Make `#[derive(Copy)]` enough for both `Clone` and `Copy`

chrefr:

The Clone derive already does that

Interesting, I wasn't aware of that. It seems doesn't work in all cases though, e.g. with a generic parameter I see this:

struct Foo<T> {
    a: T,
    b: T,
    c: T,
}
#[attr = AutomaticallyDerived]
impl <T> ::core::clone::Clone for Foo<T> where T: ::core::clone::Clone {
    #[attr = Inline(Hint)]
    fn clone(&self)
        ->
            Foo<T> {
        Foo {
            a: ::core::clone::Clone::clone(&self.a),
            b: ::core::clone::Clone::clone(&self.b),
            c: ::core::clone::Clone::clone(&self.c) }
    }
}

Might be something related to backward compatibility.

chrefr:

Not true, since old editions must still be supported by the compiler.

I meant dropping the original #[rustc_ignore_this_impl_in_case_of_conflict] proposal and doing this only over an edition. That is, #[derive(Copy)] in a new edition is equivalent of both Clone and Copy, and adding another Clone impl (either manually or via derive) is a hard error, and not touching the current editions at all.