1 error[E0368]: binary assignment operation `+=` cannot be applied to type `&isize`
2 --> $DIR/issue-5239-1.rs:14:30
4 LL | let x = |ref x: isize| { x += 1; };
7 | cannot use `+=` on type `&isize`
8 help: `+=` can be used on 'isize', you can dereference `x`
10 LL | let x = |ref x: isize| { *x += 1; };
13 error: aborting due to previous error
15 For more information about this error, try `rustc --explain E0368`.