change HIR typeck unification handling approach

3 files changed, 6 insertions, 36 deletions

diff --git a/compiler/rustc_next_trait_solver/src/canonicalizer.rs b/compiler/rustc_next_trait_solver/src/canonicalizer.rs
index 3e1f48610ff..da05c49756f 100644
--- a/compiler/rustc_next_trait_solver/src/canonicalizer.rs
+++ b/compiler/rustc_next_trait_solver/src/canonicalizer.rs
@@ -25,12 +25,8 @@ enum CanonicalizeInputKind {
     /// trait candidates relies on it when deciding whether a where-bound
     /// is trivial.
     ParamEnv,
-    /// When canonicalizing predicates, we don't keep `'static`. If we're
-    /// currently outside of the trait solver and canonicalize the root goal
-    /// during HIR typeck, we replace each occurrence of a region with a
-    /// unique region variable. See the comment on `InferCtxt::in_hir_typeck`
-    /// for more details.
-    Predicate { is_hir_typeck_root_goal: bool },
+    /// When canonicalizing predicates, we don't keep `'static`.
+    Predicate,
 }
 
 /// Whether we're canonicalizing a query input or the query response.
@@ -191,7 +187,6 @@ impl<'a, D: SolverDelegate<Interner = I>, I: Interner> Canonicalizer<'a, D, I> {
     pub fn canonicalize_input<P: TypeFoldable<I>>(
         delegate: &'a D,
         variables: &'a mut Vec<I::GenericArg>,
-        is_hir_typeck_root_goal: bool,
         input: QueryInput<I, P>,
     ) -> ty::Canonical<I, QueryInput<I, P>> {
         // First canonicalize the `param_env` while keeping `'static`
@@ -201,9 +196,7 @@ impl<'a, D: SolverDelegate<Interner = I>, I: Interner> Canonicalizer<'a, D, I> {
         // while *mostly* reusing the canonicalizer from above.
         let mut rest_canonicalizer = Canonicalizer {
             delegate,
-            canonicalize_mode: CanonicalizeMode::Input(CanonicalizeInputKind::Predicate {
-                is_hir_typeck_root_goal,
-            }),
+            canonicalize_mode: CanonicalizeMode::Input(CanonicalizeInputKind::Predicate),
 
             variables,
             variable_lookup_table,
@@ -481,31 +474,13 @@ impl<D: SolverDelegate<Interner = I>, I: Interner> TypeFolder<I> for Canonicaliz
             }
         };
 
-        let var = if let CanonicalizeMode::Input(CanonicalizeInputKind::Predicate {
-            is_hir_typeck_root_goal: true,
-        }) = self.canonicalize_mode
-        {
-            let var = ty::BoundVar::from(self.variables.len());
-            self.variables.push(r.into());
-            self.var_kinds.push(kind);
-            var
-        } else {
-            self.get_or_insert_bound_var(r, kind)
-        };
+        let var = self.get_or_insert_bound_var(r, kind);
 
         Region::new_anon_bound(self.cx(), self.binder_index, var)
     }
 
     fn fold_ty(&mut self, t: I::Ty) -> I::Ty {
-        if let CanonicalizeMode::Input(CanonicalizeInputKind::Predicate {
-            is_hir_typeck_root_goal: true,
-        }) = self.canonicalize_mode
-        {
-            // If we're canonicalizing a root goal during HIR typeck, we
-            // must not use the `cache` as we want to map each occurrence
-            // of a region to a unique existential variable.
-            self.inner_fold_ty(t)
-        } else if let Some(&ty) = self.cache.get(&(self.binder_index, t)) {
+        if let Some(&ty) = self.cache.get(&(self.binder_index, t)) {
             ty
         } else {
             let res = self.inner_fold_ty(t);
diff --git a/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs b/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs
index 74c5b49ea92..4644b145b18 100644
--- a/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs
@@ -57,7 +57,6 @@ where
     /// This expects `goal` and `opaque_types` to be eager resolved.
     pub(super) fn canonicalize_goal(
         &self,
-        is_hir_typeck_root_goal: bool,
         goal: Goal<I, I::Predicate>,
         opaque_types: Vec<(ty::OpaqueTypeKey<I>, I::Ty)>,
     ) -> (Vec<I::GenericArg>, CanonicalInput<I, I::Predicate>) {
@@ -65,7 +64,6 @@ where
         let canonical = Canonicalizer::canonicalize_input(
             self.delegate,
             &mut orig_values,
-            is_hir_typeck_root_goal,
             QueryInput {
                 goal,
                 predefined_opaques_in_body: self
diff --git a/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs b/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs
index a4738306181..0230f784e46 100644
--- a/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs
@@ -459,10 +459,7 @@ where
         let opaque_types = self.delegate.clone_opaque_types_lookup_table();
         let (goal, opaque_types) = eager_resolve_vars(self.delegate, (goal, opaque_types));
 
-        let is_hir_typeck_root_goal = matches!(goal_evaluation_kind, GoalEvaluationKind::Root)
-            && self.delegate.in_hir_typeck();
-        let (orig_values, canonical_goal) =
-            self.canonicalize_goal(is_hir_typeck_root_goal, goal, opaque_types);
+        let (orig_values, canonical_goal) = self.canonicalize_goal(goal, opaque_types);
         let mut goal_evaluation =
             self.inspect.new_goal_evaluation(goal, &orig_values, goal_evaluation_kind);
         let canonical_result = self.search_graph.evaluate_goal(