Auto merge of #753 - Kinrany:cleanup-clippy-warnings, r=jackh726

Fix clippy warnings

This PR contains:

* Trivial Clippy fixes such as `needless_borrow`, `redundant_clone`, `match_like_matches_macro`, `try_err`, `needless_return`, ...
* Small local refactors, which I will point out in comments.

Each type of change is in a separate commit, except for the last commit that has a mix of unique changes.

The 18 remaining clippy errors are a bit more substantial.

chalk-derive/src/lib.rs

@@ -84,7 +84,7 @@ fn find_interner(s: &mut synstructure::Structure) -> (TokenStream, DeriveKind) {
 
     let generic_param0 = get_generic_param(input);
 
-    if let Some(param) = has_interner(&generic_param0) {
+    if let Some(param) = has_interner(generic_param0) {
         // HasInterner bound:
         //
         // Example:
@@ -98,7 +98,7 @@ fn find_interner(s: &mut synstructure::Structure) -> (TokenStream, DeriveKind) {
         );
 
         (quote! { _I }, DeriveKind::FromHasInterner)
-    } else if let Some(i) = is_interner(&generic_param0) {
+    } else if let Some(i) = is_interner(generic_param0) {
         // Interner bound:
         //
         // Example:

chalk-engine/src/context.rs

@@ -27,10 +27,7 @@ pub enum AnswerResult<I: Interner> {
 
 impl<I: Interner> AnswerResult<I> {
     pub fn is_answer(&self) -> bool {
-        match self {
-            Self::Answer(_) => true,
-            _ => false,
-        }
+        matches!(self, Self::Answer(_))
     }
 
     pub fn answer(self) -> CompleteAnswer<I> {
@@ -41,17 +38,11 @@ impl<I: Interner> AnswerResult<I> {
     }
 
     pub fn is_no_more_solutions(&self) -> bool {
-        match self {
-            Self::NoMoreSolutions => true,
-            _ => false,
-        }
+        matches!(self, Self::NoMoreSolutions)
     }
 
     pub fn is_quantum_exceeded(&self) -> bool {
-        match self {
-            Self::QuantumExceeded => true,
-            _ => false,
-        }
+        matches!(self, Self::QuantumExceeded)
     }
 }
 

chalk-engine/src/logic.rs

@@ -687,7 +687,7 @@ impl<'forest, I: Interner> SolveState<'forest, I> {
                         ex_clause.answer_time.increment();
 
                         // Ok, we've applied the answer to this Strand.
-                        return Ok(());
+                        Ok(())
                     }
 
                     // This answer led nowhere. Give up for now, but of course
@@ -700,7 +700,7 @@ impl<'forest, I: Interner> SolveState<'forest, I> {
 
                         // Now we want to propogate back to the up with `QuantumExceeded`
                         self.unwind_stack();
-                        return Err(RootSearchFail::QuantumExceeded);
+                        Err(RootSearchFail::QuantumExceeded)
                     }
                 }
             }
@@ -749,9 +749,9 @@ impl<'forest, I: Interner> SolveState<'forest, I> {
                 strand.ex_clause.ambiguous = true;
 
                 // Strand is ambigious.
-                return Ok(());
+                Ok(())
             }
-        };
+        }
     }
 
     /// This is called when the selected subgoal for a strand has floundered.
@@ -951,7 +951,7 @@ impl<'forest, I: Interner> SolveState<'forest, I> {
                 Ok(_) => {
                     debug!(?strand, "merged answer into current strand");
                     canonical_strand =
-                        Forest::canonicalize_strand_from(&self.context, &mut infer, &strand);
+                        Forest::canonicalize_strand_from(self.context, &mut infer, &strand);
                     self.stack.top().active_strand = Some(canonical_strand);
                     return Ok(());
                 }
@@ -1224,7 +1224,7 @@ impl<'forest, I: Interner> SolveState<'forest, I> {
 
             // Now we yield with `QuantumExceeded`
             self.unwind_stack();
-            return Err(RootSearchFail::QuantumExceeded);
+            Err(RootSearchFail::QuantumExceeded)
         } else {
             debug!("table part of a cycle");
 
@@ -1267,7 +1267,7 @@ impl<'forest, I: Interner> SolveState<'forest, I> {
             self.forest.tables[table].enqueue_strand(active_strand);
 
             // The strand isn't active, but the table is, so just continue
-            return Ok(());
+            Ok(())
         }
     }
 
@@ -1483,7 +1483,7 @@ impl<'forest, I: Interner> SolveState<'forest, I> {
             .collect();
 
         let subst = Canonical {
-            binders: binders.clone(),
+            binders,
             value: AnswerSubst {
                 subst,
                 constraints: Constraints::from_iter(self.context.program().interner(), constraints),

chalk-engine/src/slg/aggregate.rs

@@ -31,7 +31,7 @@ impl<I: Interner> AggregateOps<I> for SlgContextOps<'_, I> {
         should_continue: impl std::ops::Fn() -> bool,
     ) -> Option<Solution<I>> {
         let interner = self.program.interner();
-        let CompleteAnswer { subst, ambiguous } = match answers.next_answer(|| should_continue()) {
+        let CompleteAnswer { subst, ambiguous } = match answers.next_answer(&should_continue) {
             AnswerResult::NoMoreSolutions => {
                 // No answers at all
                 return None;
@@ -47,7 +47,7 @@ impl<I: Interner> AggregateOps<I> for SlgContextOps<'_, I> {
         };
 
         // Exactly 1 unconditional answer?
-        let next_answer = answers.peek_answer(|| should_continue());
+        let next_answer = answers.peek_answer(&should_continue);
         if next_answer.is_quantum_exceeded() {
             if subst.value.subst.is_identity_subst(interner) {
                 return Some(Solution::Ambig(Guidance::Unknown));
@@ -95,7 +95,7 @@ impl<I: Interner> AggregateOps<I> for SlgContextOps<'_, I> {
                 }
             }
 
-            let new_subst = match answers.next_answer(|| should_continue()) {
+            let new_subst = match answers.next_answer(&should_continue) {
                 AnswerResult::Answer(answer1) => answer1.subst,
                 AnswerResult::Floundered => {
                     // FIXME: this doesn't trigger for any current tests

chalk-engine/src/slg/resolvent.rs

@@ -329,7 +329,7 @@ impl<I: Interner> AnswerSubstitutor<'_, I> {
         let result = self.table.relate(
             interner,
             db,
-            &self.environment,
+            self.environment,
             variance,
             answer_param,
             &GenericArg::new(interner, pending_shifted),

chalk-engine/src/strand.rs

@@ -45,7 +45,7 @@ impl<I: Interner> Fold<I> for Strand<I> {
         Ok(Strand {
             ex_clause: self.ex_clause.fold_with(folder, outer_binder)?,
             last_pursued_time: self.last_pursued_time,
-            selected_subgoal: self.selected_subgoal.clone(),
+            selected_subgoal: self.selected_subgoal,
         })
     }
 }

chalk-engine/src/table.rs

@@ -83,7 +83,7 @@ impl<I: Interner> Table<I> {
     }
 
     pub(crate) fn take_strands(&mut self) -> VecDeque<CanonicalStrand<I>> {
-        mem::replace(&mut self.strands, VecDeque::new())
+        mem::take(&mut self.strands)
     }
 
     /// Remove the next strand from the queue that meets the given criteria

chalk-integration/src/db.rs

@@ -40,7 +40,7 @@ impl ChalkDatabase {
 
     pub fn with_program<R>(&self, op: impl FnOnce(&Program) -> R) -> R {
         let program = &self.checked_program().unwrap();
-        tls::set_current_program(&program, || op(&program))
+        tls::set_current_program(program, || op(program))
     }
 
     pub fn parse_and_lower_goal(&self, text: &str) -> Result<Goal<ChalkIr>, ChalkError> {

chalk-integration/src/interner.rs

@@ -241,23 +241,23 @@ impl Interner for ChalkIr {
         Arc::new(TyData { kind, flags })
     }
 
-    fn ty_data<'a>(self, ty: &'a Arc<TyData<ChalkIr>>) -> &'a TyData<Self> {
+    fn ty_data(self, ty: &Arc<TyData<ChalkIr>>) -> &TyData<Self> {
         ty
     }
 
     fn intern_lifetime(self, lifetime: LifetimeData<ChalkIr>) -> LifetimeData<ChalkIr> {
         lifetime
     }
 
-    fn lifetime_data<'a>(self, lifetime: &'a LifetimeData<ChalkIr>) -> &'a LifetimeData<ChalkIr> {
+    fn lifetime_data(self, lifetime: &LifetimeData<ChalkIr>) -> &LifetimeData<ChalkIr> {
         lifetime
     }
 
     fn intern_const(self, constant: ConstData<ChalkIr>) -> Arc<ConstData<ChalkIr>> {
         Arc::new(constant)
     }
 
-    fn const_data<'a>(self, constant: &'a Arc<ConstData<ChalkIr>>) -> &'a ConstData<ChalkIr> {
+    fn const_data(self, constant: &Arc<ConstData<ChalkIr>>) -> &ConstData<ChalkIr> {
         constant
     }
 
@@ -269,18 +269,15 @@ impl Interner for ChalkIr {
         generic_arg
     }
 
-    fn generic_arg_data<'a>(
-        self,
-        generic_arg: &'a GenericArgData<ChalkIr>,
-    ) -> &'a GenericArgData<ChalkIr> {
+    fn generic_arg_data(self, generic_arg: &GenericArgData<ChalkIr>) -> &GenericArgData<ChalkIr> {
         generic_arg
     }
 
     fn intern_goal(self, goal: GoalData<ChalkIr>) -> Arc<GoalData<ChalkIr>> {
         Arc::new(goal)
     }
 
-    fn goal_data<'a>(self, goal: &'a Arc<GoalData<ChalkIr>>) -> &'a GoalData<ChalkIr> {
+    fn goal_data(self, goal: &Arc<GoalData<ChalkIr>>) -> &GoalData<ChalkIr> {
         goal
     }
 
@@ -291,7 +288,7 @@ impl Interner for ChalkIr {
         data.into_iter().collect()
     }
 
-    fn goals_data<'a>(self, goals: &'a Vec<Goal<ChalkIr>>) -> &'a [Goal<ChalkIr>] {
+    fn goals_data(self, goals: &Vec<Goal<ChalkIr>>) -> &[Goal<ChalkIr>] {
         goals
     }
 
@@ -302,21 +299,15 @@ impl Interner for ChalkIr {
         data.into_iter().collect()
     }
 
-    fn substitution_data<'a>(
-        self,
-        substitution: &'a Vec<GenericArg<ChalkIr>>,
-    ) -> &'a [GenericArg<ChalkIr>] {
+    fn substitution_data(self, substitution: &Vec<GenericArg<ChalkIr>>) -> &[GenericArg<ChalkIr>] {
         substitution
     }
 
     fn intern_program_clause(self, data: ProgramClauseData<Self>) -> ProgramClauseData<Self> {
         data
     }
 
-    fn program_clause_data<'a>(
-        self,
-        clause: &'a ProgramClauseData<Self>,
-    ) -> &'a ProgramClauseData<Self> {
+    fn program_clause_data(self, clause: &ProgramClauseData<Self>) -> &ProgramClauseData<Self> {
         clause
     }
 
@@ -327,10 +318,7 @@ impl Interner for ChalkIr {
         data.into_iter().collect()
     }
 
-    fn program_clauses_data<'a>(
-        self,
-        clauses: &'a Vec<ProgramClause<Self>>,
-    ) -> &'a [ProgramClause<Self>] {
+    fn program_clauses_data(self, clauses: &Vec<ProgramClause<Self>>) -> &[ProgramClause<Self>] {
         clauses
     }
 
@@ -341,10 +329,10 @@ impl Interner for ChalkIr {
         data.into_iter().collect()
     }
 
-    fn quantified_where_clauses_data<'a>(
+    fn quantified_where_clauses_data(
         self,
-        clauses: &'a Self::InternedQuantifiedWhereClauses,
-    ) -> &'a [QuantifiedWhereClause<Self>] {
+        clauses: &Self::InternedQuantifiedWhereClauses,
+    ) -> &[QuantifiedWhereClause<Self>] {
         clauses
     }
     fn intern_generic_arg_kinds<E>(
@@ -354,10 +342,10 @@ impl Interner for ChalkIr {
         data.into_iter().collect()
     }
 
-    fn variable_kinds_data<'a>(
+    fn variable_kinds_data(
         self,
-        variable_kinds: &'a Self::InternedVariableKinds,
-    ) -> &'a [VariableKind<ChalkIr>] {
+        variable_kinds: &Self::InternedVariableKinds,
+    ) -> &[VariableKind<ChalkIr>] {
         variable_kinds
     }
 
@@ -368,10 +356,10 @@ impl Interner for ChalkIr {
         data.into_iter().collect()
     }
 
-    fn canonical_var_kinds_data<'a>(
+    fn canonical_var_kinds_data(
         self,
-        canonical_var_kinds: &'a Self::InternedCanonicalVarKinds,
-    ) -> &'a [CanonicalVarKind<ChalkIr>] {
+        canonical_var_kinds: &Self::InternedCanonicalVarKinds,
+    ) -> &[CanonicalVarKind<ChalkIr>] {
         canonical_var_kinds
     }
 
@@ -382,10 +370,10 @@ impl Interner for ChalkIr {
         data.into_iter().collect()
     }
 
-    fn constraints_data<'a>(
+    fn constraints_data(
         self,
-        constraints: &'a Self::InternedConstraints,
-    ) -> &'a [InEnvironment<Constraint<Self>>] {
+        constraints: &Self::InternedConstraints,
+    ) -> &[InEnvironment<Constraint<Self>>] {
         constraints
     }
 
@@ -396,7 +384,7 @@ impl Interner for ChalkIr {
         data.into_iter().collect()
     }
 
-    fn variances_data<'a>(self, variances: &'a Self::InternedVariances) -> &'a [Variance] {
+    fn variances_data(self, variances: &Self::InternedVariances) -> &[Variance] {
         variances
     }
 }