Allow variant discriminant initializers to refer to other initializer…

…s of the same enum

r? @EddyB

fixes the 2.4 failure of https://github.com/rust-lang/rust/issues/49765

cc @durka @retep998

Make incremental compilation thread-safe

r? @michaelwoerister

Update rustfmt and rls

r? @alexcrichton

Allow crate:: in local paths

Currently if you want to use `crate` locally you have to do `::crate::`. This shouldn't be necessary

(will fix up tests later)

r? @petrochenkov

Make Binder's field private and clean up its usage

AKA "tour de rustc"

Closes #49814.

Introduce compile-pass

r? @alexcrichton

The plan is to move things that cannot fail (no assert, unwrap, etc) out so we don't have to run them, and in the long term we can also stop running LLVM for them.

Out of 3215 tests...

```
Language            Files        Lines         Code     Comments       Blanks
Rust                 3215       119254        64688        35135        19431
```

16% of them has an empty main (which is already moved in this PR).

```
grep -rnPzl 'fn main\(\)\s*{\s*}' | xargs rg --files-without-match cfg | wc -l
547
```

And only 50% of the tests contains assertions:

```
rg -e assert -e unwrap -e expect -e panic -l | wc -l
1600
```

The remainder is likely able to get moved, but they need check by a human so I didn't touch them in PR.

cc @rust-lang/compiler

* [ ] Update documentation

make rustdoc test follow the jobserver limit of threads

fix that to many threads is executing at the same time
when rustdoc test is executed.

Warn on all erroneous constants

fixes #49791
fixes #47054

@Zoxc this PR triggers the nondeterministic errors of https://github.com/rust-lang/rust/pull/49950#issuecomment-383074959 really often (at least on stage1).

Speed up `nearest_common_ancestor`.

`nearest_common_ancestor` can be made faster.

Here are all the benchmarks where one of the measurements improved by at least 1%.
```
clap-rs-check
	avg: -4.5%	min: -8.8%	max: -0.3%
clap-rs
	avg: -2.6%	min: -4.5%	max: 0.5%
script-servo
	avg: -1.7%	min: -3.6%	max: 0.0%
regression-31157
	avg: -1.5%	min: -2.6%	max: -0.4%
hyper
	avg: -1.2%	min: -2.5%	max: -0.0%
piston-image
	avg: -1.6%	min: -2.5%	max: 0.1%
regex
	avg: -1.2%	min: -2.2%	max: 0.0%
issue-46449
	avg: -1.8%	min: -2.1%	max: -0.7%
crates.io
	avg: -1.2%	min: -2.1%	max: 0.0%
hyper-check
	avg: -1.0%	min: -2.1%	max: -0.1%
clap-rs-opt
	avg: -1.4%	min: -2.0%	max: -0.3%
piston-image-check
	avg: -1.2%	min: -1.9%	max: -0.1%
regex-check
	avg: -0.5%	min: -1.8%	max: -0.1%
syn
	avg: -1.1%	min: -1.7%	max: -0.1%
tokio-webpush-simple-check
	avg: -1.1%	min: -1.6%	max: -0.3%
tokio-webpush-simple
	avg: -1.2%	min: -1.6%	max: -0.0%
helloworld-check
	avg: -1.4%	min: -1.6%	max: -1.2%
deeply-nested
	avg: -1.2%	min: -1.4%	max: -0.8%
encoding-check
	avg: -0.8%	min: -1.3%	max: -0.3%
unify-linearly-check
	avg: -1.0%	min: -1.3%	max: -0.8%
script-servo-check
	avg: -0.6%	min: -1.3%	max: 0.0%
regression-31157-check
	avg: -0.9%	min: -1.2%	max: -0.7%
script-servo-opt
	avg: -0.5%	min: -1.2%	max: 0.1%
deeply-nested-check
	avg: -0.8%	min: -1.2%	max: -0.7%
encoding
	avg: -0.7%	min: -1.1%	max: -0.3%
issue-46449-check
	avg: -0.9%	min: -1.1%	max: -0.6%
parser-check
	avg: -0.9%	min: -1.1%	max: -0.8%
html5ever
	avg: -0.5%	min: -1.0%	max: -0.0%
```

Edition breakage lint for absolute paths starting with modules

We plan to enable `extern_absolute_paths` in the 2018 edition. To allow for that, folks must transition their paths in a previous edition to the new one. This makes paths which import module contents via `use module::` or `::module::` obsolete, and we must edition-lint these.

https://internals.rust-lang.org/t/the-great-module-adventure-continues/6678/205?u=manishearth is the current plan for paths.

r? @nikomatsakis

Fixes #48722

Fixes #20664.

Provide better names for builtin deriving-generated attributes

First attempt at fixing #49967

Not in love with any choices here, don't be shy if you aren't happy with anything :)

I've tested that this produces nicer names in documentation, and that it no longer has issues conflicting with constants with the same name. (I guess we _could_ make a test for that... unsure if that would be valuable)

In all cases I took the names from the methods as declared in the relevant trait.

In some cases I had to prepend the names with _ otherwise there were errors about un-used variables. I'm uneasy with the inconsistency... do they all need to be like that? Is there a way to generate an alternate impl or use a different name (`_`?) in the cases where the arguments are not used?

Lastly the gensym addition to Ident I implemented largely as suggested, but I want to point out it's a little circuitous (at least, as far as I understand it). `cx.ident_of(name)` is just `Ident::from_str`, so we create an Ident then another Ident from it. `Ident::with_empty_ctxt(Symbol::gensym(string))` may or may not be equivalent, I don't know if it's important to intern it _then_ gensym it. It seems like either we could use that, or if we do want a new method to make this convenient, it could be on Ident instead (`from_str_gensymed`?)

Tweak some warnings around #[target_feature]

This commit fixes up some issues discovered when getting the `stdsimd` crate's CI compiling again.

Fix the miri tool

r? @EddyB

cc @bjorn3

fixes #49777

Android abstract unix domain sockets AddressKind correction

The prior check causes abstract unix domain sockets to return AddressKind::Unnamed instead of AddressKind::Abstract on Android.

Other than the immediately proceeding comment "macOS seems to return a len of 16 and a zeroed sun_path for unnamed addresses" the check as-implemented does not seem to have alternative explanation. I couldn't find an alternative explanation while stepping though git blame. I suspect the AddressKind::Unnamed nonzero check should instead be if macos, length 16, and zeroed array. @sfackler could you comment on this, the code as-is is the same from your initial addition of abstract uds support.

Don't allow #[should_panic] with non-() tests

Adds (removes) support for `#[should_panic]` when the test is non-`()`

work towards chalkify-ing the engine

This work towards creating a "all program clauses needed for this goal" query

r? @scalexm

Rollup of 11 pull requests

Successful merges:

 - #49461 (std: Child::kill() returns error if process has already exited)
 - #49727 (Add Cell::update)
 - #49812 (Fix revision support for UI tests.)
 - #49829 (Add doc links to `std::os` extension traits)
 - #49906 (Stabilize `std::hint::unreachable_unchecked`.)
 - #49970 (Deprecate Read::chars and char::decode_utf8)
 - #49985 (don't see issue #0)
 - #50118 (fix search bar bug)
 - #50139 (encourage descriptive issue titles)
 - #50174 (Use FxHashMap in syntax_pos::symbol::Interner::intern.)
 - #50185 (core: Fix overflow in `int::mod_euc` when `self < 0 && rhs == MIN`)

Failed merges:

core: Fix overflow in `int::mod_euc` when `self < 0 && rhs == MIN`

This commit removes usage of `abs`, which overflows when `self == MIN`.

Use FxHashMap in syntax_pos::symbol::Interner::intern.

Because it's faster than HashMap.

This change reduces the time taken for a few of the rustc-perf
benchmarks, mostly the small ones, by up to 5%.
```
coercions
        avg: -1.3%      min: -5.5%      max: -0.0%
helloworld-check
        avg: -2.3%      min: -3.5%      max: -1.8%
deeply-nested-check
        avg: -1.4%      min: -3.2%      max: -0.5%
tuple-stress-opt
        avg: -0.7%      min: -2.0%      max: -0.1%
unify-linearly-check
        avg: -1.2%      min: -1.9%      max: -0.6%
coercions-check
        avg: -0.8%      min: -1.3%      max: -0.4%
unused-warnings-check
        avg: -1.0%      min: -1.3%      max: -0.8%
deeply-nested-opt
        avg: -0.5%      min: -1.2%      max: -0.2%
deeply-nested
        avg: -0.7%      min: -1.2%      max: -0.4%
helloworld
        avg: -0.8%      min: -1.1%      max: -0.7%
tuple-stress-check
        avg: -0.5%      min: -1.0%      max: -0.1%
unused-warnings
        avg: -0.8%      min: -1.0%      max: -0.7%
unused-warnings-opt
        avg: -0.8%      min: -1.0%      max: -0.7%
coercions-opt
        avg: -0.5%      min: -1.0%      max: -0.1%
helloworld-opt
        avg: -0.7%      min: -1.0%      max: -0.6%
```

encourage descriptive issue titles

There are two sides to avoiding duplicate issues, searching for existing ones, and making sure existing ones can be searched for. This addresses the later.

r? @steveklabnik

fix search bar bug

Fixes #50064.

r? @QuietMisdreavus

don't see issue #0

The unstable-feature attribute requires an issue (neglecting it is
E0547), which gets used in the error messages. Unfortunately, there are
some cases where "0" is apparently used a placeholder where no issue
exists, directing the user to see the (nonexistent) issue #0. (It would
have been better to either let `issue` be optional—compare to how issue
is an `Option<u32>` in the feature-gate declarations in
libsyntax/feature-gate.rs—or actually require that an issue be created.)
Rather than endeavoring to change how `#[unstable]` works at this time
(given competing contributor and reviewer priorities), this simple patch
proposes the less-ambitious solution of just not adding the "(see
issue)" note when the number is zero.

Resolves #49983.

Deprecate Read::chars and char::decode_utf8

Per FCP:

* https://github.com/rust-lang/rust/issues/27802#issuecomment-377537778
* https://github.com/rust-lang/rust/issues/33906#issuecomment-377534308

Stabilize `std::hint::unreachable_unchecked`.

Closes #43751.

Add doc links to `std::os` extension traits

Addresses a small subset of #29367.

This adds documentation links to the original type for various OS-specific extension traits, and uses a common sentence for introducing such traits (which now consistently ends in a period).

Fix revision support for UI tests.

Fixes #48878