Revert "remove Term"

This reverts commit 3b5879841aedecba5057c70c71da0ba23e5cd84a.

src/machine/gc.rs

@@ -1,3 +1,10 @@
+#[cfg(test)]
+use fxhash::FxBuildHasher;
+#[cfg(test)]
+use indexmap::IndexMap;
+#[cfg(test)]
+use std::collections::BTreeMap;
+
 #[cfg(test)]
 use crate::atom_table::*;
 #[cfg(test)]
@@ -8,17 +15,6 @@ use crate::types::*;
 #[cfg(test)]
 use crate::heap_iter::{FocusedHeapIter, HeapOrStackTag, IterStackLoc};
 
-#[cfg(test)]
-use std::collections::BTreeMap;
-#[cfg(test)]
-use std::ops::Deref;
-
-#[cfg(test)]
-use fxhash::FxBuildHasher;
-
-#[cfg(test)]
-use indexmap::IndexMap;
-
 #[cfg(test)]
 pub(crate) trait UnmarkPolicy {
     fn forward_attr_var(iter: &mut StacklessPreOrderHeapIter<Self>) -> Option<HeapCellValue>
@@ -185,15 +181,6 @@ pub(crate) struct StacklessPreOrderHeapIter<'a, UMP: UnmarkPolicy> {
     pstr_loc_values: PStrLocValuesMap,
 }
 
-#[cfg(test)]
-impl<'a> Deref for StacklessPreOrderHeapIter<'a, IteratorUMP> {
-    type Target = Heap;
-
-    fn deref(&self) -> &Self::Target {
-        self.heap
-    }
-}
-
 #[cfg(test)]
 impl<'a> FocusedHeapIter for StacklessPreOrderHeapIter<'a, IteratorUMP> {
     #[inline]
@@ -778,7 +765,7 @@ mod tests {
         // two-part complete string, then a three-part cyclic string
         // involving an uncompacted list of chars.
 
-        let pstr_cell = wam.machine_st.allocate_pstr("abc ").unwrap();
+        let pstr_cell = wam.machine_st.heap.allocate_pstr("abc ").unwrap();
 
         wam.machine_st.heap.push_cell(heap_loc_as_cell!(1)).unwrap();
 
@@ -812,7 +799,7 @@ mod tests {
 
         wam.machine_st.heap[1] = pstr_loc_as_cell!(heap_index!(3));
 
-        wam.machine_st.allocate_pstr("abcdef ").unwrap();
+        wam.machine_st.heap.allocate_pstr("abcdef ").unwrap();
         wam.machine_st.heap.push_cell(heap_loc_as_cell!(5)).unwrap();
 
         mark_cells(&mut wam.machine_st.heap, 2);