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

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.

rustdoc: Remove most fields from ExternalCrate

Once https://github.com/rust-lang/rust/issues/84304 is fixed, I can get rid of ExternCrate altogether in favor of CrateNum, but in the meantime, this shrinks ExternalCrate quite a lot.

This might hurt compile-times; if it does, I can add `primitive` and `keyword` queries. I expect this to improve compilemem.

Helps with https://github.com/rust-lang/rust/issues/76382.

r? GuillaumeGomez

Looks like this platform still isn't quite working yet due to
https://bugs.llvm.org/show_bug.cgi?id=50083

rustdoc: Hide `#text` in doc-tests

Since `#![attr]` and `#[attr]` are the only valid syntax that start with `#`, we can just special case those two tokens.

Fixes https://github.com/rust-lang/rust/issues/83284.

RustWrapper: work around unification of diagnostic handlers

This lets me build against llvm/main as of March 23rd, 2021. I'm not
entirely sure this is _correct_, but it appears to be functionally
identical to what was done in LLVM: existing callsites of
setInlineAsmDiagnosticHandler were moved to SetDiagnosticHandler() on
the context object, which we already set up in both places that we
called setInlineAsmDiagnosticHandler().

Added CharIndices::offset function

The CharIndices iterator has a field internally called front_offset, that I think would be very useful to have access to.

You can already do something like ``char_indices.next().map(|(offset, _)| offset)``, but that is wordy, in addition to not handling the case where the iterator has ended, where you'd want the offset to be equal to the length.

I'm very new to the open source world and the rust repository, so I'm sorry if I missed a step or did something weird.

Improve rebuilding behaviour of BinaryHeap::retain.

This changes `BinaryHeap::retain` such that it doesn't always fully rebuild the heap, but only rebuilds the parts for which that's necessary.

This makes use of the fact that retain gives out `&T`s and not `&mut T`s.

Retaining every element or removing only elements at the end results in no rebuilding at all. Retaining most elements results in only reordering the elements that got moved (those after the first removed element), using the same logic as was already used for `append`.

cc `@KodrAus` `@sfackler` - We briefly discussed this possibility in the meeting last week while we talked about stabilization of this function (#71503).

Fixes: #84421

Since `#![attr]` and `#[attr]` are the only valid syntax that start with `#`, we can just special case those two tokens.

Use arrayvec 0.7, drop smallvec 0.6

With the arrival of min const generics, many alt-vec libraries have
updated to use it in some way and arrayvec is no exception. Use the
latest with minor refactoring.

Also, rustc_workspace_hack is the only user of smallvec 0.6 in the
entire tree, so drop it.

This lets me build against llvm/main as of March 23rd, 2021. I'm not
entirely sure this is _correct_, but it appears to be functionally
identical to what was done in LLVM: existing callsites of
setInlineAsmDiagnosticHandler were moved to SetDiagnosticHandler() on
the context object, which we already set up in both places that we
called setInlineAsmDiagnosticHandler().

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

Rollup of 7 pull requests

Successful merges:

 - #84343 (Remove `ScopeTree::closure_tree`)
 - #84376 (Uses flex to fix formatting of h1 at any width)
 - #84377 (Followup to #83944)
 - #84396 (Update LLVM submodule)
 - #84402 (Move `sys_common::rwlock::StaticRWLock` etc. to `sys::unix::rwlock`)
 - #84404 (Check for intrinsics before coercing to a function pointer)
 - #84413 (Remove `sys::args::Args::inner_debug` and use `Debug` instead)

Failed merges:

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

Remove `sys::args::Args::inner_debug` and use `Debug` instead

This removes the method `sys::args::Args::inner_debug` on all platforms and implements `Debug` for `Args` instead.

I believe this creates a more natural API for the different platforms under `sys`: export a type `Args: Debug + Iterator + ...` vs. `Args: Iterator + ...` and with a method `inner_debug`.