…fter struct fields.

This speeds up lots of rustc-perf benchmark runs. The maximum
improvement is 1%, but there are a lot in the 0.5--1.0% range.

This speeds up a few rustc-perf benchmark runs, most notably ones
involving 'coercions', the best by 2%.

This commit fixes an accidental regression from rust-lang#50473 where lifetime tokens
produced by procedural macros ended up getting lost in translation in the
compiler and not actually producing parseable code. The issue lies in the fact
that a lifetime's `Ident` is prefixed with `'`. The `glue` implementation for
gluing joint tokens together forgot to take this into account so the lifetime
inside of `Ident` was missing the leading tick!

The `glue` implementation here is updated to create a new `Symbol` in these
situations to manufacture a new `Ident` with a leading tick to ensure it parses
correctly.

Closes rust-lang#50942

The default capacity of a VecDeque is 8, which is excessive here. In a
"base incremental" check build of rustc-perf's tuple-stress benchmark,
this decreases total heap allocation by 26%. I couldn't see a clear
speedup, but it can't hurt.

Add E0665

…woerister

CheckLoopVisitor: also visit closure arguments

This turns the ICE rust-lang#50581 in this code:

```rust
fn main() {
    |_: [u8; break]| ();
}
```

from
```
    'assertion failed: self.tcx.sess.err_count() > 0', librustc_typeck/check/mod.rs
```
to
```
    librustc_mir/hair/cx/expr.rs:543: invalid loop id for break: not inside loop scope
```

which is an ICE as well but at a later stage during compilation and most importantly
fixes of bug rust-lang#50576 will fix this as well.

As this "only" moves an ICE to a later stage, I didn't add any tests.

Now I have manually verified the default impls of the visitor trait to check whether we have missed any other opportunity to visit more stuff and coudln't find anything (except the missing `break` visit I've fixed in rust-lang#50829 but that one was already r+'d so I didn't want to push more commits).

Make `[T]::len` and `str::len` const fn

r? @gankro

…uillaumeGomez

rustdoc: use "short form" doc(cfg) printing even when combined with other conditionals

Fixes rust-lang#49334

The original "short form" printing was introduced when `target_feature` was added to the `doc(cfg)` handling. However, it didn't properly propagate the "short form" indicator if the cfg was a combination of multiple conditionals, so the linked issue happened. This changes the handling to use a bool in the original `Html` wrapper, rather than a separate wrapper struct that defers to the original one.

Fix typo in cell.rs

Issue rust-lang#50636: Improve error diagnostic with missing commas after struct fields.

Fixes rust-lang#50636

…elwoerister

Inline `try_get`.

This speeds up lots of rustc-perf benchmark runs. The maximum
improvement is 1%, but there are a lot in the 0.5--1.0% range.

Optimize seen Predicate filtering.

This speeds up a few rustc-perf benchmark runs, most notably ones
involving 'coercions', the best by 2%.

…nSapin

Stabilize feature from_ref

Function `from_ref_mut` is now renamed to `from_mut`, as discussed in rust-lang#45703.

Closes rust-lang#45703.

r? @SimonSapin

…petrochenkov

rustc: Fix procedural macros generating lifetime tokens

This commit fixes an accidental regression from rust-lang#50473 where lifetime tokens
produced by procedural macros ended up getting lost in translation in the
compiler and not actually producing parseable code. The issue lies in the fact
that a lifetime's `Ident` is prefixed with `'`. The `glue` implementation for
gluing joint tokens together forgot to take this into account so the lifetime
inside of `Ident` was missing the leading tick!

The `glue` implementation here is updated to create a new `Symbol` in these
situations to manufacture a new `Ident` with a leading tick to ensure it parses
correctly.

Closes rust-lang#50942

…umeGomez

rustdoc: set tab width in rust source blocks

cc rust-lang#49155 (fixes it?)

This sets the tab width ([in supported browsers](https://developer.mozilla.org/en-US/docs/Web/CSS/tab-size)) in Rust source blocks to 4 spaces wide (instead of the default 8), to correspond with the style guidelines.

Add the 2018 edition of the book to doc.rust-lang.org

The second edition of the book is on its way to the printers, and as such, is frozen. We've forked off the 2018 edition to add new stuff to; this PR now builds it so that people can read it on doc.rust-lang.org.

Micro-optimization on PR#50697

We should stop iterating through the indices in the `init_path_map` once we've already found a match for the local.

r? @nikomatsakis or @pnkfelix

Fix FileCheck finding with MSVC