Types on numeric generics are not respected

[TomAFrench]

fn main() -> pub [u8; BAZ] {
    Foo::bar()
}

struct Foo;

trait Bar<let N: u1> {
    fn bar() -> [u8; N];
}

global BAZ: Field = 8;

impl Bar<BAZ> for Foo {
    fn bar() -> [u8; BAZ] {
        [0; BAZ]
    }

}

Consider the above program. I've specified that the Bar trait has a numeric generic parameter which is of the type u1. I'm then allowed to implement this trait using a Field of value 8. This then allows me to have Foo::bar() return a [u8; 8] whereas reading the trait definition this should not be allowed.

[vezenovm]

I made an issue for this here (#5447). This is easier to implement as part of #5156