Multiple Fn bounds

[SoniEx2]

Given the following code: https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=cedda74405870f1697d8323ea0fa041d

fn foo<F: Fn(&char) -> bool + Fn(char) -> bool>(f: F) {
    todo!();
}

fn main() {
    let v = true;
    foo(move |x| v);
}

The current output is:

error[[E0631]](https://doc.rust-lang.org/stable/error-index.html#E0631): type mismatch in closure arguments
 --> src/main.rs:7:5
  |
7 |     foo(move |x| v);
  |     ^^^ ---------- found signature of `for<'r> fn(&'r char) -> _`
  |     |
  |     expected signature of `fn(char) -> _`
  |
note: required by a bound in `foo`
 --> src/main.rs:1:31
  |
1 | fn foo<F: Fn(&char) -> bool + Fn(char) -> bool>(f: F) {
  |                               ^^^^^^^^^^^^^^^^ required by this bound in `foo`

Ideally the output should look like:

We don't have a specific output in mind, but it'd be nice if the error helpfully specified that this bound is impossible to satisfy with a closure. However, we do acknowledge that Fn traits (specifically, implementing them) are still unstable.