[Rust] if as an expression

fn main() {
    let score = 83;

    let grade = if score > 90 {
        "A"
    } else if score > 80 {
        "B"
    } else if score > 70 {
        "C"
    } else if score > 60 {
        "D"
    } else {
        "F"
    };

    assert_eq!(grade, "B");
}