The version was removed in rust-lang#77145

This builder is the slowest in the fleet. This should cut a considerable
amount of time. The manifest should now include the docs from
x86_64-apple-darwin. Although those docs are slightly different, it
should be close enough. When aarch64-apple-darwin heads towards tier 1,
we can revisit whether or not to re-enable the docs.

mangling_v0: Skip extern blocks during mangling

There's no need to include the dummy `Nt` into the symbol name, items in extern blocks belong to their parent modules for all purposes except for inheriting the ABI and attributes.

Follow up to rust-lang#92032

(There's also a drive-by fix to the `rust-demangler` tool's tests, which don't run on CI, I initially attempted using them for testing this PR.)

…Default, r=yaahc

Change PhantomData type for `BuildHasherDefault` (and more)

Changes `PhantomData<H>` to `PhantomData<fn() -> H>` for `BuildHasherDefault`. This preserves the covariance of `H`, while it lifts the currently inferred unnecessary bounds like [`H: Send` for `BuildHasherDefault<H>: Send`](https://doc.rust-lang.org/1.57.0/std/hash/struct.BuildHasherDefault.html#impl-Send), etc.

_Edit:_ Also does a similar change for `iter::Empty` and `future::Pending`.

Add manifest docs fallback.

This adds a fallback so that the rustup manifest will contain the rust-docs component for all hosts. There is a mapping so that the docs that get downloaded are roughly close to the actual host. There inevitably will be things that don't match. Ideally the standard library docs would be the same for every platform (`cfg(doc)` goes a long way towards this), but there are still lots of minor differences.

Closes rust-lang#69525

…=notriddle

Move back templates into html folder

Follow-up of rust-lang#92526.

r? `@notriddle`

Pretty printer algorithm revamp step 2

This PR follows rust-lang#92923 as a second chunk of modernizations backported from https:/dtolnay/prettyplease into rustc_ast_pretty.

I've broken this up into atomic commits that hopefully are sensible in isolation. At every commit, the pretty printer is compilable and has runtime behavior that is identical to before and after the PR. None of the refactoring so far changes behavior.

The general theme of this chunk of commits is: the logic in the old pretty printer is doing some very basic things (pushing and popping tokens on a ring buffer) but expressed in a too-low-level way that I found makes it quite complicated/subtle to reason about. There are a number of obvious invariants that are "almost true" -- things like `self.left == self.buf.offset` and `self.right == self.buf.offset + self.buf.data.len()` and `self.right_total == self.left_total + self.buf.data.sum()`. The reason these things are "almost true" is the implementation tends to put updating one side of the invariant unreasonably far apart from updating the other side, leaving the invariant broken while unrelated stuff happens in between. The following code from master is an example of this:

https:/rust-lang/rust/blob/e5e2b0be26ea177527b60d355bd8f56cd473bd00/compiler/rustc_ast_pretty/src/pp.rs#L314-L317

In this code the `advance_right` is reserving an entry into which to write a next token on the right side of the ring buffer, the `check_stack` is doing something totally unrelated to the right boundary of the ring buffer, and the `scan_push` is actually writing the token we previously reserved space for. Much of what this PR is doing is rearranging code to shrink the amount of stuff in between when an invariant is broken to when it is restored, until the whole thing can be factored out into one indivisible method call on the RingBuffer type.

The end state of the PR is that we can entirely eliminate `self.left` (because it's now just equal to `self.buf.offset` always) and `self.right` (because it's equal to `self.buf.offset + self.buf.data.len()` always) and the whole `Token::Eof` state which used to be the value of tokens that have been reserved space for but not yet written.

I found without these changes the pretty printer implementation to be hard to reason about and I wasn't able to confidently introduce improvements like trailing commas in `prettyplease` until after this refactor. The logic here is 43 years old at this point (Graydon translated it as directly as possible from the 1979 pretty printing paper) and while there are advantages to following the paper as closely as possible, in `prettyplease` I decided if we're going to adapt the algorithm to work better for Rust syntax, it was worthwhile making it easier to follow than the original.

remove `List::is_noop`

think that `is_noop` is actually less clear than just using `is_empty`