Auto merge of #44888 - tirr-c:binder-hr-region, r=arielb1

Refactor fmt::Display and fmt::Debug impls in ppaux

Also fixes #44887.

There was a problem that unnamed late-bound regions are *always* named `'r` while they are displayed using `std::fmt::Display`.

---

```rust
fn main() {
    f(|_: (), _: ()| {});
}
fn f<F>(_: F) where F: Fn(&(), for<'r> fn(&'r ())) {}
```

Before (incorrectly shadows lifetime, `for<'r>` omitted for the second argument):

```
error[E0631]: type mismatch in closure arguments
 --> test.rs:2:5
  |
2 |     f(|_: (), _: ()| {});
  |     ^ ----------------- found signature of `fn((), ()) -> _`
  |     |
  |     expected signature of `for<'r> fn(&'r (), fn(&'r ())) -> _`
  |
  = note: required by `f`
```

After:

```
error[E0631]: type mismatch in closure arguments
 --> test.rs:2:5
  |
2 |     f(|_: (), _: ()| {});
  |     ^ ----------------- found signature of `fn((), ()) -> _`
  |     |
  |     expected signature of `for<'s> fn(&'s (), for<'r> fn(&'r ())) -> _`
  |
  = note: required by `f`
```

r? @nikomatsakis

0 files changed, 0 insertions, 0 deletions