…g_span_from_free_region, r=estebank

Fix ICE in msg_span_from_free_region on ReEmpty

On an example like this:

```rust
#![feature(conservative_impl_trait)]

fn server() -> impl FilterBase2 {
    segment2(|| { loop { } }).map2(|| "")
}

trait FilterBase2 {
    fn map2<F>(self, _fn: F) -> Map2<F> where Self: Sized { loop { } }
}

struct Map2<F> { _func: F }

impl<F> FilterBase2 for Map2<F> { }

fn segment2<F>(_fn: F) -> Map2<F> where F: Fn() -> Result<(), ()> {
    loop { }
}
```

we now, instead of ICE'ing, get a diagnostic like:

```
error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
 --> issue-55608.rs:3:16
  |
3 | fn server() -> impl FilterBase2 {
  |                ^^^^^^^^^^^^^^^^
  |
  = note: hidden type `Map2<[[email protected]:4:36: 4:41]>` captures an empty lifetime
```

Fix rust-lang#55608

…g_span_from_free_region, r=estebank

Fix ICE in msg_span_from_free_region on ReEmpty

On an example like this:

```rust
#![feature(conservative_impl_trait)]

fn server() -> impl FilterBase2 {
    segment2(|| { loop { } }).map2(|| "")
}

trait FilterBase2 {
    fn map2<F>(self, _fn: F) -> Map2<F> where Self: Sized { loop { } }
}

struct Map2<F> { _func: F }

impl<F> FilterBase2 for Map2<F> { }

fn segment2<F>(_fn: F) -> Map2<F> where F: Fn() -> Result<(), ()> {
    loop { }
}
```

we now, instead of ICE'ing, get a diagnostic like:

```
error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
 --> issue-55608.rs:3:16
  |
3 | fn server() -> impl FilterBase2 {
  |                ^^^^^^^^^^^^^^^^
  |
  = note: hidden type `Map2<[[email protected]:4:36: 4:41]>` captures an empty lifetime
```

Fix rust-lang#55608

Rollup of 17 pull requests

Successful merges:

 - #55576 (Clarify error message for -C opt-level)
 - #55633 (Support memcpy/memmove with differing src/dst alignment)
 - #55638 (Fix ICE in msg_span_from_free_region on ReEmpty)
 - #55659 (rustc: Delete grouping logic from the musl target)
 - #55719 (Sidestep link error from rustfix'ed code by using a *defined* static.)
 - #55736 (Elide anon lifetimes in conflicting impl note)
 - #55739 (Consume optimization fuel from the MIR inliner)
 - #55742 (Avoid panic when matching function call)
 - #55753 (borrow_set: remove a helper function and a clone it uses)
 - #55755 (Improve creation of 3 IndexVecs)
 - #55758 ([regression - rust2018]: unused_mut lint false positives on nightly)
 - #55760 (Remove intermediate font specs)
 - #55761 (mir: remove a hacky recursive helper function)
 - #55774 (wasm32-unknown-emscripten expects the rust_eh_personality symbol)
 - #55777 (Use `Lit` rather than `P<Lit>` in `ast::ExprKind`.)
 - #55783 (Deprecate mpsc channel selection)
 - #55788 (rustc: Request ansi colors if stderr isn't a tty)

Failed merges:

r? @ghost