This also gives a better error message when a span is missing.

This adds a new lint to `rustc` that is used in rustdoc when a code
block is empty or cannot be parsed as valid Rust code.

Previously this was unconditionally a warning. As such some
documentation comments were (unknowingly) abusing this to pass despite
the `-Dwarnings` used when compiling `rustc`, this should not be the
case anymore.

Rollup of 8 pull requests

Successful merges:

 - #85087 (`eval_fn_call`: check the ABI of `body.source`)
 - #85302 (Expand WASI abbreviation in docs)
 - #85355 (More tests for issue-85255)
 - #85367 (Fix invalid input:disabled CSS selector)
 - #85374 (mark internal inplace_iteration traits as hidden)
 - #85408 (remove size field from Allocation)
 - #85409 (Simplify `cfg(any(unix, target_os="redox"))` in example to just `cfg(unix)`)
 - #85412 (remove some functions that were only used by Miri)

Failed merges:

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

remove some functions that were only used by Miri

and Miri does not need them any more with https://github.com/rust-lang/miri/pull/1805.

r? ``@oli-obk``

Simplify `cfg(any(unix, target_os="redox"))` in example to just `cfg(unix)`

Update example for `OsString` that handled `redox` seperately from `unix`: Redox has been completely integrated under `target_family="unix"`, so `cfg(unix)` implies `target_os="redox"`

https://github.com/rust-lang/rust/blob/35dbef235048f9a2939dc20effe083ca483c37ff/compiler/rustc_target/src/spec/redox_base.rs#L26

remove size field from Allocation

This is a part of https://github.com/rust-lang/rust/pull/85376 that can be easily split out.
r? ``@oli-obk``

mark internal inplace_iteration traits as hidden

resolves #85373

r? ``@SimonSapin``

Fix invalid input:disabled CSS selector

For some reason, we used "search-focus" instead of "search-input"...

r? ``@jsha``

More tests for issue-85255

Add more test for `pub(crate)`.

r? ``@varkor``

Expand WASI abbreviation in docs

I was pretty sure this was related to something for WebAssembly but wasn't 100% sure so I checked but even on these top-level docs I couldn't find the abbreviation expanded. I'm normally used to Rust docs being detailed and explanatory and writing abbreviations like this out in full at least once so I thought it was worth the change. Feel free to close this if it's too much.

`eval_fn_call`: check the ABI of `body.source`

And stop checking `instance_ty.fn_sig(*self.tcx).abi()`, if the function is not an intrinsic.
Addresses https://github.com/rust-lang/miri/pull/1776#discussion_r615381169.
No idea how to test this without Miri...

Update RLS

Contains https://github.com/rust-lang/rls/pull/1736. With #82208 merged, this should now close https://github.com/rust-lang/rust/issues/85225. Tested locally with `./x.py test src/tools/rls` and seems to be working as expected.

I noticed the rustfmt merge didn't trigger toolstate upgrade (because we pruned most but not all of the related machinery?), so I'd rather get this rubber-stamped by someone more knowledgeable with infra/the merged changes in case I missed something and need to include something else here to unbreak the RLS toolstate.

r? `@Mark-Simulacrum`

Parse unnamed fields of struct and union type

Added the `unnamed_fields` feature gate.

This is a prototype of [RFC 2102](https://github.com/rust-lang/rust/issues/49804), so any suggestions are greatly appreciated.

r? `@petrochenkov`

Allow `async {}` expressions in const contexts

Gated behind a new `const_async_blocks` feature.

Remove CrateNum parameter for queries that only work on local crate

The pervasive `CrateNum` parameter is a remnant of the multi-crate rustc idea.

Using `()` as query key in those cases avoids having to worry about the validity of the query key.

rustc_codegen_ssa: only create backend `BasicBlock`s as-needed.

Instead of creating one backend (e.g. LLVM) block per MIR block ahead of time, and then deleting the ones that weren't visited, this PR moves to creating the blocks as they're needed (either reached via the RPO visit, or used as the target of a branch from a different block).

As deleting a block was the only `unsafe` builder method (generally we only *create* backend objects, not *remove* them), that's gone now and codegen is overall a bit safer.

The only change in output is the order of LLVM blocks (which AFAIK has no semantic meaning, other than the first block being the entry block). This happens because the blocks are now created due to control-flow edges, rather than MIR block order.

I'm making this a standalone PR because I keep getting wild perf results when I change *anything* in codegen, but if you want to read more about my plans in this area, see https://github.com/rust-lang/rust/pull/84771#issuecomment-830636256 (and https://github.com/rust-lang/rust/pull/84771#issue-628295651 - but that may be a bit outdated).

(You may notice some of the APIs in this PR, like `append_block`, don't help with the future plans - but I didn't want to include the necessary refactors that pass a build around everywhere, in this PR, so it's a small compromise)

r? `@nagisa` `@bjorn3`

Fix unused attributes on macro_rules.

The `unused_attributes` lint wasn't firing on attributes of `macro_rules` definitions. The consequence is that many attributes are silently ignored on `macro_rules`. The reason is that `unused_attributes` is a late-lint pass, and only has access to the HIR, which does not have macro_rules definitions.

My solution here is to change `non_exported_macro_attrs` to be `macro_attrs` (a list of all attributes used for `macro_rules`, instead of just those for `macro_export`), and then to check this list in the `unused_attributes` lint. There are a number of alternate approaches, but this seemed the most reliable and least invasive. I am open to completely different approaches, though.

One concern is that I don't fully understand the implications of extending `non_exported_macro_attrs` to include non-exported macros. That list was originally added in #62042 to handle stability attributes, so I suspect it was just an optimization since that was all that was needed. It was later extended to be included in SVH in #83901. #80641 also added a use to check for `invalid` attributes, which seems a little odd to me (it didn't validate non-exported macros, and seems highly specific).

Overall, there doesn't seem to be a clear story of when `unused_attributes` should be used versus an error like E0518. I considered alternatively using an "allow list" of built-in attributes that can be used on macro_rules (allow, warn, deny, forbid, cfg, cfg_attr, macro_export, deprecated, doc), but I feel like that could be a pain to maintain.

Some built-in attributes already present hard-errors when used with macro_rules. These are each hard-coded in various places:
- `derive`
- `test` and `bench`
- `proc_macro` and `proc_macro_derive`
- `inline`
- `global_allocator`

The primary motivation is that I sometimes see people use `#[macro_use]` in front of `macro_rules`, which indicates there is some confusion out there (evident that there was even a case of it in rustc).

Remove support for floating-point constants in asm!

Floating-point constants aren't very useful anyways and this simplifies
the code since the type check can now be done in typeck.

cc `@rust-lang/wg-inline-asm`

r? `@nagisa`

Reachable statics have reachable initializers

Static initializer can read other statics. Initializers are evaluated at
compile time, and so their content could become inlined into another
crate. Ensure that initializers of reachable statics are also reachable.

Previously, when an item incorrectly considered to be unreachable was
reached from another crate an attempt would be made to codegen it. The
attempt could fail with an ICE (in the case MIR wasn't available to do
so) in some circumstances the attempt could also succeed resulting in
a local codegen of non-local items, including static ones.

Fixes #84455.

Add unnamed_fields feature gate and gate unnamed fields on parsing

rustc_codegen_ssa: generate MSVC cleanup pads on demand, like GNU landing pads.

This unblocks #84993 in terms of codegen tests, as it brings the MSVC-style (`cleanup_pad`) EH (LLVM) block order in line with the GNU-style (`landing_pad`) EH (LLVM) block order, by having both of them be on-demand (instead of MSVC-style being eager and GNU-style lazy/on-demand).

It also unifies the two implementations a bit, similar to #84699, but in the opposite direction (as that attempt made both kinds of EH pads eagerly built).

~~Opening as draft because I haven't done enough Windows testing just yet, of both this PR, and of #84993 rebased on it.~~ (**EDIT**: seems to be working as expected)

r? `@nagisa`

CTFE validation: handle pointers in str

I also finally learned how I can match *some* NOTEs in a ui test without matching all of them, and applied that to some const tests in the 2nd commit where I added NOTE because I did not know what I was doing. I can separate this into its own PR if you prefer.

Fixes https://github.com/rust-lang/rust/issues/83182
r? `@oli-obk`

rustdoc: Call `initSidebarItems` in root module of crate

r? `@jsha`

Resolves #85301

Add asm!() support for PowerPC64

I was anticipating this to be difficult so I didn't do it as part of #84732... but this was pretty easy to do 👀

Check for inline assembly in THIR unsafeck

#83129 was merged recently and added a THIR unsafe checker. This adds a check for inline assembly. (and this is 2x simpler than the MIR version, which has to check for `asm` and `llvm_asm` in two separate spots!)

 see also rust-lang/project-thir-unsafeck#7