broken-fundamental.rs

// Parent crate //////////

trait ParentTrait {}

// impl supposedly allowed to be added due to `fundamental` rules
impl<T> ParentTrait for Vec<T> {}

trait Assoc {
    type Out;
}

impl<T> Assoc for T where T: ParentTait {
    type Out = ();
}

// Child crate //////////

impl<T> Foo for T where Vec<T>: Assoc
impl<T> Foo for T where Vec<T>: Assoc<Out = ()>