Detect object safety errors when assoc type is missing
When an associated type with GATs isn't specified in a `dyn Trait`, emit an object safety error instead of only complaining about the missing associated type, as it will lead the user down a path of three different errors before letting them know that what they were trying to do is impossible to begin with.
Fix#103155.
When an associated type with GATs isn't specified in a `dyn Trait`, emit
an object safety error instead of only complaining about the missing
associated type, as it will lead the user down a path of three different
errors before letting them know that what they were trying to do is
impossible to begin with.
Fix#103155.
When we encounter a `dyn Trait` that isn't object safe, look for its
implementors. If there's one, mention using it directly If there are
less than 9, mention the possibility of creating a new enum and using
that instead.
Account for object unsafe `impl Trait on dyn Trait {}`. Make a
distinction between public and sealed traits.
Fix#80194.
Consider `tests/ui/const-generics/generic_const_exprs/issue-102768.stderr`,
the error message where it gives additional notes about where the associated
type is defined, and how the dead code lint doesn't have an article,
like in `tests/ui/lint/dead-code/issue-85255.stderr`. They don't have
articles, so it seems unnecessary to have one here.
