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

An attempt to implement the `Copy` trait for an enum failed because one of the
variants does not implement `Copy`. To fix this, you must implement `Copy` for
the mentioned variant. Note that this may not be possible, as in the example of

```compile_fail,E0204
enum Foo {
    Bar(Vec<u32>),
    Baz,
}

impl Copy for Foo { }
```

This fails because `Vec<T>` does not implement `Copy` for any `T`.

Here's another example that will fail:

```compile_fail,E0204
#[derive(Copy)]
enum Foo<'a> {
    Bar(&'a mut bool),
    Baz,
}
```

This fails because `&mut T` is not `Copy`, even when `T` is `Copy` (this
differs from the behavior for `&T`, which is always `Copy`).