use std::collections::HashMap;

fn main() {
    let mut hm = HashMap::new();
    hm.insert(1, "test");

    // This does not work
    if let Some(first) = hm.get_mut(&1) {
        // do things
    } else {
        match some_enum {
            SomeEnum::Foo(x) => {
                let value = get_value(x);
                hm.insert(1, value);
            }
            SomeEnum::Bar(_) => { }
        }
    }

    // this works but is a bit ugly
    /*
    let need_insert = {
        if let Some(first) = hm.get_mut(&1) {
            false
        } else { true }
    };

    if need_insert {
        hm.insert(1, "test");
    }
    */
}