diff options
Diffstat (limited to 'compiler/rustc_trait_selection/src')
| -rw-r--r-- | compiler/rustc_trait_selection/src/traits/project.rs | 18 |
1 files changed, 14 insertions, 4 deletions
diff --git a/compiler/rustc_trait_selection/src/traits/project.rs b/compiler/rustc_trait_selection/src/traits/project.rs index 9de4d3a646c..ad5817d2716 100644 --- a/compiler/rustc_trait_selection/src/traits/project.rs +++ b/compiler/rustc_trait_selection/src/traits/project.rs @@ -252,10 +252,20 @@ fn project_and_unify_type<'cx, 'tcx>( Err(InProgress) => return ProjectAndUnifyResult::Recursive, }; debug!(?normalized, ?obligations, "project_and_unify_type result"); - match infcx - .at(&obligation.cause, obligation.param_env) - .eq(normalized, obligation.predicate.term) - { + let actual = obligation.predicate.term; + // For an example where this is neccessary see src/test/ui/impl-trait/nested-return-type2.rs + // This allows users to omit re-mentioning all bounds on an associated type and just use an + // `impl Trait` for the assoc type to add more bounds. + let InferOk { value: actual, obligations: new } = + selcx.infcx().replace_opaque_types_with_inference_vars( + actual, + obligation.cause.body_id, + obligation.cause.span, + obligation.param_env, + ); + obligations.extend(new); + + match infcx.at(&obligation.cause, obligation.param_env).eq(normalized, actual) { Ok(InferOk { obligations: inferred_obligations, value: () }) => { obligations.extend(inferred_obligations); ProjectAndUnifyResult::Holds(obligations) |