Trait bounds are not propagated through type equality constraints

[programmerjake]

I tried this code:

https://play.rust-lang.org/?version=nightly&mode=debug&edition=2018&gist=e13f9ef0a5c88c03fca13d57418f4986

pub trait Trait1 {
    fn f();
}

pub trait Trait2 {
    type Type: Trait1;
}

pub trait Trait3 {
    type Type2: Trait2<Type = Self>;
    fn f2() {
        <Self as Trait1>::f();
    }
}

I expected to see this compile successfully since in Trait3, Self is guaranteed to implement Trait1 because Self = Trait2::Type and Trait2::Type: Trait1.

Instead, this happened:

error[E0277]: the trait bound `Self: Trait1` is not satisfied

[jonas-schievink]

Duplicate of #20671