pub trait Foo {
    type Assoc<T>;
}

pub fn sample<X: Foo<Assoc<u8> = u8>>(_: X) -> u32 { loop {} }
pub fn synergy(_: impl Foo<Assoc<u8> = u8>) -> ! { loop {} }
pub fn consider(_: impl Foo<Assoc<u8> = u32>) -> bool { loop {} }
pub fn integrate<T>(_: impl Foo<Assoc<T> = T>) -> T { loop {} }