Possible E0301 false positive

[Nadrieril]

This code fails with error[E0301]: cannot mutably borrow in a pattern guard:

match Some(1) {
    x if x.iter().all(|x| *x == 1) => {}
    _ => {}
}

Error

error[E0301]: cannot mutably borrow in a pattern guard
   --> blah/src/lib.rs:230:14
    |
230 |         x if x.iter().all(|x| *x == 1) => {}
    |              ^^^^^^^^ borrowed mutably in pattern guard
    |
    = help: add #![feature(bind_by_move_pattern_guards)] to the crate attributes to enable

However the following works:

let is_all_1 = |x: &Option<usize>| x.iter().all(|x| *x == 1);
match Some(1) {
    x if is_all_1(&x) => {}
    _ => {}
}

Which is rather surprising and looks like a false positive to me. Could the compiler allow a match if the lifetime of the mutable borrow is limited to the match guard ?

[Nadrieril]

This appears to be fixed (playground link)