fix failing lint warnings in beta build

src/machine/mod.rs

@@ -109,7 +109,7 @@ impl LoadContext {
 #[derive(Debug)]
 pub struct Machine {
     pub(super) machine_st: MachineState,
-    pub(super) inner_heap: Heap,
+    pub(super) _inner_heap: Heap,
     pub(super) policies: MachinePolicies,
     pub(super) indices: IndexStore,
     pub(super) code_repo: CodeRepo,
@@ -280,7 +280,7 @@ impl Machine {
 
         let mut wam = Machine {
             machine_st: MachineState::new(),
-            inner_heap: Heap::new(),
+            _inner_heap: Heap::new(),
             policies: MachinePolicies::new(),
             indices: IndexStore::new(),
             code_repo: CodeRepo::new(),

src/machine/preprocessor.rs

@@ -553,14 +553,14 @@ fn qualified_clause_to_query_term<'a>(
 
 #[derive(Debug)]
 pub(crate) struct Preprocessor {
-    flags: MachineFlags,
+    _flags: MachineFlags,
     queue: VecDeque<VecDeque<Term>>,
 }
 
 impl Preprocessor {
     pub(super) fn new(flags: MachineFlags) -> Self {
         Preprocessor {
-            flags,
+            _flags: flags,
             queue: VecDeque::new(),
         }
     }

src/machine/stack.rs

@@ -109,7 +109,7 @@ pub(crate) struct OrFramePrelude {
     pub(crate) b: usize,
     pub(crate) bp: LocalCodePtr,
     pub(crate) tr: usize,
-    pub(crate) pstr_tr: usize,
+    pub(crate) _pstr_tr: usize,
     pub(crate) h: usize,
     pub(crate) b0: usize,
 }