This initial commit provides implementations for HIR, MIR, and
everything that also needs to be supported for those two.

Update cargo submodule

Pulls in a fix for rust-lang/rust#40956

Rollup of 5 pull requests

- Successful merges: #40908, #41011, #41026, #41037, #41050
- Failed merges:

macros: fix bug parsing `#[derive]` invocations

Fixes #40962 (introduced in #40346).
r? @nrc

Move libXtest into libX/tests

This change moves:

1. `libcoretest` into `libcore/tests`
2. `libcollectionstest` into `libcollections/tests`

This is a follow-up to #39561.

r? @alexcrichton

Handle symlinks in src/bootstrap/clean.rs (mostly) -- resolves #40860.

In response to #40860

The broken condition can be replicated with:

```shell
export MYARCH=x86_64-apple-darwin && mkdir -p build/$MYARCH/subdir &&
touch build/$MYARCH/subdir/file && ln -s build/$MYARCH/subdir/file
build/$MYARCH/subdir/symlink
```

`src/bootstrap/clean.rs` has a custom implementation of removing a tree
`fn rm_rf` that used `std::path::Path::{is_file, is_dir, exists}` while
recursively deleting directories and files.  Unfortunately, `Path`'s
implementation of `is_file()` and `is_dir()` and `exists()` always
unconditionally follow symlinks, which is the exact opposite of standard
implementations of deleting file trees.

It appears that this custom implementation is being used to workaround a
behavior in Windows where the files often get marked as read-only, which
prevents us from simply using something nice and simple like
`std::fs::remove_dir_all`, which properly deletes links instead of
following them.

So it looks like the fix is to use `.symlink_metadata()` to figure out
whether tree items are files/symlinks/directories.  The one corner case
this won't cover is if there is a broken symlink in the "root"
`build/$MYARCH` directory, because those initial entries are run through
`Path::canonicalize()`, which panics with broken symlinks.  So lets just
never use symlinks in that one directory. :-)

Overhaul Bootstrap (x.py) Command-Line-Parsing & Help Output

While working on #40417, I got frustrated with the behavior of x.py and the bootstrap binary it wraps, so I decided to do something about it.  This PR should improve documentation, make the command-line-parsing more flexible, and clean up some of the internals.  No command that worked before should stop working.  At least that's the theory. :-)

This should resolve at least #40920 and #38373.

Changes:

- No more manual args manipulation -- getopts used everywhere except the one place it's not possible.  As a result, options can be in any position, now, even before the subcommand.
- The additional options for test, bench, and dist now appear in the help output.
- No more single-letter variable bindings used internally for large scopes.
- Don't output the time measurement when just invoking `x.py` or explicitly passing `-h` or `--help`
- Logic is now much more linear.  We build strings up, and then print them.
- Refer to subcommands as subcommands everywhere (some places we were saying "command")
- Other minor stuff.

@alexcrichton This is my first PR. Do I need to do something specific to request reviewers or anything?

Emit proper lifetime start intrinsics for personality slots

We currently only emit a single call to the lifetime start intrinsic
for the personality slot alloca. This happens because we create that
call at the time that we create the alloca, instead of creating it each
time we start using it. Because LLVM usually removes the alloca before
the lifetime intrinsics are even considered, this didn't cause any
problems yet, but we should fix this anyway.

[Windows] Enable building rustc with "pthreads" flavor of mingw.

Tested on mingw-w64 packaged with msys2.

r? @alexcrichton

cc #40123

Rollup of 12 pull requests

- Successful merges: #40479, #40561, #40709, #40815, #40909, #40927, #40943, #41015, #41028, #41052, #41054, #41065
- Failed merges:

[T]::rsplit() and rsplit_mut(), #41020

Replace magic number with readable sig constant

SIG_ERR is defined as 'pub const SIG_ERR: sighandler_t = !0 as sighandler_t;'

Make 'overlapping_inherent_impls' lint a hard error

This is ought to be implemented in PR #40728. Unfortunately, when I rebased the PR to resolve merge conflict, the "hard error" code disappeared. This PR complements the initial PR.

Now the following rust code gives the following error:
```rust
struct Foo;

impl Foo {
    fn id() {}
}

impl Foo {
    fn id() {}
}

fn main() {}
```
```
error[E0592]: duplicate definitions with name `id`
 --> /home/topecongiro/test.rs:4:5
  |
4 |     fn id() {}
  |     ^^^^^^^^^^ duplicate definitions for `id`
...
8 |     fn id() {}
  |     ---------- other definition for `id`

error: aborting due to previous error
```

Let .rev()'s find use the underlying rfind and vice versa

- Connect the plumbing in an obvious way from Rev's find → underlying rfind and vice versa
- A style change in the provided implementation for Iterator::rfind, using simple next_back when it is enough

mark build::cfg::start_new_block as inline(never)

LLVM has a bug - [PR32488](https://bugs.llvm.org//show_bug.cgi?id=32488) - where it fails to deduplicate allocas in some
circumstances. The function `start_new_block` has allocas totalling 1216
bytes, and when LLVM inlines several copies of that function into
the recursive function `expr::into`, that function's stack space usage
goes into tens of kiBs, causing stack overflows.

Mark `start_new_block` as inline(never) to keep it from being inlined,
getting stack usage under control.

Fixes #40493.
Fixes #40573.

r? @EddyB

Add ptr::offset_to

This PR adds a method to calculate the signed distance (in number of elements) between two pointers. The resulting value can then be passed to `offset` to get one pointer from the other. This is similar to pointer subtraction in C/C++.

There are 2 special cases:

- If the distance is not a multiple of the element size then the result is rounded towards zero. (in C/C++ this is UB)
-  ZST return `None`, while normal types return `Some(isize)`. This forces the user to handle the ZST case in unsafe code. (C/C++ doesn't have ZSTs)

Add a note about overflow for fetch_add/fetch_sub

Fixes #40916
Fixes #34618

r? @steveklabnik

Allow using Vec::<T>::place_back for T: !Clone

The place_back was likely put into block with `T: Clone` bound by mistake.

Identify missing item category in `impl`s

```rust
struct S;
impl S {
    pub hello_method(&self) {
        println!("Hello");
    }
}
fn main() { S.hello_method(); }
```

```rust
error: missing `fn` for method declaration
 --> file.rs:3:4
  |
3 |     pub hello_method(&self) {
  |        ^ missing `fn`
```

Fix #40006. r? @pnkfelix CC @jonathandturner @GuillaumeGomez

Reduce a table used for `Debug` impl of `str`.

This commit shrinks the size of the aforementioned table from 2,102 bytes to 1,197 bytes. This is achieved by an observation that most `u16` entries are common in its upper byte. Specifically:

- `SINGLETONS` now uses two tables, one for (upper byte, lower count) and another for a series of lower bytes. For each upper byte given number of lower bytes are read and compared.

- `NORMAL` now uses a variable length format for the count of "true" codepoints and "false" codepoints (one byte with MSB unset, or two big-endian bytes with the first MSB set).

The code size and relative performance roughly remains same as this commit tries to optimize for both. The new table and algorithm has been verified for the equivalence to older ones.

In my x86-64 macOS laptop with `rustc 1.17.0-nightly (0aeb9c12 2017-03-15)`, `-C opt-level=3 -C lto` gives the following:

* The old routine compiles to 2,102 bytes of data and 416 bytes of code.
* The new routine compiles to 1,197 bytes of data and 448 bytes of code.

Counting a number of all printable Unicode scalar values (128,003, if you wonder) by filtering `0..0x110000` with `std::char::from_u32` and `is_printable` took 50±7ms for both. This can be surprising as the new routine *has* to do more calculations; this is partly explained by the fact that a linear search of `SINGLETONS` has been replaced by *two* linear searches for upper and lower bytes, which greatly reduces the iteration count.

Simplify HashMap Bucket interface

> Simplify HashMap Bucket interface
>
> * Store capacity_mask instead of capacity
> * Move bucket index into RawBucket
> * Valid bucket index is now always within [0..table_capacity)
> * Simplify iterators by moving logic into RawBuckets
> * Clone RawTable using RawBucket
> * Make retain aware of the number of elements

The idea was to put idx in RawBucket instead of the other Bucket types and simplify next() and prev() as much as possible. The rest was a side-effect of that change, except maybe the last 2.

This change makes iteration and other next/prev() heavy operations noticeably faster. Clone is way faster.

```
➜  hashmap2 git:(adapt) ✗ cargo benchcmp pre:: adp:: bench.txt
 name                        pre:: ns/iter  adp:: ns/iter  diff ns/iter   diff %
 clone_10_000                74,364         39,736              -34,628  -46.57%
 grow_100_000                8,343,553      8,233,785          -109,768   -1.32%
 grow_10_000                 817,825        723,958             -93,867  -11.48%
 grow_big_value_100_000      18,418,979     17,906,186         -512,793   -2.78%
 grow_big_value_10_000       1,219,242      1,103,334          -115,908   -9.51%
 insert_1000                 74,546         58,343              -16,203  -21.74%
 insert_100_000              6,743,770      6,238,017          -505,753   -7.50%
 insert_10_000               798,079        719,123             -78,956   -9.89%
 insert_1_000_000            275,215,605    266,975,875      -8,239,730   -2.99%
 insert_int_bigvalue_10_000  1,517,387      1,419,838           -97,549   -6.43%
 insert_str_10_000           316,179        278,896             -37,283  -11.79%
 insert_string_10_000        770,927        747,449             -23,478   -3.05%
 iter_keys_100_000           386,099        333,104             -52,995  -13.73%
 iterate_100_000             387,320        355,707             -31,613   -8.16%
 lookup_100_000              206,757        193,063             -13,694   -6.62%
 lookup_100_000_unif         219,366        193,180             -26,186  -11.94%
 lookup_1_000_000            206,456        205,716                -740   -0.36%
 lookup_1_000_000_unif       659,934        629,659             -30,275   -4.59%
 lru_sim                     20,194,334     18,442,149       -1,752,185   -8.68%
 merge_shuffle               1,168,044      1,063,055          -104,989   -8.99%
```

Note 2: I may have messed up porting the diff, let's see what CI says.

Fixes other targets rustlibs installation

When the user select more than one target to generate rustlibs for, rustbuild will only install the host one.

This patch fixes it, more info in https://github.com/rust-lang/rust/issues/39235#issuecomment-285878858

Handle extern functions and statics in save-analysis

r? @EddyB

Rollup of 19 pull requests

- Successful merges: #40608, #40870, #40949, #40977, #40981, #40988, #40992, #40997, #40999, #41007, #41014, #41019, #41035, #41043, #41049, #41062, #41066, #41076, #41085
- Failed merges:

Properly adjust filenames when multiple emissions

Fixes #40993

Should backport just fine to beta but not sure if we want to do this since this is quite old stable regression.

travis: Update sccache binaries

I've tracked down what I believe is the last spurious sccache failure on #40240
to behavior in mio (carllerche/mio#583), and this commit updates the binaries to
a version which has that fix incorporated.

Fix links

part of https://github.com/rust-lang/rust/issues/40912

[]\n() is not actually a link.

r? @frewsxcv @GuillaumeGomez

Do not recommend private fields called as method

```rust
error: no method named `dog_age` found for type `animal::Dog` in the current scope
  --> $DIR/private-field.rs:26:23
   |
26 |     let dog_age = dog.dog_age();
   |                       ^^^^^^^ private field, not a method
```
Fix #27654.

Handle ordered lists as well

Part of #40912.

r? @rust-lang/docs

Replace ^ with <sup> html balise

r? @steveklabnik

Revert "Implement AsRawFd/IntoRawFd for RawFd"

This reverts commit 2cf686f2 (#40842)

RawFd is a type alias for c_int, which is itself a type alias for i32.
As a result, adding AsRawFd and IntoRawFd impls for RawFd actually adds
them for i32.

As a result, the reverted commit makes this valid:

```
use std::os::unix::io::AsRawFd;

fn arf<T: AsRawFd>(_: T) {}

fn main() {
    arf(32i32)
}
```

Implimenting AsRawFd and IntoRawFd for i32 breaks the promises of both
those traits that their methods return a valid RawFd.

r? @aturon
cc @Mic92 @kamalmarhubi

Fixed typo in doc comments for swap_remove

While reading the Vec docs, I came across the docs for swap_remove. I believe there is a typo in the comment and ```return``` should be ```returns```. This PR fixes this issue.

I also feel that the entire doc comment is a bit of a run-on and could be changed to something along the lines of ```Removes an element from anywhere in the vector and returns it. The vector is mutated and the removed element is replaced by the last element of the vector. ```

Thoughts?

std::thread docs: fix link to current()

Improve documentation for `std::fs::DirBuilder`

Improve option API docs

Associated Issue: #29366

Improve `option` API docs for
* `IntoIter` struct
* `Iter` struct
* `IterMut` struct

r? @steveklabnik

Added links to types in from_utf8 description

References #29375. Link to types mentioned in the documentation for `from_utf8` (`str`, `&[u8`], etc). Paragraphs were reformatted to keep any one line from being excessively long, but are otherwise unchanged.

Added links to from_utf8 methods in Utf8Error

Referencing  #29375. Linked the `from_utf8` methods for both `String` and `str` in the description. Also linked the `u8` to its documentation

API Docs: ascii

Add/update docs for the `ascii` module per #29341.

r? @steveklabnik

Add links and some examples to std::sync::mpsc docs

Addresses part of #29377
r? @steveklabnik

I took a stab at adding links to the `std::sync::mpsc` docs, and I also wrote a few examples.

Edit: Whoops, typed in `?r` instead of `r?`.

Updating the description for BarrierWaitResult #29377

Referencing `Barrier`, removing reference to `is_leader`.