error[E0378]: the trait `DispatchFromDyn` may only be implemented for structs containing the field being coerced, ZST fields with 1 byte alignment, and nothing else --> $DIR/invalid_dispatch_from_dyn_impls.rs:10:1 | LL | impl<T, U> DispatchFromDyn<WrapperWithExtraField<U>> for WrapperWithExtraField<T> | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | = note: extra field `1` of type `i32` is not allowed error[E0378]: implementing the `DispatchFromDyn` trait requires multiple coercions --> $DIR/invalid_dispatch_from_dyn_impls.rs:21:1 | LL | impl<T: ?Sized, U: ?Sized> DispatchFromDyn<MultiplePointers<U>> for MultiplePointers<T> | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | = note: the trait `DispatchFromDyn` may only be implemented for a coercion between structures with a single field being coerced = note: currently, 2 fields need coercions: `ptr1` (`*const T` to `*const U`), `ptr2` (`*const T` to `*const U`) error[E0378]: the trait `DispatchFromDyn` may only be implemented for a coercion between structures with a single field being coerced, none found --> $DIR/invalid_dispatch_from_dyn_impls.rs:31:1 | LL | impl<T: ?Sized, U: ?Sized> DispatchFromDyn<NothingToCoerce<T>> for NothingToCoerce<U> {} | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ error[E0378]: structs implementing `DispatchFromDyn` may not have `#[repr(packed)]` or `#[repr(C)]` --> $DIR/invalid_dispatch_from_dyn_impls.rs:37:1 | LL | impl<T: ?Sized, U: ?Sized> DispatchFromDyn<HasReprC<U>> for HasReprC<T> | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ error[E0378]: the trait `DispatchFromDyn` may only be implemented for structs containing the field being coerced, ZST fields with 1 byte alignment, and nothing else --> $DIR/invalid_dispatch_from_dyn_impls.rs:46:1 | LL | impl<T: ?Sized, U: ?Sized> DispatchFromDyn<OverAligned<U>> for OverAligned<T> | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | = note: extra field `1` of type `OverAlignedZst` is not allowed error: aborting due to 5 previous errors For more information about this error, try `rustc --explain E0378`.