Conflicts:
	mk/platform.mk
	src/librustc/session/config.rs
	src/librustc_back/target/aarch64_apple_ios.rs
	src/librustc_back/target/aarch64_linux_android.rs
	src/librustc_back/target/arm_linux_androideabi.rs
	src/librustc_back/target/arm_unknown_linux_gnueabi.rs
	src/librustc_back/target/arm_unknown_linux_gnueabihf.rs
	src/librustc_back/target/armv7_apple_ios.rs
	src/librustc_back/target/armv7s_apple_ios.rs
	src/librustc_back/target/i386_apple_ios.rs
	src/librustc_back/target/i686_apple_darwin.rs
	src/librustc_back/target/i686_pc_windows_gnu.rs
	src/librustc_back/target/i686_unknown_dragonfly.rs
	src/librustc_back/target/i686_unknown_linux_gnu.rs
	src/librustc_back/target/mips_unknown_linux_gnu.rs
	src/librustc_back/target/mipsel_unknown_linux_gnu.rs
	src/librustc_back/target/mod.rs
	src/librustc_back/target/powerpc_unknown_linux_gnu.rs
	src/librustc_back/target/x86_64_apple_darwin.rs
	src/librustc_back/target/x86_64_apple_ios.rs
	src/librustc_back/target/x86_64_pc_windows_gnu.rs
	src/librustc_back/target/x86_64_unknown_dragonfly.rs
	src/librustc_back/target/x86_64_unknown_freebsd.rs
	src/librustc_back/target/x86_64_unknown_linux_gnu.rs
	src/librustc_back/target/x86_64_unknown_openbsd.rs
	src/librustc_llvm/lib.rs
	src/librustc_trans/back/link.rs
	src/librustc_trans/trans/base.rs
	src/libstd/os.rs
	src/rustllvm/RustWrapper.cpp

Revert an accidental revert.

core::slice was originally written to tolerate overflow (notably, with
slices of zero-sized elements), but it was never updated to use wrapping
arithmetic when overflow traps were added.

Also correctly handle the case of calling .nth() on an Iter with a
zero-sized element type. The iterator was assuming that the pointer
value of the returned reference was meaningful, but that's not true for
zero-sized elements.

Fixes #25016.

It is currently broken to use syntax such as `<T as Foo>::U::static_method()` where `<T as Foo>::U` is an associated type. I was able to fix this and simplify the parser a bit at the same time.

This also fixes the corresponding issue with associated types (#22139), but that's somewhat irrelevant because #22519 is still open, so this syntax still causes an error in type checking.

Similarly, although this fix applies to associated consts, #25046 forbids associated constants from using type parameters or `Self`, while #19559 means that associated types have to always have one of those two. Therefore, I think that you can't use an associated const from an associated type anyway.

The loop to load all the known impls from external crates seems to have been used because `ty::populate_implementations_for_trait_if_necessary` wasn't doing its job, and solely relying on it resulted in loading only impls in the same crate as the trait.

Coherence for `librustc` was reduced from 18.310s to 0.610s, from stage1 to stage2.
Interestingly, type checking also went from 46.232s to 42.003s, though that could be noise or unrelated improvements.

On a smaller scale, `fn main() {}` now spends 0.003s in coherence instead of 0.368s, which fixes #22068.
It also peaks at only 1.2MB, instead of 16MB of heap usage.

This isn't quite right, but it's interesting.

r? @nikomatsakis 

Fix ty::populate_implementations_for_trait_if_necessary to load the trait's impls from all the crates.

rustc: rename ty::populate_implementations_for_type_if_necessary to make it clear that it only populates inherent impls.

- Successful merges: #25254, #25272, #25278, #25282, #25283, #25288, #25292, #25302, #25304, #25314
- Failed merges: 

A few errors slipped through my filter. Markdown formatting is especially important now that http://doc.rust-lang.org/error-index.html is live!

Speaking of, the error index should probably be linked to from somewhere. It doesn't quite fit under any of the sections in the index, but I could create a new one for it? Or add it under "tools" despite it not exactly being an executable tool.

I think someday I'd like to make these drawings rather than text, but for now, this will have to be good enough.

The functions BitSet::{iter,union,symmetric_difference} each had docs that claimed u32s were output when their actual output each end up being usizes.

r? @steveklabnik 

and remove references to the unit type, which no longer exists

Fixes #24999

As mentioned in https://github.com/rust-lang/rust/issues/16676#issuecomment-100676326 this makes it a little bit more correct.

I'm a bit unsure whether or not it should be explained that the transcriber can be wrapped in parentheses or curly braces if necessary.

Change from "must be used with behind a pointer" to "must be used behind a pointer"

Adds long diagnostic messages for:

 - E0184
 - E0204
 - E0205
 - E0206
 - E0243
 - E0244
 - E0249
 - E0250

This PR also adds some comments to the error codes in `librustc_typeck/diagnostics.rs`.

cc #24407 

They're only enabled in debug builds, but a panic is usually more
welcome than UB in debug builds.

Previous review at https://github.com/rust-lang/rust/pull/22069

r? @Gankro
cc @huon

Rustdoc fixes for associated items

This is related to isssue #22442 and solves it partly.

This solves the search index links of associated types and constants,
so that they link to the trait page.

Also add an Associated Constants section if constants are present.

core::slice::Iter.ptr can be null when iterating a slice of zero-sized
elements, but the pointer value used for the slice itself cannot. Handle
this case by always returning a dummy pointer for slices of zero-sized
elements.

The previous assumptions were not valid for slices of zero-sized
elements.

cc @aturon

and remove references to the unit type, which no longer exists

Fixes #24999

We don't need to copy any elements if `at` is behind the last element
in the map. The last element is at index `self.v.len() - 1`, so we
should not copy if `at` is greater **or equals** `self.v.len()`.

r? @Gankro

- Successful merges: #25280, #25284, #25286, #25287, #25290, #25291, #25297
- Failed merges: 

Hiiii, I've got another chunk of updates to the grammar documentation! ⭐ 🌟 🌠 

Chipping away at #22445, still have some more to go. I'm learning so much!!!

Maybe it's me, but I really needed an example to understand if let and refutable statements.
Playpen: http://is.gd/mjX3Gf

Let me know if the variable names are too, uh, culinary.

Several Minor API / Reference Documentation Fixes

- Fix a few small errors in the reference.
- Fix paper cuts in the API docs.

Fixes #24882
Fixes #25233
Fixes #25250

The reference was claiming all vectors all bounds-checked at run-time, when constant vectors are usually checked at compile-time.

For the changed example see http://is.gd/28ak9E

Also fixed a minor grammar issue.