Keep track of the origin of a `T: Future` obligation when caused by an
`.await` expression.

Address rust-lang#66731.

…" suggestion

Keep the `HirId` of `.await`ed expressions so in the case of a `fn` call
on on a sync `fn`, we can suggest maybe turning it into an `async fn`.

The spans no longer overlap, so we no longer need to specialize the
output depending on whether they would.

…f not set."

This reverts commit b376f56, which is
the main part of rust-lang#90499, because it turns out that this causes a good
amount of breakage in crates relying on the old behavior.

Fixes rust-lang#91372.

Tweak errors coming from `for`-loop, `?` and `.await` desugaring

 * Suggest removal of `.await` on non-`Future` expression
 * Keep track of obligations introduced by desugaring
 * Remove span pointing at method for obligation errors coming from desugaring
 * Point at called local sync `fn` and suggest making it `async`

```
error[E0277]: `()` is not a future
  --> $DIR/unnecessary-await.rs:9:10
   |
LL |     boo().await;
   |     -----^^^^^^ `()` is not a future
   |     |
   |     this call returns `()`
   |
   = help: the trait `Future` is not implemented for `()`
help: do not `.await` the expression
   |
LL -     boo().await;
LL +     boo();
   |
help: alternatively, consider making `fn boo` asynchronous
   |
LL | async fn boo () {}
   | +++++
```

Fix rust-lang#66731.

…rt, r=Mark-Simulacrum

Revert setting a default for the MACOSX_DEPLOYMENT_TARGET env var for linking

This reverts commit b376f56, which is the main part of rust-lang#90499, because it turns out that this causes a good amount of breakage in crates relying on the old behavior. In particular `winit`, `coreaudio` and crates that depend on them are affected. Fixes rust-lang#91372.

Background:
Before rust-lang#90499 the behavior was the following: If MACOSX_DEPLOYMENT_TARGET is not set,  we pass the minimum supported OS version to LLVM but not to the linker. The linker default depends on the Xcode version and the version of the OS it is running on. That caused one known problem in libcurl with the most recent Xcode versions. rust-lang#90499 passed the minumum supported version (10.7 for Macos x86-64) to the linker instead. This has shown to be problematic because some crates such as winit, coreaudio implicitly expect a newer minimum OS version. The libcurl issue has been fixed independently (see alexcrichton/curl-rust#417), so a revert should not really be problematic.

Eventually we should probably mimic clang's behavior and fall back to the default of the currently configured Macos SDK for both the LLVM min os target version and MACOSX_DEPLOYMENT_TARGET for linking. That would entail looking at the `Version` property of the `SDKSettings.json` in the currently configured SDK.

fix clippy::single_char_pattern perf findings

…times-from-rustc-typeck, r=jackh726

Remove `in_band_lifetimes` from `rustc_typeck`

Joining in on the effort to remove the `in_band_lifetimes` features, as described in issue rust-lang#91867.

…stc_trait_selection, r=petrochenkov

Remove `in_band_lifetimes` from `rustc_trait_selection`

Another one for rust-lang#91867

…es_library_proc_macro, r=petrochenkov

Removed `in_band_lifetimes` from `library\proc_macro`

Issue [rust-lang#91867](rust-lang#91867)

This is my first try, I followed the instructions given. Fixed all the errors that were thrown while compiling.
Compiled with stage 0,1, and 2 all of them compiled successfully.

…=lnicola

⬆️ rust-analyzer

r? ``@ghost``