How can I test if a value lies within a Range?

I'd like to be able to create a Range and then test if a variable is contained in that range. Something that looks like this:

fn main() {
    let a = 3..5;
    assert!(a.contains(4));
}

Right now, the only obvious thing I see is to use Iterator::any. This is ugly because it would take an O(1) operation and make it O(n):

fn main() {
    let mut a = 3..5;
    assert!(a.any(|v: i32| v == 4));
}

As of Rust 1.35, the original code will almost1 compile as-is using Range::contains:

fn main() {
    let a = 3..5;
    assert!(a.contains(&4));
}

1 Passing &4 instead of 4 to contains().

Stack Overflow Q#28265036, score: 79