trait Foo {
    const U: usize;
}

trait Bar<T: Foo> {
    const V: usize = 5 - T::U;
}

impl<T: Foo> Bar<T> for T {
}

impl Foo for u32 {
    const U: usize = 6;
}

fn foo<T: Foo>(t: T) -> T {
    let x = T::V;
    println!("{}", x);
    t
}

fn main() {
    // uncomment for error
    //foo(5u32);
}