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: `Fn` and `FnMut` closures require captured values to be able to be consumed multiple times, but `FnOnce` closures may consume them only once
  --> $DIR/issue-87456-point-to-closure.rs:3:24
   |
LL | fn take_mut(_val: impl FnMut()) {}
   |                        ^^^^^^^
help: consider borrowing here
   |
LL |         let _foo: String = &val;
   |                            +
help: consider cloning the value if the performance cost is acceptable
   |
LL |         let _foo: String = val.clone();
   |                               ++++++++

error: aborting due to 1 previous error

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