the `check_ptr_ptr_cast` function had an early return when the source and destination dyn trait objects shared the same principal trait def id: if src_principal == dst_principal { return Ok(()); } this bypassed all three remaining checks that the code comment explicitly listed as required: generic argument equality, projection equality, and the auto-trait superset check. as a result, casts like `*mut dyn Trait as *mut (dyn Trait + Send)` were silently accepted instead of emitting E0804. the fix removes the early return. `CastError::PtrPtrAddingAutoTraits` and its diagnostic were already implemented — they just couldn't be reached. the supertrait case (`trait Trait: Send`) continues to work correctly because the auto-trait check already accounts for implied auto traits via supertrait elaboration.