rustdoc: Turn `JsonRenderer::mod_item_in` into `unreachable!()`

The JSON renderer no longer gets called on modules (since https://github.com/rust-lang/rust/pull/83055).

r? ``@aDotInTheVoid``

Update Clippy

r? ```@Manishearth```

Biweekly Clippy update.

Explicitly implement `!Send` and `!Sync` for `sys::{Args, Env}`

Remove the field `_dont_send_or_sync_me: PhantomData<*mut ()>` in favor of an explicit implementation of `!Send` and `!Sync`.

stabilize `core::array::{from_ref,from_mut}` in `1.53.0`

I didn't get any response in https://github.com/rust-lang/rust/issues/77101#issuecomment-761831104, so I figured out I can try opening stabilization pr.

---

This PR stabilizes following functions:
```rust
// core::array
pub fn from_ref<T>(s: &T) -> &[T; 1];
pub fn from_mut<T>(s: &mut T) -> &mut [T; 1];
```

Functions are similar to already stabilized `core::slice::{`[`from_ref`](https://doc.rust-lang.org/std/slice/fn.from_ref.html),[`from_mut`](https://doc.rust-lang.org/std/slice/fn.from_mut.html)`}` and were unstable without any problems/questions for a while now.

---

resolves #77101

``@rustbot`` modify labels: +T-libs

Implement a lint that highlights all moves larger than a configured limit

Tracking issue: #83518
[MCP 420](https://github.com/rust-lang/compiler-team/issues/420) still ~blazing~ in progress

r? ```@pnkfelix```

The main open issue I see with this minimal impl of the feature is that the lint is immediately "stable" (so it can be named on stable), even if it is never executed on stable. I don't think we have the concept of unstable lint names or hiding lint names without an active feature gate, so that would be a bigger change.

The JSON renderer no longer gets called on modules.

Rollup of 10 pull requests

Successful merges:

 - #83990 (implement `TrustedRandomAccess` for `Take` iterator adapter)
 - #84250 (bootstrap: use bash on illumos to run install scripts)
 - #84320 (Use details tag for trait implementors.)
 - #84436 (Make a few functions private)
 - #84453 (Document From implementations for Waker and RawWaker)
 - #84458 (Remove unnecessary fields and parameters in rustdoc)
 - #84485 (Add some associated type bounds tests)
 - #84489 (Mention FusedIterator case in Iterator::fuse doc)
 - #84492 (rustdoc: Remove unnecessary dummy span)
 - #84496 (Add some specialization tests)

Failed merges:

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

Add some specialization tests

Closes #33017
Closes #51892

r? `@JohnTitor`

rustdoc: Remove unnecessary dummy span

Follow-up to https://github.com/rust-lang/rust/pull/84460#discussion_r619447655.

r? `@camelid`

Mention FusedIterator case in Iterator::fuse doc

Using `fuse` on an iterator that incorrectly implements
`FusedIterator` does not fuse the iterator. This commit adds a
note about this in the documentation of this method to increase
awareness about this potential issue (esp. when relying on fuse
in unsafe code).

Closes #83969

Add some associated type bounds tests

Closes #83017
Closes #81193

r? `@jackh726`

Remove unnecessary fields and parameters in rustdoc

r? `@GuillaumeGomez`

Document From implementations for Waker and RawWaker

CC #51430

Make a few functions private

These were made public in 3105bcfd. This
is so long ago I doubt anyone remembers why they're public. No one outside rustc_session uses
them, including in-tree tools.

Use details tag for trait implementors.

Part of #83332 and following on from #83337 and #83355.

This removes one category of JS-generated toggles (implementors), and replaces them with a `<details>` tag. This simplifies the JS, and fixes some bugs where things that were supposed to be hidden by the toggle were not hidden. Compare https://hoffman-andrews.com/rust/details-implementors/std/io/trait.Read.html#impl-Read vs https://doc.rust-lang.org/nightly/std/io/trait.Read.html#implementors.

This introduces a `left: -23px` to put the toggle in the correct place, matching the current style for `.collapse-toggle`.

It's worth noting this introduces a slight behavior change: since the entire line is now a `<summary>`, any part of the line is clickable. So for instance, in `impl Read for File`, clicking `impl` or `for` will collapse / expand the docs. Clicking `Read` or `File` still links to the appropriate documentation as before.

bootstrap: use bash on illumos to run install scripts

The default illumos shell ("sh" in the default PATH) is ksh93, rather
than bash, and does not support constructs like "local" that came from
bash.  The bootstrap function for invoking "install.sh" scripts should
use "bash" explicitly there to avoid issues.

implement `TrustedRandomAccess` for `Take` iterator adapter

`TrustedRandomAccess` requires the iterator length to fit within `usize`. `take(n)` only constrains the upper bound of an iterator. So if the inner is `TrustedRandomAccess` (which already implies a finite length) then so can be `Take`.

```````@rustbot``````` label T-libs-impl

On stable, suggest removing `#![feature]` for features that have been stabilized

I don't know how to test this (https://rust-lang.zulipchat.com/#narrow/stream/182449-t-compiler.2Fhelp/topic/Run.20tests.20without.20enabling.20nightly.20features.3F). I confirmed locally that this gives the
appropriate help with `channel = "beta"`:

```
error[E0554]: `#![feature]` may not be used on the beta release channel
 --> src/lib.rs:2:1
  |
2 | #![feature(min_const_generics)]
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: remove the attribute
  |
  = help: the feature `min_const_generics` has been stable since 1.51.0 and no longer requires an attribute to enable

error[E0554]: `#![feature]` may not be used on the beta release channel
 --> src/lib.rs:3:1
  |
3 | #![feature(min_const_generics, min_specialization)]
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = help: the feature `min_const_generics` has been stable since 1.51.0 and no longer requires an attribute to enable

error[E0554]: `#![feature]` may not be used on the beta release channel
 --> src/lib.rs:4:1
  |
4 | #![feature(box_patterns)]
  | ^^^^^^^^^^^^^^^^^^^^^^^^^
```

Closes https://github.com/rust-lang/rust/issues/83715.

Add a suggestion when using a type alias instead of trait alias

Fixes #43913

r? `@estebank`

Rollup of 11 pull requests

Successful merges:

 - #80805 (Improve `Iterator::by_ref` example)
 - #84248 (Remove duplicated fn(Box<[T]>) -> Vec<T>)
 - #84321 (rustdoc: Convert sub-variant toggle to HTML)
 - #84359 (⬆ rust-analyzer)
 - #84374 (Clean up .gitignore)
 - #84387 (Move `sys_common::poison` to `sync::poison`)
 - #84430 (doc/platform-support: clarify UEFI support)
 - #84433 (Prevent control, shift and alt keys to make search input lose focus)
 - #84444 (doc: Get rid of "[+] show undocumented items" toggle on numeric From impls)
 - #84456 (Fix ICE if original_span(fn_sig) returns a span not in body sourcefile)
 - #84469 (Update comment on `PrimTy::name_str`)

Failed merges:

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

Update comment on `PrimTy::name_str`

It's no longer used by rustdoc.

Fix ICE if original_span(fn_sig) returns a span not in body sourcefile

Fixes: #84421

r? ````@tmandry````

fyi: ````@wesleywiser```` ````@sdroege```` ````@rajivshah3````

doc: Get rid of "[+] show undocumented items" toggle on numeric From impls

On most From implementations, the docstring is attached to the function. This is also how people have been [recommended] to do it.

Screenshots:

* [before](https://user-images.githubusercontent.com/1593513/115767662-323c5480-a35e-11eb-9918-98aba83e9183.png)
* [after](https://user-images.githubusercontent.com/1593513/115767675-35374500-a35e-11eb-964f-c28eeb6c807a.png)

[recommended]: https://github.com/rust-lang/rust/issues/51430#issuecomment-398322434

Prevent control, shift and alt keys to make search input lose focus

Part of #84384.

r? ````@jsha````

doc/platform-support: clarify UEFI support

Add missing information on what standard-library features are supported by the UEFI targets.

All current UEFI targets (which is i686 and x86_64) only support no_std cross-compilations. `std` support has not been worked on and is unlikely to emerge anytime soon, due to the much restricted environment that UEFI provides.

Move `sys_common::poison` to `sync::poison`

`sys_common` should not contain publicly exported types, only platform-independent abstractions on top of `sys`, which `sys_common::poison` is not. There is thus no reason for the module to not live under `sync`.

Part of #84187.

Clean up .gitignore

Categorizes entries in the `.gitignore` file.

Other changes:
- added `desktop.ini` (Windows equivalent of `.DS_Store`)
- removed `.hg/` and `.hgignore`

⬆ rust-analyzer

rustdoc: Convert sub-variant toggle to HTML

Instead of creating a JS toggle, this injects details/summary for
sub-variants of enums. This also fixes the CSS so that the toggle button
does not jump when expanding/collapsing.

Takes inspiration from #83337 and should be considered part of #83332. Not quite sure if the `.sub-variant` selectors could be further simplified? AFAICS it is only used in that place, and that does not seem to allow any recursion.

Remove duplicated fn(Box<[T]>) -> Vec<T>

`<[T]>::into_vec()` does the same thing as `Vec::from::<Box<[T]>>()`, so they can be implemented in terms of each other. This was the previous implementation of `Vec::from()`, but was changed in #78461. I'm not sure what the rationale was for that change, but it seems preferable to maintain a single implementation.

Improve `Iterator::by_ref` example

I split the example into two: one that fails to compile, and one that
works. I also made them identical except for the addition of `by_ref`
so we don't confuse readers with random differences.

cc `@steveklabnik,` who is the one that added the previous version of this example

rustc: Use LLVM's new saturating float-to-int intrinsics

This commit updates rustc, with an applicable LLVM version, to use
LLVM's new `llvm.fpto{u,s}i.sat.*.*` intrinsics to implement saturating
floating-point-to-int conversions. This results in a little bit tighter
codegen for x86/x86_64, but the main purpose of this is to prepare for
upcoming changes to the WebAssembly backend in LLVM where wasm's
saturating float-to-int instructions will now be implemented with these
intrinsics.

This change allows simplifying a good deal of surrounding code, namely
removing a lot of wasm-specific behavior. WebAssembly no longer has any
special-casing of saturating arithmetic instructions and the need for
`fptoint_may_trap` is gone and all handling code for that is now
removed. This means that the only wasm-specific logic is in the
`fpto{s,u}i` instructions which only get used for "out of bounds is
undefined behavior". This does mean that for the WebAssembly target
specifically the Rust compiler will no longer be 100% compatible with
pre-LLVM 12 versions, but it seems like that's unlikely to be relied on
by too many folks.

Note that this change does immediately regress the codegen of saturating
float-to-int casts on WebAssembly due to the specialization of the LLVM
intrinsic not being present in our LLVM fork just yet. I'll be following
up with an LLVM update to pull in those patches, but affects a few other
SIMD things in flight for WebAssembly so I wanted to separate this change.

Eventually the entire `cast_float_to_int` function can be removed when
LLVM 12 is the minimum version, but that will require sinking the
complexity of it into other backends such as Cranelfit.

Using `fuse` on an iterator that incorrectly implements
`FusedIterator` does not fuse the iterator. This commit adds a
note about this in the documentation of this method to increase
awareness about this potential issue (esp. when relying on fuse
in unsafe code).