f338a1f7ee
Don't check unnecessarily that impl trait is RPIT We have this random `return_type_impl_trait` function to detect if a function returns an RPIT which is used in outlives suggestions, but removing it doesn't actually change any diagnostics. Let's just remove it. Also, suppress a spurious outlives error from a ReError. Fixes #114274
For high-level intro to how type checking works in rustc, see the type checking chapter of the rustc dev guide.