Re-use memory in program_clauses_for_env

Author: scalexm

src/librustc/ich/impls_ty.rs

@@ -1424,15 +1424,12 @@ impl_stable_hash_for!(enum traits::QuantifierKind {
     Existential
 });
 
-<<<<<<< HEAD
 impl_stable_hash_for!(struct ty::subst::UserSubsts<'tcx> { substs, user_self_ty });
 
 impl_stable_hash_for!(struct ty::subst::UserSelfTy<'tcx> { impl_def_id, self_ty });
 
-=======
 impl_stable_hash_for!(
     impl<'tcx> for struct traits::Environment<'tcx> {
         clauses,
     }
 );
->>>>>>> Use `Environment` instead of `ty::ParamEnv` in chalk context

src/librustc_traits/lowering/environment.rs

@@ -21,7 +21,7 @@ use rustc::ty::{self, TyCtxt, Ty};
 use rustc::hir::def_id::DefId;
 use rustc_data_structures::fx::FxHashSet;
 
-struct ClauseVisitor<'set, 'a, 'tcx: 'a> {
+struct ClauseVisitor<'set, 'a, 'tcx: 'a + 'set> {
     tcx: TyCtxt<'a, 'tcx, 'tcx>,
     round: &'set mut FxHashSet<Clause<'tcx>>,
 }
@@ -154,12 +154,12 @@ crate fn program_clauses_for_env<'a, 'tcx>(
     let mut next_round = FxHashSet();
     while !last_round.is_empty() {
         let mut visitor = ClauseVisitor::new(tcx, &mut next_round);
-        for clause in last_round {
+        for clause in last_round.drain() {
             visitor.visit_clause(clause);
         }
-        last_round = next_round.drain()
-            .filter(|&clause| closure.insert(clause))
-            .collect();
+        last_round.extend(
+            next_round.drain().filter(|&clause| closure.insert(clause))
+        );
     }
 
     debug!("program_clauses_for_env: closure = {:#?}", closure);