global old solver cache: use TypingEnv

compiler/rustc_infer/src/infer/mod.rs

@@ -264,11 +264,12 @@ pub struct InferCtxt<'tcx> {
     lexical_region_resolutions: RefCell<Option<LexicalRegionResolutions<'tcx>>>,
 
     /// Caches the results of trait selection. This cache is used
-    /// for things that have to do with the parameters in scope.
-    pub selection_cache: select::SelectionCache<'tcx>,
+    /// for things that depends on inference variables or placeholders.
+    pub selection_cache: select::SelectionCache<'tcx, ty::ParamEnv<'tcx>>,
 
-    /// Caches the results of trait evaluation.
-    pub evaluation_cache: select::EvaluationCache<'tcx>,
+    /// Caches the results of trait evaluation. This cache is used
+    /// for things that depends on inference variables or placeholders.
+    pub evaluation_cache: select::EvaluationCache<'tcx, ty::ParamEnv<'tcx>>,
 
     /// The set of predicates on which errors have been reported, to
     /// avoid reporting the same error twice.

compiler/rustc_middle/src/traits/mod.rs

@@ -551,7 +551,7 @@ pub struct DerivedCause<'tcx> {
     pub parent_code: InternedObligationCauseCode<'tcx>,
 }
 
-#[derive(Clone, Debug, TypeVisitable)]
+#[derive(Clone, Debug, PartialEq, Eq, TypeVisitable)]
 pub enum SelectionError<'tcx> {
     /// The trait is not implemented.
     Unimplemented,
@@ -573,7 +573,7 @@ pub enum SelectionError<'tcx> {
     ConstArgHasWrongType { ct: ty::Const<'tcx>, ct_ty: Ty<'tcx>, expected_ty: Ty<'tcx> },
 }
 
-#[derive(Clone, Debug, TypeVisitable)]
+#[derive(Clone, Debug, PartialEq, Eq, TypeVisitable)]
 pub struct SignatureMismatchData<'tcx> {
     pub found_trait_ref: ty::TraitRef<'tcx>,
     pub expected_trait_ref: ty::TraitRef<'tcx>,

compiler/rustc_middle/src/traits/select.rs

@@ -11,20 +11,10 @@ use self::EvaluationResult::*;
 use super::{SelectionError, SelectionResult};
 use crate::ty;
 
-pub type SelectionCache<'tcx> = Cache<
-    // This cache does not use `ParamEnvAnd` in its keys because `ParamEnv::and` can replace
-    // caller bounds with an empty list if the `TraitPredicate` looks global, which may happen
-    // after erasing lifetimes from the predicate.
-    (ty::ParamEnv<'tcx>, ty::TraitPredicate<'tcx>),
-    SelectionResult<'tcx, SelectionCandidate<'tcx>>,
->;
-
-pub type EvaluationCache<'tcx> = Cache<
-    // See above: this cache does not use `ParamEnvAnd` in its keys due to sometimes incorrectly
-    // caching with the wrong `ParamEnv`.
-    (ty::ParamEnv<'tcx>, ty::PolyTraitPredicate<'tcx>),
-    EvaluationResult,
->;
+pub type SelectionCache<'tcx, ENV> =
+    Cache<(ENV, ty::TraitPredicate<'tcx>), SelectionResult<'tcx, SelectionCandidate<'tcx>>>;
+
+pub type EvaluationCache<'tcx, ENV> = Cache<(ENV, ty::PolyTraitPredicate<'tcx>), EvaluationResult>;
 
 /// The selection process begins by considering all impls, where
 /// clauses, and so forth that might resolve an obligation. Sometimes

compiler/rustc_middle/src/ty/context.rs

@@ -1328,12 +1328,12 @@ pub struct GlobalCtxt<'tcx> {
 
     /// Caches the results of trait selection. This cache is used
     /// for things that do not have to do with the parameters in scope.
-    pub selection_cache: traits::SelectionCache<'tcx>,
+    pub selection_cache: traits::SelectionCache<'tcx, ty::TypingEnv<'tcx>>,
 
     /// Caches the results of trait evaluation. This cache is used
     /// for things that do not have to do with the parameters in scope.
     /// Merge this with `selection_cache`?
-    pub evaluation_cache: traits::EvaluationCache<'tcx>,
+    pub evaluation_cache: traits::EvaluationCache<'tcx, ty::TypingEnv<'tcx>>,
 
     /// Caches the results of goal evaluation in the new solver.
     pub new_solver_evaluation_cache: Lock<search_graph::GlobalCache<TyCtxt<'tcx>>>,

compiler/rustc_trait_selection/src/traits/select/mod.rs

@@ -1310,13 +1310,19 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         param_env: ty::ParamEnv<'tcx>,
         trait_pred: ty::PolyTraitPredicate<'tcx>,
     ) -> Option<EvaluationResult> {
-        let tcx = self.tcx();
+        let infcx = self.infcx;
+        let tcx = infcx.tcx;
         if self.can_use_global_caches(param_env, trait_pred) {
-            if let Some(res) = tcx.evaluation_cache.get(&(param_env, trait_pred), tcx) {
-                return Some(res);
+            let key = (infcx.typing_env(param_env), trait_pred);
+            if let Some(res) = tcx.evaluation_cache.get(&key, tcx) {
+                Some(res)
+            } else {
+                debug_assert_eq!(infcx.evaluation_cache.get(&(param_env, trait_pred), tcx), None);
+                None
             }
+        } else {
+            self.infcx.evaluation_cache.get(&(param_env, trait_pred), tcx)
         }
-        self.infcx.evaluation_cache.get(&(param_env, trait_pred), tcx)
     }
 
     fn insert_evaluation_cache(
@@ -1332,18 +1338,21 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             return;
         }
 
-        if self.can_use_global_caches(param_env, trait_pred) && !trait_pred.has_infer() {
+        let infcx = self.infcx;
+        let tcx = infcx.tcx;
+        if self.can_use_global_caches(param_env, trait_pred) {
             debug!(?trait_pred, ?result, "insert_evaluation_cache global");
             // This may overwrite the cache with the same value
-            // FIXME: Due to #50507 this overwrites the different values
-            // This should be changed to use HashMapExt::insert_same
-            // when that is fixed
-            self.tcx().evaluation_cache.insert((param_env, trait_pred), dep_node, result);
+            tcx.evaluation_cache.insert(
+                (infcx.typing_env(param_env), trait_pred),
+                dep_node,
+                result,
+            );
             return;
+        } else {
+            debug!(?trait_pred, ?result, "insert_evaluation_cache local");
+            self.infcx.evaluation_cache.insert((param_env, trait_pred), dep_node, result);
         }
-
-        debug!(?trait_pred, ?result, "insert_evaluation_cache");
-        self.infcx.evaluation_cache.insert((param_env, trait_pred), dep_node, result);
     }
 
     fn check_recursion_depth<T>(
@@ -1485,7 +1494,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         // If there are any inference variables in the `ParamEnv`, then we
         // always use a cache local to this particular scope. Otherwise, we
         // switch to a global cache.
-        if param_env.has_infer() {
+        if param_env.has_infer() || pred.has_infer() {
             return false;
         }
 
@@ -1522,15 +1531,20 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         param_env: ty::ParamEnv<'tcx>,
         cache_fresh_trait_pred: ty::PolyTraitPredicate<'tcx>,
     ) -> Option<SelectionResult<'tcx, SelectionCandidate<'tcx>>> {
-        let tcx = self.tcx();
+        let infcx = self.infcx;
+        let tcx = infcx.tcx;
         let pred = cache_fresh_trait_pred.skip_binder();
 
         if self.can_use_global_caches(param_env, cache_fresh_trait_pred) {
-            if let Some(res) = tcx.selection_cache.get(&(param_env, pred), tcx) {
-                return Some(res);
+            if let Some(res) = tcx.selection_cache.get(&(infcx.typing_env(param_env), pred), tcx) {
+                Some(res)
+            } else {
+                debug_assert_eq!(infcx.selection_cache.get(&(param_env, pred), tcx), None);
+                None
             }
+        } else {
+            infcx.selection_cache.get(&(param_env, pred), tcx)
         }
-        self.infcx.selection_cache.get(&(param_env, pred), tcx)
     }
 
     /// Determines whether can we safely cache the result
@@ -1567,7 +1581,8 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         dep_node: DepNodeIndex,
         candidate: SelectionResult<'tcx, SelectionCandidate<'tcx>>,
     ) {
-        let tcx = self.tcx();
+        let infcx = self.infcx;
+        let tcx = infcx.tcx;
         let pred = cache_fresh_trait_pred.skip_binder();
 
         if !self.can_cache_candidate(&candidate) {
@@ -1578,10 +1593,16 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         if self.can_use_global_caches(param_env, cache_fresh_trait_pred) {
             if let Err(Overflow(OverflowError::Canonical)) = candidate {
                 // Don't cache overflow globally; we only produce this in certain modes.
-            } else if !pred.has_infer() && !candidate.has_infer() {
+            } else {
                 debug!(?pred, ?candidate, "insert_candidate_cache global");
+                debug_assert!(!candidate.has_infer());
+
                 // This may overwrite the cache with the same value.
-                tcx.selection_cache.insert((param_env, pred), dep_node, candidate);
+                tcx.selection_cache.insert(
+                    (infcx.typing_env(param_env), pred),
+                    dep_node,
+                    candidate,
+                );
                 return;
             }
         }