closes rust-lang#47751

Implementing Send for a specific field rather than the whole struct is
safer: if a field is changed/modified and becomes non-Send, we can catch
it.

If an error message is emitted that spans several files, only the
primary file currently has line and column data attached. This is
useful information, even in files other than the one in which the error
occurs. We can often work out which line and column the error
corresponds to in other files — in this case it is helpful to add them
(in the case of ambiguity, the first relevant line/column is picked,
which is still helpful than none).

Required to fix rust-lang/stdarch#295 in stdsimd.

r? @alexcrichton

Needed for `v7` features in `coresimd`. 

See https://github.com/rust-lang-nursery/stdsimd/blob/b2f7be24d5043a88427f9a5258ca9a51ede6d029/coresimd/src/arm/v7.rs#L40 which used to work but doesn't anymore.

r? alexcrichton

Fixes rust-lang#47011.

…NOT_0

Fixes rust-lang#47658.

Remove the assumption that home_dir always returns Some

This allows the test to be executed with
[cross](https://github.com/japaric/cross).

The link title needs to be HTML escaped.

Punctuation and clarity fixes.

…eyfried

Run rustfmt and add doc comments to libsyntax/ext/tt/quoted.rs

I was already going to try to understand this code to try to implement rust-lang/rfcs#2298. I figured I would put that knowledge into comments and share... This PR contains _no changes_ to the code itself -- just formatting and comments.

I'm not sure what the best way to do this is. I plan to make more such PR for other files, but I figured it would have fewer conflicts if I do it file by file...

Make run-pass/env-home-dir.rs test more robust

Remove the assumption that home_dir always returns Some.

This allows the test to be executed with [cross](https://github.com/japaric/cross).

…eyfried

Run rustfmt and add doc comments to libsyntax/ext/tt/macro_parser.rs

Similar to rust-lang#47603

cc @theotherphil since you reviewed my other PR 😄

And because they are already assigned on rust-lang#47603:

r? @arielb1

implement Send for process::Command on unix

closes rust-lang#47751

…r=estebank

Add line numbers and columns to error messages spanning multiple files

If an error message is emitted that spans several files, only the
primary file currently has line and column data attached. This is
useful information, even in files other than the one in which the error
occurs. We can often work out which line and column the error
corresponds to in other files — in this case it is helpful to add them
(in the case of ambiguity, the first relevant line/column is picked,
which is still helpful than none).

Whitelist aes x86 feature flag

Required to fix rust-lang/stdarch#295 in stdsimd.

Closes rust-lang#44544 .

r? @alexcrichton

Whitelist v7 feature for ARM and AARCH64.

Needed for `v7` features in `coresimd`.

See https://github.com/rust-lang-nursery/stdsimd/blob/b2f7be24d5043a88427f9a5258ca9a51ede6d029/coresimd/src/arm/v7.rs#L40 which used to work but doesn't anymore.

r? alexcrichton

…crichton

Add per-stage RUSTFLAGS: RUSTFLAGS_STAGE_{0,1,2} and RUSTFLAGS_STAGE_NOT_0

Fixes rust-lang#47658.

r? @alexcrichton

…tMisdreavus

Document that `Index` ops can panic on `HashMap` & `BTreeMap`.

Fixes rust-lang#47011.

…st-coverage, r=nikomatsakis

Increase test coverage of use_nested_groups

r? @nikomatsakis

… r=QuietMisdreavus

rustdoc: Fix link title rendering with hoedown

The link title needs to be HTML escaped.

It was broken by rust-lang#47046.

r? @QuietMisdreavus