Fixes rendering of the end of the `Configure and Make` section.

Keeps MIR cleaner, `StorageLive(_: !)` makes no sense anyway.

gdb will now reliably detect the lanugage as rust even before any
code is run.

I can't find anything that'd cause unexpected EOF in the source, so let's try
taking a look at the error logs on failures.

This causes problems when first cloning and bootstrapping the repository
unfortunately, so let's ensure that Cargo sticks around in its own workspace.
Because Cargo is a submodule it's not available by default on the inital clone
of the rust-lang/rust repository. Normally it's the responsibility of the
rustbuild to take care of this, but unfortunately to build rustbuild itself we
need to resolve the workspace conflicts.

To deal with this we'll just have to ensure that all submodules are in their own
workspace, which sort of makes sense anyway as updates to dependencies as
bugfixes to Cargo should go to rust-lang/cargo instead of rust-lang/rust. In any
case this commit removes Cargo from the global workspace which should resolve
the issues that we've been seeing.

To actually perform this the `cargo` submodule has been moved to the top
directory to ensure it's outside the scope of `src/Cargo.toml` as a workspace.

When declaring nested unsafe blocks (`unsafe {unsafe {}}`) that trigger
the "unnecessary `unsafe` block" error, point out the enclosing `unsafe
block` or `unsafe fn` that makes it unnecessary.

Some annotations like the "test" annotations might be of interest for
other projects, especially rls. Export all attributes in a new
attributes item.

Remove the AST structure

This commit fixes rust-lang#38749 by building documentation for the `proc_macro` crate by
default for configured hosts. Unfortunately did not turn out to be a trivial
fix. Currently rustbuild generates documentation into multiple locations: one
for std, one for test, and one for rustc. The initial fix for this issue simply
actually executed `cargo doc -p proc_macro` which was otherwise completely
elided before.

Unfortunately rustbuild was the left to merge two documentation trees together.
One for the standard library and one for the rustc tree (which only had docs for
the `proc_macro` crate). Rustdoc itself knows how to merge documentation files
(specifically around search indexes, etc) but rustbuild was unaware of this, so
an initial fix ended up destroying the sidebar and the search bar from the
libstd docs.

To solve this issue the method of documentation has been tweaked slightly in
rustbuild. The build system will not use symlinks (or directory junctions on
Windows) to generate all documentation into the same location initially. This'll
rely on rustdoc's logic to weave together all the output and ensure that it ends
up all consistent.

Closes rust-lang#38749

In recent months there have been a few different people investigating how to make a plugin that
registers a MIR-pass – one that isn’t intended to be eventually merged into rustc proper.

The interface to register MIR passes was added primarily for miri (& later was
found to make prototyping of rustc-proper MIR passes a tiny bit faster). Since miri does not use
this interface anymore it seems like a good time to remove this "feature".

For prototyping purposes a similar interface can be added by developers themselves in their custom
rustc build.

This is a last-ditch attempt to help our pain with dealing with rust-lang#38878 on the
bots. A new environment variable is added to the compiler,
`RUSTC_RETRY_LINKER_ON_SEGFAULT`, which will instruct the compiler to
automatically retry the final linker invocation if it looks like the linker
segfaulted (up to 2 extra times).

Unfortunately there have been no successful attempts to debug rust-lang#38878. The only
information seems to be that the linker (e.g. `ld` on OSX) is segfaulting
somewhere in some thread pool implementation. This appears to be spurious as
failed PRs will later merge.

The hope is that this helps the queue keep moving without clogging and delaying
PRs due to rust-lang#38878.

cc rust-lang#40373

…turner

Point to enclosing block/fn on nested unsafe

When declaring nested unsafe blocks (`unsafe {unsafe {}}`) that trigger
the "unnecessary `unsafe` block" error, point out the enclosing `unsafe
block` or `unsafe fn` that makes it unnecessary.

<img width="621" alt="" src="https://cloud.githubusercontent.com/assets/1606434/22139922/26ad468a-de9e-11e6-8884-2945be882ea8.png">

Fixes rust-lang#39144.

Export attributes in save-analysis data

Since this is my first pull-request to rust, I would like to get some feedback about obvious errors in this implementation.

I would like to change the save-analysis data to include arbitrary attribute data.
A use-case I have in mind for this is identifying functions with `#[test]` annotations such that tools like rls can offer a test-runner feature. I described my idea here [rls#173](rust-lang/rls#173).

My changes contain:

1. track a vector of attributes in the various `*Data` types in `data.rs` and `external_data.rs`
2. implement lowering for `Attribute` and `MetaItem`
3. adjust `JsonDumper` to print the attributes

In the lowering of `Attribute` I remove the distinction between `MetaItem` and `NestedMetaItem`. I did this because this distinction is somewhat confusing. For example, `NestedMetaItemKind::Literal` has two identical spans, because both `NestedMetaItem` and `Lit` are defined as `Spanned<_>`.
My model is strictly more general, as it allows an `LitKind` instead of a `Symbol` for `MetaItem` and `Symbol`s are converted into a cooked string. As a consumer of the save-analysis data this shouldn't affect you much.

Example json output of `#[test]` annotation:
```
"attributes": [
  {
    "value": {
      "name": {
        "variant": "Str",
        "fields": [
          "test",
          "Cooked"
        ]
      },
      "kind": "Literal",
      "span": {
        "file_name": "test.rs",
        "byte_start": 2,
        "byte_end": 6,
        "line_start": 1,
        "line_end": 1,
        "column_start": 3,
        "column_end": 7
      }
    },
    "span": {
      "file_name": "test.rs",
      "byte_start": 0,
      "byte_end": 7,
      "line_start": 1,
      "line_end": 1,
      "column_start": 1,
      "column_end": 8
    }
  }
]
```

…elix

Fix suggestion span error with a line containing multibyte characters

This PR fixes broken suggestions caused by multibyte characters.

e.g. for this code, rustc provides a broken suggestion ([playground](https://is.gd/DWGLu7)):

```rust
fn main() {
    let tup = (1,);
    println!("☃{}", tup[0]);
}
```

```
error: cannot index a value of type `({integer},)`
 --> <anon>:3:21
  |
3 |     println!("☃{}", tup[0]);
  |                     ^^^^^^
  |
help: to access tuple elements, use tuple indexing syntax as shown
  |     println!("☃{}"tup.00]);

error: aborting due to previous error
```

`CodeSuggestion::splice_lines` is misusing `Loc.col` (`CharPos`) as a byte offset when slicing source.

Better docs of rusty parts of typeck

rustbuild: Build documentation for `proc_macro`

This commit fixes rust-lang#38749 by building documentation for the `proc_macro` crate by
default for configured hosts. Unfortunately did not turn out to be a trivial
fix. Currently rustbuild generates documentation into multiple locations: one
for std, one for test, and one for rustc. The initial fix for this issue simply
actually executed `cargo doc -p proc_macro` which was otherwise completely
elided before.

Unfortunately rustbuild was the left to merge two documentation trees together.
One for the standard library and one for the rustc tree (which only had docs for
the `proc_macro` crate). Rustdoc itself knows how to merge documentation files
(specifically around search indexes, etc) but rustbuild was unaware of this, so
an initial fix ended up destroying the sidebar and the search bar from the
libstd docs.

To solve this issue the method of documentation has been tweaked slightly in
rustbuild. The build system will not use symlinks (or directory junctions on
Windows) to generate all documentation into the same location initially. This'll
rely on rustdoc's logic to weave together all the output and ensure that it ends
up all consistent.

Closes rust-lang#38749

… r=alexcrichton

Restore creating the channel-rust-$channel-date.txt files

I have **not** run this (because I don't know how to 😇), but it *does* compile.

r? @alexcrichton

…akis

Remove ability for plugins to register a MIR pass

In recent months there have been a few different people investigating how to make a plugin that
registers a MIR-pass – one that isn’t intended to be eventually merged into rustc proper.

The interface to register MIR passes was added primarily for miri (& later was
found to make prototyping of rustc-proper MIR passes a tiny bit faster). Since miri does not use
this interface anymore it seems like a good time to remove this "feature".

For prototyping purposes a similar interface can be added by developers themselves in their custom
rustc build.

cc @nikomatsakis

…richton

Fix emscripten test detection

Without this change `rustbuild` will attempt to run `.js.map` files (if they exist) resulting in lots of sadness.

r? @alexcrichton

Clean up rustdoc css

r? @rust-lang/docs

Fix incorrect span label formatting

Fix rust-lang#40157.

Don't put Cargo into the rustc workspace

This causes problems when first cloning and bootstrapping the repository
unfortunately, so let's ensure that Cargo sticks around in its own workspace.
Because Cargo is a submodule it's not available by default on the inital clone
of the rust-lang/rust repository. Normally it's the responsibility of the
rustbuild to take care of this, but unfortunately to build rustbuild itself we
need to resolve the workspace conflicts.

To deal with this we'll just have to ensure that all submodules are in their own
workspace, which sort of makes sense anyway as updates to dependencies as
bugfixes to Cargo should go to rust-lang/cargo instead of rust-lang/rust. In any
case this commit removes Cargo from the global workspace which should resolve
the issues that we've been seeing.

To actually perform this the `cargo` submodule has been moved to a new `vendor`
directory to ensure it's outside the scope of `src/Cargo.toml` as a workspace.

Closes rust-lang#40284

…r=nikomatsakis

Disallow subtyping between T and U in T: Unsize<U>.

Because `&mut T` can be coerced to `&mut U`, `T` and `U` must be unified invariantly. Fixes rust-lang#40288.
E.g. coercing `&mut [&'a X; N]` to `&mut [&'b X]` must require `'a` be equal to `'b`, otherwise you can convert between `&'a X` and `&'b X` (in either direction), potentially unsoundly lengthening lifetimes.

Subtyping here was introduced with `Unsize` in rust-lang#24619 (landed in 1.1, original PR is rust-lang#23785).

travis: Attempt to debug sccache failures

I can't find anything that'd cause unexpected EOF in the source, so let's try
taking a look at the error logs on failures.

Fix missing backtick typo

Fixes rendering of the end of the `Configure and Make` section.

Do not bother creating StorageLive for TyNever

Keeps MIR cleaner, `StorageLive(_: !)` makes no sense anyway.

r? @eddyb

Fix UB in repr(packed) tests

r? @arielb1

cc rust-lang#37609 and rust-lang#27060

emit !align attributes on stores of operand pairs

This avoids another case of missing-align UB. cc rust-lang#40373

r? @eddyb

…or, r=alexcrichton

Distinguish the ways `CStr::from_bytes_with_nul` can fail

Implement placement-in protocol for `VecDeque`

CC rust-lang#30172

r? @nagisa

Update gdbr tests

gdb will now reliably detect the lanugage as rust even before any code is run.

fix rust-lang#40294 obligation cause.body_id is not always a NodeExpr

Hello!

This fixes rust-lang#40294 and moves tests related to rust-lang#38812 to a much more sensible directory.

Thanks to @nikomatsakis and @eddyb

…r=alexcrichton

OsString::shrink_to_fit.

Considering how the other capacity-related methods are there, I found it odd that this one wasn't included.

Will create a tracking issue once I get an OK on this.

… r=arielb1

rustc: Support auto-retry linking on a segfault

This is a last-ditch attempt to help our pain with dealing with rust-lang#38878 on the
bots. A new environment variable is added to the compiler,
`RUSTC_RETRY_LINKER_ON_SEGFAULT`, which will instruct the compiler to
automatically retry the final linker invocation if it looks like the linker
segfaulted (up to 2 extra times).

Unfortunately there have been no successful attempts to debug rust-lang#38878. The only
information seems to be that the linker (e.g. `ld` on OSX) is segfaulting
somewhere in some thread pool implementation. This appears to be spurious as
failed PRs will later merge.

The hope is that this helps the queue keep moving without clogging and delaying
PRs due to rust-lang#38878.

Clarify docs in `VecDeque::resize`