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rustoption-type

Why does Rust need the `if let` syntax?

Coming from other functional languages (and being a Rust newbie), I'm a bit surprised by the motivation of Rust's if let syntax. The RFC mentions that without if let, the "idiomatic solution today for testing and unwrapping an Option<T>" is either 

match opt_val {
    Some(x) => {
        do_something_with(x);
    }
    None => {}
}

or

if opt_val.is_some() {
    let x = opt_val.unwrap();
    do_something_with(x);
}

In Scala, it would be possible to do exactly the same, but the idiomatic solution is rather to map over an Option (or to foreach if it is only for the side effect of doing_something_with(x)).

Why isn't it an idiomatic solution to do the same in Rust?

opt_val.map(|x| do_something_with(x));
Solution

  • .map() is specific to the Option<T> type, but if let (and while let!) are features that work with all Rust types.