By creating a *mut [T] directly (without going through &mut [T]), avoid
questions of validity of the contents of the slice.
Consider the following risky code:
```rust
unsafe {
let mut v = Vec::<bool>::with_capacity(16);
v.set_len(16);
}
```
The intention is that with this change, the above snippet will be
sound because Vec::drop does no longer produces a mutable slice of
the vector's contents.
Remove the last remnant of unsigned Neg
It's been gone since #23945, before Rust 1.0. The former wrapping
semantics have also been available as inherent methods for a long time
now. There's no reason to keep this unused macro around.
Improve async-await/generator obligation errors in some cases
Fixes#68112.
This change is best read one commit at a time (I add a test at the beginning and update it in each change after).
The `test2` function is a case I found while writing the test that we don't handle with this code yet. I don't attempt to fix it in this PR, but it's a good candidate for future work.
r? @davidtwco, @nikomatsakis
It's been gone since #23945, before Rust 1.0. The former wrapping
semantics have also been available as inherent methods for a long time
now. There's no reason to keep this unused macro around.
Rollup of 4 pull requests
Successful merges:
- #70654 (Explain how to work with subtree)
- #71092 (Remove some usage of `DUMMY_HIR_ID`)
- #71103 (Add test case for type aliasing `impl Sized`)
- #71109 (allow const generics in const fn)
Failed merges:
r? @ghost
allow const generics in const fn
This was explicitly forbidden before. As we were unable to think of a reason
why this should still be the case, this check has been removed.
r? @eddyb
cc @varkor @Centril
Suggest .into() over try_into() when it would work
It would be better to suggest x.into() instead, which is shorter, cannot fail, and doesn't require importing a trait.
Tests have been added and made up to date.
Fixes#70851
ci: run mir-opt tests on PR CI also as 32-bit (for `EMIT_MIR_FOR_EACH_BIT_WIDTH`).
Background: #69916 and [`src/test/mir-opt/README.md`](https://github.com/rust-lang/rust/blob/master/src/test/mir-opt/README.md):
> By default 32 bit and 64 bit targets use the same dump files, which can be problematic in the
presence of pointers in constants or other bit width dependent things. In that case you can add
>
> ```
> // EMIT_MIR_FOR_EACH_BIT_WIDTH
> ```
>
> to your test, causing separate files to be generated for 32bit and 64bit systems.
However, if you change the output of such a test (intentionally or not), or if you add a test and it varies between 32-bit and 64-bit platforms, you have to run this command (for a x64 linux host):
`./x.py test --stage 1 --target x86_64-unknown-linux-gnu --target i686-unknown-linux-gnu --bless src/test/mir-opt`
Otherwise, bors trying to merge the PR will fail, since we test 32-bit targets there.
But we don't on PR CI, which means there's no way the PR author would know (unless they were burnt by this already and know what to look for).
This PR resolves that by running `mir-opt` tests for ~~`i686-unknown-linux-gnu`~~, on PR CI.
**EDIT**: switched to `armv5te-unknown-linux-gnueabi` to work around LLVM 7 crashes (see https://github.com/rust-lang/compiler-builtins/pull/311#issuecomment-612270089), found during testing.
cc @rust-lang/wg-mir-opt @rust-lang/infra
