don't special case `DefKind::Ctor` in encoding

considering that we still use `DefKind::Ctor` for these in `Res`, this seems weird and definitely felt like a bug when encountering it while working on #89862.

r? `@cjgillot`

Extend toggle GUI test a bit

Fixes #84422.

r? `@jsha`

Remove in band lifetimes

As discussed in t-lang backlog bonanza, the `in_band_lifetimes` FCP closed in favor for the feature not being stabilized. This PR removes `#![feature(in_band_lifetimes)]` in its entirety.

Let me know if this PR is too hasty, and if we should instead do something intermediate for deprecate the feature first.

r? `@scottmcm` (or feel free to reassign, just saw your last comment on #44524)
Closes #44524

Rollup of 6 pull requests

Successful merges:

 - #92714 (Provide ignore message in the result of test)
 - #93273 (Always check cg_llvm with ./x.py check)
 - #94068 (Consider mutations as borrows in generator drop tracking)
 - #94184 (BTree: simplify test code)
 - #94297 (update const_generics_defaults release notes)
 - #94341 (Remove a duplicate space)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

Remove a duplicate space

rustfmt doesn't format `let ... else`.

update const_generics_defaults release notes

supersedes #94294

r? `@Mark-Simulacrum`

BTree: simplify test code

Mostly, use `from` & `from_iter`.

Consider mutations as borrows in generator drop tracking

This is needed to match MIR more conservative approximation of any borrowed value being live across a suspend point (See #94067). This change considers an expression such as `x.y = z` to be a borrow of `x` and therefore keeps `x` live across suspend points.

r? `@nikomatsakis`

Always check cg_llvm with ./x.py check

Previously it would be skipped if codegen-backends doesn't contain llvm.

Provide ignore message in the result of test

Provide ignore the message in the result of the test.

This PR does not need RFC, because it is about the presentation of the report of `cargo test`.

However, the following document listed here helps you to know about PR.

- [RFC](https://github.com/rust-lang/rfcs/pull/3217)
- [Rendered](https://github.com/yanganto/rfcs/blob/ignore-test-message/text/0000-ignore-test-message.md)
- [Previous discussion on IRLO](https://internals.rust-lang.org/t/pre-rfc-provide-ignore-message-when-the-test-ignored/15904)

If there is something improper, please let me know.
Thanks.

Use undef for (some) partially-uninit constants

There needs to be some limit to avoid perf regressions on large arrays
with undef in each element (see comment in the code).

Fixes: #84565
Original PR: #83698

Depends on LLVM 14: #93577

Convert `newtype_index` to a proc macro

The `macro_rules!` implementation was becomng excessively complicated,
and difficult to modify. The new proc macro implementation should make
it much easier to add new features (e.g. skipping certain `#[derive]`s)

rustc_errors: let `DiagnosticBuilder::emit` return a "guarantee of emission".

That is, `DiagnosticBuilder` is now generic over the return type of `.emit()`, so we'll now have:
* `DiagnosticBuilder<ErrorReported>` for error (incl. fatal/bug) diagnostics
  * can only be created via a `const L: Level`-generic constructor, that limits allowed variants via a `where` clause, so not even `rustc_errors` can accidentally bypass this limitation
  * asserts `diagnostic.is_error()` on emission, just in case the construction restriction was bypassed (e.g. by replacing the whole `Diagnostic` inside `DiagnosticBuilder`)
  * `.emit()` returns `ErrorReported`, as a "proof" token that `.emit()` was called
    (though note that this isn't a real guarantee until after completing the work on
     #69426)
* `DiagnosticBuilder<()>` for everything else (warnings, notes, etc.)
  * can also be obtained from other `DiagnosticBuilder`s by calling `.forget_guarantee()`

This PR is a companion to other ongoing work, namely:
* #69426
  and it's ongoing implementation:
  #93222
  the API changes in this PR are needed to get statically-checked "only errors produce `ErrorReported` from `.emit()`", but doesn't itself provide any really strong guarantees without those other `ErrorReported` changes
* #93244
  would make the choices of API changes (esp. naming) in this PR fit better overall

In order to be able to let `.emit()` return anything trustable, several changes had to be made:
* `Diagnostic`'s `level` field is now private to `rustc_errors`, to disallow arbitrary "downgrade"s from "some kind of error" to "warning" (or anything else that doesn't cause compilation to fail)
  * it's still possible to replace the whole `Diagnostic` inside the `DiagnosticBuilder`, sadly, that's harder to fix, but it's unlikely enough that we can paper over it with asserts on `.emit()`
* `.cancel()` now consumes `DiagnosticBuilder`, preventing `.emit()` calls on a cancelled diagnostic
  * it's also now done internally, through `DiagnosticBuilder`-private state, instead of having a `Level::Cancelled` variant that can be read (or worse, written) by the user
  * this removes a hazard of calling `.cancel()` on an error then continuing to attach details to it, and even expect to be able to `.emit()` it
  * warnings were switched to *only* `can_emit_warnings` on emission (instead of pre-cancelling early)
  * `struct_dummy` was removed (as it relied on a pre-`Cancelled` `Diagnostic`)
* since `.emit()` doesn't consume the `DiagnosticBuilder` <sub>(I tried and gave up, it's much more work than this PR)</sub>,
  we have to make `.emit()` idempotent wrt the guarantees it returns
  * thankfully, `err.emit(); err.emit();` can return `ErrorReported` both times, as the second `.emit()` call has no side-effects *only* because the first one did do the appropriate emission
* `&mut Diagnostic` is now used in a lot of function signatures, which used to take `&mut DiagnosticBuilder` (in the interest of not having to make those functions generic)
  * the APIs were already mostly identical, allowing for low-effort porting to this new setup
  * only some of the suggestion methods needed some rework, to have the extra `DiagnosticBuilder` functionality on the `Diagnostic` methods themselves (that change is also present in #93259)
  * `.emit()`/`.cancel()` aren't available, but IMO calling them from an "error decorator/annotator" function isn't a good practice, and can lead to strange behavior (from the caller's perspective)
  * `.downgrade_to_delayed_bug()` was added, letting you convert any `.is_error()` diagnostic into a `delay_span_bug` one (which works because in both cases the guarantees available are the same)

This PR should ideally be reviewed commit-by-commit, since there is a lot of fallout in each.

r? `@estebank` cc `@Manishearth` `@nikomatsakis` `@mark-i-m`

rustfmt doesn't format `let ... else`.

As an example:

    #[test]
    #[ignore = "not yet implemented"]
    fn test_ignored() {
        ...
    }

Will now render as:

    running 2 tests
    test tests::test_ignored ... ignored, not yet implemented

    test result: ok. 1 passed; 0 failed; 1 ignored; 0 measured; 0 filtered out; finished in 0.00s

Rollup of 9 pull requests

Successful merges:

 - #91795 (resolve/metadata: Stop encoding macros as reexports)
 - #93714 (better ObligationCause for normalization errors in `can_type_implement_copy`)
 - #94175 (Improve `--check-cfg` implementation)
 - #94212 (Stop manually SIMDing in `swap_nonoverlapping`)
 - #94242 (properly handle fat pointers to uninhabitable types)
 - #94308 (Normalize main return type during mono item collection & codegen)
 - #94315 (update auto trait lint for `PhantomData`)
 - #94316 (Improve string literal unescaping)
 - #94327 (Avoid emitting full macro body into JSON errors)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

These links never worked, but the lint was suppressed due to the fact
that the span was pointing into the macro. With the new macro
implementation, the span now points directly to the doc comment in the
macro invocation, so it's no longer suppressed.

The `macro_rules!` implementation was becomng excessively complicated,
and difficult to modify. The new proc macro implementation should make
it much easier to add new features (e.g. skipping certain `#[derive]`s)

Avoid emitting full macro body into JSON errors

While investigating https://github.com/rust-lang/rust/issues/94322, it was noted that currently the JSON diagnostics for macro backtraces include the full def_site span -- the whole macro body.

It seems like this shouldn't be necessary, so this PR adjusts the span to just be the "guessed head", typically the macro name. It doesn't look like we keep enough information to synthesize a nicer span here at this time.

Atop #92123, this reduces output for the src/test/ui/suggestions/missing-lifetime-specifier.rs test from 660 KB to 156 KB locally.

Improve string literal unescaping

Some easy wins that affect a few popular crates.

r? ```@matklad```

update auto trait lint for `PhantomData`

cc https://github.com/rust-lang/rust/issues/93367#issuecomment-1047898410

Normalize main return type during mono item collection & codegen

The issue can be observed with `-Zprint-mono-items=lazy` in:

```rust
#![feature(termination_trait_lib)]
fn main() -> impl std::process::Termination { }
```
```
BEFORE: MONO_ITEM fn std::rt::lang_start::<impl std::process::Termination> ````@@```` t.93933fa2-cgu.2[External]
AFTER:  MONO_ITEM fn std::rt::lang_start::<()> ````@@```` t.df56e625-cgu.1[External]
```

properly handle fat pointers to uninhabitable types

Calculate the pointee metadata size by using `tcx.struct_tail_erasing_lifetimes` instead of duplicating the logic in `fat_pointer_kind`. Open to alternatively suggestions on how to fix this.

Fixes #94149

r? ````@michaelwoerister```` since you touched this code last, I think!

Stop manually SIMDing in `swap_nonoverlapping`

Like I previously did for `reverse` (#90821), this leaves it to LLVM to pick how to vectorize it, since it can know better the chunk size to use, compared to the "32 bytes always" approach we currently have.

A variety of codegen tests are included to confirm that the various cases are still being vectorized.

It does still need logic to type-erase in some cases, though, as while LLVM is now smart enough to vectorize over slices of things like `[u8; 4]`, it fails to do so over slices of `[u8; 3]`.

As a bonus, this change also means one no longer gets the spurious `memcpy`(s?) at the end up swapping a slice of `__m256`s: <https://rust.godbolt.org/z/joofr4v8Y>

<details>

<summary>ASM for this example</summary>

## Before (from godbolt)

note the `push`/`pop`s and `memcpy`

```x86
swap_m256_slice:
        push    r15
        push    r14
        push    r13
        push    r12
        push    rbx
        sub     rsp, 32
        cmp     rsi, rcx
        jne     .LBB0_6
        mov     r14, rsi
        shl     r14, 5
        je      .LBB0_6
        mov     r15, rdx
        mov     rbx, rdi
        xor     eax, eax
.LBB0_3:
        mov     rcx, rax
        vmovaps ymm0, ymmword ptr [rbx + rax]
        vmovaps ymm1, ymmword ptr [r15 + rax]
        vmovaps ymmword ptr [rbx + rax], ymm1
        vmovaps ymmword ptr [r15 + rax], ymm0
        add     rax, 32
        add     rcx, 64
        cmp     rcx, r14
        jbe     .LBB0_3
        sub     r14, rax
        jbe     .LBB0_6
        add     rbx, rax
        add     r15, rax
        mov     r12, rsp
        mov     r13, qword ptr [rip + memcpy@GOTPCREL]
        mov     rdi, r12
        mov     rsi, rbx
        mov     rdx, r14
        vzeroupper
        call    r13
        mov     rdi, rbx
        mov     rsi, r15
        mov     rdx, r14
        call    r13
        mov     rdi, r15
        mov     rsi, r12
        mov     rdx, r14
        call    r13
.LBB0_6:
        add     rsp, 32
        pop     rbx
        pop     r12
        pop     r13
        pop     r14
        pop     r15
        vzeroupper
        ret
```

## After (from my machine)

Note no `rsp` manipulation, sorry for different ASM syntax

```x86
swap_m256_slice:
	cmpq	%r9, %rdx
	jne	.LBB1_6
	testq	%rdx, %rdx
	je	.LBB1_6
	cmpq	$1, %rdx
	jne	.LBB1_7
	xorl	%r10d, %r10d
	jmp	.LBB1_4
.LBB1_7:
	movq	%rdx, %r9
	andq	$-2, %r9
	movl	$32, %eax
	xorl	%r10d, %r10d
	.p2align	4, 0x90
.LBB1_8:
	vmovaps	-32(%rcx,%rax), %ymm0
	vmovaps	-32(%r8,%rax), %ymm1
	vmovaps	%ymm1, -32(%rcx,%rax)
	vmovaps	%ymm0, -32(%r8,%rax)
	vmovaps	(%rcx,%rax), %ymm0
	vmovaps	(%r8,%rax), %ymm1
	vmovaps	%ymm1, (%rcx,%rax)
	vmovaps	%ymm0, (%r8,%rax)
	addq	$2, %r10
	addq	$64, %rax
	cmpq	%r10, %r9
	jne	.LBB1_8
.LBB1_4:
	testb	$1, %dl
	je	.LBB1_6
	shlq	$5, %r10
	vmovaps	(%rcx,%r10), %ymm0
	vmovaps	(%r8,%r10), %ymm1
	vmovaps	%ymm1, (%rcx,%r10)
	vmovaps	%ymm0, (%r8,%r10)
.LBB1_6:
	vzeroupper
	retq
```

</details>

This does all its copying operations as either the original type or as `MaybeUninit`s, so as far as I know there should be no potential abstract machine issues with reading padding bytes as integers.

<details>

<summary>Perf is essentially unchanged</summary>

Though perhaps with more target features this would help more, if it could pick bigger chunks

## Before

```
running 10 tests
test slice::swap_with_slice_4x_usize_30                            ... bench:         894 ns/iter (+/- 11)
test slice::swap_with_slice_4x_usize_3000                          ... bench:      99,476 ns/iter (+/- 2,784)
test slice::swap_with_slice_5x_usize_30                            ... bench:       1,257 ns/iter (+/- 7)
test slice::swap_with_slice_5x_usize_3000                          ... bench:     139,922 ns/iter (+/- 959)
test slice::swap_with_slice_rgb_30                                 ... bench:         328 ns/iter (+/- 27)
test slice::swap_with_slice_rgb_3000                               ... bench:      16,215 ns/iter (+/- 176)
test slice::swap_with_slice_u8_30                                  ... bench:         312 ns/iter (+/- 9)
test slice::swap_with_slice_u8_3000                                ... bench:       5,401 ns/iter (+/- 123)
test slice::swap_with_slice_usize_30                               ... bench:         368 ns/iter (+/- 3)
test slice::swap_with_slice_usize_3000                             ... bench:      28,472 ns/iter (+/- 3,913)
```

## After

```
running 10 tests
test slice::swap_with_slice_4x_usize_30                            ... bench:         868 ns/iter (+/- 36)
test slice::swap_with_slice_4x_usize_3000                          ... bench:      99,642 ns/iter (+/- 1,507)
test slice::swap_with_slice_5x_usize_30                            ... bench:       1,194 ns/iter (+/- 11)
test slice::swap_with_slice_5x_usize_3000                          ... bench:     139,761 ns/iter (+/- 5,018)
test slice::swap_with_slice_rgb_30                                 ... bench:         324 ns/iter (+/- 6)
test slice::swap_with_slice_rgb_3000                               ... bench:      15,962 ns/iter (+/- 287)
test slice::swap_with_slice_u8_30                                  ... bench:         281 ns/iter (+/- 5)
test slice::swap_with_slice_u8_3000                                ... bench:       5,324 ns/iter (+/- 40)
test slice::swap_with_slice_usize_30                               ... bench:         275 ns/iter (+/- 5)
test slice::swap_with_slice_usize_3000                             ... bench:      28,277 ns/iter (+/- 277)
```

</detail>

Improve `--check-cfg` implementation

This pull-request is a mix of improvements regarding the `--check-cfg` implementation:

- Simpler internal representation (usage of `Option` instead of separate bool)
- Add --check-cfg to the unstable book (based on the RFC)
- Improved diagnostics:
    * List possible values when the value is unexpected
    * Suggest if possible a name or value that is similar
- Add more tests (well known names, mix of combinations, ...)

r? ```@petrochenkov```

better ObligationCause for normalization errors in `can_type_implement_copy`

Some logic is needed so we can point to the field when given totally nonsense types like `struct Foo(<u32 as Iterator>::Item);`

Fixes #93687

resolve/metadata: Stop encoding macros as reexports

Supersedes https://github.com/rust-lang/rust/pull/88335.
r? `@cjgillot`

To make the `macro_rules` flag more readily available without decoding everything else

Previously it always returned `MacroKind::Bang` while some of those macros are actually attributes and derives

Always format to internal String in FmtPrinter

This avoids monomorphizing for different parameters, decreasing generic code
instantiated downstream from rustc_middle -- locally seeing 7% unoptimized LLVM IR
line wins on rustc_borrowck, for example.

We likely can't/shouldn't get rid of the Result-ness on most functions, though some
further cleanup avoiding fmt::Error where we now know it won't occur may be possible,
though somewhat painful -- fmt::Write is a pretty annoying API to work with in practice
when you're trying to use it infallibly.