Is it possible to create a mutable value of a mutable reference in a pattern?

Question

When pattern-matching, you can specify that you\'d like to get a mutable reference to the contained value by using ref mut:

let mut score = Som         


        

Answer 1

Not a direct answer, but possible workarounds

Create an intermediate variable

if let Some(ref mut s) = score {
    let mut s = s;
    &mut s;
}

#[derive(Debug)]
struct X;

enum Foo {
    Bar(T),
    _Baz,
}

fn main() {
    let mut score = Foo::Bar(X);

    if let Foo::Bar(ref mut s) = score {
        //let x = s;
        //println!("{:?}", **x); ! not possible
        let x = &mut &mut *s; // &mut &mut X
        println!("{:?}", **x);
    }
}

For Option specifically

if let Some(ref mut s) = score.as_mut() {
    s; //:&mut &mut i32
}

if let Some(mut s) = score.as_mut() {
    &mut s;
}