If it ran too soon there wasn't a `test` directory lying around but we'll need
one!

Stabilize `..` in tuple (struct) patterns

I'd like to nominate `..` in tuple and tuple struct patterns for stabilization.
This feature is a relatively small extension to existing stable functionality and doesn't have known blockers.
The feature first appeared in Rust 1.10 6 months ago.
An example of use: https://github.com/rust-lang/rust/pull/36203

Closes https://github.com/rust-lang/rust/issues/33627
r? @nikomatsakis

fix silent overflows on `Step` impls

Part of https://github.com/rust-lang/rust/issues/36110

r? @EddyB

rustbuild: support MIPS host builds

There is a *little* code duplication, but primarily for sake of "match exhaustiveness". Let's blame Linux/MIPS for not exposing endianness explicitly in `uname -m` (that's user-space interface and as such is frozen).

Currently the build won't work as we have to wait for a new stage0 for the MIPS host compilers, but this paves the way to self-hosted Rust on MIPS. The cross-compiled MIPS binaries are confirmed to work on the Loongson 3A2000 (MIPS64r2-compatible) so we have plenty of confidence that they'll work on other MIPS platforms too, as Linux/MIPS user-space ABI is consistent across machines of the same bitness.

r? @alexcrichton

Remove mention of mipsel target_arch

This is the only remaining instance in rustc. All others were in the libc repo, removed with rust-lang/libc#445.

Actually there's more to clean in `libsyntax/abi.rs`, but let's save that for another commit...

Fix Arc::clone()'s MAX_REFCOUNT check (off-by-one)

Before, the strong count of an `Arc` could be set to
`MAX_REFCOUNT + 1`, because when this happened, `old_size` would
be exactly `MAX_REFCOUNT`. `Arc::clone()` would not abort.

This commit changes the check in `Arc::clone()` to also abort if
the old value is equal to `MAX_REFCOUNT`, because then the new
value will be equal to `MAX_REFCOUNT + 1`.

A test would require allocating memory for `isize::MAX` pointers.
This would probably crash any machine, so no test is submitted
with this commit.

There is a *little* code duplication, but primarily for sake of "match
exhaustiveness". Let's blame Linux/MIPS for not exposing endianness
explicitly in `uname -m` (that's user-space interface and as such is
frozen).

Currently the build won't work as we have to wait for a new stage0 for
the MIPS host compilers, but this paves the way to self-hosted Rust on
MIPS. The cross-compiled MIPS binaries are confirmed to work on the
Loongson 3A2000 (MIPS64r2-compatible) so we have plenty of confidence
that they'll work on other MIPS platforms too, as Linux/MIPS user-space
ABI is consistent across machines of the same bitness.

The `mipsel` `target_arch` was introduced with the initial MIPSel
support (rust-lang/rust@82ec1aef293ddc5c6373bd7f5ec323fafbdf7901),
but was subsequently removed with implementation of the Flexible Target
Specification (Rust RFC 0131,
rust-lang/rust@3a8f4ec32a80d372db2d02c76acba0276c4effd0).
This is the only remaining instance in rustc. All others are in the libc
repo, and are fixed in rust-lang/libc@b3676593f6930c32d947c59e210789bbfcb30960.

macros: improve shadowing checks

This PR improves macro-expanded shadowing checks to work with out-of-(pre)order expansion.

Out-of-order expansion became possible in #37084, so this technically a [breaking-change] for nightly.
The regression test from this PR is an example of code that would break.

r? @nrc

use arm abi blacklist for aarch64 fuchsia

r? @alexcrichton

Force static linking of LLVM

Run `llvm-config` with `--link-static` if available, to force static linking of LLVM.
This option was added in LLVM 3.8.

This is my first pull request, any feedback is welcome!

Fixes #36854
See also: #36996

The constant name `MAX_REFCOUNT` suggests that the value is a
_hard_ limit on the amount of references to an `Arc`. This is
a more soft limit however. This commit adds a comment to the
constant to annotate this.

See also: PR #37605

Add test for issue 18060.

Closes #18060

Run llvm-config with "--link-static" if available, to force static linking of LLVM.
This option was added in LLVM 3.8.

Fixes #36854
See also: #36996

[4/n] rustc: harden against InferOk having obligations in more cases.

_This is part of a series ([prev](https://github.com/rust-lang/rust/pull/37402) | [next](https://github.com/rust-lang/rust/pull/37408)) of patches designed to rework rustc into an out-of-order on-demand pipeline model for both better feature support (e.g. [MIR-based](https://github.com/solson/miri) early constant evaluation) and incremental execution of compiler passes (e.g. type-checking), with beneficial consequences to IDE support as well.
If any motivation is unclear, please ask for additional PR description clarifications or code comments._

<hr>

This adds more asserts that `InferOk` results have no obligations, pending completion of #32730.

Each of these could accidentally drop obligations on the floor if they start getting produced by unification, and a future change does just that, in order to produce a "shallow success" (hopefully leading to ambiguities during trait selection), _without_ the possibility of an eventual success - mostly guarded by ICEs for now.

Add example using Self to reference

When I first came across `Self` I had a hard time finding references to it in the docs (and it's also been asked about on [StackOverflow](http://stackoverflow.com/questions/32304595/whats-the-difference-between-self-and-self).

I hope this example provides someone who comes across it for the first time a little more help.  If there is a better way to show an example actually using `Self`, I'm happy to modify this.  It was just the simplest place to start I could see.

Rollup of 24 pull requests

- Successful merges: #37255, #37317, #37408, #37410, #37422, #37427, #37470, #37501, #37537, #37556, #37557, #37564, #37565, #37566, #37569, #37574, #37577, #37579, #37583, #37585, #37586, #37587, #37589, #37596
- Failed merges: #37521, #37547

Add error when proc_macro_derive is used not on functions

Fixes #37590

std: Track change to cprng syscall signature (Fuchsia)

The mx_cprng_draw syscall has changed signature to separate the status
and size return values, rather than multiplexing them into a single
value with errors interpreted as a negative value. This patch tracks
that change.

Remove recursive call from Cow::to_mut

It seems to prevent it from being inlined.

fix #37559: update compiler-rt

Fixes #37559

r? @alexcrichton

Change `Into<Vec<u8>> for String` and `Into<OsString> for PathBuf` to From

Fixes #37561. First contribution, happy with any and all feedback!

Add `-Z hir-stats` for collecting statistics on HIR and AST

The data collected will be printed to the commandline and looks like the following:

```
// stats for libcore

PRE EXPANSION AST STATS

Name                Accumulated Size         Count     Item Size
----------------------------------------------------------------
TypeBinding                    2_280            57            40
Mod                            3_560            89            40
PathListItem                   6_516           181            36
Variant                        7_872            82            96
LifetimeDef                   21_280           380            56
StructField                   22_880           260            88
Lifetime                      23_800         1_190            20
Local                         30_192           629            48
ForeignItem                   31_504           179           176
Arm                           42_880           670            64
Mac                           46_960           587            80
FnDecl                        57_792         1_204            48
TraitItem                     69_504           362           192
TyParamBound                  98_280           945           104
Block                        108_384         2_258            48
Stmt                         144_720         3_618            40
ImplItem                     230_272         1_028           224
Item                         467_456         1_826           256
Pat                          517_776         4_623           112
Attribute                    745_680        15_535            48
Ty                         1_114_848         9_954           112
PathSegment                1_218_528        16_924            72
Expr                       3_082_408        20_279           152
----------------------------------------------------------------
Total                      8_095_372

POST EXPANSION AST STATS

Name                Accumulated Size         Count     Item Size
----------------------------------------------------------------
MacroDef                       1_056            12            88
Mod                            3_400            85            40
TypeBinding                    4_280           107            40
PathListItem                   6_516           181            36
Variant                        7_872            82            96
StructField                   24_904           283            88
ForeignItem                   31_504           179           176
TraitItem                     69_504           362           192
Local                         85_008         1_771            48
Arm                          100_288         1_567            64
Lifetime                     123_980         6_199            20
LifetimeDef                  126_728         2_263            56
TyParamBound                 297_128         2_857           104
FnDecl                       305_856         6_372            48
Block                        481_104        10_023            48
Stmt                         535_120        13_378            40
Item                       1_469_952         5_742           256
Attribute                  1_629_840        33_955            48
ImplItem                   1_732_864         7_736           224
Pat                        2_360_176        21_073           112
PathSegment                5_888_448        81_784            72
Ty                         6_237_168        55_689           112
Expr                      12_013_320        79_035           152
----------------------------------------------------------------
Total                     33_536_016

HIR STATS

Name                Accumulated Size         Count     Item Size
----------------------------------------------------------------
MacroDef                         864            12            72
Mod                            2_720            85            32
TypeBinding                    3_424           107            32
PathListItem                   5_068           181            28
Variant                        6_560            82            80
StructField                   20_376           283            72
ForeignItem                   27_208           179           152
WherePredicate                43_776           684            64
TraitItem                     52_128           362           144
Decl                          68_992         2_156            32
Local                         89_184         1_858            48
Arm                           94_368         1_966            48
LifetimeDef                  108_624         2_263            48
Lifetime                     123_980         6_199            20
Stmt                         168_000         4_200            40
TyParamBound                 251_416         2_857            88
FnDecl                       254_880         6_372            40
Block                        583_968        12_166            48
Item                       1_240_272         5_742           216
ImplItem                   1_361_536         7_736           176
Attribute                  1_620_480        33_760            48
Pat                        2_073_120        21_595            96
Path                       2_385_856        74_558            32
Ty                         4_455_040        55_688            80
PathSegment                5_587_904        87_311            64
Expr                       7_588_992        79_052            96
----------------------------------------------------------------
Total                     28_218_736
```

reference full path DefaultHasher

Since `DefaultHasher` does not in scope, it's not obvious where to find it.

Shrink `hir::Expr` slightly

r? @EddyB

Fix issues with the Add/AddAssign impls for Cow<str>

* Correct the stability attributes.
* Make Add and AddAssign actually behave the same.
* Use String::with_capacity when allocating a new string.
* Fix the tests.

macros: improve expansion performance

This PR fixes that regression, further improves performance on recursive, `tt`-heavy workloads, and makes a variety of other improvements to parsing and expansion performance.

Expansion performance improvements:

| Test case      | Run-time | Memory usage |
| -------------- | -------- | ------------ |
| libsyntax      | 8%       | 10%          |
| librustc       | 15%      | 6%           |
| librustc_trans | 30%      | 6%           |
| #37074         | 20%      | 15%          |
| #34630         | 40%      | 8%           |

r? @EddyB

Set RUSTC_BOOTSTRAP to some value.

Environment variables on windows can't be empty.

Peekable::peek(): Use Option::as_ref()

Replace the match expression in .peek() with Option::as_ref() since it's the same functionality.

Fix ICE when querying DefId on Def::Err.

Also moves computations into check that `kind_id` is `Ok(_)`, which is in theory an optimization, though I expect it's minor.

Fixes #37534.

r? @EddyB.

Use DefId's in const eval for cross-crate const fn's

Fixes #36954.

r? @EddyB

cc @raphaelcohn