and give return of async fn a better span

- Add more well-known traits
- Use the correct binders when lowering trait objects
- Use correct substs when lowering trait objects
- Use the correct binders for opaque_ty_data
- Lower negative impls with the correct polarity
- Supply associated type values
- Use `predicates_defined_on` for where clauses

While technically the i686-unknown-freebsd target has been a tier 2
development platform for a long time, with full toolchain tarballs
available on static.rust-lang.org, due to a bug in the manifest
generation the target was never available for download through rustup.

The infrastructure team privately inquired the FreeBSD package
maintainers, and they weren't relying on those tarballs either, so it's
a fair assumption to say practically nobody is using those tarballs.

This PR then removes the CI builder that produces full tarballs for the
target, and moves the compilation of rust-std for the target in
dist-various-2.

The x86_64-unknown-freebsd target is *not* affected.

This fixes ongoing issues where x.py will detect the wrong host triple
between MSVC and GNU.

- Add line to changelog

This wasn't necessary until MIR inliner started to consider drop glue as
a candidate for inlining; introducing for the first time a generic use
of size-of operation.

No test at this point since this only happens with a custom inlining
threshold.

The inliner does not support inlining of divering calls. Reject them
early on and turn `inline_call` into an infallible operation.

When examining candidates for inlining, reject those that are determined
to be recursive either because of self-recursive calls or calls to any
instances already inlined.

…orse

Add `#[cfg(panic = '...')]`

This PR adds conditional compilation according to the panic strategy.

I've come across a need for a flag like this a couple of times while writing tests: rust-lang#74301 , rust-lang#73670 (comment)

I'm not sure if I need to add a feature gate for this flag?

…mulacrum

Improve lifetime name annotations for closures & async functions

* Don't refer to async functions as "generators" in error output
* Where possible, emit annotations pointing exactly at the `&` in the return type of closures (when they have explicit return types) and async functions, like we do for arguments.
Addresses rust-lang#74072, but I wouldn't call that *closed* until annotations are identical for async and non-async functions.
* Emit a better annotation when the lifetime doesn't appear in the full name type, which currently happens for opaque types like `impl Future`. Addresses rust-lang#74497, but further improves could probably be made (why *doesn't* it appear in the type as `impl Future + '1`?)
This is included in the same PR because the changes to `give_name_if_anonymous_region_appears_in_output` would introduce ICE otherwise (it would return `None` in cases where it didn't previously, which then gets `unwrap`ped)

…troalbini

Test clippy on PR CI on changes

This runs the tools builder (which builds and tests tools, including clippy) when the clippy submodule changes. This essentially returns us to the prior state when clippy was a submodule; it makes sense for us to test it on CI when it changes. It might make sense for it to be tested regardless of changing but it is somewhat rare for it to fail and we don't want to add to CI time for the majority of PRs which don't affect it.

Fixes rust-lang#76999.

BTreeMap: fix pointer provenance rules

Fixes rust-lang#78477 and includes rust-lang#78476

r? `@Mark-Simulacrum`

Update Chalk to 0.36.0

This PR updates Chalk and fixes a number of bugs in the chalk integration code.

cc `@rust-lang/wg-traits`
r? `@nikomatsakis`

…ulacrum

Infer the default host target from the host toolchain if possible

- `beta-x86_64-unknown-linux-gnu` has beta stripped
- `rustc2` is ignored

This fixes ongoing issues where x.py will detect the wrong host triple
between MSVC and GNU.

I don't think this will break anyone's workflow - I'd be very surprised if you a) had no `[build]` section in `config.toml`, b) had rustc installed, and c) expected the default target to be something other than the default target used by `rustc`. But I could be wrong - I'm happy to hear user stories :)

Fixes rust-lang#78150.

r? ``@Mark-Simulacrum``
cc ``@Lokathor``

Enable LLVM Polly via llvm-args.

I think doing it this way is better than in rust-lang#51061. Polly has other useful options and we probably don't want to create a `-Z` flag for each one of them.

![results](https://user-images.githubusercontent.com/7283601/97695555-338f7180-1adf-11eb-82bd-5130e0e6fa89.png)

[Benchmark](https://gist.github.com/JRF63/9a6268b91720958e90dbe7abffe20298)

I noticed that `-lto` seems to interfere with polly in this specific microbenchmark, as enabling it causes the perf to drop to that of non-polly builds.

Other related PRs: rust-lang#75615

inliner: Break inlining cycles

Keep track of all instances inlined so far. When examining a new call
sites from an inlined body, skip those where callee had been inlined
already to avoid potential inlining cycles.

Fixes rust-lang#78573.

rustc_ast: Do not panic by default when visiting macro calls

Panicking by default made sense when we didn't have HIR or MIR and everything worked on AST, but now all AST visitors run early and majority of them have to deal with macro calls, often by ignoring them.

The second commit renames `visit_mac` to `visit_mac_call`, the corresponding structures were renamed earlier in rust-lang#69589.

…imulacrum

Demote i686-unknown-freebsd to tier 2 compiler target

While technically the `i686-unknown-freebsd` target has been a tier 2 development platform for a long time, with full toolchain tarballs available on static.rust-lang.org, due to a bug in the manifest generation the target was never available for download through rustup.

The infrastructure team privately inquired the FreeBSD package maintainers, and they weren't relying on those tarballs either, so it's a fair assumption to say practically nobody is using those tarballs.

This PR then removes the CI builder that produces full tarballs for the target, and moves the compilation of `rust-std` for the target in `dist-various-2`. The `x86_64-unknown-freebsd` target is *not* affected.

cc `@rust-lang/infra` `@rust-lang/compiler` `@rust-lang/release`
r? `@Mark-Simulacrum`

fix `super_visit_with` for `Terminator`

fixes rust-lang#78182 (comment)

r? `@oli-obk`

cc `@LeSeulArtichaut`

Monomorphize a type argument of size-of operation during codegen

This wasn't necessary until MIR inliner started to consider drop glue as
a candidate for inlining; introducing for the first time a generic use
of size-of operation.

No test at this point since this only happens with a custom inlining
threshold.