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

rustc: Request ansi colors if stderr isn't a tty

Currently Cargo will always capture the output of rustc meaning that
rustc is never hooked up to a tty. To retain colors Cargo uses the
`fwdansi` crate to ensure that ansi color codes are translated to
windows terminal methods (and ansi codes otherwise just go their natural
route on Unix).

Cargo passes `--color always` to rustc to ensure that using a pipe
doesn't trick it into not emitting colors at all. It turns out, however,
that `--color always` ends up still accidentally using the native shell
api on native windows shells.

The fix here is to instead pass `AlwaysAnsi` to `termcolor` instead of
`Always`, ensuring that when `--color always` is passed to rustc and its
output isn't a terminal, we're always generating ansi colors regardless
of the platform.

Closes #55769

Deprecate mpsc channel selection

Rationale: https://github.com/rust-lang/rust/issues/27800#issuecomment-421760863

r? @SimonSapin

Use `Lit` rather than `P<Lit>` in `ast::ExprKind`.

Because it results in fewer allocations and small speedups on some
benchmarks.

wasm32-unknown-emscripten expects the rust_eh_personality symbol

The `wasm32-unknown-emscripten` expects the `rust_eh_personality` symbol to be there, but a cfg checking for `target_arch = "wasm32"` which was meant to remove the symbol from the `wasm32-unknown-unknown` target, didn't check for whether `emscripten` is targeted or not, so the symbol accidentally got filtered out there as well.

Fixes #55276

mir: remove a hacky recursive helper function

It can be replaced with a `while let` loop.

Remove intermediate font specs

This is a (much) more constrained version of #54772 that also aims at improving the situation in #34681. It removes any font specifications that are not the "official" rustdoc font, and instead relies on the browser to provide the fallback font if the official on is not available. On Linux systems, this is particularly important, as fonts like Helvetica, Arial, and Times often look pretty bad since they're pulled from extracted MS fonts. A specification like `serif` or `sans-serif` lets the browser instead choose a good font.

[regression - rust2018]: unused_mut lint false positives on nightly

Fixes #55344.

This commit filters out locals that have never been initialized for
consideration in the `unused_mut` lint.

This is intended to detect when the statement that would have
initialized the local was removed as unreachable code. In these cases,
we would not want to lint. This is the same behaviour as the AST borrow
checker.

This is achieved by taking advantage of an existing pass over the MIR
for the `unused_mut` lint and creating a set of those locals that were
never initialized.

r? @pnkfelix

Improve creation of 3 IndexVecs

- preallocate when the minimal size is known
- use `from_elem_n` instead of `new`+`resize`

borrow_set: remove a helper function and a clone it uses

This clone doesn't seem necessary.

r? @oli-obk

Avoid panic when matching function call

Fix #55718

This bug is introduced by #53751. The original code checked `Def::AssociatedConst(..) | Def::Method(..)` before `pat_ty.no_bound_vars().expect("expected fn type")`. But somehow I exchanged the sequence carelessly. Sorry about that.

r? @petrochenkov

Consume optimization fuel from the MIR inliner

This makes it easier to debug mis-optimizations that occur during
inlining. Thanks to @nikomatsakis for the suggestion!

Elide anon lifetimes in conflicting impl note

Fix #54690.

Rollup merge of #55719 - pnkfelix:issue-54388-sidestep-link-error-from-rustfixed-code, r=alexcrichton

Sidestep link error from rustfix'ed code by using a *defined* static.

As a drive-by, added `-g` to the compile-flags so that the test more
reliably fails to compile when the extern static in question is *not*
provided. (I.e. this is making the test more robust in the face of
potential future revisions.)

Fix #54388.

rustc: Delete grouping logic from the musl target

This commit deletes the injection of `-(` and `-)` options to the linker
for the musl targets. This actually causes problems today on nightly if
you execute:

    $ echo 'fn main() {}' >> foo.rs
    $ rustc --target x86_64-unknown-linux-musl -C panic=abort

you get a linker error about "cannot nest groups". This comes about
because rustc injects its own `--start-group` and `--end-group`
variables which clash with the outer `-(` and `-)` variables. It's not
entirely clear to me why this doesn't affect the musl target by default
(in `-C panic=unwind` mode).

The compiler's own injection of `--start-group` and `--end-group` should
solve the issues mentioned in the comment for injecting `-(` and `-)` as
well.

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<[closure@issue-55608.rs:4:36: 4:41]>` captures an empty lifetime
```

Fix #55608

Support memcpy/memmove with differing src/dst alignment

If LLVM 7 is used, generate memcpy/memmove with differing src/dst alignment. I've added new FFI functions to construct these through the builder API, which is more convenient than dealing with differing intrinsic signatures depending on the LLVM version.

Fixes #49740.

Clarify error message for -C opt-level

The new levels s and z are not mentioned as possible values.

Currently Cargo will always capture the output of rustc meaning that
rustc is never hooked up to a tty. To retain colors Cargo uses the
`fwdansi` crate to ensure that ansi color codes are translated to
windows terminal methods (and ansi codes otherwise just go their natural
route on Unix).

Cargo passes `--color always` to rustc to ensure that using a pipe
doesn't trick it into not emitting colors at all. It turns out, however,
that `--color always` ends up still accidentally using the native shell
api on native windows shells.

The fix here is to instead pass `AlwaysAnsi` to `termcolor` instead of
`Always`, ensuring that when `--color always` is passed to rustc and its
output isn't a terminal, we're always generating ansi colors regardless
of the platform.

Closes #55769

#[rustc_error] survey

Fix #55505

Because it results in fewer allocations and small speedups on some
benchmarks.

Add tracking issue for Layout methods (and some API changes)

These methods are already useful when used with the stable global allocator API (stabilized in #51241).

```rust
pub fn align_to(&self, align: usize) -> Result<Layout, LayoutErr>;
pub fn padding_needed_for(&self, align: usize) -> usize;
pub fn repeat(&self, n: usize) -> Result<(Layout, usize), LayoutErr>;
pub fn extend(&self, next: Layout) -> Result<(Layout, usize), LayoutErr>;
pub fn repeat_packed(&self, n: usize) -> Result<Layout, LayoutErr>;
pub fn extend_packed(&self, next: Layout) -> Result<Layout, LayoutErr>;
pub fn array<T>(n: usize) -> Result<Layout, LayoutErr>;
```

cc #32838

r? @SimonSapin

The `wasm32-unknown-emscripten` expects the `rust_eh_personality` symbol to be there, but a cfg checking for `target_arch = "wasm32"` which was meant to remove the symbol from the `wasm32-unknown-unknown` target, didn't check for whether `emscripten` is targeted or not, so the symbol accidentally got filtered out there as well.

Fixes #55276

Remove targets from the manifest that are not built on travis

Fixes https://github.com/rust-lang/rust/issues/55020

Fixes https://github.com/rust-lang/rust/issues/55020

Rollup of 14 pull requests

Successful merges:

 - #55377 (Slight copy-editing for `std::cell::Cell` docs)
 - #55441 (Remove unused re import in gdb_rust_pretty_printing)
 - #55453 (Choose predicates without inference variables over those with them)
 - #55495 (Don't print opt fuel messages to stdout because it breaks Rustbuild)
 - #55501 (Make `process_obligations`' computation of `completed` optional.)
 - #55510 (Fix feature gate only being checked on first repr attr.)
 - #55609 (Run name-anon-globals after LTO passes as well)
 - #55645 (do not print wrapping ranges like normal ranges in validity diagnostics)
 - #55688 (Standardised names and location of ui issue tests)
 - #55692 (-C remark: fix incorrect warning about requiring "--debuginfo" instead of "-C debuginfo=n")
 - #55702 (Add `aarch64-pc-windows-msvc` to deployed targets)
 - #55728 (Update lldb)
 - #55730 (Use trait impl method span when type param mismatch is due to impl Trait)
 - #55734 (refactor: use shorthand fields)

This is a (much) more constrained version of #54772 that also aims at
improving the situation in #34681. It removes any font specifications
that are not the "official" rustdoc font, and instead relies on the
browser to provide the fallback font if the official on is not
available. On Linux systems, this is particularly important, as fonts
like Helvetica, Arial, and Times often look pretty bad since they're
pulled from extracted MS fonts. A specification like `serif` or
`sans-serif` lets the browser instead choose a good font.

This commit filters out locals that have never been initialized for
consideration in the `unused_mut` lint.

This is intended to detect when the statement that would have
initialized the local was removed as unreachable code. In these cases,
we would not want to lint. This is the same behaviour as the AST borrow
checker.

This is achieved by taking advantage of an existing pass over the MIR
for the `unused_mut` lint and creating a set of those locals that were
never initialized.

(The fact that output differs under `opt-level=0` is an instance of #55757.)

do not print wrapping ranges like normal ranges in validity diagnostics

refactor: use shorthand fields

refactor: use shorthand for single fields everywhere (excluding tests).

Use trait impl method span when type param mismatch is due to impl Trait

Fix #55374.