Make overflowing and wrapping negation const
Remember that the signed and unsigned versions are slightly different here, so there's four functions made const instead of just two.
Fix typo in std::future::Future docs
I am not quite sure if this is actually a typo but
1. to me the sentence doesn't make sense if it says "expect"
2. I hope that `Future`s are not really allowed to cause memory unsafety if they are polled after completion.
There are two big categories of changes in here
- Removing lifetimes from common traits that can essentially never user a lifetime from an input (particularly `Drop` & `Debug`)
- Forwarding impls that are only possible because the lifetime doesn't matter (like `impl<R: Read + ?Sized> Read for &mut R`)
I omitted things that seemed like they could be more controversial, like the handful of iterators that have a `Item: 'static` despite the iterator having a lifetime or the `PartialEq` implementations where the flipped one cannot elide the lifetime.
split MaybeUninit into several features, expand docs a bit
This splits the `maybe_uninit` feature gate into several:
* `maybe_uninit` for what we will hopefully stabilize soon-ish.
* `maybe_uninit_ref` for creating references into `MaybeUninit`, for which the rules are not yet clear.
* `maybe_uninit_slice` for handling slices of `MaybeUninit`, which needs more API design work.
* `maybe_uninit_array` for creating arrays of `MaybeUninit` using a macro (because we don't have https://github.com/rust-lang/rust/issues/49147 yet).
Is that an okay thing to do? The goal is to help people avoid APIs we do not want to stabilize yet. I used this to make sure rustc itself does not use `get_ref` and `get_mut`.
I also extended the docs to advise against uninitialized integers -- again this is something for which the rules are still being discussed.
Stabilize slice_sort_by_cached_key
I was going to ask on the tracking issue (https://github.com/rust-lang/rust/issues/34447), but decided to just send this and hope for an FCP here. The method was added last March by https://github.com/rust-lang/rust/pull/48639.
Signature: https://doc.rust-lang.org/std/primitive.slice.html#method.sort_by_cached_key
```rust
impl [T] {
pub fn sort_by_cached_key<K, F>(&mut self, f: F)
where F: FnMut(&T) -> K, K: Ord;
}
```
That's an identical signature to the existing `sort_by_key`, so I think the questions are just naming, implementation, and the usual "do we want this?".
The implementation seems to have proven its use in rustc at least, which many uses: https://github.com/rust-lang/rust/search?l=Rust&q=sort_by_cached_key
(I'm asking because it's exactly what I just needed the other day:
```rust
all_positions.sort_by_cached_key(|&n|
data::CITIES.iter()
.map(|x| *metric_closure.get_edge(n, x.pos).unwrap())
.sum::<usize>()
);
```
since caching that key is a pretty obviously good idea.)
Closes#34447
Update the future/task API
This change updates the future and task API as discussed in the stabilization RFC at https://github.com/rust-lang/rfcs/pull/2592.
Changes:
- Replacing UnsafeWake with RawWaker and RawWakerVtable
- Removal of LocalWaker
- Removal of Arc-based Wake trait
fix str mutating through a ptr derived from &self
Found by Miri: In `get_unchecked_mut` (also used by the checked variants internally) uses `str::as_ptr` to create a mutable reference, but `as_ptr` takes `&self`. This means the mutable references we return here got created from a shared reference, which violates the shared-references-are-read-only discipline!
For this by using a newly introduced `as_mut_ptr` instead.
Speed up the fast path for assert_eq! and assert_ne!
Currently, the panic!() calls directly borrow the value bindings. This
causes those bindings to always be initialized, i.e. they're initialized
even before the values are even compared. This causes noticeable
overhead in what should be a really cheap operation.
By performing a reborrow of the value in the call to panic!(), we allow
LLVM to optimize that code, so that the extra borrow only happens in the
error case.
We could achieve the same result by dereferencing the values passed to
panic!(), as the format machinery borrows them anyway, but this causes
assertions to fail to compile if one of the values is unsized, i.e. it
would be a breaking change.
Cosmetic improvements to doc comments
This has been factored out from https://github.com/rust-lang/rust/pull/58036 to only include changes to documentation comments (throughout the rustc codebase).
r? @steveklabnik
Once you're happy with this, maybe we could get it through with r=1, so it doesn't constantly get invalidated? (I'm not sure this will be an issue, but just in case...) Anyway, thanks for your advice so far!
Require a list of features in `#[allow_internal_unstable]`
The blanket-permission slip is not great and will likely give us trouble some point down the road.
