a395214a3a
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.
For high-level intro to how type checking works in rustc, see the type checking chapter of the rustc dev guide.