'Mismatched type' error doesn't use aliased type names

[kornelski]

type mytype = f32;

fn main() {
    let foo: mytype = 1usize;
}

fails with:

expected f32,
found usize

but I'd expect it to say something along the lines:

expected mytype (f32)
found usize

(The problem has been mentioned in comments of #3417)

[ebfull]

Associated types act as type synonyms in the same sense, and it would be nice if error message included those where applicable as well.

[Mark-Simulacrum]

Closing in favor of #17164.