Cache projections in trans
This introduces a cache for the results of projection and normalization in trans. This is in addition to the existing cache that is per-inference-context. Trans is an easy place to put the cache because we are guaranteed not to have type parameters and also we don't expect any failures or inference variables, so there is no need to cache or follow-up on obligations that come along with. (As evidenced by the fact that this particular code would panic if any error occurred.)
That said, I am not sure this is 100% the best place for it; I sort of wanted a cache like we have in the fulfillment context for global names; but that cache only triggers when all subsequent obligations are satisfied, and since projections don't have an entry in the obligation jungle there is no easy place to put it. I considered caching both the result and obligations globally, but haven't really tried implementing it. It might be a good next step.
Regardless, this cache seems to have no real effect on bootstrap time (maybe a slight improvement), but on [the futures.rs test case I was looking at](https://github.com/rust-lang-nursery/rustc-benchmarks/pull/6), it improves performance quite a bit:
| phase | before | after |
| ----- | ------ | ----- |
| collection | 0.79s | 0.46s |
| translation | 6.8s | 3.2s |
| total | 11.92s | 7.15s |
r? @arielb1
Allow specification of the system V AMD64 ABI constraint.
This can be specified using `extern "sysV64" fn` on all platforms.
This ABI is used as the C ABI on unix platforms, but can only be specified there using extern "C". It was impossible to specify on other platforms. Meanwhile the win64 ABI, which was the extern "C" ABI on the windows platform could be specified on other platforms using extern "win64".
This pull request adds the the "sysV64" ABI constraint which exposes this calling convention on platforms where it is not the C ABI.
Turn the RFC1592 warnings into hard errors
The warnings have already reached stable, and I want to improve the trait error reporting code.
Turning warnings into errors, this is obviously a [breaking-change].
r? @nikomatsakis
cc @rust-lang/compiler
Implement std::convert traits for char
This is motivated by avoiding the `as` operator, which sometimes silently truncates, and instead use conversions that are explicitly lossless and infallible.
I’m less certain that `From<u8> for char` should be implemented: while it matches an existing behavior of `as`, it’s not necessarily the right thing to use for non-ASCII bytes. It effectively decodes bytes as ISO/IEC 8859-1 (since Unicode designed its first 256 code points to be compatible with that encoding), but that is not apparent in the API name.
Fix run-pass/signal-exit-status to not trigger UB by writing to NULL.
`run-pass/signal-exit-status` has had UB (NULL dereference) since it was introduced in #10109.
Fixes the test failure found by @camlorn while running under Windows Subsystem for Linux.
