Introduce `DeepRejectCtxt::substs_refs_may_unify`.

It factors out a repeated code pattern.

4 files changed, 12 insertions, 13 deletions

diff --git a/compiler/rustc_trait_selection/src/solve/project_goals.rs b/compiler/rustc_trait_selection/src/solve/project_goals.rs
index 2b104703aab..91b56fe3522 100644
--- a/compiler/rustc_trait_selection/src/solve/project_goals.rs
+++ b/compiler/rustc_trait_selection/src/solve/project_goals.rs
@@ -17,7 +17,6 @@ use rustc_middle::ty::ProjectionPredicate;
 use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_middle::ty::{ToPredicate, TypeVisitableExt};
 use rustc_span::{sym, DUMMY_SP};
-use std::iter;
 
 impl<'tcx> EvalCtxt<'_, 'tcx> {
     #[instrument(level = "debug", skip(self), ret)]
@@ -144,9 +143,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {
         let goal_trait_ref = goal.predicate.projection_ty.trait_ref(tcx);
         let impl_trait_ref = tcx.impl_trait_ref(impl_def_id).unwrap();
         let drcx = DeepRejectCtxt { treat_obligation_params: TreatParams::ForLookup };
-        if iter::zip(goal_trait_ref.substs, impl_trait_ref.skip_binder().substs)
-            .any(|(goal, imp)| !drcx.generic_args_may_unify(goal, imp))
-        {
+        if !drcx.substs_refs_may_unify(goal_trait_ref.substs, impl_trait_ref.skip_binder().substs) {
             return Err(NoSolution);
         }
 
diff --git a/compiler/rustc_trait_selection/src/solve/trait_goals.rs b/compiler/rustc_trait_selection/src/solve/trait_goals.rs
index 718c82c8f1f..f522a8f7e65 100644
--- a/compiler/rustc_trait_selection/src/solve/trait_goals.rs
+++ b/compiler/rustc_trait_selection/src/solve/trait_goals.rs
@@ -1,7 +1,5 @@
 //! Dealing with trait goals, i.e. `T: Trait<'a, U>`.
 
-use std::iter;
-
 use super::{assembly, EvalCtxt, SolverMode};
 use rustc_hir::def_id::DefId;
 use rustc_hir::LangItem;
@@ -41,9 +39,10 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
 
         let impl_trait_ref = tcx.impl_trait_ref(impl_def_id).unwrap();
         let drcx = DeepRejectCtxt { treat_obligation_params: TreatParams::ForLookup };
-        if iter::zip(goal.predicate.trait_ref.substs, impl_trait_ref.skip_binder().substs)
-            .any(|(goal, imp)| !drcx.generic_args_may_unify(goal, imp))
-        {
+        if !drcx.substs_refs_may_unify(
+            goal.predicate.trait_ref.substs,
+            impl_trait_ref.skip_binder().substs,
+        ) {
             return Err(NoSolution);
         }
 
diff --git a/compiler/rustc_trait_selection/src/traits/coherence.rs b/compiler/rustc_trait_selection/src/traits/coherence.rs
index 4e5e756dc4a..d360158fdf8 100644
--- a/compiler/rustc_trait_selection/src/traits/coherence.rs
+++ b/compiler/rustc_trait_selection/src/traits/coherence.rs
@@ -79,8 +79,9 @@ pub fn overlapping_impls(
     let impl1_ref = tcx.impl_trait_ref(impl1_def_id);
     let impl2_ref = tcx.impl_trait_ref(impl2_def_id);
     let may_overlap = match (impl1_ref, impl2_ref) {
-        (Some(a), Some(b)) => iter::zip(a.skip_binder().substs, b.skip_binder().substs)
-            .all(|(arg1, arg2)| drcx.generic_args_may_unify(arg1, arg2)),
+        (Some(a), Some(b)) => {
+            drcx.substs_refs_may_unify(a.skip_binder().substs, b.skip_binder().substs)
+        }
         (None, None) => {
             let self_ty1 = tcx.type_of(impl1_def_id).skip_binder();
             let self_ty2 = tcx.type_of(impl2_def_id).skip_binder();
diff --git a/compiler/rustc_trait_selection/src/traits/select/mod.rs b/compiler/rustc_trait_selection/src/traits/select/mod.rs
index 98c3e7c13ac..827c107c8b1 100644
--- a/compiler/rustc_trait_selection/src/traits/select/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/mod.rs
@@ -2542,8 +2542,10 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
         // substitution if we find that any of the input types, when
         // simplified, do not match.
         let drcx = DeepRejectCtxt { treat_obligation_params: TreatParams::ForLookup };
-        iter::zip(obligation.predicate.skip_binder().trait_ref.substs, impl_trait_ref.substs)
-            .any(|(obl, imp)| !drcx.generic_args_may_unify(obl, imp))
+        !drcx.substs_refs_may_unify(
+            obligation.predicate.skip_binder().trait_ref.substs,
+            impl_trait_ref.substs,
+        )
     }
 
     /// Normalize `where_clause_trait_ref` and try to match it against