From b16c811f1cbaf4d2e7e61409a0bd39aef5a6b1b4 Mon Sep 17 00:00:00 2001
From: Oli Scherer <git-spam-no-reply9815368754983@oli-obk.de>
Date: Thu, 21 Oct 2021 18:12:19 +0000
Subject: [PATCH] Prefer TraitPredicate over ConstnessAnd<TraitRef>

---
 compiler/rustc_middle/src/traits/select.rs    |  2 +-
 .../src/traits/select/mod.rs                  | 33 +++++--------------
 2 files changed, 10 insertions(+), 25 deletions(-)

diff --git a/compiler/rustc_middle/src/traits/select.rs b/compiler/rustc_middle/src/traits/select.rs
index 560660517f34..621bc0c5786c 100644
--- a/compiler/rustc_middle/src/traits/select.rs
+++ b/compiler/rustc_middle/src/traits/select.rs
@@ -12,7 +12,7 @@ use rustc_hir::def_id::DefId;
 use rustc_query_system::cache::Cache;
 
 pub type SelectionCache<'tcx> = Cache<
-    (ty::ConstnessAnd<ty::ParamEnvAnd<'tcx, ty::TraitRef<'tcx>>>, ty::ImplPolarity),
+    ty::ParamEnvAnd<'tcx, ty::TraitPredicate<'tcx>>,
     SelectionResult<'tcx, SelectionCandidate<'tcx>>,
 >;
 
diff --git a/compiler/rustc_trait_selection/src/traits/select/mod.rs b/compiler/rustc_trait_selection/src/traits/select/mod.rs
index 173eb1c5894c..2690fdbea6b0 100644
--- a/compiler/rustc_trait_selection/src/traits/select/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/mod.rs
@@ -1231,19 +1231,13 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             return None;
         }
         let tcx = self.tcx();
-        let pred = &cache_fresh_trait_pred.skip_binder();
-        let trait_ref = pred.trait_ref;
+        let pred = cache_fresh_trait_pred.skip_binder();
         if self.can_use_global_caches(param_env) {
-            if let Some(res) = tcx
-                .selection_cache
-                .get(&(param_env.and(trait_ref).with_constness(pred.constness), pred.polarity), tcx)
-            {
+            if let Some(res) = tcx.selection_cache.get(&param_env.and(pred), tcx) {
                 return Some(res);
             }
         }
-        self.infcx
-            .selection_cache
-            .get(&(param_env.and(trait_ref).with_constness(pred.constness), pred.polarity), tcx)
+        self.infcx.selection_cache.get(&param_env.and(pred), tcx)
     }
 
     /// Determines whether can we safely cache the result
@@ -1288,36 +1282,27 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
     ) {
         let tcx = self.tcx();
         let pred = cache_fresh_trait_pred.skip_binder();
-        let trait_ref = pred.trait_ref;
 
         if !self.can_cache_candidate(&candidate) {
-            debug!(?trait_ref, ?candidate, "insert_candidate_cache - candidate is not cacheable");
+            debug!(?pred, ?candidate, "insert_candidate_cache - candidate is not cacheable");
             return;
         }
 
         if self.can_use_global_caches(param_env) {
             if let Err(Overflow) = candidate {
                 // Don't cache overflow globally; we only produce this in certain modes.
-            } else if !trait_ref.needs_infer() {
+            } else if !pred.needs_infer() {
                 if !candidate.needs_infer() {
-                    debug!(?trait_ref, ?candidate, "insert_candidate_cache global");
+                    debug!(?pred, ?candidate, "insert_candidate_cache global");
                     // This may overwrite the cache with the same value.
-                    tcx.selection_cache.insert(
-                        (param_env.and(trait_ref).with_constness(pred.constness), pred.polarity),
-                        dep_node,
-                        candidate,
-                    );
+                    tcx.selection_cache.insert(param_env.and(pred), dep_node, candidate);
                     return;
                 }
             }
         }
 
-        debug!(?trait_ref, ?candidate, "insert_candidate_cache local");
-        self.infcx.selection_cache.insert(
-            (param_env.and(trait_ref).with_constness(pred.constness), pred.polarity),
-            dep_node,
-            candidate,
-        );
+        debug!(?pred, ?candidate, "insert_candidate_cache local");
+        self.infcx.selection_cache.insert(param_env.and(pred), dep_node, candidate);
     }
 
     /// Matches a predicate against the bounds of its self type.