E0404 error explanation is too narrow

[nagisa]

The E0404 is explaining something about implementing non-traits, but the error code is also presented for cases like in #31686. The error explanation should either be expanded to include the current case or a different error code should be used.

cc @GuillaumeGomez on the thing described in this comment, since you originally authored the explanation for the code.

[GuillaumeGomez]

Thanks! I'll take a look as soon as I can.

[GuillaumeGomez]

The following code (wrote by @nagisa) reproduces it:

struct A<'a> {
    a: ::std::marker::PhantomData<&'a ()>
}

struct B {
    b: for<'a> A<'a>
}

fn main(){}

I think the best solution here is to create another error code.

[oli-obk]

I think updating the docs to also include dyn Trait types is the best solution here as it looks like the same underlying problem to me

[Dylan-DPC-zz]

This is fixed as E0404 is now reworked with the other error code in #69887