Stop bubbling out hidden types from the eval obligation queries

Author: oli-obk

compiler/rustc_trait_selection/src/infer.rs

@@ -46,6 +46,7 @@ pub trait InferCtxtExt<'tcx> {
         param_env: ty::ParamEnv<'tcx>,
     ) -> traits::EvaluationResult;
 }
+
 impl<'tcx> InferCtxtExt<'tcx> for InferCtxt<'tcx> {
     fn type_is_copy_modulo_regions(
         &self,

compiler/rustc_traits/src/evaluate_obligation.rs

@@ -1,4 +1,4 @@
-use rustc_infer::infer::{DefiningAnchor, TyCtxtInferExt};
+use rustc_infer::infer::TyCtxtInferExt;
 use rustc_middle::ty::query::Providers;
 use rustc_middle::ty::{ParamEnvAnd, TyCtxt};
 use rustc_span::source_map::DUMMY_SP;
@@ -16,12 +16,8 @@ fn evaluate_obligation<'tcx>(
     canonical_goal: CanonicalPredicateGoal<'tcx>,
 ) -> Result<EvaluationResult, OverflowError> {
     debug!("evaluate_obligation(canonical_goal={:#?})", canonical_goal);
-    // HACK This bubble is required for this tests to pass:
-    // impl-trait/issue99642.rs
-    let (ref infcx, goal, _canonical_inference_vars) = tcx
-        .infer_ctxt()
-        .with_opaque_type_inference(DefiningAnchor::Bubble)
-        .build_with_canonical(DUMMY_SP, &canonical_goal);
+    let (ref infcx, goal, _canonical_inference_vars) =
+        tcx.infer_ctxt().build_with_canonical(DUMMY_SP, &canonical_goal);
     debug!("evaluate_obligation: goal={:#?}", goal);
     let ParamEnvAnd { param_env, value: predicate } = goal;
 

compiler/rustc_traits/src/type_op.rs

@@ -1,6 +1,6 @@
 use rustc_hir as hir;
 use rustc_infer::infer::canonical::{Canonical, QueryResponse};
-use rustc_infer::infer::{DefiningAnchor, TyCtxtInferExt};
+use rustc_infer::infer::TyCtxtInferExt;
 use rustc_infer::traits::ObligationCauseCode;
 use rustc_middle::ty::query::Providers;
 use rustc_middle::ty::{self, FnSig, Lift, PolyFnSig, Ty, TyCtxt, TypeFoldable};
@@ -212,15 +212,10 @@ fn type_op_prove_predicate<'tcx>(
     tcx: TyCtxt<'tcx>,
     canonicalized: Canonical<'tcx, ParamEnvAnd<'tcx, ProvePredicate<'tcx>>>,
 ) -> Result<&'tcx Canonical<'tcx, QueryResponse<'tcx, ()>>, NoSolution> {
-    // HACK This bubble is required for this test to pass:
-    // impl-trait/issue-99642.rs
-    tcx.infer_ctxt().with_opaque_type_inference(DefiningAnchor::Bubble).enter_canonical_trait_query(
-        &canonicalized,
-        |ocx, key| {
-            type_op_prove_predicate_with_cause(ocx, key, ObligationCause::dummy());
-            Ok(())
-        },
-    )
+    tcx.infer_ctxt().enter_canonical_trait_query(&canonicalized, |ocx, key| {
+        type_op_prove_predicate_with_cause(ocx, key, ObligationCause::dummy());
+        Ok(())
+    })
 }
 
 /// The core of the `type_op_prove_predicate` query: for diagnostics purposes in NLL HRTB errors,

tests/ui/type-alias-impl-trait/issue-53398-cyclic-types.stderr

@@ -1,11 +1,8 @@
-error[E0275]: overflow evaluating the requirement `Foo: Sized`
+error[E0275]: overflow evaluating the requirement `<fn() -> Foo {foo} as FnOnce<()>>::Output == fn() -> Foo {foo}`
   --> $DIR/issue-53398-cyclic-types.rs:5:13
    |
 LL | fn foo() -> Foo {
    |             ^^^
-   |
-   = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]` attribute to your crate (`issue_53398_cyclic_types`)
-   = note: required because it appears within the type `fn() -> Foo {foo}`
 
 error: aborting due to previous error