error[E0499]: cannot borrow `f` as mutable more than once at a time
  --> $DIR/borrowck-call-is-borrow-issue-12224.rs:12:16
   |
LL |     f(Box::new(|| {
   |     -          ^^ second mutable borrow occurs here
   |     |
   |     first mutable borrow occurs here
   |     first borrow later used by call
LL |
LL |         f((Box::new(|| {})))
   |         - second borrow occurs due to use of `f` in closure

error[E0596]: cannot borrow `*f` as mutable, as it is behind a `&` reference
  --> $DIR/borrowck-call-is-borrow-issue-12224.rs:25:5
   |
LL |     (*f)();
   |     ^^^^ `f` is a `&` reference, so the data it refers to cannot be borrowed as mutable
   |
help: consider changing this to be a mutable reference
   |
LL | fn test2<F>(f: &mut F) where F: FnMut() {
   |                 +++

error[E0596]: cannot borrow `f.f` as mutable, as it is behind a `&` reference
  --> $DIR/borrowck-call-is-borrow-issue-12224.rs:34:5
   |
LL |     f.f.call_mut(())
   |     ^^^ `f` is a `&` reference, so the data it refers to cannot be borrowed as mutable
   |
help: consider changing this to be a mutable reference
   |
LL | fn test4(f: &mut Test) {
   |              +++

error[E0507]: cannot move out of `f`, a captured variable in an `FnMut` closure
  --> $DIR/borrowck-call-is-borrow-issue-12224.rs:57:13
   |
LL |     let mut f = move |g: Box<dyn FnMut(isize)>, b: isize| {
   |         ----- captured outer variable
...
LL |     f(Box::new(|a| {
   |                --- captured by this `FnMut` closure
LL |
LL |         foo(f);
   |             ^ move occurs because `f` has type `{closure@$DIR/borrowck-call-is-borrow-issue-12224.rs:52:17: 52:58}`, which does not implement the `Copy` trait

error[E0505]: cannot move out of `f` because it is borrowed
  --> $DIR/borrowck-call-is-borrow-issue-12224.rs:55:16
   |
LL |     let mut f = move |g: Box<dyn FnMut(isize)>, b: isize| {
   |         ----- binding `f` declared here
...
LL |     f(Box::new(|a| {
   |     -          ^^^ move out of `f` occurs here
   |     |
   |     borrow of `f` occurs here
LL |
LL |         foo(f);
   |             - move occurs due to use in closure

error: aborting due to 5 previous errors

Some errors have detailed explanations: E0499, E0505, E0507, E0596.
For more information about an error, try `rustc --explain E0499`.