while let all the things

Remove a couple of `isize` references from hashmap docs

Also fix a spelling mistake.

Remove useless powerpc64 entry from ARCH_TABLE

Hope, I understood the scope of the fix correctly. closes #47737

Refactor contrived match.

Optimize str::repeat

Improves the performance of `str::repeat` by bulk copying. Here is the benchmarks of `"abcde".repeat(n)`:

|`n`|old [ns/iter]|new [ns/iter]|diff [%]|
---|---|---|---
|1|27.205|27.421|+0.794|
|2|27.500|27.516|+0.0581|
|3|27.923|27.648|-0.985|
|4|31.206|30.145|-3.40|
|5|35.144|31.861|-9.34|
|7|43.131|34.621|-19.7|
|10|54.945|36.203|-34.1|
|100|428.31|52.895|-87.7|

doc: no need for the reference

Also, we are well within line length limit

Add functions for reversing the bit pattern in an integer

I'm reviving PR #32798 now that the LLVM issues have been resolved.

> This adds the bitreverse intrinsic and adds a reverse_bits function to all integer types.

Raw string error note

Fixes #48395.

I think this note should be helpful enough to solve the issue.

Suggest type for overflowing bin/hex-literals

Fixes #48073

For hexadecimal and binary literals, which overflow, it gives an additional note to the warning message, like in this [comment](https://github.com/rust-lang/rust/issues/48073#issuecomment-365370113).

Additionally it will suggest a type (`X < Y`):
- `iX`: if literal fits in `uX` => `uX`, else => `iY`
- `-iX` => `iY`
- `uX` => `uY`

Exceptions: `isize`, `usize`. I don't think you can make a good suggestion here. The programmer has to figure it out on it's own in this case.

r? @oli-obk

Fix spelling s/casted/cast/

r? @GuillaumeGomez

Whitelist rustc dependencies

As per https://internals.rust-lang.org/t/rustc-dependency-policy/6537/8?u=nikomatsakis

cc @alexcrichton @nikomatsakis

Turn feature-gate table into a query so it is covered by dependency tracking.

Turn access to feature gates into a query so we handle them correctly during incremental compilation.

Features are still available via `Session` through `features_untracked()`. I wish we had a better way of hiding untracked information. It would be great if we could remove the `sess` field from `TyCtxt`.

Fixes #47003.

Also fix a spelling mistake.

Include stdsimd in rust-src component

Closes #48734

Closes #48734

[NLL] Avoid borrowed value must be valid for lifetime '_#2r..." in errors

Closes #48428

- [x] If NLL is enabled, [do not invoke `note_and_explain_region`](https://github.com/rust-lang/rust/issues/48428#issuecomment-367691123)
- [x] Modify `-Zdump-nll-cause` to not print [the overwhelming debug output here](https://github.com/rust-lang/rust/blob/master/src/librustc_mir/borrow_check/nll/region_infer/mod.rs#L1288-L1299). This way we should I believe at least get nice-ish output for [our original example](https://github.com/rust-lang/rust/issues/48428#issue-299364536).
- [x] Extend `explain_why_borrow_contains_point` to also work for "universal lifetimes" like the `'a` in [the example at the end of this comment](https://github.com/rust-lang/rust/issues/48428#issuecomment-367691123).
- [ ] Figure out how to enable causal information all the time (but that is https://github.com/rust-lang/rust/issues/46590).