region binding at the impl site, so for method types that come from impls,
it is necessary to liberate/instantiate late-bound regions at multiple
depths.

use simple pattern matching to take a guess at what the method's self
category is in astconv, and check it more thoroughly later.

`Box<for<'a> Foo<&'a T> + 'a>` can be accepted. Also cleanup the visitor/fold
in general, exposing more callbacks.

something other than a trait type.

Pull out the fn-sig sub/lub/glb code and generalize it into a `higher_ranked` module. Also moves the docs to a more suitable place.

Consolidate the `unboxed_closure_sugar` and `unboxed_closure` feature gates.

Reduces memory usage significantly and opens opportunities for more parallel compilation.

This PR was previously #19002 but I closed it because bors didn't seem to recognize the `r+` annotations there.

[breaking-change]

Deprecates `core::num::pow` in favor of `Int::pow`.

Move trans, back, driver, and back into a new crate, rustc_trans. Reduces memory usage significantly and opens opportunities for more parallel compilation.

r?

(I realise this needs a rebase, but I will probably have to chop it up in order to land and I'd like to get r+ first so I can do that quicker)

The trait has an obvious, sensible implementation directly on vectors so
the MemWriter wrapper is unnecessary. This will halt the trend towards
providing all of the vector methods on MemWriter along with eliminating
the noise caused by conversions between the two types. It also provides
the useful default Writer methods on Vec<u8>.

After the type is removed and code has been migrated, it would make
sense to add a new implementation of MemWriter with seeking support. The
simple use cases can be covered with vectors alone, and ones with the
need for seeks can use a new MemWriter implementation.

The trait has an obvious, sensible implementation directly on vectors so
the MemWriter wrapper is unnecessary. This will halt the trend towards
providing all of the vector methods on MemWriter along with eliminating
the noise caused by conversions between the two types. It also provides
the useful default Writer methods on Vec<u8>.

After the type is removed and code has been migrated, it would make
sense to add a new implementation of MemWriter with seeking support. The
simple use cases can be covered with vectors alone, and ones with the
need for seeks can use a new MemWriter implementation.

r? @aturon 
cc #16918

Signed-off-by: NNODA, Kai <nodakai@gmail.com>

r? @alexcrichton

- CFG_CFLAGS is only used for jemalloc
- We grew an extra set of flags for jemalloc (CFG_JEMALLOC_CFLAGS) in addition to CFG_CFLAGS
- This kills of CFG_CFLAGS and keeps the more specific and less confusing CFG_JEMALLOC_CFLAGS
- Additionally, pass CFG_JEMALLOC_CFLAGS to jemalloc's configure slightly differently so things work when people use --sysroot in their CFLAGS.

Closes #19037
cc #16918

r? @aturon

Baby steps here...

Fixed some comments in liblog, libregex, librustc, libstd.

Items defined in the body of a function has no visibility outside it, and thus have no reason to inherit its stability.

Closes #17488

Updated all the adjacent character literals in the BCNF that cannot have an optional space between them

Came up on IRC that this was a bit unhelpful as to what should actually be *done*. I am new to changing compiler messages, please let me know if there's anything else that needs to be done to accomadate this change.

(My build system is still constantly crashing [Is bors contagious?], so this hasn't been formally `check`ed. I figure it's a simple enough change that any consequences [like compile-fail expected messages?] can be eyeballed by someone more experienced.)

Make struct variant syntax more consistent with struct syntax and fix an
assert in middle::typeck.

Fix #19003

This code is identical to io::util::copy()

Fixes #18986.

Hello,

`dylib` [seems][1] to be no longer an option for the `kind` key of the `link` attribute.

UPDATE: It should be the other way around: It [seems][1] `dylib` has been lost as a possible variant of the `kind` key of the `link` attribute. See the comment below.

Regards,
Ivan

[1]: https://github.com/rust-lang/rust/blob/8f8753878644b0bfb38d24781edb9ef2028730f2/src/librustc/metadata/creader.rs#L237

Due to not being able to parametrize over array sizes, `Clone` is only
implemented for element types that are `Copy`able.

creating a new Id object requires the format to match a subset of `ID` format defined by the DOT language. When the format did not match, the function called assert. This was not mentioned in the docs or the spec. I made the failure explicit by returning an Result<Id, ()>.

`slice_shift_char` splits a `str` into it's leading `char` and the remainder of the `str`. Currently, it returns a `(Option<char>, &str)` such that:

    "bar".slice_shift_char() => (Some('b'), "ar")
    "ar".slice_shift_char()  => (Some('a'), "r")
    "r".slice_shift_char()   => (Some('r'), "")
    "".slice_shift_char()    => (None,      "")

This is a little odd. Either a `str` can be split into both a head and a tail or it cannot. So the return type should be `Option<(char, &str)>`. With the current behaviour, in the case of the empty string, the `str` returned is meaningless - it is always the empty string.

This PR changes `slice_shift_char` so that:

    "bar".slice_shift_char() => Some(('b', "ar"))
    "ar".slice_shift_char()  => Some(('a', "r"))
    "r".slice_shift_char()   => Some(('r', ""))
    "".slice_shift_char()    => None

Following [the collections reform RFC](https://github.com/rust-lang/rfcs/pull/235), this PR:

* Adds a new `borrow` module to libcore. The module contains traits for borrowing data (`BorrowFrom` and `BorrowFromMut`), generalized cloning (`ToOwned`), and a clone-on-write smartpointer (`Cow`).

* Deprecates the `_equiv` family of methods on `HashMap` and `HashSet` by instead generalizing the "normal" methods like `get` and `remove` to use the new `std::borrow` infrastructure.

* Generalizes `TreeMap`, `TreeSet`, `BTreeMap` and `BTreeSet` to use the new `std::borrow` infrastructure for lookups.

[breaking-change]