Use DeepRejectCtxt to quickly reject ParamEnv candidates

compiler/rustc_trait_selection/src/traits/project.rs

@@ -13,6 +13,7 @@ use rustc_infer::traits::ObligationCauseCode;
 use rustc_middle::traits::select::OverflowError;
 pub use rustc_middle::traits::Reveal;
 use rustc_middle::traits::{BuiltinImplSource, ImplSource, ImplSourceUserDefinedData};
+use rustc_middle::ty::fast_reject::DeepRejectCtxt;
 use rustc_middle::ty::fold::TypeFoldable;
 use rustc_middle::ty::visit::{MaxUniverse, TypeVisitable, TypeVisitableExt};
 use rustc_middle::ty::{self, Term, Ty, TyCtxt, Upcast};
@@ -885,6 +886,7 @@ fn assemble_candidates_from_predicates<'cx, 'tcx>(
     potentially_unnormalized_candidates: bool,
 ) {
     let infcx = selcx.infcx;
+    let drcx = DeepRejectCtxt::relate_rigid_rigid(selcx.tcx());
     for predicate in env_predicates {
         let bound_predicate = predicate.kind();
         if let ty::ClauseKind::Projection(data) = predicate.kind().skip_binder() {
@@ -893,6 +895,12 @@ fn assemble_candidates_from_predicates<'cx, 'tcx>(
                 continue;
             }
 
+            if !drcx
+                .args_may_unify(obligation.predicate.args, data.skip_binder().projection_term.args)
+            {
+                continue;
+            }
+
             let is_match = infcx.probe(|_| {
                 selcx.match_projection_projections(
                     obligation,