mem_categorization: handle type-based paths in variant patterns

These can't be used in correct programs, but must be handled in order to
prevent ICEs.

Fixes #42880.

r? @EddyB

Coerce fields to the expected field type

Fully fixes #31260.

This needs a crater run. I was supposed to do this last month but it slipped. Let's get this done.

Add `Iterator::for_each`

This works like a `for` loop in functional style, applying a closure to
every item in the `Iterator`.  It doesn't allow `break`/`continue` like
a `for` loop, nor any other control flow outside the closure, but it may
be a more legible style for tying up the end of a long iterator chain.

This was tried before in #14911, but nobody made the case for using it
with longer iterators.  There was also `Iterator::advance` at that time
which was more capable than `for_each`, but that no longer exists.

The `itertools` crate has `Itertools::foreach` with the same behavior,
but thankfully the names won't collide.  The `rayon` crate also has a
`ParallelIterator::for_each` where simple `for` loops aren't possible.

> I really wish we had `for_each` on seq iterators. Having to use a
> dummy operation is annoying.  - [@nikomatsakis][1]

[1]: https://github.com/nikomatsakis/rayon/pull/367#issuecomment-308455185

Rebase LLVM on top of LLVM 4.0.1

Fixes #42893.

Please don't backport this to beta as-is - I'm not sure I want rust-lang/llvm#84 to sneak to beta before it gets sufficient testing.

r? @alexcrichton

Shift mir-dataflow from `rustc_borrowck` to `rustc_mir` crate.

Shift mir-dataflow from `rustc_borrowck` to `rustc_mir` crate.

Turn `elaborate_drops` and `rustc_peek` implementations into MIR passes that also live in `rustc_mir` crate.

Rewire things so `rustc_driver` uses the `ElaborateDrops` from `rustc_mir` crate.

(This PR is another baby step for mir-borrowck; it is a piece of work that other people want to rebase their stuff on top of, namely developers who are doing other dataflow analyses on top of MIR.)

I have deliberately architected this PR in an attempt to minimize the number of actual code changes. The majority of the diff should be little more than changes to mod and use declarations, as well as a few visibility promotions to pub(crate) when a declaration was moved downward in the module hierarchy.

(I have no problem with other PR's that move declarations around to try to clean this up; my goal was to ensure that the diff here was as small as possible, to make the review nearly trivial.)

Make `$crate` a keyword

Fixes https://github.com/rust-lang/rust/issues/42898

r? @jseyfried or @nrc

Stop disabling fill in jemalloc

The underlying bug has been fixed for over 2 years!

r? @alexcrichton

These can't be used in correct programs, but must be handled in order to
prevent ICEs.

Fixes #42880.

Unsized tuple coercions

Part of #18469. Fixes #32702.

#37685 and #34451 might also be related.

This PR does the following:

- Introduce explicit `Sized` constraints on tuple initializers, similar to that of record-struct initializers. Not much relevant to the main contribution but I noticed this when making tests for unsized tuple coercions.
- Implement `(.., T): Unsize<(.., U)>` where `T: Unsize<U>`.
- Assume `(.., T)` is MaybeUnsizedUnivariant.
- Modify `src/librustc/ty/util.rs` and `src/librustc_trans/glue.rs` so that tuples and structs are uniformly traversed when translating.

Remove err methods

To be merged after #42519.

cc @Susurrus @QuietMisdreavus

Rollup of 12 pull requests

- Successful merges: #42219, #42831, #42832, #42884, #42886, #42901, #42919, #42920, #42946, #42953, #42955, #42958
- Failed merges:

Better timestamps in builds

r? @Mark-Simulacrum

Document that `/` works as separator on Windows

Hi Whenever I see code like `Path::new("./src/bin/main.rs")` or `path.ends_with("foo/bar")`, I wonder if it will work on Windows as I expect. Unfortunately, reading the current docs does not help to answer this question, because all examples are Unix-specific.

However, I believe that using `/` is fine, because both Windows itself [and Rust stdlib](https://github.com/rust-lang/rust/blob/47faf1d51952ecd9d4c8a7325332fba34fbe00bd/src/libstd/sys/windows/path.rs#L26) do treat it as a file separator, and because it is [actually used](https://github.com/rust-lang/cargo/blob/abf01e1eddb3145c83f71b469ea7bee37141e5e1/tests/git.rs#L579) in Cargo. So looks like we can just document it?

r? @steveklabnik

cc @retep998 I don't actually program for windows that much, so I might be totally wrong, and perhaps we should advise to always use (allocating) `.join` method to construct paths of more than one component?

Move type parameter shadowing test to `ui`

Fix #20729.

compile-error.md: Fix link reference

Was a copy-paste mistake, I guess

[libcore/cmp] Expand Ord/PartialOrd Derivable doc for enum types

Expand Derivable docblock section for `Ord` and `PartialOrd` to cover
`enum` types, in addition to the existing language explaining it for
`struct` types.

make lint on-by-default/implied-by messages appear only once

From review discussion on #38103 (https://github.com/rust-lang/rust/pull/38103#discussion_r94845060).

![we_heard](https://user-images.githubusercontent.com/1076988/27564103-6284b78e-5a8a-11e7-9d35-f7f297ca9573.png)

r? @nikomatsakis

std: Fix implementation of `Alloc::alloc_one`

This had an accidental `u8 as *mut T` where it was intended to have just a
normal pointer-to-pointer cast.

Closes #42827

syntax: allow negative integer literal expression to be interpolated as pattern

Fixes #42820.

r? @jseyfried

Move global vars changing tests into run-pass

Should fix race #42795

Update docs for std::fmt::format #29355.

This rewords and removes the `Arguments` section from the docs for
fmt::format.

r? @steveklabnik

Update docs for fmt::write.

#29355

I reworded it slightly to make it more clear that the function only take
two arguments - the output and the Arguments struct that can be
generated from the format_args! macro.

r? @steveklabnik

add `allow_fail` test attribute

This change allows the user to add an `#[allow_fail]` attribute to
tests that will cause the test to compile & run, but if the test fails
it will not cause the entire test run to fail. The test output will
show the failure, but in yellow instead of red, and also indicate that
it was an allowed failure.

Here is an example of the output: http://imgur.com/a/wt7ga

Fix Redox build, broken in ecbb896b

rustc_typeck: enforce argument type is sized

closes #42312

r? @nikomatsakis

avoid translating roots with predicates that do not hold

Finally I got around to doing this.

Fixes #37725.

r? @nikomatsakis