buitlin-`derive` constrains non-qualified paths

[lcnr]

trait Trait {
    type Assoc;
}

#[derive(Clone)]
struct Foo<T: Trait> {
    value: T::Assoc, // ok, gets a `T::Assoc: Clone` bound
}

#[derive(Clone)]
struct Bar<T: Trait> {
    value: <T as Trait>::Assoc, // error
}