diff options
| -rw-r--r-- | src/librustc_middle/ty/error.rs | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/src/librustc_middle/ty/error.rs b/src/librustc_middle/ty/error.rs index 8d57f39c1a2..4b0b648b3b4 100644 --- a/src/librustc_middle/ty/error.rs +++ b/src/librustc_middle/ty/error.rs @@ -584,6 +584,19 @@ impl<T> Trait<T> for X { false } + /// An associated type was expected and a different type was found. + /// + /// We perform a few different checks to see what we can suggest: + /// + /// - In the current item, look for associated functions that return the expected type and + /// suggest calling them. (Not a structured suggestion.) + /// - If any of the item's generic bounds can be constrained, we suggest constraining the + /// associated type to the found type. + /// - If the associated type has a default type and was expected inside of a `trait`, we + /// mention that this is disallowed. + /// - If all other things fail, and the error is not because of a mismatch between the `trait` + /// and the `impl`, we provide a generic `help` to constrain the assoc type or call an assoc + /// fn that returns the type. fn expected_projection( &self, db: &mut DiagnosticBuilder<'_>, @@ -600,6 +613,7 @@ impl<T> Trait<T> for X { let body_owner = self.hir().get_if_local(body_owner_def_id); let current_method_ident = body_owner.and_then(|n| n.ident()).map(|i| i.name); + // We don't want to suggest calling an assoc fn in a scope where that isn't feasible. let callable_scope = match body_owner { Some( hir::Node::Item(hir::Item { @@ -784,6 +798,8 @@ fn foo(&self) -> Self::T { String::new() } } } + /// Given a slice of `hir::GenericBound`s, if any of them corresponds to the `trait_ref` + /// requirement, provide a strucuted suggestion to constrain it to a given type `ty`. fn constrain_generic_bound_associated_type_structured_suggestion( &self, db: &mut DiagnosticBuilder<'_>, @@ -812,6 +828,8 @@ fn foo(&self) -> Self::T { String::new() } false } + /// Given a span corresponding to a bound, provide a structured suggestion to set an + /// associated type to a given type `ty`. fn constrain_associated_type_structured_suggestion( &self, db: &mut DiagnosticBuilder<'_>, |