Fix Redox build, broken in ecbb896b

rustc_typeck: enforce argument type is sized

closes #42312

r? @nikomatsakis

avoid translating roots with predicates that do not hold

Finally I got around to doing this.

Fixes #37725.

r? @nikomatsakis

Detect missing `;` on methods with return type `()`

 - Point out the origin of a type requirement when it is the return type
   of a method
 - Point out possibly missing semicolon when the return type is `()` and
   the implicit return makes sense as a statement
 - Suggest changing the return type of methods with default return type
 - Don't suggest changing the return type on `fn main()`
 - Don't suggest changing the return type on impl fn
 - Suggest removal of semicolon (instead of being help)

Reuse the mem::swap optimizations to speed up slice::rotate

This is most helpful for compound types where LLVM didn't vectorize the loop.  Highlight: bench slice::rotate_medium_by727_strings gets 38% faster.

Exposes the swapping logic from PR https://github.com/rust-lang/rust/pull/40454 as `pub unsafe fn ptr::swap_nonoverlapping` under library feature `swap_nonoverlapping` https://github.com/rust-lang/rust/issues/42818.

(The new method seemed plausible, and was the simplest way to share the logic.  I'm not attached to it, though, so let me know if a different way would be better.)

1.19 stabilization

r? @alexcrichton

re-add the call to `super_statement` in EraseRegions

The move gathering code is sensitive to type-equality - that is rather
un-robust and I plan to fix it eventually, but that's a more invasive
change. And we want to fix the visitor anyway.

Fixes #42903.

r? @EddyB

The move gathering code is sensitive to type-equality - that is rather
un-robust and I plan to fix it eventually, but that's a more invasive
change. And we want to fix the visitor anyway.

Fixes #42903.

deriv(Hash) for single-variant enum should not hash discriminant

Fixes #39137

Fix NaN handling in is_sign_negative/positive

This would be my proposed fix for the #42425 provided we decide it is indeed a problem.

Note this would technically be a breaking change to a stable API. We might want to consider deprecating these methods and adding new ones.

Don't drag function signatures along function item types.

This PR separates the signature of a function from the "function item type" (`TyFnDef`), leaving only the `DefId` and parameter `Substs`, making them even more like (captureless) closure types.

The motivation for this change is reducing typesystem complexity, and its consequences:
* operating on the signature instead of just the parameters was less efficient
  * specifically, signatures can easily add several levels of depth on top of the parameter types
  * and the signatured were always substituted and normalized, so typically even more complex
* it was *the only* type that was *both* nominal (identity) and structural (signature)
  * harder to model in Chalk than either a purely nominal or structural type
  * subtyping worked on the signature but parameters were always invariant
  * call type-checking was transforming signatures but keeping the nominal half intact
  * the signature could therefore get out of sync during type inference in several ways

That last point comes with a `[breaking-change]`, because functions with `'static` in their return types will now *not* be as usable as if they were using lifetime parameters instead:
```rust
// Will cause lifetime mismatch in main after this PR.
fn bar() -> &'static str { "bar" }
// Will continue to work fine, as every use can choose its own lifetime.
fn bar<'a>() -> &'a str { "bar" }

fn main() {
    let s = String::from("foo");
    Some(&s[..]).unwrap_or_else(bar);
}
```

r? @nikomatsakis

- Fix typo
- Add docstring
- Remove spurious test output file

Rollup of 5 pull requests

- Successful merges: #42519, #42871, #42874, #42905, #42917
- Failed merges:

compiletest: show details why GDB failed to execute.

Help finding reasons of spurious errors due to GDB failing to run (#42693).

Reword OsStr docs to clarify that utf8 may contain nulls

The use of the word "but" in the OsStr docs implies (at least to me) that valid UTF-8 does not contain null bytes.

Using "which" instead makes it clear that valid UTF-8 may contain null bytes.

only set "overruled by outer forbid" once for lint groups, by group name

Previously, conflicting forbid/allow attributes for a lint group would
result in a separate "allow(L) overruled by outer forbid(L)" error for
every lint L in the group. This was needlessly and annoyingly verbose;
we prefer to just have one error pointing out the conflicting
attributes.

(Also, while we're touching context.rs, clean up some unused arguments.)

Resolves #42873.

change binding name of for loop lowering to appease clippy

With the latest change to for loop lowering (#42634), a `_next` binding was introduced.
Unfortunately, this [disturbs](https://github.com/Manishearth/rust-clippy/issues/1846) clippy's `used_underscore_binding` lint. This commit just renames the binding to `__next` so clippy will be happy. It should have no other effect.

Create more error codes

Fixes #31174.
Part of #42229.

cc @Susurrus

Update Cargo

Haven't run extensive tests locally (not really sure what to test) but this primarily pulls in minor changes: https://github.com/rust-lang/cargo/pull/4215, https://github.com/rust-lang/cargo/pull/4209, and https://github.com/rust-lang/cargo/pull/4218. The last one fixes the flaky cargo test by ignoring it, which should unblock https://github.com/rust-lang/rust/pull/42745 -- that's beta nominated.

r? @alexcrichton

rustdoc: Don't ICE on `use *;`

Fixes #42875

rustdoc: Fix a few issues with associated consts

* Make sure private consts are stripped.
* Don't show a code block for the value if there is none.
* Make sure default values are shown in impls.
* Make sure docs from the trait are used if the impl has no docs.

Move it and Bound to core::ops while we're at it.

Closes #30877

Closes #21507

Closes #40421

Closes #40893

Closes #38526

Make wasm32 buildbot test LLVM backend

This adds the experimental targets option to configure so it can be used
by the builders and changes the wasm32 Dockerfile accordingly. Instead
of using LLVM from the emsdk, the builder's emscripten tools now uses
the Rust in-tree LLVM, since this is the one built with wasm support.