Apply lint attrs to individual "use" declarations

Fixes #10534
Register new snapshots

These are the first successful snapshots after the LLVM upgrade, built with LLVM
that requires C++11
Fix Vim indent regressions from #13600.

The change in #13600 was incorrect, containing a bad regular expression;
inside an indent function, errors are silently ignored (and the ``~=``
operation will return 0), so it just always failed, causing the cases
that were supposed to be caught to not be caught and making things like
the ``match`` example shown above or struct field definitions regress.

I have fixed the regular expression to what it should have been. This is
still imperfect, of course, not handling cases like where the first
argument to a function is a function call (``foo(bar(),``), but it'll do
for now.
fix O(n^2) perf bug for std::io::fs::walk_dir

The `walk_dir` iterator was simulating a queue using a vector (in particular, using `shift`),
leading to O(n^2) performance. Since the order was not well-specified (see issue #13411),
the simplest fix is to use the vector as a stack (and thus yield a depth-first traversal).
This patch does exactly that.  It leaves the order as originally specified -- "some top-down
order" -- and adds a test to ensure a top-down traversal.

Note that the underlying `readdir` function does not specify any particular order, nor
does the system call it uses.

Closes #13411.
auto merge of #13720 : aturon/rust/walk_dir-perf, r=alexcrichton

The `walk_dir` iterator was simulating a queue using a vector (in particular, using `shift`),
leading to O(n^2) performance. Since the order was not well-specified (see issue #13411),
the simplest fix is to use the vector as a stack (and thus yield a depth-first traversal).
This patch does exactly that, and adds a test checking for depth-first behavior.

Note that the underlying `readdir` function does not specify any particular order, nor
does the system call it uses.

Closes #13411.
auto merge of #13729 : chris-morgan/rust/fix-vim-indent, r=alexcrichton

The change in #13600 was incorrect, containing a bad regular expression;
inside an indent function, errors are silently ignored (and the ``~=``
operation will return 0), so it just always failed, causing the cases
that were supposed to be caught to not be caught and making things like
the ``match`` example shown above or struct field definitions regress.

I have fixed the regular expression to what it should have been. This is
still imperfect, of course, not handling cases like where the first
argument to a function is a function call (``foo(bar(),``), but it'll do
for now.

----

I have a general request to make of reviewers about any changes made to `src/etc/vim`: **please tell me**. As a general rule I want to review them. (I’ll make an exception for changes the prelude; it needs fixing from time to time when some people don’t update the syntax file, anyway.)

cc @brandonw
native: Remove unused and untested UnixDatagram
std: Add timeouts to unix connect/accept

This adds support for connecting to a unix socket with a timeout (a named pipe
on windows), and accepting a connection with a timeout. The goal is to bring
unix pipes/named sockets back in line with TCP support for timeouts.

Similarly to the TCP sockets, all methods are marked #[experimental] due to
uncertainty about the type of the timeout argument.

This internally involved a good bit of refactoring to share as much code as
possible between TCP servers and pipe servers, but the core implementation did
not change drastically as part of this commit.

cc #13523
add min_pos_value constant for floats

Follow-up on issue #13297 and PR #13710.  Instead of following the (confusing) C/C++ approach
of using `MIN_VALUE` for the smallest *positive* number, we introduce `MIN_POS_VALUE` (and
in the Float trait, `min_pos_value`) to represent this number.

This patch also removes a few remaining redundantly-defined constants that were missed last
time around.
auto merge of #13671 : dcrewi/rust/lint-directives-on-use-items, r=alexcrichton

Fixes #10534
auto merge of #13711 : alexcrichton/rust/snapshots, r=brson

These are the first successful snapshots after the LLVM upgrade, built with LLVM
that requires C++11
auto merge of #13723 : alexcrichton/rust/pipe-connect-timeout, r=brson

This adds support for connecting to a unix socket with a timeout (a named pipe
on windows), and accepting a connection with a timeout. The goal is to bring
unix pipes/named sockets back in line with TCP support for timeouts.

Similarly to the TCP sockets, all methods are marked #[experimental] due to
uncertainty about the type of the timeout argument.

This internally involved a good bit of refactoring to share as much code as
possible between TCP servers and pipe servers, but the core implementation did
not change drastically as part of this commit.

cc #13523
Add a regex crate to the Rust distribution.

Also adds a regex_macros crate, which provides natively compiled
regular expressions with a syntax extension.

Closes #3591.

RFC: 0007-regexps
mk: Copy fewer libraries into the host artifacts
Cleaned up os::consts. The module only exposes constants for the target OS and arch.

Constants for other OS's and arch's must be defined manually.
[breaking-change]
auto merge of #13697 : pongad/rust/consts, r=alexcrichton

I decided to put architecture constants in another mod. They are not used, so a part of me is thinking of just getting rid of them altogether. The rest should be similar to what @brson wants.
Fixes #13536
Ignore regex tests (regular, cfail and benchmark) on Windows (for now).
auto merge of #13700 : BurntSushi/rust/regexp, r=alexcrichton

Implements [RFC 7](https://github.com/rust-lang/rfcs/blob/master/active/0007-regexps.md) and will hopefully resolve #3591. The crate is marked as experimental. It includes a syntax extension for compiling regexps to native Rust code.

Embeds and passes the `basic`, `nullsubexpr` and `repetition` tests from [Glenn Fowler's (slightly modified by Russ Cox for leftmost-first semantics) testregex test suite](http://www2.research.att.com/~astopen/testregex/testregex.html). I've also hand written a plethora of other tests that exercise Unicode support, the parser, public API, etc. Also includes a `regex-dna` benchmark for the shootout.

I know the addition looks huge at first, but consider these things:

1. More than half the number of lines is dedicated to Unicode character classes.
2. Of the ~4,500 lines remaining, 1,225 of them are comments.
3. Another ~800 are tests.
4. That leaves 2500 lines for the meat. The parser is ~850 of them. The public API, compiler, dynamic VM and code generator (for `regexp!`) make up the rest.
test: Enable extern-fn-reachable test

It didn't work because it tried to call itself but symbols are not
exported as default in executables.

Note that `fun5` is not internal anymore since it is in library.
test: Remove/update some old ignored tests