Fully qualified path to nested consts complains about ambiguous associated type

[estebank]

I believe the following code should be accepted by the compiler, but currently complains with error[E0223]: ambiguous associated type:

struct C;

impl C {
    const X: usize = 42;
}

struct S;

impl S {
    const foo: C = C;
}

fn main() {
    let _ = S::foo::X;
}

Might be needed before #26760 (comment) can be done.

[jplatte]

Probably the same root cause as #38078?