error: captured variable cannot escape `FnMut` closure body
  --> $DIR/issue-69446-fnmut-capture.rs:19:17
   |
LL |       let mut x = Foo;
   |           ----- variable defined here
LL |       bar(move || async {
   |  _______________-_^
   | |               |
   | |               inferred to be a `FnMut` closure
LL | |         x.foo();
   | |         - variable captured here
LL | |     });
   | |_____^ returns an `async` block that contains a reference to a captured variable, which then escapes the closure body
   |
   = note: `FnMut` closures only have access to their captured variables while they are executing...
   = note: ...therefore, they cannot allow references to captured variables to escape

error: aborting due to 1 previous error