…ions.

read_to_end()

reallocation strategy since extend() calls reserve() and/or
push() for us.

context private.

… and onto the

`UnificationTable`, and renaming/collapsing some methods.

so that it is closer to standalone.

trait matching more tailored. We now detect recursion where the
obligations "match" -- meaning basically that they are the same for some
substitution of any unbound type variables.

F`, so that if we have `x: &mut FnMut()`, then `x()` is translated to
`FnMut::call_mut(&mut *x, ())` rather than `&mut x`. The latter would
require `mut x: &mut FnMut()`, which is really a lot of mut. (Actually,
the `mut` is normally required except for the special case of a `&mut F`
reference, because that's the one case where we distinguish a unique
path like `x` from a mutable path.)

Fixes rust-lang#22914

local only if matches `FUNDAMENTAL(LocalType)`, where `FUNDAMENTAL`
includes `&T` and types marked as fundamental (which includes `Box`).
Also apply these tests to negative reasoning.

`Fn` traits are considered fundamental, along with `Box` (though that is
mostly for show; the real type is `~T` in the compiler).

probing the specifics of `Fundamental`.

Fixes rust-lang#23086.
Fixes rust-lang#23516.

since `Option` is not fundamental and hence the old impls run afoul of
the orphan rules.

…pnkfelix

This PR solves rust-lang#21559 by making sure that unreachable if-expressions are not further translated.

Could someone who knows their way around `trans` take a look at the changes in `controlflow.rs`? I'm not sure if any other code relies on any side-effects of translating unreachable things.

cc @nikomatsakis @nrc @eddyb

While trying to implement parallel ECS processing, I stumbled upon the need to mutate `Arc` contents. The only existed method that allowed that was `make_unique`, but it has issues:
  - it may clone the data as if nothing happened, where the program may just need to crash
  - it forces `Clone` bound, which I don't have

The new `try_unique` allows accessing the contents mutably without `Clone` bound and error out if the pointer is not unique.

…kler

This introduces no functional changes except for reducing a few unnecessary operations and variables.  Vec has the behavior that, if you request space past the capacity with reserve(), it will round up to the nearest power of 2.  What that effectively means is that after the first call to reserve(16), we are doubling our capacity every time.  So using the DEFAULT_BUF_SIZE and doubling cap_size() here is meaningless and has no effect on the call to reserve().

Note that with rust-lang#23842 implemented this will hopefully have a clearer API and less of a need for commenting.  If rust-lang#23842 is not implemented then the most clear implementation would be to call reserve_exact(buf.capacity()) at every step (and making sure that buf.capacity() is not zero at the beginning of the function of course).

Edit- functional change now introduced.  We will now zero 16 bytes of the vector first, then double to 32, then 64, etc. until we read 64kB.  This stops us from zeroing the entire vector when we double it, some of which may be wasted work.  Reallocation still follows the doubling strategy, but the responsibility has been moved to vec.extend(), which calls reserve() and push_back().

…pnkfelix

This PR implements rust-lang/rfcs#1023. In the process it fixes rust-lang#23086 and rust-lang#23516. A few impls in libcore had to be updated, but the impact is generally pretty minimal. Most of the fallout is in the tests that probed the limits of today's coherence.

I tested and we were able to build the most popular crates along with iron (modulo errors around errors being sendable).

Fixes rust-lang#23918.

…dd-impls, r=pnkfelix

The primary purpose of this PR is to add blanket impls for the `Fn` traits of the following (simplified) form:

    impl<F:Fn> Fn for &F
    impl<F:FnMut> FnMut for &mut F

However, this wound up requiring two changes:

1. A slight hack so that `x()` where `x: &mut F` is translated to `FnMut::call_mut(&mut *x, ())` vs `FnMut::call_mut(&mut x, ())`. This is achieved by just autoderef'ing one time when calling something whose type is `&F` or `&mut F`.
2. Making the infinite recursion test in trait matching a bit more tailored. This involves adding a notion of "matching" types that looks to see if types are potentially unifiable (it's an approximation).

The PR also includes various small refactorings to the inference code that are aimed at moving the unification and other code into a library (I've got that particular change in a branch, these changes just lead the way there by removing unnecessary dependencies between the compiler and the more general unification code). 

Note that per rust-lang/rfcs#1023, adding impls like these would be a breaking change in the future. 

cc @japaric
cc @alexcrichton 
cc @aturon 

Fixes rust-lang#23015.

Basically stuff I did for unqualified assoc types which is worth landing by itself.

Fixes rust-lang#22914

Said issue was mostly fixed, as there wasn't any examples when it was initially posted. This is mostly just some re-wording of some things and some cleanup