#### Note: this error code is no longer emitted by the compiler.

`CoerceUnsized` or `DispatchFromDyn` was implemented between two types that
are not structs.

Erroneous code example:

```compile_fail,E0377
#![feature(coerce_unsized)]
use std::ops::CoerceUnsized;

struct Foo<T: ?Sized> {
    a: T,
}

// error: The type `U` is not a struct
impl<T, U> CoerceUnsized<U> for Foo<T> {}
```

`CoerceUnsized` or `DispatchFromDyn` can only be implemented between structs.