error[E0507]: cannot move out of `val`, a captured variable in an `FnMut` closure
  --> $DIR/issue-87456-point-to-closure.rs:10:28
   |
LL |     let val = String::new();
   |         --- captured outer variable
LL |
LL |     take_mut(|| {
   |              -- captured by this `FnMut` closure
LL |
LL |         let _foo: String = val;
   |                            ^^^ move occurs because `val` has type `String`, which does not implement the `Copy` trait
   |
help: consider borrowing here
   |
LL |         let _foo: String = &val;
   |                            +

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0507`.