Rollup of 6 pull requests

Successful merges:

 - #87744 (Add x.py option to --force-rerun compiletest tests)
 - #87789 (Make vec-shrink-panic test compatible with v0 mangling)
 - #87833 (Fix typo -- "The" -> "They")
 - #87834 (Fix small typo)
 - #87838 (Document that fs::read_dir skips . and ..)
 - #87842 (Fix intra doc link in hidden doc of Iterator::__iterator_get_unchecked)

Failed merges:

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

Fix intra doc link in hidden doc of Iterator::__iterator_get_unchecked

Recently, I edited the import list of the `core::iter::traits::iterator` module (in #85874). This results in a broken intra doc link in a hidden documentation with the effect that `RUSTDOCFLAGS='--document-private-items --document-hidden-items' x doc library/std` fails. (This can be worked around by adding `-Arustdoc::broken-intra-doc-links`; still, it’s a broken link so let’s fix it.)

``@rustbot`` label C-cleanup, T-libs

Document that fs::read_dir skips . and ..

Hi,

I think this is worth noting in the docs since it differs from POSIX `readdir`. I didn’t put it under platform-specific notes because it seems to be consistent across platforms, and changing this behavior in the future could cause pretty nasty bugs.

Thanks!

Fix small typo

The closing backtick was outside the closing bracket,
which is why the intra-doc link wasn't working.

Fix typo -- "The" -> "They"

I was reading through source code to try to learn more about the language and how to make the most of it when I ran into a small typo, so I figured I'd offer up a fix! I'm pretty new now, but hopefully I can offer up more substantial changes later. :D

Make vec-shrink-panic test compatible with v0 mangling

The v0 mangling includes an instantiating crate in a mangled name,
which crates a false positive match for a word `panic`.
Rename crate name / test case to avoid the issue.

Add x.py option to --force-rerun compiletest tests

This can be used like `./x.py test src/test/ui/abi/ --force-rerun`, and is useful when verifying that newly blessed tests don't change between test runs (such as due to being dependent on the current time or memory layout or RNG), without needing to change the test file or find the right file in `build` to remove.

update Miri

Fixes https://github.com/rust-lang/rust/issues/87778
r? `@ghost`

current_exe haiku code path simplification all of these part of libc

Update socket2 dependency from 0.4.0 to 0.4.1

This update contains a fix for building the tools that depend on this package on Haiku (tier 3).

Hide allocator details from TryReserveError

I think there's [no need for TryReserveError to carry detailed information](https://github.com/rust-lang/rust/issues/48043#issuecomment-825139280), but I wouldn't want that issue to delay stabilization of the `try_reserve` feature.

So I'm proposing to stabilize `try_reserve` with a `TryReserveError` as an opaque structure, and if needed, expose error details later.

This PR moves the `enum` to an unstable inner `TryReserveErrorKind` that lives under a separate feature flag. `TryReserveErrorKind` could possibly be left as an implementation detail forever, and the `TryReserveError` get methods such as `allocation_size() -> Option<usize>` or `layout() -> Option<Layout>` instead, or the details could be dropped completely to make try-reserve errors just a unit struct, and thus smaller and cheaper.

The closing backtick was outside the closing bracket,
which is why the intra-doc link wasn't working.

I was reading through source code to try to learn more about the language and how to make the most of it when I ran into a small typo, so I figured I'd offer up a fix! I'm pretty new now, but hopefully I can offer up more substantial changes later. :D

Fix typo

Add missing "by".

Rollup of 7 pull requests

Successful merges:

 - #85807 (bootstrap: Disable initial-exec TLS model on powerpc)
 - #87761 (Fix overflow in rustc happening if the `err_count()` is reduced in a stage.)
 - #87775 (Add hint for unresolved associated trait items if the trait has a single item)
 - #87779 (Remove special case for statement `NodeId` assignment)
 - #87787 (Use `C-unwind` ABI for `__rust_start_panic` in `panic_abort`)
 - #87809 (Fix typo in the ptr documentation)
 - #87816 (Sync rustc_codegen_cranelift)

Failed merges:

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

Sync rustc_codegen_cranelift

05677b6b removes two assertions that should have been removed in https://github.com/rust-lang/rust/pull/87515. They are no longer correct and trigger while compiling the sysroot.

r? `@ghost`

`@rustbot` label +A-codegen +A-cranelift +T-compiler

Fix typo in the ptr documentation

Spotted a minor typo in the docs ;). Pointers are cool!

Use `C-unwind` ABI for `__rust_start_panic` in `panic_abort`

The function originally has `C` ABI but is called using `C-unwind` ABI in `std`:
https://github.com/rust-lang/rust/blob/d4ad1cfc63ba5824196bfb2370451ddb5af2e020/library/std/src/panicking.rs#L49-L54
Which might be [problematic](https://github.com/rust-lang/miri/pull/1745#discussion_r596096876) and triggers this [Miri error](https://github.com/rust-lang/rust/issues/87778#issuecomment-893306222):
```
error: Undefined Behavior: calling a function with ABI C using caller ABI C-unwind
   --> /home/hyd-dev/.rustup/toolchains/miri/lib/rustlib/src/rust/library/std/src/panicking.rs:672:9
    |
672 |         __rust_start_panic(obj)
    |         ^^^^^^^^^^^^^^^^^^^^^^^ calling a function with ABI C using caller ABI C-unwind
    |
    = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
    = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
```
Changing the ABI of the function to `C-unwind` fixes the error above.

Remove special case for statement `NodeId` assignment

We now let `noop_flat_map_stmt` assign `NodeId`s (via `visit_id`),
just as we do for other AST nodes.

Add hint for unresolved associated trait items if the trait has a single item

This PR introduces a special-cased hint for unresolved trait items paths. It is shown if:
- the path was not resolved to any existing trait item
- and no existing trait item's name was reasonably close with regard to edit distance
- and the trait only has a single item in the corresponding namespace

I didn't know where I should put tests, therefore so far I just managed to bless two existing tests. I would be glad for hints where should tests for a hint like this be created, how should they be named (with reference to the original issue?) and what tests should I create (is it enough to test it just for types? or create separate tests also for functions and constants?).

It could also be turned into a machine applicable suggestion I suppose.

This is my first `rustc` PR, so please go easy on me :)

Fixes: https://github.com/rust-lang/rust/issues/87638

Fix overflow in rustc happening if the `err_count()` is reduced in a stage.

This can happen if stashed diagnostics are removed or replaced with fewer errors. The semantics stay the same if built without overflow checks. Fixes #84219.

Background: I came across this independently by running `RUSTFLAGS="-C overflow-checks=on" ./x.py test`. Fixing this will allow us to move on and find further overflow errors with testing or fuzzing.

bootstrap: Disable initial-exec TLS model on powerpc

Fixes #81334.

Add config.toml options for enabling overflow checks in rustc and std

The names are `overflow-checks` and `overflow-checks-std` and they work similar to  `debug-assertions` and `debug-assertions-std`. Once added we can measure how big the performance impact actually is and maybe enable them for CI tests.

Enabling them already makes two ui tests fail:
```
failures:
    [ui] ui/parser/item-free-const-no-body-semantic-fail.rs
    [ui] ui/parser/item-free-static-no-body-semantic-fail.rs
```
(See #84219 and #87761.)

We now let `noop_flat_map_stmt` assign `NodeId`s (via `visit_id`),
just as we do for other AST nodes.

Use zeroed allocations in the mir interpreter instead eagerly touching the memory

#86255 introduced a 30% regression in [page faults](https://perf.rust-lang.org/compare.html?start=64ae15ddd3f3cca7036ab2b2f3a6b130b62af4da&end=39e20f1ae5f13451eb35247808d6a2527cb7d060&stat=faults
) and a 3% regression in [max-rss](https://perf.rust-lang.org/index.html?start=2021-07-01&end=&absolute=false&stat=max-rss) in the ctfe-stress benchmarks.
That's most likely happened because it separated allocation from initialization of the vec which defeats the zero-optimization.

Currently there's no allocation API that is fallible, zeroing and returns a slice, so this PR introduces one and then uses that to solve the problem. In principle `vec.resize(len, 0)` could be optimized to use `alloc::grow_zeroed` where appropriate but that would require new specializations and new plumbing in `RawVec`.

The options are `overflow-checks` and `overflow-checks-std`
defaulting to false.

Rollup of 9 pull requests

Successful merges:

 - #87561 (thread set_name haiku implementation.)
 - #87715 (Add long error explanation for E0625)
 - #87727 (explicit_generic_args_with_impl_trait: fix min expected number of generics)
 - #87742 (Validate FFI-safety warnings on naked functions)
 - #87756 (Add back -Zno-profiler-runtime)
 - #87759 (Re-use std::sealed::Sealed in os/linux/process.)
 - #87760 (Promote `aarch64-apple-ios-sim` to Tier 2)
 - #87770 (permit drop impls with generic constants in where clauses)
 - #87780 (alloc: Use intra doc links for the reserve function)

Failed merges:

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

alloc: Use intra doc links for the reserve function

The sentence exists to highlight the existence of a
performance footgun of repeated calls of the
reserve_exact function.

permit drop impls with generic constants in where clauses

Fixes #79248

`==` is not sufficient to check for equality between unevaluated consts which causes the above issue because the const in `[(); N - 1]:` on the impl and the const in `[(); N - 1]:` on the struct def are not seen as equal. Any predicate that can contain an unevaluated const cant use `==` here as it will cause us to incorrectly emit an error.

I dont know much about chalk but it seems like we ought to be relating the `TypeWellFormedFromEnv` instead of `==` as it contains a `Ty` so I added that too...

r? ``````@lcnr``````

Promote `aarch64-apple-ios-sim` to Tier 2

As per https://github.com/rust-lang/compiler-team/issues/428 this target becomes Tier 2.

---

I tested that the latest nightly has the target and I'm already building my project with that on CI and locally.

Re-use std::sealed::Sealed in os/linux/process.

This uses `std::sealed::Sealed` in `std::os::linux::process` instead of defining new `Sealed` traits there.

Add back -Zno-profiler-runtime

This was removed by #85284 in favor of `-Zprofiler-runtime=<name>`.However the suggested `-Zprofiler-runtime=None` doesn't work because`None` is treated as a crate name.

Validate FFI-safety warnings on naked functions

Test that FFI-safety warnings don't get accidentally dropped on naked
functions. The big picture is that if you implement a naked function
with the Rust ABI you'll get a warning. Further, if you implement a
naked function with a standardized ABI, but use non-FFI-safe types you
will still get a warning.

rust-lang/rfcs#2774
rust-lang/rfcs#2972

cc ``````@joshtriplett`````` ``````@Amanieu`````` ``````@haraldh``````