error[E0594]: cannot assign to `x`, as it is not declared as mutable
  --> $DIR/generator-upvar-mutability.rs:8:9
   |
LL |     let x = 0;
   |         - help: consider changing this to be mutable: `mut x`
LL |     move || {
LL |         x = 1;
   |         ^^^^^ cannot assign

error: aborting due to previous error

For more information about this error, try `rustc --explain E0594`.