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

You can use match too:

fn main() {
    let v = 132;
    match v {
        1...100 => println!("Inside"),
        _ => println!("Outside")
    }
}

There is nothing on Range itself (at present, anyway), but it is not difficult to do this; after all, it just takes a couple of comparisons:

4 >= a.start && 4 < a.end

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().

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