vlib/v/checker/tests/option_mut_non_mut_err.vv:3:9: error: `option_1` is immutable, declare it with `mut` to make it mutable
    1 | fn main() {
    2 |     option_1 := ?int(10)
    3 |     if mut option_1 != none {
      |            ~~~~~~~~
    4 |         option_1 = 11
    5 |     }
