                     .map(|skeleton| skeleton.core.is_dynamic)

src/machine/machine_state.rs

@@ -413,7 +413,7 @@ impl MachineState {
     }
 
     pub(crate) fn increment_call_count(&mut self) -> bool {
-        if self.cwil.inference_limit_exceeded || self.ball.stub.len() > 0 {
+        if self.cwil.inference_limit_exceeded || !self.ball.stub.is_empty() {
             return true;
         }
 
@@ -590,7 +590,9 @@ impl MachineState {
 
         let mut singleton_var_set: IndexMap<Ref, bool> = IndexMap::new();
 
-        for cell in stackful_preorder_iter::<NonListElider>(&mut self.heap, &mut self.stack, heap_loc) {
+        for cell in
+            stackful_preorder_iter::<NonListElider>(&mut self.heap, &mut self.stack, heap_loc)
+        {
             let cell = unmark_cell_bits!(cell);
 
             if let Some(var) = cell.as_var() {
@@ -644,10 +646,8 @@ impl MachineState {
     ) -> Result<OnEOF, MachineStub> {
         self.eof_action(self.registers[2], stream, atom!("read_term"), 3)?;
 
-        if stream.options().eof_action() == EOFAction::Reset {
+        if stream.options().eof_action() == EOFAction::Reset && !self.fail {
-            if self.fail == false {
+            return Ok(OnEOF::Continue);
-                return Ok(OnEOF::Continue);
-            }
         }
 
         Ok(OnEOF::Return)
@@ -674,10 +674,10 @@ impl MachineState {
 
         if let Stream::Byte(_) = stream {
             return self.read_term(
-                stream, 
+                stream,
-                indices, 
+                indices,
-                MachineState::read_term_from_user_input_eof_handler
+                MachineState::read_term_from_user_input_eof_handler,
-            )
+            );
         }
 
         unreachable!("Stream must be a Stream::Readline(_)")
@@ -691,10 +691,8 @@ impl MachineState {
         } else if stream.past_end_of_stream() {
             self.eof_action(self.registers[2], stream, atom!("read_term"), 3)?;
 
-            if stream.options().eof_action() == EOFAction::Reset {
+            if stream.options().eof_action() == EOFAction::Reset && !self.fail {
-                if self.fail == false {
+                return Ok(OnEOF::Continue);
-                    return Ok(OnEOF::Continue);
-                }
             }
         }
 
@@ -716,11 +714,7 @@ impl MachineState {
         )?;
 
         if stream.past_end_of_stream() {
-            if EOFAction::Reset != stream.options().eof_action() {
+            return Ok(());
-                return Ok(());
-            } else if self.fail {
-                return Ok(());
-            }
         }
 
         loop {
@@ -970,6 +964,7 @@ impl MachineState {
     }
 }
 
+#[allow(clippy::upper_case_acronyms)]
 #[derive(Debug)]
 pub(crate) struct CWIL {
     count: Integer,

src/machine/machine_state_impl.rs

@@ -149,7 +149,7 @@ impl MachineState {
             TrailRef::BlackboardEntry(key_atom) => {
                 self.trail.push(TrailEntry::build_with(
                     TrailEntryTag::TrailedBlackboardEntry,
-                    key_atom.index as u64,
+                    key_atom.index,
                 ));
 
                 self.tr += 1;
@@ -157,7 +157,7 @@ impl MachineState {
             TrailRef::BlackboardOffset(key_atom, value_cell) => {
                 self.trail.push(TrailEntry::build_with(
                     TrailEntryTag::TrailedBlackboardOffset,
-                    key_atom.index as u64,
+                    key_atom.index,
                 ));
 
                 self.trail
@@ -432,8 +432,7 @@ impl MachineState {
     pub fn compare_term_test(&mut self, var_comparison: VarComparison) -> Option<Ordering> {
         let mut tabu_list = IndexSet::new();
 
-        while !self.pdl.is_empty() {
+        while let Some(s1) = self.pdl.pop() {
-            let s1 = self.pdl.pop().unwrap();
             let s1 = self.deref(s1);
 
             let s2 = self.pdl.pop().unwrap();
@@ -896,7 +895,7 @@ impl MachineState {
 
         let s = string.as_str();
 
-        match heap_pstr_iter.compare_pstr_to_string(&*s) {
+        match heap_pstr_iter.compare_pstr_to_string(&s) {
             Some(PStrPrefixCmpResult {
                 focus,
                 offset,
@@ -1142,7 +1141,7 @@ impl MachineState {
 
         let cycle_found = {
             let mut iter = cycle_detecting_stackless_preorder_iter(&mut self.heap, h);
-            while let Some(_) = iter.next() {}
+            for _ in iter.by_ref() {}
             iter.cycle_found()
         };
 
@@ -1376,7 +1375,7 @@ impl MachineState {
 
                 let mut type_error = |arity| {
                     let err = self.type_error(ValidType::Integer, arity);
-                    return Err(self.error_form(err, stub_gen()));
+                    Err(self.error_form(err, stub_gen()))
                 };
 
                 let arity = match Number::try_from(arity) {
@@ -1573,7 +1572,7 @@ impl MachineState {
     ) -> Result<Vec<HeapCellValue>, MachineStub> {
         let mut heap_pstr_iter = HeapPStrIter::new(&self.heap, h);
 
-        while let Some(iteratee) = heap_pstr_iter.next() {
+        for iteratee in heap_pstr_iter.by_ref() {
             match iteratee {
                 PStrIteratee::Char(_, c) => chars.push(char_as_cell!(c)),
                 PStrIteratee::PStrSegment(_, pstr_atom, n) => {
@@ -1644,10 +1643,11 @@ impl MachineState {
                     let addr = self.store(self.deref(addr));
 
                     match Number::try_from(addr) {
-                        Ok(Number::Fixnum(n)) => match u8::try_from(n.get_num()) {
+                        Ok(Number::Fixnum(n)) => {
-                            Ok(b) => bytes.push(b),
+                            if let Ok(b) = u8::try_from(n.get_num()) {
-                            Err(_) => {}
+                                bytes.push(b)
-                        },
+                            }
+                        }
                         Ok(Number::Integer(n)) => {
                             let b: u8 = (&*n).try_into().unwrap();
 

src/machine/mock_wam.rs

@@ -82,6 +82,12 @@ impl MockWAM {
     }
 }
 
+impl Default for MockWAM {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
 #[cfg(test)]
 pub struct TermCopyingMockWAM<'a> {
     pub wam: &'a mut MockWAM,
@@ -109,14 +115,14 @@ impl<'a> Deref for TermCopyingMockWAM<'a> {
     type Target = MockWAM;
 
     fn deref(&self) -> &Self::Target {
-        &self.wam
+        self.wam
     }
 }
 
 #[cfg(test)]
 impl<'a> DerefMut for TermCopyingMockWAM<'a> {
     fn deref_mut(&mut self) -> &mut Self::Target {
-        &mut self.wam
+        self.wam
     }
 }
 
@@ -165,9 +171,8 @@ impl<'a> CopierTarget for TermCopyingMockWAM<'a> {
 #[cfg(test)]
 pub fn all_cells_marked_and_unforwarded(heap: &[HeapCellValue]) {
     for (idx, cell) in heap.iter().enumerate() {
-        assert_eq!(
+        assert!(
             cell.get_mark_bit(),
-            true,
             "cell {:?} at index {} is not marked",
             cell,
             idx
@@ -230,20 +235,16 @@ impl Machine {
             &mut self.machine_st.arena,
         );
 
-        self.load_file(file.into(), stream);
+        self.load_file(file, stream);
         self.user_output.bytes().map(|b| b.unwrap()).collect()
     }
 
     pub fn test_load_string(&mut self, code: &str) -> Vec<u8> {
-        let stream = Stream::from_owned_string(
+        let stream = Stream::from_owned_string(code.to_owned(), &mut self.machine_st.arena);
-            code.to_owned(),
-            &mut self.machine_st.arena,
-        );
 
-        self.load_file("<stdin>".into(), stream);
+        self.load_file("<stdin>", stream);
         self.user_output.bytes().map(|b| b.unwrap()).collect()
     }
-
 }
 
 #[cfg(test)]

src/machine/mod.rs

@@ -53,6 +53,8 @@ use indexmap::IndexMap;
 use lazy_static::lazy_static;
 use ordered_float::OrderedFloat;
 
+use rand::rngs::StdRng;
+use rand::SeedableRng;
 use std::cmp::Ordering;
 use std::env;
 use std::io::Read;
@@ -61,8 +63,6 @@ use std::sync::atomic::AtomicBool;
 
 use self::config::MachineConfig;
 use self::parsed_results::*;
-use rand::rngs::StdRng;
-use rand::SeedableRng;
 
 lazy_static! {
     pub static ref INTERRUPT: AtomicBool = AtomicBool::new(false);
@@ -172,7 +172,7 @@ pub(crate) fn import_builtin_impls(code_dir: &CodeDir, builtins: &mut Module) {
 
     for key in keys {
         let idx = code_dir.get(&key).unwrap();
-        builtins.code_dir.insert(key, idx.clone());
+        builtins.code_dir.insert(key, *idx);
         builtins
             .module_decl
             .exports
@@ -225,7 +225,7 @@ impl Machine {
         key: PredicateKey,
     ) -> std::process::ExitCode {
         if let Some(module) = self.indices.modules.get(&module_name) {
-            if let Some(ref code_index) = module.code_dir.get(&key) {
+            if let Some(code_index) = module.code_dir.get(&key) {
                 let p = code_index.local().unwrap();
 
                 self.machine_st.cp = BREAK_FROM_DISPATCH_LOOP_LOC;
@@ -252,9 +252,7 @@ impl Machine {
         path_buf.push("src/toplevel.pl");
 
         let path = path_buf.to_str().unwrap();
-        let toplevel_stream = 
+        let toplevel_stream = Stream::from_static_string(program, &mut self.machine_st.arena);
-            Stream::from_static_string(program, &mut self.machine_st.arena);
-
 
         self.load_file(path, toplevel_stream);
 
@@ -300,7 +298,11 @@ impl Machine {
         }
     }
 
-    pub fn run_top_level(&mut self, module_name: Atom, key: PredicateKey) -> std::process::ExitCode {
+    pub fn run_top_level(
+        &mut self,
+        module_name: Atom,
+        key: PredicateKey,
+    ) -> std::process::ExitCode {
         let mut arg_pstrs = vec![];
 
         for arg in env::args() {
@@ -400,57 +402,51 @@ impl Machine {
     pub(crate) fn add_impls_to_indices(&mut self) {
         let impls_offset = self.code.len() + 4;
 
-        self.code.extend(
+        self.code.extend(vec![
-            vec![
+            Instruction::BreakFromDispatchLoop,
-                Instruction::BreakFromDispatchLoop,
+            Instruction::InstallVerifyAttr,
-                Instruction::InstallVerifyAttr,
+            Instruction::VerifyAttrInterrupt,
-                Instruction::VerifyAttrInterrupt,
+            Instruction::BreakFromDispatchLoop, // the location of LIB_QUERY_SUCCESS
-                Instruction::BreakFromDispatchLoop, // the location of LIB_QUERY_SUCCESS
+            Instruction::ExecuteTermGreaterThan,
-                Instruction::ExecuteTermGreaterThan,
+            Instruction::ExecuteTermLessThan,
-                Instruction::ExecuteTermLessThan,
+            Instruction::ExecuteTermGreaterThanOrEqual,
-                Instruction::ExecuteTermGreaterThanOrEqual,
+            Instruction::ExecuteTermLessThanOrEqual,
-                Instruction::ExecuteTermLessThanOrEqual,
+            Instruction::ExecuteTermEqual,
-                Instruction::ExecuteTermEqual,
+            Instruction::ExecuteTermNotEqual,
-                Instruction::ExecuteTermNotEqual,
+            Instruction::ExecuteNumberGreaterThan(ar_reg!(temp_v!(1)), ar_reg!(temp_v!(2))),
-                Instruction::ExecuteNumberGreaterThan(ar_reg!(temp_v!(1)), ar_reg!(temp_v!(2))),
+            Instruction::ExecuteNumberLessThan(ar_reg!(temp_v!(1)), ar_reg!(temp_v!(2))),
-                Instruction::ExecuteNumberLessThan(ar_reg!(temp_v!(1)), ar_reg!(temp_v!(2))),
+            Instruction::ExecuteNumberGreaterThanOrEqual(ar_reg!(temp_v!(1)), ar_reg!(temp_v!(2))),
-                Instruction::ExecuteNumberGreaterThanOrEqual(
+            Instruction::ExecuteNumberLessThanOrEqual(ar_reg!(temp_v!(1)), ar_reg!(temp_v!(2))),
-                    ar_reg!(temp_v!(1)),
+            Instruction::ExecuteNumberEqual(ar_reg!(temp_v!(1)), ar_reg!(temp_v!(2))),
-                    ar_reg!(temp_v!(2)),
+            Instruction::ExecuteNumberNotEqual(ar_reg!(temp_v!(1)), ar_reg!(temp_v!(2))),
-                ),
+            Instruction::ExecuteIs(temp_v!(1), ar_reg!(temp_v!(2))),
-                Instruction::ExecuteNumberLessThanOrEqual(ar_reg!(temp_v!(1)), ar_reg!(temp_v!(2))),
+            Instruction::ExecuteAcyclicTerm,
-                Instruction::ExecuteNumberEqual(ar_reg!(temp_v!(1)), ar_reg!(temp_v!(2))),
+            Instruction::ExecuteArg,
-                Instruction::ExecuteNumberNotEqual(ar_reg!(temp_v!(1)), ar_reg!(temp_v!(2))),
+            Instruction::ExecuteCompare,
-                Instruction::ExecuteIs(temp_v!(1), ar_reg!(temp_v!(2))),
+            Instruction::ExecuteCopyTerm,
-                Instruction::ExecuteAcyclicTerm,
+            Instruction::ExecuteFunctor,
-                Instruction::ExecuteArg,
+            Instruction::ExecuteGround,
-                Instruction::ExecuteCompare,
+            Instruction::ExecuteKeySort,
-                Instruction::ExecuteCopyTerm,
+            Instruction::ExecuteSort,
-                Instruction::ExecuteFunctor,
+            Instruction::ExecuteN(1),
-                Instruction::ExecuteGround,
+            Instruction::ExecuteN(2),
-                Instruction::ExecuteKeySort,
+            Instruction::ExecuteN(3),
-                Instruction::ExecuteSort,
+            Instruction::ExecuteN(4),
-                Instruction::ExecuteN(1),
+            Instruction::ExecuteN(5),
-                Instruction::ExecuteN(2),
+            Instruction::ExecuteN(6),
-                Instruction::ExecuteN(3),
+            Instruction::ExecuteN(7),
-                Instruction::ExecuteN(4),
+            Instruction::ExecuteN(8),
-                Instruction::ExecuteN(5),
+            Instruction::ExecuteN(9),
-                Instruction::ExecuteN(6),
+            Instruction::ExecuteIsAtom(temp_v!(1)),
-                Instruction::ExecuteN(7),
+            Instruction::ExecuteIsAtomic(temp_v!(1)),
-                Instruction::ExecuteN(8),
+            Instruction::ExecuteIsCompound(temp_v!(1)),
-                Instruction::ExecuteN(9),
+            Instruction::ExecuteIsInteger(temp_v!(1)),
-                Instruction::ExecuteIsAtom(temp_v!(1)),
+            Instruction::ExecuteIsNumber(temp_v!(1)),
-                Instruction::ExecuteIsAtomic(temp_v!(1)),
+            Instruction::ExecuteIsRational(temp_v!(1)),
-                Instruction::ExecuteIsCompound(temp_v!(1)),
+            Instruction::ExecuteIsFloat(temp_v!(1)),
-                Instruction::ExecuteIsInteger(temp_v!(1)),
+            Instruction::ExecuteIsNonVar(temp_v!(1)),
-                Instruction::ExecuteIsNumber(temp_v!(1)),
+            Instruction::ExecuteIsVar(temp_v!(1)),
-                Instruction::ExecuteIsRational(temp_v!(1)),
+        ]);
-                Instruction::ExecuteIsFloat(temp_v!(1)),
-                Instruction::ExecuteIsNonVar(temp_v!(1)),
-                Instruction::ExecuteIsVar(temp_v!(1)),
-            ]
-            .into_iter(),
-        );
 
         for (p, instr) in self.code[impls_offset..].iter().enumerate() {
             let key = instr.to_name_and_arity();
@@ -464,6 +460,7 @@ impl Machine {
         }
     }
 
+    #[allow(clippy::new_without_default)]
     pub fn new(config: MachineConfig) -> Self {
         use ref_thread_local::RefThreadLocal;
 
@@ -1048,7 +1045,7 @@ impl Machine {
         self.reset_attr_var_state(or_frame.prelude.attr_var_queue_len);
 
         self.machine_st.hb = target_h;
-        self.machine_st.p = self.machine_st.p + offset;
+        self.machine_st.p += offset;
 
         self.machine_st.stack.truncate(b);
         self.machine_st.heap.truncate(target_h);
@@ -1174,21 +1171,23 @@ impl Machine {
             } else {
                 Err(self.machine_st.throw_undefined_error(name, arity))
             }
-        } else {
+        } else if let Some(module) = self.indices.modules.get(&module_name) {
-            if let Some(module) = self.indices.modules.get(&module_name) {
+            if let Some(idx) = module.code_dir.get(&(name, arity)).cloned() {
-                if let Some(idx) = module.code_dir.get(&(name, arity)).cloned() {
+                self.try_call(name, arity, idx.get())
-                    self.try_call(name, arity, idx.get())
-                } else {
-                    self.undefined_procedure(name, arity)
-                }
             } else {
-                let stub = functor_stub(name, arity);
+                self.undefined_procedure(name, arity)
-                let err = self
-                    .machine_st
-                    .existence_error(ExistenceError::QualifiedProcedure { module_name, name, arity });
-
-                Err(self.machine_st.error_form(err, stub))
             }
+        } else {
+            let stub = functor_stub(name, arity);
+            let err = self
+                .machine_st
+                .existence_error(ExistenceError::QualifiedProcedure {
+                    module_name,
+                    name,
+                    arity,
+                });
+
+            Err(self.machine_st.error_form(err, stub))
         }
     }
 
@@ -1202,21 +1201,23 @@ impl Machine {
             } else {
                 self.undefined_procedure(name, arity)
             }
-        } else {
+        } else if let Some(module) = self.indices.modules.get(&module_name) {
-            if let Some(module) = self.indices.modules.get(&module_name) {
+            if let Some(idx) = module.code_dir.get(&(name, arity)).cloned() {
-                if let Some(idx) = module.code_dir.get(&(name, arity)).cloned() {
+                self.try_execute(name, arity, idx.get())
-                    self.try_execute(name, arity, idx.get())
-                } else {
-                    self.undefined_procedure(name, arity)
-                }
             } else {
-                let stub = functor_stub(name, arity);
+                self.undefined_procedure(name, arity)
-                let err = self
-                    .machine_st
-                    .existence_error(ExistenceError::QualifiedProcedure { module_name, name, arity });
-
-                Err(self.machine_st.error_form(err, stub))
             }
+        } else {
+            let stub = functor_stub(name, arity);
+            let err = self
+                .machine_st
+                .existence_error(ExistenceError::QualifiedProcedure {
+                    module_name,
+                    name,
+                    arity,
+                });
+
+            Err(self.machine_st.error_form(err, stub))
         }
     }
 

src/machine/parsed_results.rs

@@ -1,6 +1,6 @@
 use crate::atom_table::*;
-use ordered_float::OrderedFloat;
 use dashu::*;
+use ordered_float::OrderedFloat;
 use std::collections::BTreeMap;
 use std::collections::HashMap;
 
@@ -67,13 +67,10 @@ impl From<Vec<QueryResolutionLine>> for QueryResolution {
 
         // If there is only one line, and it is an empty match, return true.
         if query_result_lines.len() == 1 {
-            match query_result_lines[0].clone() {
+            if let QueryResolutionLine::Match(m) = query_result_lines[0].clone() {
-                QueryResolutionLine::Match(m) => {
+                if m.is_empty() {
-                    if m.is_empty() {
+                    return QueryResolution::True;
-                        return QueryResolution::True;
-                    }
                 }
-                _ => {}
             }
         }
 
@@ -81,13 +78,9 @@ impl From<Vec<QueryResolutionLine>> for QueryResolution {
         if query_result_lines
             .iter()
             .any(|l| l == &QueryResolutionLine::True)
-            && !query_result_lines.iter().any(|l| {
+            && !query_result_lines
-                if let &QueryResolutionLine::Match(_) = l {
+                .iter()
-                    true
+                .any(|l| matches!(l, QueryResolutionLine::Match(_)))
-                } else {
-                    false
-                }
-            })
         {
             return QueryResolution::True;
         }
@@ -95,13 +88,7 @@ impl From<Vec<QueryResolutionLine>> for QueryResolution {
         // If there is at least one match, return all matches.
         let all_matches = query_result_lines
             .into_iter()
-            .filter(|l| {
+            .filter(|l| matches!(l, QueryResolutionLine::Match(_)))
-                if let &QueryResolutionLine::Match(_) = l {
-                    true
-                } else {
-                    false
-                }
-            })
             .map(|l| match l {
                 QueryResolutionLine::Match(m) => QueryMatch::from(m),
                 _ => unreachable!(),
@@ -132,7 +119,11 @@ fn split_response_string(input: &str) -> Vec<String> {
             ')' => level_parenthesis -= 1,
             '"' => in_double_quotes = !in_double_quotes,
             '\'' => in_single_quotes = !in_single_quotes,
-            ',' if level_bracket == 0 && level_parenthesis == 0 && !in_double_quotes && !in_single_quotes => {
+            ',' if level_bracket == 0
+                && level_parenthesis == 0
+                && !in_double_quotes
+                && !in_single_quotes =>
+            {
                 result.push(input[start..i].trim().to_string());
                 start = i + 1;
             }
@@ -167,13 +158,13 @@ fn parse_prolog_response(input: &str) -> HashMap<String, String> {
         let key = result.0;
         let value = result.1;
         // cut off at given characters/strings:
-        let value = value.split("\n").next().unwrap().to_string();
+        let value = value.split('\n').next().unwrap().to_string();
-        let value = value.split("  ").next().unwrap().to_string();
+        let value = value.split(' ').next().unwrap().to_string();
-        let value = value.split("\t").next().unwrap().to_string();
+        let value = value.split('\t').next().unwrap().to_string();
         let value = value.split("error").next().unwrap().to_string();
         map.insert(key, value);
     }
-    
+
     map
 }
 
@@ -192,9 +183,8 @@ impl TryFrom<String> for QueryResolutionLine {
                         Ok((key, Value::try_from(value)?))
                     })
                     .filter_map(Result::ok)
-                    .collect::<BTreeMap<_, _>>()
+                    .collect::<BTreeMap<_, _>>(),
-                )
+            )),
-            ),
         }
     }
 }
@@ -229,25 +219,25 @@ impl TryFrom<String> for Value {
             Ok(Value::Float(OrderedFloat(float_value)))
         } else if let Ok(int_value) = string.parse::<i128>() {
             Ok(Value::Integer(int_value.into()))
-        } else if trimmed.starts_with("'") && trimmed.ends_with("'") {
+        } else if trimmed.starts_with('\'') && trimmed.ends_with('\'')
+            || trimmed.starts_with('"') && trimmed.ends_with('"')
+        {
             Ok(Value::String(trimmed[1..trimmed.len() - 1].into()))
-        } else if trimmed.starts_with("\"") && trimmed.ends_with("\"") {
+        } else if trimmed.starts_with('[') && trimmed.ends_with(']') {
-            Ok(Value::String(trimmed[1..trimmed.len() - 1].into()))
-        } else if trimmed.starts_with("[") && trimmed.ends_with("]") {
             let split = split_nested_list(&trimmed[1..trimmed.len() - 1]);
-            
+
             let values = split
                 .into_iter()
                 .map(Value::try_from)
                 .collect::<Result<Vec<_>, _>>()?;
 
             Ok(Value::List(values))
-        } else if trimmed.starts_with("{") && trimmed.ends_with("}") {
+        } else if trimmed.starts_with('{') && trimmed.ends_with('}') {
-            let mut iter = trimmed[1..trimmed.len() - 1].split(",");
+            let iter = trimmed[1..trimmed.len() - 1].split(',');
             let mut values = vec![];
 
-            while let Some(value) = iter.next() {
+            for value in iter {
-                let items: Vec<_> = value.split(":").collect();
+                let items: Vec<_> = value.split(':').collect();
                 if items.len() == 2 {
                     let _key = items[0].to_string();
                     let value = items[1].to_string();
@@ -257,11 +247,11 @@ impl TryFrom<String> for Value {
 
             Ok(Value::Structure(atom!("{}"), values))
         } else if trimmed.starts_with("<<") && trimmed.ends_with(">>") {
-            let mut iter = trimmed[2..trimmed.len() - 2].split(",");
+            let iter = trimmed[2..trimmed.len() - 2].split(',');
             let mut values = vec![];
 
-            while let Some(value) = iter.next() {
+            for value in iter {
-                let items: Vec<_> = value.split(":").collect();
+                let items: Vec<_> = value.split(':').collect();
                 if items.len() == 2 {
                     let _key = items[0].to_string();
                     let value = items[1].to_string();
@@ -270,7 +260,7 @@ impl TryFrom<String> for Value {
             }
 
             Ok(Value::Structure(atom!("<<>>"), values))
-        } else if !trimmed.contains(",") && !trimmed.contains("'") && !trimmed.contains("\"") {
+        } else if !trimmed.contains(',') && !trimmed.contains('\'') && !trimmed.contains('"') {
             Ok(Value::String(trimmed.into()))
         } else {
             Err(())

src/machine/partial_string.rs

@@ -34,10 +34,10 @@ impl From<Atom> for PartialString {
     }
 }
 
-impl Into<Atom> for PartialString {
+impl From<PartialString> for Atom {
     #[inline]
-    fn into(self: Self) -> Atom {
+    fn from(val: PartialString) -> Self {
-        self.0
+        val.0
     }
 }
 
@@ -45,7 +45,7 @@ impl PartialString {
     #[inline]
     pub(super) fn new<'a>(src: &'a str, atom_tbl: &AtomTable) -> Option<(Self, &'a str)> {
         let terminator_idx = scan_for_terminator(src.chars());
-        let pstr = PartialString(AtomTable::build_with(&atom_tbl, &src[..terminator_idx]));
+        let pstr = PartialString(AtomTable::build_with(atom_tbl, &src[..terminator_idx]));
         Some(if terminator_idx < src.as_bytes().len() {
             (pstr, &src[terminator_idx + 1..])
         } else {
@@ -154,13 +154,13 @@ impl<'a> HeapPStrIter<'a> {
                     let s = &s[result.prefix_len..];
 
                     if s.len() >= t.len() {
-                        if (&*s).starts_with(&*t) {
+                        if s.starts_with(&*t) {
                             result.prefix_len += t.len();
                             result.offset += t.len();
                         } else {
                             return None;
                         }
-                    } else if t.starts_with(&s) {
+                    } else if t.starts_with(s) {
                         result.prefix_len += s.len();
                         result.offset += s.len();
 
@@ -218,10 +218,11 @@ impl<'a> HeapPStrIter<'a> {
         self.brent_st.hare = orig_hare;
     }
 
+    #[allow(clippy::inherent_to_string)]
     pub fn to_string(&mut self) -> String {
         let mut buf = String::with_capacity(32);
 
-        while let Some(iteratee) = self.next() {
+        for iteratee in self.by_ref() {
             match iteratee {
                 PStrIteratee::Char(_, c) => {
                     buf.push(c);
@@ -334,14 +335,10 @@ impl<'a> HeapPStrIter<'a> {
                         heap_bound_deref(self.heap, self.heap[h]),
                     );
 
-                    return if let Some(c) = value.as_char() {
+                    return value.as_char().map(|c| PStrIterStep {
-                        Some(PStrIterStep {
                             iteratee: PStrIteratee::Char(curr_hare, c),
                             next_hare: h+1,
-                        })
+                        });
-                    } else {
-                        None
-                    };
                 }
                 (HeapCellValueTag::Str, s) => {
                     let (name, arity) = cell_as_atom_cell!(self.heap[s])
@@ -353,14 +350,10 @@ impl<'a> HeapPStrIter<'a> {
                             heap_bound_deref(self.heap, self.heap[s+1]),
                         );
 
-                        if let Some(c) = value.as_char() {
+                        value.as_char().map(|c| PStrIterStep {
-                            Some(PStrIterStep {
                                 iteratee: PStrIteratee::Char(curr_hare, c),
                                 next_hare: s+2,
                             })
-                        } else {
-                            None
-                        }
                     } else {
                         None
                     };
@@ -405,10 +398,7 @@ impl<'a> HeapPStrIter<'a> {
 
         match self.brent_st.step(next_hare) {
             Some(cycle_result) => {
-                debug_assert!(match cycle_result {
+                debug_assert!(matches!(cycle_result, CycleSearchResult::Cyclic(..)));
-                    CycleSearchResult::Cyclic(..) => true,
-                    _ => false,
-                });
 
                 self.walk_hare_to_cycle_end();
                 self.stepper = HeapPStrIter::post_cycle_discovery_stepper;
@@ -550,11 +540,7 @@ pub enum PStrCmpResult {
 impl PStrCmpResult {
     #[inline]
     pub fn is_second_iter(&self) -> bool {
-        if let PStrCmpResult::SecondIterContinuable(_) = self {
+        matches!(self, PStrCmpResult::SecondIterContinuable(_))
-            true
-        } else {
-            false
-        }
     }
 }
 
@@ -600,8 +586,8 @@ pub fn compare_pstr_prefixes<'a>(
                             return PStrCmpResult::Ordered(c1.cmp(&c2));
                         }
 
-                        cycle_detection_step(i1, i2, &step_1);
+                        cycle_detection_step(i1, i2, step_1);
-                        let both_cyclic = cycle_detection_step(i2, i1, &step_2);
+                        let both_cyclic = cycle_detection_step(i2, i1, step_2);
 
                         r1 = step(i1, i1.brent_st.hare);
                         r2 = step(i2, i2.brent_st.hare);
@@ -623,15 +609,15 @@ pub fn compare_pstr_prefixes<'a>(
                             if n1 < pstr_atom.len() {
                                 step_2.iteratee = PStrIteratee::PStrSegment(f2, pstr_atom, n1);
 
-                                let c1_result = cycle_detection_step(i1, i2, &step_1);
+                                let c1_result = cycle_detection_step(i1, i2, step_1);
                                 r1 = step(i1, i1.brent_st.hare);
 
                                 if !c1_result {
                                     continue;
                                 }
                             } else {
-                                cycle_detection_step(i1, i2, &step_1);
+                                cycle_detection_step(i1, i2, step_1);
-                                let both_cyclic = cycle_detection_step(i2, i1, &step_2);
+                                let both_cyclic = cycle_detection_step(i2, i1, step_2);
 
                                 r1 = step(i1, i1.brent_st.hare);
                                 r2 = step(i2, i2.brent_st.hare);
@@ -641,7 +627,7 @@ pub fn compare_pstr_prefixes<'a>(
                                 }
                             }
                         } else {
-                            let c2_result = cycle_detection_step(i2, i1, &step_2);
+                            let c2_result = cycle_detection_step(i2, i1, step_2);
                             r2 = step(i2, i2.brent_st.hare);
 
                             if !c2_result {
@@ -662,15 +648,15 @@ pub fn compare_pstr_prefixes<'a>(
                             if n1 < pstr_atom.len() {
                                 step_1.iteratee = PStrIteratee::PStrSegment(f1, pstr_atom, n1);
 
-                                let c2_result = cycle_detection_step(i2, i1, &step_2);
+                                let c2_result = cycle_detection_step(i2, i1, step_2);
                                 r2 = step(i2, step_2.next_hare);
 
                                 if !c2_result {
                                     continue;
                                 }
                             } else {
-                                cycle_detection_step(i1, i2, &step_1);
+                                cycle_detection_step(i1, i2, step_1);
-                                let both_cyclic = cycle_detection_step(i2, i1, &step_2);
+                                let both_cyclic = cycle_detection_step(i2, i1, step_2);
 
                                 r1 = step(i1, i1.brent_st.hare);
                                 r2 = step(i2, i2.brent_st.hare);
@@ -680,7 +666,7 @@ pub fn compare_pstr_prefixes<'a>(
                                 }
                             }
                         } else {
-                            let c1_result = cycle_detection_step(i1, i2, &step_1);
+                            let c1_result = cycle_detection_step(i1, i2, step_1);
                             r1 = step(i1, i1.brent_st.hare);
 
                             if !c1_result {
@@ -693,8 +679,8 @@ pub fn compare_pstr_prefixes<'a>(
                         PStrIteratee::PStrSegment(f2, pstr2_atom, n2),
                     ) => {
                         if pstr1_atom == pstr2_atom && n1 == n2 {
-                            cycle_detection_step(i1, i2, &step_1);
+                            cycle_detection_step(i1, i2, step_1);
-                            let both_cyclic = cycle_detection_step(i2, i1, &step_2);
+                            let both_cyclic = cycle_detection_step(i2, i1, step_2);
 
                             r1 = step(i1, i1.brent_st.hare);
                             r2 = step(i2, i2.brent_st.hare);
@@ -713,9 +699,9 @@ pub fn compare_pstr_prefixes<'a>(
                         let str2 = pstr2.as_str_from(n2);
 
                         match str1.len().cmp(&str2.len()) {
-                            Ordering::Equal if &*str1 == &*str2 => {
+                            Ordering::Equal if *str1 == *str2 => {
-                                cycle_detection_step(i1, i2, &step_1);
+                                cycle_detection_step(i1, i2, step_1);
-                                let both_cyclic = cycle_detection_step(i2, i1, &step_2);
+                                let both_cyclic = cycle_detection_step(i2, i1, step_2);
 
                                 r1 = step(i1, i1.brent_st.hare);
                                 r2 = step(i2, i2.brent_st.hare);
@@ -727,7 +713,7 @@ pub fn compare_pstr_prefixes<'a>(
                             Ordering::Less if str2.starts_with(&*str1) => {
                                 step_2.iteratee =
                                     PStrIteratee::PStrSegment(f2, pstr2_atom, n2 + str1.len());
-                                let c1_result = cycle_detection_step(i1, i2, &step_1);
+                                let c1_result = cycle_detection_step(i1, i2, step_1);
                                 r1 = step(i1, i1.brent_st.hare);
 
                                 if !c1_result {
@@ -737,7 +723,7 @@ pub fn compare_pstr_prefixes<'a>(
                             Ordering::Greater if str1.starts_with(&*str2) => {
                                 step_1.iteratee =
                                     PStrIteratee::PStrSegment(f1, pstr1_atom, n1 + str2.len());
-                                let c2_result = cycle_detection_step(i2, i1, &step_2);
+                                let c2_result = cycle_detection_step(i2, i1, step_2);
                                 r2 = step(i2, i2.brent_st.hare);
 
                                 if !c2_result {
@@ -786,12 +772,10 @@ pub fn compare_pstr_prefixes<'a>(
         } else {
             PStrCmpResult::FirstIterContinuable(r1.unwrap().iteratee)
         }
+    } else if i1.is_continuable() && i2.is_continuable() {
+        PStrCmpResult::Ordered(Ordering::Equal)
     } else {
-        if i1.is_continuable() && i2.is_continuable() {
+        PStrCmpResult::Unordered
-            PStrCmpResult::Ordered(Ordering::Equal)
-        } else {
-            PStrCmpResult::Unordered
-        }
     }
 }
 
@@ -885,7 +869,7 @@ mod test {
         {
             let mut iter = HeapPStrIter::new(&wam.machine_st.heap, 0);
 
-            while let Some(_) = iter.next() {}
+            for _ in iter.by_ref() {}
 
             assert!(!iter.at_string_terminator());
         }
@@ -1009,7 +993,7 @@ mod test {
 
         unify!(wam.machine_st, cstr_var_cell, heap_loc_as_cell!(1));
 
-        assert_eq!(wam.machine_st.fail, false);
+        assert!(!wam.machine_st.fail);
 
         assert_eq!(wam.machine_st.heap[2], char_as_cell!('a'),);
 
@@ -1032,7 +1016,7 @@ mod test {
 
         unify!(wam.machine_st, cstr_var_cell, heap_loc_as_cell!(1));
 
-        assert_eq!(wam.machine_st.fail, false);
+        assert!(!wam.machine_st.fail);
 
         // test "abc" = [X,b,Z].
 
@@ -1054,7 +1038,7 @@ mod test {
 
         unify!(wam.machine_st, cstr_var_cell, heap_loc_as_cell!(1));
 
-        assert_eq!(wam.machine_st.fail, false);
+        assert!(!wam.machine_st.fail);
 
         assert_eq!(wam.machine_st.heap[2], char_as_cell!('a'),);
 
@@ -1075,7 +1059,7 @@ mod test {
 
         print_heap_terms(wam.machine_st.heap.iter(), 0);
 
-        assert_eq!(wam.machine_st.fail, false);
+        assert!(!wam.machine_st.fail);
 
         assert_eq!(wam.machine_st.heap[2], pstr_loc_as_cell!(5));
         assert_eq!(wam.machine_st.heap[3], pstr_loc_as_cell!(1));
@@ -1107,7 +1091,7 @@ mod test {
 
             // assert!(iter.next().is_none());
 
-            while let Some(_) = iter.next() {}
+            for _ in iter {}
         }
     }
 }

src/machine/preprocessor.rs

@@ -100,7 +100,7 @@ fn setup_module_export(
 }
 
 pub(crate) fn build_rule_body(vars: &[Term], body_term: Term) -> Term {
-    let head_term = Term::Clause(Cell::default(), atom!(""), vars.iter().cloned().collect());
+    let head_term = Term::Clause(Cell::default(), atom!(""), vars.to_vec());
     let rule = vec![head_term, body_term];
 
     Term::Clause(Cell::default(), atom!(":-"), rule)
@@ -238,7 +238,7 @@ fn setup_meta_predicate<'a, LS: LoadState<'a>>(
     ) -> Result<(Atom, Vec<MetaSpec>), CompilationError> {
         let mut meta_specs = vec![];
 
-        for meta_spec in terms.into_iter() {
+        for meta_spec in terms.iter_mut() {
             match meta_spec {
                 Term::Literal(_, Literal::Atom(meta_spec)) => {
                     let meta_spec = match meta_spec {
@@ -310,11 +310,11 @@ pub(super) fn setup_declaration<'a, LS: LoadState<'a>>(
             }
             (atom!("module"), 2) => {
                 let atom_tbl = &mut LS::machine_st(&mut loader.payload).atom_tbl;
-                Ok(Declaration::Module(setup_module_decl(terms, &atom_tbl)?))
+                Ok(Declaration::Module(setup_module_decl(terms, atom_tbl)?))
             }
             (atom!("op"), 3) => {
                 let atom_tbl = &mut LS::machine_st(&mut loader.payload).atom_tbl;
-                Ok(Declaration::Op(setup_op_decl(terms, &atom_tbl)?))
+                Ok(Declaration::Op(setup_op_decl(terms, atom_tbl)?))
             }
             (atom!("non_counted_backtracking"), 1) => {
                 let (name, arity) = setup_predicate_indicator(&mut terms.pop().unwrap())?;
@@ -323,7 +323,7 @@ pub(super) fn setup_declaration<'a, LS: LoadState<'a>>(
             (atom!("use_module"), 1) => Ok(Declaration::UseModule(setup_use_module_decl(terms)?)),
             (atom!("use_module"), 2) => {
                 let atom_tbl = &mut LS::machine_st(&mut loader.payload).atom_tbl;
-                let (name, exports) = setup_qualified_import(terms, &atom_tbl)?;
+                let (name, exports) = setup_qualified_import(terms, atom_tbl)?;
 
                 Ok(Declaration::UseQualifiedModule(name, exports))
             }

src/machine/stack.rs

@@ -56,7 +56,7 @@ impl Index<usize> for AndFrame {
         let index_offset = (index - 1) * mem::size_of::<HeapCellValue>();
 
         unsafe {
-            let ptr = mem::transmute::<&AndFrame, *const u8>(self);
+            let ptr = self as *const crate::machine::stack::AndFrame as *const u8;
             let ptr = ptr as usize + prelude_offset + index_offset;
 
             &*(ptr as *const HeapCellValue)
@@ -70,7 +70,7 @@ impl IndexMut<usize> for AndFrame {
         let index_offset = (index - 1) * mem::size_of::<HeapCellValue>();
 
         unsafe {
-            let ptr = mem::transmute::<&mut AndFrame, *const u8>(self);
+            let ptr = self as *mut crate::machine::stack::AndFrame as *const u8;
             let ptr = ptr as usize + prelude_offset + index_offset;
 
             &mut *(ptr as *mut HeapCellValue)
@@ -129,7 +129,7 @@ impl Index<usize> for OrFrame {
         let index_offset = index * mem::size_of::<HeapCellValue>();
 
         unsafe {
-            let ptr = mem::transmute::<&OrFrame, *const u8>(self);
+            let ptr = self as *const crate::machine::stack::OrFrame as *const u8;
             let ptr = ptr as usize + prelude_offset + index_offset;
 
             &*(ptr as *const HeapCellValue)
@@ -144,7 +144,7 @@ impl IndexMut<usize> for OrFrame {
         let index_offset = index * mem::size_of::<HeapCellValue>();
 
         unsafe {
-            let ptr = mem::transmute::<&mut OrFrame, *const u8>(self);
+            let ptr = self as *mut crate::machine::stack::OrFrame as *const u8;
             let ptr = ptr as usize + prelude_offset + index_offset;
 
             &mut *(ptr as *mut HeapCellValue)

src/machine/streams.rs

@@ -21,9 +21,9 @@ use std::fmt::Debug;
 use std::fs::{File, OpenOptions};
 use std::hash::Hash;
 use std::io;
-use std::io::{Cursor, ErrorKind, Read, Seek, SeekFrom, Write};
 #[cfg(feature = "http")]
 use std::io::BufRead;
+use std::io::{Cursor, ErrorKind, Read, Seek, SeekFrom, Write};
 use std::mem;
 use std::net::{Shutdown, TcpStream};
 use std::ops::{Deref, DerefMut};
@@ -161,7 +161,7 @@ impl StreamLayout<CharReader<InputFileStream>> {
         // its pending buffer length from position.
         self.get_mut()
             .file
-            .seek(SeekFrom::Current(0))
+            .stream_position()
             .map(|pos| pos - self.stream.rem_buf_len() as u64)
             .ok()
     }
@@ -317,33 +317,31 @@ impl Write for HttpWriteStream {
 
     #[inline]
     fn flush(&mut self) -> std::io::Result<()> {
-	Ok(())
+        Ok(())
     }
 }
 
 #[cfg(feature = "http")]
 impl HttpWriteStream {
     fn drop(&mut self) {
-	let headers = unsafe { mem::ManuallyDrop::take(&mut self.headers) };
+        let headers = unsafe { mem::ManuallyDrop::take(&mut self.headers) };
-	let buffer = unsafe { mem::ManuallyDrop::take(&mut self.buffer) };
+        let buffer = unsafe { mem::ManuallyDrop::take(&mut self.buffer) };
-	
-	let (ready, response, cvar) = &**self.response;
 
-	let mut ready = ready.lock().unwrap();
+        let (ready, response, cvar) = &**self.response;
-	{
+
-	    let mut response = response.lock().unwrap();
+        let mut ready = ready.lock().unwrap();
-	
+        {
-	    let mut response_ = warp::http::Response::builder()
+            let mut response = response.lock().unwrap();
-	        .status(self.status_code);
+
-	    *response_.headers_mut().unwrap() = headers;
+            let mut response_ = warp::http::Response::builder().status(self.status_code);
-	    *response = Some(response_.body(warp::hyper::Body::from(buffer)).unwrap());
+            *response_.headers_mut().unwrap() = headers;
-	}
+            *response = Some(response_.body(warp::hyper::Body::from(buffer)).unwrap());
-	*ready = true;
+        }
-	cvar.notify_one();
+        *ready = true;
+        cvar.notify_one();
     }
 }
 
-
 #[derive(Debug)]
 pub struct StandardOutputStream {}
 
@@ -389,7 +387,7 @@ impl StreamOptions {
     #[inline]
     pub fn get_alias(self) -> Option<Atom> {
         if self.has_alias() {
-            Some(Atom::from((self.alias() as u64) << 3))
+            Some(Atom::from(self.alias() << 3))
         } else {
             None
         }
@@ -466,6 +464,7 @@ macro_rules! arena_allocated_impl_for_stream {
                 mem::size_of::<StreamLayout<$stream_type>>()
             }
 
+            #[allow(clippy::not_unsafe_ptr_arg_deref)]
             #[inline]
             fn copy_to_arena(self, dst: *mut Self) -> Self::PtrToAllocated {
                 unsafe {
@@ -585,29 +584,17 @@ impl Stream {
 
     #[inline]
     pub fn is_stderr(&self) -> bool {
-        if let Stream::StandardError(_) = self {
+        matches!(self, Stream::StandardError(_))
-            true
-        } else {
-            false
-        }
     }
 
     #[inline]
     pub fn is_stdout(&self) -> bool {
-        if let Stream::StandardOutput(_) = self {
+        matches!(self, Stream::StandardOutput(_))
-            true
-        } else {
-            false
-        }
     }
 
     #[inline]
     pub fn is_stdin(&self) -> bool {
-        if let Stream::Readline(_) = self {
+        matches!(self, Stream::Readline(_))
-            true
-        } else {
-            false
-        }
     }
 
     pub fn as_ptr(&self) -> *const ArenaHeader {
@@ -831,7 +818,7 @@ impl CharRead for Stream {
 impl Read for Stream {
     #[inline]
     fn read(&mut self, buf: &mut [u8]) -> std::io::Result<usize> {
-        let bytes_read = match self {
+        match self {
             Stream::InputFile(file) => (*file).read(buf),
             Stream::NamedTcp(tcp_stream) => (*tcp_stream).read(buf),
             #[cfg(feature = "tls")]
@@ -853,9 +840,7 @@ impl Read for Stream {
                 ErrorKind::PermissionDenied,
                 StreamError::ReadFromOutputStream,
             )),
-        };
+        }
-
-        bytes_read
     }
 }
 
@@ -984,18 +969,14 @@ fn cursor_position<T>(
     cursor: &Cursor<T>,
     cursor_len: u64,
 ) -> AtEndOfStream {
-    let position = cursor.position();
+    match cursor.position().cmp(&cursor_len) {
-
-    let at_end_of_stream = match position.cmp(&cursor_len) {
         Ordering::Equal => AtEndOfStream::At,
         Ordering::Greater => {
             *past_end_of_stream = true;
             AtEndOfStream::Past
         }
         Ordering::Less => AtEndOfStream::Not,
-    };
+    }
-
-    at_end_of_stream
 }
 
 impl Stream {
@@ -1021,26 +1002,23 @@ impl Stream {
 
     #[inline]
     pub(crate) fn set_position(&mut self, position: u64) {
-        match self {
+        if let Stream::InputFile(stream_layout) = self {
-            Stream::InputFile(stream_layout) => {
+            let StreamLayout {
-                let StreamLayout {
+                past_end_of_stream,
-                    past_end_of_stream,
+                stream,
-                    stream,
+                ..
-                    ..
+            } = &mut **stream_layout;
-                } = &mut **stream_layout;
 
-                stream
+            stream
-                    .get_mut()
+                .get_mut()
-                    .file
+                .file
-                    .seek(SeekFrom::Start(position))
+                .seek(SeekFrom::Start(position))
-                    .unwrap();
+                .unwrap();
-                stream.reset_buffer(); // flush the internal buffer.
+            stream.reset_buffer(); // flush the internal buffer.
 
-                if let Ok(metadata) = stream.get_ref().file.metadata() {
+            if let Ok(metadata) = stream.get_ref().file.metadata() {
-                    *past_end_of_stream = position > metadata.len();
+                *past_end_of_stream = position > metadata.len();
-                }
             }
-            _ => {}
         }
     }
 
@@ -1257,15 +1235,15 @@ impl Stream {
         headers: hyper::HeaderMap,
         arena: &mut Arena,
     ) -> Self {
-	Stream::HttpWrite(arena_alloc!(
+        Stream::HttpWrite(arena_alloc!(
-	    StreamLayout::new(CharReader::new(HttpWriteStream {
+            StreamLayout::new(CharReader::new(HttpWriteStream {
-		response,
+                response,
-		status_code,
+                status_code,
-		headers: mem::ManuallyDrop::new(headers),
+                headers: mem::ManuallyDrop::new(headers),
-		buffer: mem::ManuallyDrop::new(Vec::new()),
+                buffer: mem::ManuallyDrop::new(Vec::new()),
-	    })),
+            })),
-	    arena
+            arena
-	))
+        ))
     }
 
     #[inline]
@@ -1313,8 +1291,8 @@ impl Stream {
                 Ok(())
             }
             #[cfg(feature = "http")]
-	    Stream::HttpWrite(ref mut http_stream) => {
+            Stream::HttpWrite(ref mut http_stream) => {
-		http_stream.inner_mut().drop();
+                http_stream.inner_mut().drop();
                 unsafe {
                     http_stream.set_tag(ArenaHeaderTag::Dropped);
                     std::ptr::drop_in_place(&mut http_stream.inner_mut().buffer as *mut _);
@@ -1346,11 +1324,7 @@ impl Stream {
 
     #[inline]
     pub(crate) fn is_null_stream(&self) -> bool {
-        if let Stream::Null(_) = self {
+        matches!(self, Stream::Null(_))
-            true
-        } else {
-            false
-        }
     }
 
     #[inline]
@@ -1391,29 +1365,25 @@ impl Stream {
         self.set_lines_read(0);
         self.set_past_end_of_stream(false);
 
-        loop {
+        match self {
-            match self {
+            Stream::Byte(ref mut cursor) => {
-                Stream::Byte(ref mut cursor) => {
+                cursor.stream.get_mut().0.set_position(0);
-                    cursor.stream.get_mut().0.set_position(0);
+                true
-                    return true;
-                }
-                Stream::InputFile(ref mut file_stream) => {
-                    file_stream
-                        .stream
-                        .get_mut()
-                        .file
-                        .seek(SeekFrom::Start(0))
-                        .unwrap();
-                    return true;
-                }
-                Stream::Readline(ref mut readline_stream) => {
-                    readline_stream.reset();
-                    return true;
-                }
-                _ => {
-                    return false;
-                }
             }
+            Stream::InputFile(ref mut file_stream) => {
+                file_stream
+                    .stream
+                    .get_mut()
+                    .file
+                    .seek(SeekFrom::Start(0))
+                    .unwrap();
+                true
+            }
+            Stream::Readline(ref mut readline_stream) => {
+                readline_stream.reset();
+                true
+            }
+            _ => false,
         }
     }
 
@@ -1484,12 +1454,13 @@ impl MachineState {
                     stream.set_past_end_of_stream(true);
                 }
 
-                Ok(self.fail = stream.past_end_of_stream())
+                self.fail = stream.past_end_of_stream();
+                Ok(())
             }
         }
     }
 
-    pub(crate) fn to_stream_options(
+    pub(crate) fn get_stream_options(
         &mut self,
         alias: HeapCellValue,
         eof_action: HeapCellValue,
@@ -1782,9 +1753,9 @@ impl MachineState {
         caller: Atom,
         arity: usize,
     ) -> CallResult {
-        let opt_err = if input.is_some() && !stream.is_input_stream() {
+        let opt_err = if input.is_some() && !stream.is_input_stream()
-            Some(atom!("stream")) // 8.14.2.3 g)
+            || input.is_none() && !stream.is_output_stream()
-        } else if input.is_none() && !stream.is_output_stream() {
+        {
             Some(atom!("stream")) // 8.14.2.3 g)
         } else if stream.options().stream_type() != expected_type {
             Some(expected_type.other().as_atom()) // 8.14.2.3 h)

src/machine/unify.rs

@@ -1,6 +1,6 @@
 use crate::arena::*;
 use crate::forms::*;
-use crate::heap_iter::{NonListElider, stackful_preorder_iter};
+use crate::heap_iter::{stackful_preorder_iter, NonListElider};
 use crate::machine::machine_state::*;
 use crate::machine::partial_string::*;
 use crate::machine::*;
@@ -204,7 +204,7 @@ pub(crate) trait Unifier: DerefMut<Target = MachineState> {
 
                 let mut focus = pstr_iter2.focus;
 
-                'outer: loop {
+                'outer: {
                     while let Some(c) = chars_iter.peek() {
                         read_heap_cell!(focus,
                             (HeapCellValueTag::Lis, l) => {
@@ -329,8 +329,6 @@ pub(crate) trait Unifier: DerefMut<Target = MachineState> {
 
                     machine_st.pdl.push(focus);
                     machine_st.pdl.push(chars_iter.iter.focus);
-
-                    break;
                 }
             }
             PStrCmpResult::Unordered => {
@@ -609,10 +607,8 @@ pub(crate) trait Unifier: DerefMut<Target = MachineState> {
                         }
                     }
                     (HeapCellValueTag::Lis, l1) => {
-                        if d2.is_ref() {
+                        if d2.is_ref() && tabu_list.contains(&(d1, d2)) {
-                            if tabu_list.contains(&(d1, d2)) {
+                            continue;
-                                continue;
-                            }
                         }
 
                         Self::unify_list(self, l1, d2);
@@ -720,7 +716,11 @@ fn bind_with_occurs_check<U: Unifier>(unifier: &mut U, r: Ref, value: HeapCellVa
     if !value.is_constant() {
         let machine_st: &mut MachineState = unifier.deref_mut();
 
-        for cell in stackful_preorder_iter::<NonListElider>(&mut machine_st.heap, &mut machine_st.stack, value) {
+        for cell in stackful_preorder_iter::<NonListElider>(
+            &mut machine_st.heap,
+            &mut machine_st.stack,
+            value,
+        ) {
             let cell = unmark_cell_bits!(cell);
 
             if let Some(inner_r) = cell.as_var() {
@@ -738,7 +738,7 @@ fn bind_with_occurs_check<U: Unifier>(unifier: &mut U, r: Ref, value: HeapCellVa
         U::bind(unifier, r, value);
     }
 
-    return occurs_triggered;
+    occurs_triggered
 }
 
 #[derive(Deref, DerefMut)]

src/parser/ast.rs

@@ -247,11 +247,7 @@ impl GenContext {
 
     #[inline]
     pub fn is_last(self) -> bool {
-        if let GenContext::Last(_) = self {
+        matches!(self, GenContext::Last(_))
-            true
-        } else {
-            false
-        }
     }
 }
 
@@ -303,24 +299,16 @@ impl OpDesc {
 // name and fixity -> operator type and precedence.
 pub type OpDir = IndexMap<(Atom, Fixity), OpDesc, FxBuildHasher>;
 
-#[derive(Debug, Clone, Copy)]
+#[derive(Debug, Default, Clone, Copy)]
 pub struct MachineFlags {
     pub double_quotes: DoubleQuotes,
     pub unknown: Unknown,
 }
 
-impl Default for MachineFlags {
+#[derive(Debug, Default, Clone, Copy, PartialEq)]
-    fn default() -> Self {
-        MachineFlags {
-            double_quotes: DoubleQuotes::default(),
-            unknown: Unknown::default(),
-        }
-    }
-}
-
-#[derive(Debug, Clone, Copy, PartialEq)]
 pub enum DoubleQuotes {
     Atom,
+    #[default]
     Chars,
     Codes,
 }
@@ -339,12 +327,6 @@ impl DoubleQuotes {
     }
 }
 
-impl Default for DoubleQuotes {
-    fn default() -> Self {
-        DoubleQuotes::Chars
-    }
-}
-
 #[derive(Debug, Clone, Copy)]
 pub enum Unknown {
     Error,
@@ -505,7 +487,7 @@ impl<'a, 'b> CompositeOpDir<'a, 'b> {
 
     #[inline]
     pub(crate) fn get(&self, name: Atom, fixity: Fixity) -> Option<OpDesc> {
-        let entry = if let Some(ref primary_op_dir) = &self.primary_op_dir {
+        let entry = if let Some(primary_op_dir) = &self.primary_op_dir {
             primary_op_dir.get(&(name, fixity))
         } else {
             None
@@ -567,7 +549,7 @@ impl Fixnum {
         const UPPER_BOUND: i64 = (1 << 55) - 1;
         const LOWER_BOUND: i64 = -(1 << 55);
 
-        if LOWER_BOUND <= num && num <= UPPER_BOUND {
+        if (LOWER_BOUND..=UPPER_BOUND).contains(&num) {
             Ok(Fixnum::new()
                 .with_m(false)
                 .with_f(false)
@@ -582,7 +564,7 @@ impl Fixnum {
     pub fn get_num(self) -> i64 {
         let n = self.num() as i64;
         let (n, overflowed) = (n << 8).overflowing_shr(8);
-        debug_assert_eq!(overflowed, false);
+        debug_assert!(!overflowed);
         n
     }
 }
@@ -730,11 +712,12 @@ impl Var {
     #[inline(always)]
     pub fn as_str(&self) -> Option<&str> {
         match self {
-            Var::Named(value) => Some(&value),
+            Var::Named(value) => Some(value),
             _ => None,
         }
     }
 
+    #[allow(clippy::inherent_to_string)]
     #[inline(always)]
     pub fn to_string(&self) -> String {
         match self {
@@ -800,10 +783,8 @@ impl Term {
 
 #[inline]
 pub fn source_arity(terms: &[Term]) -> usize {
-    if let Some(last_arg) = terms.last() {
+    if let Some(Term::Literal(_, Literal::CodeIndex(_))) = terms.last() {
-        if let Term::Literal(_, Literal::CodeIndex(_)) = last_arg {
+        return terms.len() - 1;
-            return terms.len() - 1;
-        }
     }
 
     terms.len()
@@ -811,10 +792,8 @@ pub fn source_arity(terms: &[Term]) -> usize {
 
 pub(crate) fn unfold_by_str_once(term: &mut Term, s: Atom) -> Option<(Term, Term)> {
     if let Term::Clause(_, ref name, ref mut subterms) = term {
-        if let Some(last_arg) = subterms.last() {
+        if let Some(Term::Literal(_, Literal::CodeIndex(_))) = subterms.last() {
-            if let Term::Literal(_, Literal::CodeIndex(_)) = last_arg {
+            subterms.pop();
-                subterms.pop();
-            }
         }
 
         if name == &s && subterms.len() == 2 {

src/parser/char_reader.rs

@@ -131,15 +131,9 @@ impl<R: Read> CharReader<R> {
 
     pub fn peek_byte(&mut self) -> Option<io::Result<u8>> {
         match self.refresh_buffer() {
-            Ok(_buf) => {}
+            Ok(_buf) => _buf.first().cloned().map(Ok),
-            Err(e) => return Some(Err(e)),
+            Err(e) => Some(Err(e)),
         }
-
-        return if let Some(b) = self.buf.get(0).cloned() {
-            Some(Ok(b))
-        } else {
-            None
-        };
     }
 }
 
@@ -194,49 +188,47 @@ impl<R: Read> CharRead for CharReader<R> {
                         io::ErrorKind::InvalidData,
                         BadUtf8Error { bytes: badbytes },
                     )));
+                } else if self.pos >= self.buf.len() {
+                    return None;
+                } else if self.buf.len() - self.pos >= 4 {
+                    return match str::from_utf8(&self.buf[self.pos..e.valid_up_to()]) {
+                        Ok(s) => {
+                            let mut chars = s.chars();
+                            let c = chars.next().unwrap();
+
+                            Some(Ok(c))
+                        }
+                        Err(e) => {
+                            let badbytes = self.buf[self.pos..e.valid_up_to()].to_vec();
+
+                            Some(Err(io::Error::new(
+                                io::ErrorKind::InvalidData,
+                                BadUtf8Error { bytes: badbytes },
+                            )))
+                        }
+                    };
                 } else {
-                    if self.pos >= self.buf.len() {
+                    let buf_len = self.buf.len();
-                        return None;
-                    } else if self.buf.len() - self.pos >= 4 {
-                        return match str::from_utf8(&self.buf[self.pos..e.valid_up_to()]) {
-                            Ok(s) => {
-                                let mut chars = s.chars();
-                                let c = chars.next().unwrap();
 
-                                Some(Ok(c))
+                    for (c, idx) in (self.pos..buf_len).enumerate() {
-                            }
+                        self.buf[c] = self.buf[idx];
-                            Err(e) => {
-                                let badbytes = self.buf[self.pos..e.valid_up_to()].to_vec();
-
-                                Some(Err(io::Error::new(
-                                    io::ErrorKind::InvalidData,
-                                    BadUtf8Error { bytes: badbytes },
-                                )))
-                            }
-                        };
-                    } else {
-                        let buf_len = self.buf.len();
-
-                        for (c, idx) in (self.pos..buf_len).enumerate() {
-                            self.buf[c] = self.buf[idx];
-                        }
-
-                        self.buf.truncate(buf_len - self.pos);
-
-                        let buf_len = self.buf.len();
-
-                        let mut word = [0u8; 4];
-                        let word_slice = &mut word[buf_len..4];
-
-                        match self.inner.read(word_slice) {
-                            Err(e) => return Some(Err(e)),
-                            Ok(nread) => {
-                                self.buf.extend_from_slice(&word_slice[0..nread]);
-                            }
-                        }
-
-                        self.pos = 0;
                     }
+
+                    self.buf.truncate(buf_len - self.pos);
+
+                    let buf_len = self.buf.len();
+
+                    let mut word = [0u8; 4];
+                    let word_slice = &mut word[buf_len..4];
+
+                    match self.inner.read(word_slice) {
+                        Err(e) => return Some(Err(e)),
+                        Ok(nread) => {
+                            self.buf.extend_from_slice(&word_slice[0..nread]);
+                        }
+                    }
+
+                    self.pos = 0;
                 }
             } else {
                 return None;

src/parser/lexer.rs

@@ -48,11 +48,7 @@ pub enum Token {
 impl Token {
     #[inline]
     pub(super) fn is_end(&self) -> bool {
-        if let Token::End = self {
+        matches!(self, Token::End)
-            true
-        } else {
-            false
-        }
     }
 }
 
@@ -604,10 +600,7 @@ impl<'a, R: CharRead> Lexer<'a, R> {
                     break;
                 }
             }
-        } else if cut_char!(c) {
+        } else if cut_char!(c) || semicolon_char!(c) {
-            self.skip_char(c);
-            token.push(c);
-        } else if semicolon_char!(c) {
             self.skip_char(c);
             token.push(c);
         } else if single_quote_char!(c) {
@@ -690,7 +683,8 @@ impl<'a, R: CharRead> Lexer<'a, R> {
             if self.reader.peek_char().is_none() {
                 self.return_char('.');
 
-                i64::from_str_radix(&token, 10)
+                token
+                    .parse::<i64>()
                     .map(|n| Token::Literal(fixnum!(Literal, n, &mut self.machine_st.arena)))
                     .or_else(|_| {
                         token
@@ -720,12 +714,12 @@ impl<'a, R: CharRead> Lexer<'a, R> {
                     token.push(c);
 
                     let c = match self.lookahead_char() {
-                        Err(_) => return Ok(self.vacate_with_float(token)?),
+                        Err(_) => return self.vacate_with_float(token),
                         Ok(c) => c,
                     };
 
                     if !sign_char!(c) && !decimal_digit_char!(c) {
-                        return Ok(self.vacate_with_float(token)?);
+                        return self.vacate_with_float(token);
                     }
 
                     if sign_char!(c) {
@@ -735,14 +729,14 @@ impl<'a, R: CharRead> Lexer<'a, R> {
                         let c = match self.lookahead_char() {
                             Err(_) => {
                                 self.return_char(token.pop().unwrap());
-                                return Ok(self.vacate_with_float(token)?);
+                                return self.vacate_with_float(token);
                             }
                             Ok(c) => c,
                         };
 
                         if !decimal_digit_char!(c) {
                             self.return_char(token.pop().unwrap());
-                            return Ok(self.vacate_with_float(token)?);
+                            return self.vacate_with_float(token);
                         }
                     }
 
@@ -769,7 +763,7 @@ impl<'a, R: CharRead> Lexer<'a, R> {
                             self.machine_st.arena
                         ))))
                     } else {
-                        return Ok(self.vacate_with_float(token)?);
+                        return self.vacate_with_float(token);
                     }
                 } else {
                     let n = parse_lossy::<f64, _>(token.as_bytes())?;
@@ -781,7 +775,147 @@ impl<'a, R: CharRead> Lexer<'a, R> {
             } else {
                 self.return_char('.');
 
-                i64::from_str_radix(&token, 10)
+                token
+                    .parse::<i64>()
+                    .map(|n| Token::Literal(fixnum!(Literal, n, &mut self.machine_st.arena)))
+                    .or_else(|_| {
+                        token
+                            .parse::<Integer>()
+                            .map(|n| {
+                                Token::Literal(Literal::Integer(arena_alloc!(
+                                    n,
+                                    &mut self.machine_st.arena
+                                )))
+                            })
+                            .map_err(|_| ParserError::ParseBigInt(self.line_num, self.col_num))
+                    })
+            }
+        } else if token.starts_with('0') && token.len() == 1 {
+            if c == 'x' {
+                self.hexadecimal_constant(c).or_else(|e| {
+                    if let ParserError::ParseBigInt(..) = e {
+                        token
+                            .parse::<i64>()
+                            .map(|n| {
+                                Token::Literal(fixnum!(Literal, n, &mut self.machine_st.arena))
+                            })
+                            .or_else(|_| {
+                                token
+                                    .parse::<Integer>()
+                                    .map(|n| {
+                                        Token::Literal(Literal::Integer(arena_alloc!(
+                                            n,
+                                            &mut self.machine_st.arena
+                                        )))
+                                    })
+                                    .map_err(|_| {
+                                        ParserError::ParseBigInt(self.line_num, self.col_num)
+                                    })
+                            })
+                    } else {
+                        Err(e)
+                    }
+                })
+            } else if c == 'o' {
+                self.octal_constant(c).or_else(|e| {
+                    if let ParserError::ParseBigInt(..) = e {
+                        token
+                            .parse::<i64>()
+                            .map(|n| {
+                                Token::Literal(fixnum!(Literal, n, &mut self.machine_st.arena))
+                            })
+                            .or_else(|_| {
+                                token
+                                    .parse::<Integer>()
+                                    .map(|n| {
+                                        Token::Literal(Literal::Integer(arena_alloc!(
+                                            n,
+                                            &mut self.machine_st.arena
+                                        )))
+                                    })
+                                    .map_err(|_| {
+                                        ParserError::ParseBigInt(self.line_num, self.col_num)
+                                    })
+                            })
+                    } else {
+                        Err(e)
+                    }
+                })
+            } else if c == 'b' {
+                self.binary_constant(c).or_else(|e| {
+                    if let ParserError::ParseBigInt(..) = e {
+                        token
+                            .parse::<i64>()
+                            .map(|n| {
+                                Token::Literal(fixnum!(Literal, n, &mut self.machine_st.arena))
+                            })
+                            .or_else(|_| {
+                                token
+                                    .parse::<Integer>()
+                                    .map(|n| {
+                                        Token::Literal(Literal::Integer(arena_alloc!(
+                                            n,
+                                            &mut self.machine_st.arena
+                                        )))
+                                    })
+                                    .map_err(|_| {
+                                        ParserError::ParseBigInt(self.line_num, self.col_num)
+                                    })
+                            })
+                    } else {
+                        Err(e)
+                    }
+                })
+            } else if single_quote_char!(c) {
+                self.skip_char(c);
+                let c = self.lookahead_char()?;
+
+                if backslash_char!(c) {
+                    self.skip_char(c);
+                    let c = self.lookahead_char()?;
+
+                    if new_line_char!(c) {
+                        self.skip_char(c);
+                        self.return_char('\'');
+
+                        return Ok(Token::Literal(Literal::Fixnum(Fixnum::build_with(0))));
+                    } else {
+                        self.return_char('\\');
+                    }
+                }
+
+                self.get_single_quoted_char()
+                    .map(|c| Token::Literal(Literal::Fixnum(Fixnum::build_with(c as i64))))
+                    .or_else(|err| {
+                        match err {
+                            ParserError::UnexpectedChar('\'', ..) => {}
+                            err => return Err(err),
+                        }
+
+                        self.return_char(c);
+
+                        token
+                            .parse::<i64>()
+                            .map(|n| {
+                                Token::Literal(fixnum!(Literal, n, &mut self.machine_st.arena))
+                            })
+                            .or_else(|_| {
+                                token
+                                    .parse::<Integer>()
+                                    .map(|n| {
+                                        Token::Literal(Literal::Integer(arena_alloc!(
+                                            n,
+                                            &mut self.machine_st.arena
+                                        )))
+                                    })
+                                    .map_err(|_| {
+                                        ParserError::ParseBigInt(self.line_num, self.col_num)
+                                    })
+                            })
+                    })
+            } else {
+                token
+                    .parse::<i64>()
                     .map(|n| Token::Literal(fixnum!(Literal, n, &mut self.machine_st.arena)))
                     .or_else(|_| {
                         token
@@ -796,155 +930,20 @@ impl<'a, R: CharRead> Lexer<'a, R> {
                     })
             }
         } else {
-            if token.starts_with('0') && token.len() == 1 {
+            token
-                if c == 'x' {
+                .parse::<i64>()
-                    self.hexadecimal_constant(c).or_else(|e| {
+                .map(|n| Token::Literal(fixnum!(Literal, n, &mut self.machine_st.arena)))
-                        if let ParserError::ParseBigInt(..) = e {
+                .or_else(|_| {
-                            i64::from_str_radix(&token, 10)
+                    token
-                                .map(|n| {
+                        .parse::<Integer>()
-                                    Token::Literal(fixnum!(Literal, n, &mut self.machine_st.arena))
+                        .map(|n| {
-                                })
+                            Token::Literal(Literal::Integer(arena_alloc!(
-                                .or_else(|_| {
+                                n,
-                                    token
+                                &mut self.machine_st.arena
-                                        .parse::<Integer>()
+                            )))
-                                        .map(|n| {
-                                            Token::Literal(Literal::Integer(arena_alloc!(
-                                                n,
-                                                &mut self.machine_st.arena
-                                            )))
-                                        })
-                                        .map_err(|_| {
-                                            ParserError::ParseBigInt(self.line_num, self.col_num)
-                                        })
-                                })
-                        } else {
-                            Err(e)
-                        }
-                    })
-                } else if c == 'o' {
-                    self.octal_constant(c).or_else(|e| {
-                        if let ParserError::ParseBigInt(..) = e {
-                            i64::from_str_radix(&token, 10)
-                                .map(|n| {
-                                    Token::Literal(fixnum!(Literal, n, &mut self.machine_st.arena))
-                                })
-                                .or_else(|_| {
-                                    token
-                                        .parse::<Integer>()
-                                        .map(|n| {
-                                            Token::Literal(Literal::Integer(arena_alloc!(
-                                                n,
-                                                &mut self.machine_st.arena
-                                            )))
-                                        })
-                                        .map_err(|_| {
-                                            ParserError::ParseBigInt(self.line_num, self.col_num)
-                                        })
-                                })
-                        } else {
-                            Err(e)
-                        }
-                    })
-                } else if c == 'b' {
-                    self.binary_constant(c).or_else(|e| {
-                        if let ParserError::ParseBigInt(..) = e {
-                            i64::from_str_radix(&token, 10)
-                                .map(|n| {
-                                    Token::Literal(fixnum!(Literal, n, &mut self.machine_st.arena))
-                                })
-                                .or_else(|_| {
-                                    token
-                                        .parse::<Integer>()
-                                        .map(|n| {
-                                            Token::Literal(Literal::Integer(arena_alloc!(
-                                                n,
-                                                &mut self.machine_st.arena
-                                            )))
-                                        })
-                                        .map_err(|_| {
-                                            ParserError::ParseBigInt(self.line_num, self.col_num)
-                                        })
-                                })
-                        } else {
-                            Err(e)
-                        }
-                    })
-                } else if single_quote_char!(c) {
-                    self.skip_char(c);
-                    let c = self.lookahead_char()?;
-
-                    if backslash_char!(c) {
-                        self.skip_char(c);
-                        let c = self.lookahead_char()?;
-
-                        if new_line_char!(c) {
-                            self.skip_char(c);
-                            self.return_char('\'');
-
-                            return Ok(Token::Literal(Literal::Fixnum(Fixnum::build_with(0))));
-                        } else {
-                            self.return_char('\\');
-                        }
-                    }
-
-                    self.get_single_quoted_char()
-                        .map(|c| Token::Literal(Literal::Fixnum(Fixnum::build_with(c as i64))))
-                        .or_else(|err| {
-                            match err {
-                                ParserError::UnexpectedChar('\'', ..) => {}
-                                err => return Err(err),
-                            }
-
-                            self.return_char(c);
-
-                            i64::from_str_radix(&token, 10)
-                                .map(|n| {
-                                    Token::Literal(fixnum!(Literal, n, &mut self.machine_st.arena))
-                                })
-                                .or_else(|_| {
-                                    token
-                                        .parse::<Integer>()
-                                        .map(|n| {
-                                            Token::Literal(Literal::Integer(arena_alloc!(
-                                                n,
-                                                &mut self.machine_st.arena
-                                            )))
-                                        })
-                                        .map_err(|_| {
-                                            ParserError::ParseBigInt(self.line_num, self.col_num)
-                                        })
-                                })
                         })
-                } else {
+                        .map_err(|_| ParserError::ParseBigInt(self.line_num, self.col_num))
-                    i64::from_str_radix(&token, 10)
+                })
-                        .map(|n| Token::Literal(fixnum!(Literal, n, &mut self.machine_st.arena)))
-                        .or_else(|_| {
-                            token
-                                .parse::<Integer>()
-                                .map(|n| {
-                                    Token::Literal(Literal::Integer(arena_alloc!(
-                                        n,
-                                        &mut self.machine_st.arena
-                                    )))
-                                })
-                                .map_err(|_| ParserError::ParseBigInt(self.line_num, self.col_num))
-                        })
-                }
-            } else {
-                i64::from_str_radix(&token, 10)
-                    .map(|n| Token::Literal(fixnum!(Literal, n, &mut self.machine_st.arena)))
-                    .or_else(|_| {
-                        token
-                            .parse::<Integer>()
-                            .map(|n| {
-                                Token::Literal(Literal::Integer(arena_alloc!(
-                                    n,
-                                    &mut self.machine_st.arena
-                                )))
-                            })
-                            .map_err(|_| ParserError::ParseBigInt(self.line_num, self.col_num))
-                    })
-            }
         }
     }
 
@@ -953,6 +952,7 @@ impl<'a, R: CharRead> Lexer<'a, R> {
         c: Option<char>,
         layout_info: &mut LayoutInfo,
     ) -> Result<(), ParserError> {
+        #[allow(clippy::redundant_guards)]
         match c {
             Some(c) if layout_char!(c) => {
                 self.skip_char(c);

src/parser/macros.rs

@@ -77,7 +77,7 @@ macro_rules! cut_char {
 #[macro_export]
 macro_rules! decimal_digit_char {
     ($c: expr) => {
-        ('0'..='9').contains(&$c)
+        $c.is_ascii_digit()
     };
 }
 
@@ -125,7 +125,7 @@ macro_rules! graphic_token_char {
 #[macro_export]
 macro_rules! hexadecimal_digit_char {
     ($c: expr) => {
-        ('0'..='9').contains(&$c) || ('A'..='F').contains(&$c) || ('a'..='f').contains(&$c)
+        $c.is_ascii_digit() || ('A'..='F').contains(&$c) || ('a'..='f').contains(&$c)
     };
 }
 

src/parser/mod.rs

@@ -11,4 +11,5 @@ pub mod ast;
 #[macro_use]
 pub mod macros;
 pub mod lexer;
+#[allow(clippy::module_inception)]
 pub mod parser;

src/parser/parser.rs

@@ -464,7 +464,12 @@ impl<'a, R: CharRead> Parser<'a, R> {
             Token::End => TokenType::End,
         };
 
-        self.stack.push(TokenDesc { tt, priority, spec, unfold_bounds: 0, });
+        self.stack.push(TokenDesc {
+            tt,
+            priority,
+            spec,
+            unfold_bounds: 0,
+        });
     }
 
     fn reduce_op(&mut self, priority: usize) {
@@ -472,10 +477,9 @@ impl<'a, R: CharRead> Parser<'a, R> {
             if let Some(desc1) = self.stack.pop() {
                 if let Some(desc2) = self.stack.pop() {
                     if let Some(desc3) = self.stack.pop() {
-                        if is_xfx!(desc2.spec) && affirm_xfx(priority, desc2, desc3, desc1) {
+                        if is_xfx!(desc2.spec) && affirm_xfx(priority, desc2, desc3, desc1)
-                            self.push_binary_op(desc2, LTERM);
+                            || is_yfx!(desc2.spec) && affirm_yfx(priority, desc2, desc3, desc1)
-                            continue;
+                        {
-                        } else if is_yfx!(desc2.spec) && affirm_yfx(priority, desc2, desc3, desc1) {
                             self.push_binary_op(desc2, LTERM);
                             continue;
                         } else if is_xfy!(desc2.spec) && affirm_xfy(priority, desc2, desc3, desc1) {
@@ -555,10 +559,12 @@ impl<'a, R: CharRead> Parser<'a, R> {
         if self.stack.len() > 2 * arity {
             let idx = self.stack.len() - 2 * arity - 1;
 
-            if is_infix!(self.stack[idx].spec) && idx > 0 {
+            if is_infix!(self.stack[idx].spec)
-                if !is_op!(self.stack[idx - 1].spec) && !self.stack[idx - 1].tt.is_sep() {
+                && idx > 0
-                    return false;
+                && !is_op!(self.stack[idx - 1].spec)
-                }
+                && !self.stack[idx - 1].tt.is_sep()
+            {
+                return false;
             }
         } else {
             return false;
@@ -571,59 +577,57 @@ impl<'a, R: CharRead> Parser<'a, R> {
         let stack_len = self.stack.len() - 2 * arity - 1;
         let idx = self.terms.len() - arity;
 
-        if TokenType::Term == self.stack[stack_len].tt {
+        if TokenType::Term == self.stack[stack_len].tt
-            if atomize_term(&self.lexer.machine_st.atom_tbl, &self.terms[idx - 1]).is_some() {
+            && atomize_term(&self.lexer.machine_st.atom_tbl, &self.terms[idx - 1]).is_some()
-                self.stack.truncate(stack_len + 1);
+        {
+            self.stack.truncate(stack_len + 1);
 
-                let mut subterms: Vec<_> = self.terms.drain(idx..).collect();
+            let mut subterms: Vec<_> = self.terms.drain(idx..).collect();
 
-                if let Some(name) = self
+            if let Some(name) = self
-                    .terms
+                .terms
-                    .pop()
+                .pop()
-                    .and_then(|t| atomize_term(&self.lexer.machine_st.atom_tbl, &t))
+                .and_then(|t| atomize_term(&self.lexer.machine_st.atom_tbl, &t))
-                {
+            {
-                    // reduce the '.' functor to a cons cell if it applies.
+                // reduce the '.' functor to a cons cell if it applies.
-                    if name == atom!(".") && subterms.len() == 2 {
+                if name == atom!(".") && subterms.len() == 2 {
-                        let tail = subterms.pop().unwrap();
+                    let tail = subterms.pop().unwrap();
-                        let head = subterms.pop().unwrap();
+                    let head = subterms.pop().unwrap();
 
-                        self.terms.push(match as_partial_string(head, tail) {
+                    self.terms.push(match as_partial_string(head, tail) {
-                            Ok((string_buf, Some(tail))) => {
+                        Ok((string_buf, Some(tail))) => {
-                                Term::PartialString(Cell::default(), string_buf, tail)
+                            Term::PartialString(Cell::default(), string_buf, tail)
-                            }
-                            Ok((string_buf, None)) => {
-                                let atom = AtomTable::build_with(
-                                    &self.lexer.machine_st.atom_tbl,
-                                    &string_buf,
-                                );
-                                Term::CompleteString(Cell::default(), atom)
-                            }
-                            Err(term) => term,
-                        });
-                    } else {
-                        self.terms
-                            .push(Term::Clause(Cell::default(), name, subterms));
-                    }
-
-                    if let Some(&mut TokenDesc {
-                        ref mut tt,
-                        ref mut priority,
-                        ref mut spec,
-                        ref mut unfold_bounds,
-                    }) = self.stack.last_mut()
-                    {
-                        if *spec == BTERM {
-                            return false;
                         }
+                        Ok((string_buf, None)) => {
+                            let atom =
+                                AtomTable::build_with(&self.lexer.machine_st.atom_tbl, &string_buf);
+                            Term::CompleteString(Cell::default(), atom)
+                        }
+                        Err(term) => term,
+                    });
+                } else {
+                    self.terms
+                        .push(Term::Clause(Cell::default(), name, subterms));
+                }
 
-                        *tt = TokenType::Term;
+                if let Some(&mut TokenDesc {
-                        *priority = 0;
+                    ref mut tt,
-                        *spec = TERM;
+                    ref mut priority,
-                        *unfold_bounds = 0;
+                    ref mut spec,
+                    ref mut unfold_bounds,
+                }) = self.stack.last_mut()
+                {
+                    if *spec == BTERM {
+                        return false;
                     }
 
-                    return true;
+                    *tt = TokenType::Term;
+                    *priority = 0;
+                    *spec = TERM;
+                    *unfold_bounds = 0;
                 }
+
+                return true;
             }
         }
 
@@ -642,34 +646,31 @@ impl<'a, R: CharRead> Parser<'a, R> {
                 /* '|' is a head-tail separator here, not
                  * an operator, so expand the
                  * terms it compacted out again. */
-                match (term.name(), term.arity()) {
+                if let (Some(atom!(",")), 2) = (term.name(), term.arity()) {
-                    (Some(name), 2) if name == atom!(",") => {
+                    let terms = if op_desc.unfold_bounds == 0 {
-                        let terms = if op_desc.unfold_bounds == 0 {
+                        unfold_by_str(term, atom!(","))
-                            unfold_by_str(term, atom!(","))
+                    } else {
-                        } else {
+                        let mut terms = vec![];
-                            let mut terms = vec![];
 
-                            while let Some((fst, snd)) = unfold_by_str_once(&mut term, atom!(",")) {
+                        while let Some((fst, snd)) = unfold_by_str_once(&mut term, atom!(",")) {
-                                terms.push(fst);
+                            terms.push(fst);
-                                term = snd;
+                            term = snd;
 
-                                op_desc.unfold_bounds -= 2;
+                            op_desc.unfold_bounds -= 2;
 
-                                if op_desc.unfold_bounds == 0 {
+                            if op_desc.unfold_bounds == 0 {
-                                    break;
+                                break;
-                                }
                             }
+                        }
 
-                            terms.push(term);
+                        terms.push(term);
-                            terms
+                        terms
-                        };
+                    };
 
-                        let arity = terms.len() - 1;
+                    let arity = terms.len() - 1;
 
-                        self.terms.extend(terms.into_iter());
+                    self.terms.extend(terms);
-                        return arity;
+                    return arity;
-                    }
-                    _ => {}
                 }
             }
 
@@ -692,18 +693,15 @@ impl<'a, R: CharRead> Parser<'a, R> {
                 } else {
                     return None;
                 }
-            } else {
+            } else if desc.tt == TokenType::HeadTailSeparator {
-                if desc.tt == TokenType::HeadTailSeparator {
+                if arity == 1 {
-                    if arity == 1 {
+                    continue;
-                        continue;
-                    }
-
-                    return None;
-                } else if desc.tt == TokenType::OpenList {
-                    return Some(arity);
-                } else if desc.tt != TokenType::Comma {
-                    return None;
                 }
+                return None;
+            } else if desc.tt == TokenType::OpenList {
+                return Some(arity);
+            } else if desc.tt != TokenType::Comma {
+                return None;
             }
         }
 
@@ -882,7 +880,11 @@ impl<'a, R: CharRead> Parser<'a, R> {
                         .push(Term::Literal(Cell::default(), Literal::Atom(atom)));
                 }
 
-                self.stack[idx].spec = if self.stack[idx].priority > 0 { TERM } else { BTERM };
+                self.stack[idx].spec = if self.stack[idx].priority > 0 {
+                    TERM
+                } else {
+                    BTERM
+                };
                 self.stack[idx].tt = TokenType::Term;
                 self.stack[idx].priority = 0;
 
@@ -1018,13 +1020,11 @@ impl<'a, R: CharRead> Parser<'a, R> {
             Token::Open => self.shift(Token::Open, 1300, DELIMITER),
             Token::OpenCT => self.shift(Token::OpenCT, 1300, DELIMITER),
             Token::Close => {
-                if !self.reduce_term() {
+                if !self.reduce_term() && !self.reduce_brackets() {
-                    if !self.reduce_brackets() {
+                    return Err(ParserError::IncompleteReduction(
-                        return Err(ParserError::IncompleteReduction(
+                        self.lexer.line_num,
-                            self.lexer.line_num,
+                        self.lexer.col_num,
-                            self.lexer.col_num,
+                    ));
-                        ));
-                    }
                 }
             }
             Token::OpenList => self.shift(Token::OpenList, 1300, DELIMITER),

src/raw_block.rs

@@ -28,6 +28,7 @@ impl<T: RawBlockTraits> RawBlock<T> {
         }
     }
 
+    #[allow(clippy::new_without_default)]
     pub fn new() -> Self {
         let mut block = Self::empty_block();
 
@@ -71,7 +72,7 @@ impl<T: RawBlockTraits> RawBlock<T> {
             } else {
                 let allocated = (*self.ptr.get()) as usize - self.base as usize;
                 self.base.copy_to(new_block.base.cast_mut(), allocated);
-                *new_block.ptr.get_mut() = new_block.base.offset(allocated as isize).cast_mut();
+                *new_block.ptr.get_mut() = new_block.base.add(allocated).cast_mut();
                 Some(new_block)
             }
         }

src/rcu.rs

@@ -6,7 +6,7 @@ use std::{
     ptr::NonNull,
     sync::{
         atomic::{AtomicPtr, AtomicU8},
-        Arc, Weak, RwLock
+        Arc, RwLock, Weak,
     },
 };
 
@@ -52,7 +52,7 @@ impl<T> Rcu<T> {
                 // register the current threads epoch counter on init
                 EPOCH_COUNTERS
                     .write()
-		    .unwrap()
+                    .unwrap()
                     .push(Arc::downgrade(&epoch_counter));
                 epoch_counter
             });

src/read.rs

@@ -31,8 +31,8 @@ use std::sync::Arc;
 
 type SubtermDeque = VecDeque<(usize, usize)>;
 
-pub(crate) fn devour_whitespace<'a, R: CharRead>(
+pub(crate) fn devour_whitespace<R: CharRead>(
-    parser: &mut Parser<'a, R>,
+    parser: &mut Parser<'_, R>,
 ) -> Result<bool, ParserError> {
     match parser.lexer.scan_for_layout() {
         Err(e) if e.is_unexpected_eof() => Ok(true),
@@ -86,7 +86,7 @@ impl MachineState {
 
 static mut PROMPT: bool = false;
 #[cfg(feature = "repl")]
-const HISTORY_FILE: &'static str = ".scryer_history";
+const HISTORY_FILE: &str = ".scryer_history";
 
 pub(crate) fn set_prompt(value: bool) {
     unsafe {
@@ -137,7 +137,7 @@ impl ReadlineStream {
             ReadlineStream {
                 rl,
                 pending_input: CharReader::new(Cursor::new(pending_input.to_owned())),
-                add_history: add_history,
+                add_history,
             }
         }
 
@@ -145,7 +145,7 @@ impl ReadlineStream {
         {
             ReadlineStream {
                 pending_input: CharReader::new(Cursor::new(pending_input.to_owned())),
-                add_history: add_history,
+                add_history,
             }
         }
     }
@@ -187,7 +187,7 @@ impl ReadlineStream {
                         PROMPT = false;
                     }
 
-                    if self.pending_input.get_ref().get_ref().chars().last() != Some('\n') {
+                    if !self.pending_input.get_ref().get_ref().ends_with('\n') {
                         *self.pending_input.get_mut().get_mut() += "\n";
                     }
                 }
@@ -292,9 +292,9 @@ impl CharRead for ReadlineStream {
 }
 
 #[inline]
-pub(crate) fn write_term_to_heap<'a, 'b>(
+pub(crate) fn write_term_to_heap(
-    term: &'a Term,
+    term: &Term,
-    heap: &'b mut Heap,
+    heap: &mut Heap,
     atom_tbl: &AtomTable,
 ) -> Result<TermWriteResult, CompilationError> {
     let term_writer = TermWriter::new(heap, atom_tbl);
@@ -347,7 +347,7 @@ impl<'a, 'b> TermWriter<'a, 'b> {
         match term {
             &TermRef::Cons(..) => list_loc_as_cell!(h),
             &TermRef::AnonVar(_) | &TermRef::Var(..) => heap_loc_as_cell!(h),
-            &TermRef::CompleteString(_, _, ref src) => {
+            TermRef::CompleteString(_, _, src) => {
                 if src.as_str().is_empty() {
                     empty_list_as_cell!()
                 } else if self.heap[h].get_tag() == HeapCellValueTag::CStr {
@@ -358,7 +358,7 @@ impl<'a, 'b> TermWriter<'a, 'b> {
             }
             &TermRef::PartialString(..) => pstr_loc_as_cell!(h),
             &TermRef::Literal(_, _, literal) => HeapCellValue::from(*literal),
-            &TermRef::Clause(_, _, _, subterms) if subterms.len() == 0 => heap_loc_as_cell!(h),
+            &TermRef::Clause(_, _, _, subterms) if subterms.is_empty() => heap_loc_as_cell!(h),
             &TermRef::Clause(..) => str_loc_as_cell!(h),
         }
     }
@@ -390,7 +390,7 @@ impl<'a, 'b> TermWriter<'a, 'b> {
                         return Err(CompilationError::ExceededMaxArity);
                     }
 
-                    self.heap.push(if subterms.len() == 0 {
+                    self.heap.push(if subterms.is_empty() {
                         heap_loc_as_cell!(heap_loc + 1)
                     } else {
                         str_loc_as_cell!(heap_loc + 1)
@@ -438,11 +438,11 @@ impl<'a, 'b> TermWriter<'a, 'b> {
 
                     continue;
                 }
-                &TermRef::CompleteString(_, _, ref src) => {
+                TermRef::CompleteString(_, _, src) => {
                     let src = src.as_str().to_owned();
                     put_complete_string(self.heap, &src, self.atom_tbl);
                 }
-                &TermRef::PartialString(lvl, _, ref src, _) => {
+                &TermRef::PartialString(lvl, _, src, _) => {
                     if let Level::Root = lvl {
                         // Var tags can't refer directly to partial strings,
                         // so a PStrLoc cell must be pushed.
@@ -458,7 +458,7 @@ impl<'a, 'b> TermWriter<'a, 'b> {
                         continue;
                     }
                 }
-                &TermRef::Var(.., ref var) => {
+                TermRef::Var(.., var) => {
                     if let Some((arity, site_h)) = self.queue.pop_front() {
                         let var_key = VarKey::VarPtr(var.clone());
 

src/targets.rs

@@ -64,10 +64,7 @@ impl<'a> CompilationTarget<'a> for FactInstruction {
     }
 
     fn is_void_instr(instr: &Instruction) -> bool {
-        match instr {
+        matches!(instr, &Instruction::UnifyVoid(_))
-            &Instruction::UnifyVoid(_) => true,
-            _ => false,
-        }
     }
 
     fn to_pstr(lvl: Level, string: Atom, r: RegType, has_tail: bool) -> Instruction {
@@ -75,9 +72,8 @@ impl<'a> CompilationTarget<'a> for FactInstruction {
     }
 
     fn incr_void_instr(instr: &mut Instruction) {
-        match instr {
+        if let &mut Instruction::UnifyVoid(ref mut incr) = instr {
-            &mut Instruction::UnifyVoid(ref mut incr) => *incr += 1,
+            *incr += 1
-            _ => {}
         }
     }
 
@@ -146,16 +142,12 @@ impl<'a> CompilationTarget<'a> for QueryInstruction {
     }
 
     fn is_void_instr(instr: &Instruction) -> bool {
-        match instr {
+        matches!(instr, &Instruction::SetVoid(_))
-            &Instruction::SetVoid(_) => true,
-            _ => false,
-        }
     }
 
     fn incr_void_instr(instr: &mut Instruction) {
-        match instr {
+        if let &mut Instruction::SetVoid(ref mut incr) = instr {
-            &mut Instruction::SetVoid(ref mut incr) => *incr += 1,
+            *incr += 1
-            _ => {}
         }
     }
 

src/types.rs

@@ -194,6 +194,7 @@ pub enum TrailRef {
     BlackboardOffset(Atom, HeapCellValue), // key atom, key value
 }
 
+#[allow(clippy::enum_variant_names)]
 #[derive(BitfieldSpecifier, Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
 #[bits = 6]
 pub(crate) enum TrailEntryTag {
@@ -331,7 +332,7 @@ impl From<ConsPtr> for HeapCellValue {
     }
 }
 
-impl<'a> From<(Number, &mut Arena)> for HeapCellValue {
+impl From<(Number, &mut Arena)> for HeapCellValue {
     #[inline(always)]
     fn from((n, arena): (Number, &mut Arena)) -> HeapCellValue {
         use ordered_float::OrderedFloat;
@@ -393,16 +394,16 @@ impl HeapCellValue {
 
     #[inline]
     pub fn is_ref(self) -> bool {
-        match self.get_tag() {
+        matches!(
+            self.get_tag(),
             HeapCellValueTag::Str
-            | HeapCellValueTag::Lis
+                | HeapCellValueTag::Lis
-            | HeapCellValueTag::Var
+                | HeapCellValueTag::Var
-            | HeapCellValueTag::StackVar
+                | HeapCellValueTag::StackVar
-            | HeapCellValueTag::AttrVar
+                | HeapCellValueTag::AttrVar
-            | HeapCellValueTag::PStrLoc
+                | HeapCellValueTag::PStrLoc
-            | HeapCellValueTag::PStrOffset => true,
+                | HeapCellValueTag::PStrOffset
-            _ => false,
+        )
-        }
     }
 
     #[inline]
@@ -491,7 +492,7 @@ impl HeapCellValue {
 
     #[inline]
     pub fn get_value(self) -> u64 {
-        self.val() as u64
+        self.val()
     }
 
     #[inline]
@@ -739,10 +740,7 @@ impl UntypedArenaPtr {
 
     #[inline]
     pub fn payload_offset(self) -> *const u8 {
-        unsafe {
+        unsafe { self.get_ptr().add(mem::size_of::<ArenaHeader>()) }
-            self.get_ptr()
-                .offset(mem::size_of::<ArenaHeader>() as isize)
-        }
     }
 
     #[inline]
@@ -806,7 +804,7 @@ impl Sub<i64> for HeapCellValue {
                 | tag @ HeapCellValueTag::PStrLoc
                 | tag @ HeapCellValueTag::Var
                 | tag @ HeapCellValueTag::AttrVar => {
-                    HeapCellValue::build_with(tag, self.get_value() + rhs.abs() as u64)
+                    HeapCellValue::build_with(tag, self.get_value() + rhs.unsigned_abs())
                 }
                 _ => self,
             }

src/variable_records.rs

@@ -74,10 +74,7 @@ impl PermVarAllocation {
 
     #[inline]
     pub(crate) fn pending(&self) -> bool {
-        match self {
+        matches!(self, &PermVarAllocation::Pending)
-            &PermVarAllocation::Pending => true,
-            _ => false,
-        }
     }
 }
 
@@ -96,9 +93,9 @@ pub enum VarAlloc {
 impl VarAlloc {
     #[inline]
     pub(crate) fn as_reg_type(&self) -> RegType {
-        match self {
+        match *self {
-            &VarAlloc::Temp { temp_reg, .. } => RegType::Temp(temp_reg),
+            VarAlloc::Temp { temp_reg, .. } => RegType::Temp(temp_reg),
-            &VarAlloc::Perm(r, _) => RegType::Perm(r),
+            VarAlloc::Perm(r, _) => RegType::Perm(r),
         }
     }
 
@@ -129,7 +126,7 @@ impl TempVarData {
             }
         }
 
-        return false;
+        false
     }
 
     pub(crate) fn populate_conflict_set(&mut self) {
@@ -201,16 +198,13 @@ impl VariableRecords {
             IndexMap::new();
 
         for (var_gen_index, record) in self.0.iter_mut().enumerate() {
-            match &mut record.allocation {
+            if let VarAlloc::Temp { temp_var_data, .. } = &mut record.allocation {
-                VarAlloc::Temp { temp_var_data, .. } => {
+                let use_set = std::mem::replace(
-                    let use_set = std::mem::replace(
+                    &mut temp_var_data.use_set,
-                        &mut temp_var_data.use_set,
+                    IndexSet::with_hasher(FxBuildHasher::default()),
-                        IndexSet::with_hasher(FxBuildHasher::default()),
+                );
-                    );
 
-                    use_sets.insert(var_gen_index, use_set);
+                use_sets.insert(var_gen_index, use_set);
-                }
-                _ => {}
             }
         }
 
@@ -219,19 +213,18 @@ impl VariableRecords {
             for &(term_loc, reg) in &use_set {
                 if let GenContext::Last(cn_u) = term_loc {
                     for (var_gen_index, record) in self.0.iter_mut().enumerate() {
-                        match &mut record.allocation {
+                        if let VarAlloc::Temp {
-                            VarAlloc::Temp {
+                            term_loc,
-                                term_loc,
+                            temp_var_data,
-                                temp_var_data,
+                            ..
-                                ..
+                        } = &mut record.allocation
-                            } => {
+                        {
-                                if cn_u == term_loc.chunk_num() && u != var_gen_index {
+                            if cn_u == term_loc.chunk_num()
-                                    if !temp_var_data.uses_reg(reg) {
+                                && u != var_gen_index
-                                        temp_var_data.no_use_set.insert(reg);
+                                && !temp_var_data.uses_reg(reg)
-                                    }
+                            {
-                                }
+                                temp_var_data.no_use_set.insert(reg);
                             }
-                            _ => {}
                         }
                     }
                 }

tests/scryer/issues.rs

@@ -69,7 +69,7 @@ fn handle_residual_goal() {
 #[test]
 fn occurs_check_flag() {
     run_top_level_test_with_args(
-        &["tests-pl/issue841-occurs-check.pl"],
+        ["tests-pl/issue841-occurs-check.pl"],
         "\
          f(X, X).\n\
          halt.\n\
@@ -102,14 +102,14 @@ fn occurs_check_flag2() {
 // issue #839
 #[test]
 fn op3() {
-    run_top_level_test_with_args(&["tests-pl/issue839-op3.pl", "-g", "halt"], "", "")
+    run_top_level_test_with_args(["tests-pl/issue839-op3.pl", "-g", "halt"], "", "")
 }
 
 // issue #820
 #[test]
 fn multiple_goals() {
     run_top_level_test_with_args(
-        &["-g", "test", "-g", "halt", "tests-pl/issue820-goals.pl"],
+        ["-g", "test", "-g", "halt", "tests-pl/issue820-goals.pl"],
         "",
         "helloworld\n",
     );
@@ -119,7 +119,7 @@ fn multiple_goals() {
 #[test]
 fn compound_goal() {
     run_top_level_test_with_args(
-        &["-g", "test,halt", "tests-pl/issue820-goals.pl"],
+        ["-g", "test,halt", "tests-pl/issue820-goals.pl"],
         "",
         "helloworld\n",
     )

tests/scryer/src_tests.rs

@@ -58,7 +58,7 @@ fn setup_call_cleanup_load() {
 #[test]
 fn setup_call_cleanup_process() {
     run_top_level_test_with_args(
-        &["src/tests/setup_call_cleanup.pl", "-f", "-g", "halt"],
+        ["src/tests/setup_call_cleanup.pl", "-f", "-g", "halt"],
         "",
         "1+21+31+2>A+B1+G1+2>41+2>B1+2>31+2>31+2>4ba",
     );
@@ -79,7 +79,7 @@ fn iso_conformity_tests() {
 #[test]
 fn dif_tests() {
     run_top_level_test_with_args(
-        &["src/tests/dif.pl", "-f", "-g", "main_quiet"],
+        ["src/tests/dif.pl", "-f", "-g", "main_quiet"],
         "",
         "All tests passed",
     );
@@ -88,7 +88,7 @@ fn dif_tests() {
 #[test]
 fn ground_tests() {
     run_top_level_test_with_args(
-        &["src/tests/ground.pl", "-f", "-g", "main_quiet"],
+        ["src/tests/ground.pl", "-f", "-g", "main_quiet"],
         "",
         "All tests passed",
     );
@@ -97,7 +97,7 @@ fn ground_tests() {
 #[test]
 fn term_variables_tests() {
     run_top_level_test_with_args(
-        &["src/tests/term_variables.pl", "-f", "-g", "main_quiet"],
+        ["src/tests/term_variables.pl", "-f", "-g", "main_quiet"],
         "",
         "All tests passed",
     );
@@ -106,7 +106,7 @@ fn term_variables_tests() {
 #[test]
 fn acyclic_term_tests() {
     run_top_level_test_with_args(
-        &["src/tests/acyclic_term.pl", "-f", "-g", "main_quiet"],
+        ["src/tests/acyclic_term.pl", "-f", "-g", "main_quiet"],
         "",
         "All tests passed",
     );