Eliminated mutable reference requirement and substitution clones.

Author: aatxe

chalk-engine/src/context/mod.rs

@@ -291,15 +291,15 @@ pub trait Environment<C: Context, I: InferenceContext<C>>: Debug + Clone {
 
 pub trait CanonicalExClause<C: Context>: Debug {
     /// Extracts the inner normalized substitution.
-    fn inference_normalized_subst(&self) -> C::InferenceNormalizedSubst;
+    fn inference_normalized_subst(&self) -> &C::InferenceNormalizedSubst;
 }
 
 pub trait CanonicalConstrainedSubst<C: Context>: Clone + Debug + Eq + Hash + Ord {
     /// True if this solution has no region constraints.
     fn empty_constraints(&self) -> bool;
 
     /// Extracts the inner normalized substitution.
-    fn inference_normalized_subst(&self) -> C::InferenceNormalizedSubst;
+    fn inference_normalized_subst(&self) -> &C::InferenceNormalizedSubst;
 }
 
 pub trait DomainGoal<C: Context, I: InferenceContext<C>>: Debug {
@@ -358,6 +358,6 @@ pub trait AnswerStream<C: Context> {
     /// if we find any answer for which `test` returns true.
     fn any_future_answer(
         &mut self,
-        test: impl FnMut(&mut C::InferenceNormalizedSubst) -> bool,
+        test: impl FnMut(&C::InferenceNormalizedSubst) -> bool,
     ) -> bool;
 }

chalk-engine/src/forest.rs

@@ -174,7 +174,7 @@ where
 
     fn any_future_answer(
         &mut self,
-        test: impl FnMut(&mut C::InferenceNormalizedSubst) -> bool,
+        test: impl FnMut(&C::InferenceNormalizedSubst) -> bool,
     ) -> bool {
         self.forest.any_future_answer(self.table, self.answer, test)
     }

chalk-engine/src/logic.rs

@@ -107,15 +107,15 @@ impl<C: Context> Forest<C> {
         &mut self,
         table: TableIndex,
         answer: AnswerIndex,
-        mut test: impl FnMut(&mut C::InferenceNormalizedSubst) -> bool,
+        mut test: impl FnMut(&C::InferenceNormalizedSubst) -> bool,
     ) -> bool {
         if let Some(answer) = self.tables[table].answer(answer) {
             info!("answer cached = {:?}", answer);
-            return test(&mut answer.subst.inference_normalized_subst());
+            return test(answer.subst.inference_normalized_subst());
         }
 
         self.tables[table].strands_mut().any(|strand| {
-            test(&mut strand.canonical_ex_clause.inference_normalized_subst())
+            test(strand.canonical_ex_clause.inference_normalized_subst())
         })
     }
 

src/solve/slg/implementation/mod.rs

@@ -240,7 +240,7 @@ impl context::Environment<SlgContext, SlgContext> for Arc<Environment> {
 }
 
 impl Substitution {
-    fn may_invalidate(&mut self, subst: &Canonical<Substitution>) -> bool {
+    fn may_invalidate(&self, subst: &Canonical<Substitution>) -> bool {
         self.parameters
             .iter()
             .zip(&subst.value.parameters)
@@ -413,8 +413,8 @@ impl context::DomainGoal<SlgContext, SlgContext> for DomainGoal {
 }
 
 impl context::CanonicalExClause<SlgContext> for Canonical<ExClause<SlgContext, SlgContext>> {
-    fn inference_normalized_subst(&self) -> Substitution {
-        self.value.subst.clone()
+    fn inference_normalized_subst(&self) -> &Substitution {
+        &self.value.subst
     }
 }
 
@@ -423,8 +423,8 @@ impl context::CanonicalConstrainedSubst<SlgContext> for Canonical<ConstrainedSub
         self.value.constraints.is_empty()
     }
 
-    fn inference_normalized_subst(&self) -> Substitution {
-        self.value.subst.clone()
+    fn inference_normalized_subst(&self) -> &Substitution {
+        &self.value.subst
     }
 }