fn check_dyn(t: &Type) {
    check_is_unsize::<Type, dyn Trait>(); // Success
    t.method(); //~ERROR
}

fn check_array(t: &[i32; 3]) {
    check_is_unsize::<[i32; 3], [i32]>(); // Success
    t.len(); // Success
    // ^ Note that len is only defined on [T].
}

fn check_is_unsize<From: ?Sized, To: ?Sized>()
where
    From: std::marker::Unsize<To>,
{}

struct Type;

trait Trait {}

impl dyn Trait {
    fn method(&self) {}
}

impl Trait for Type {}