1 error[E0389]: cannot borrow data mutably in a `&` reference
2 --> $DIR/issue-38147-4.rs:6:5
4 LL | fn f(x: usize, f: &Foo) {
5 | ---- use `&mut Foo` here to make mutable
6 LL | f.s.push('x'); //~ ERROR cannot borrow data mutably
7 | ^^^ assignment into an immutable reference
9 error: aborting due to previous error
11 For more information about this error, try `rustc --explain E0389`.