1 error[E0502]: cannot borrow `foo` as mutable because it is also borrowed as immutable
2 --> $DIR/borrowck-issue-49631.rs:30:9
4 LL | while let Some(Ok(string)) = foo.get() {
5 | --- - immutable borrow ends here
7 | immutable borrow occurs here
9 | ^^^ mutable borrow occurs here
11 error: aborting due to previous error
13 For more information about this error, try `rustc --explain E0502`.