Remove ~const from alloc
There is currently an effort underway to stop using `~const Trait`, temporarily, so as to refactor the logic underlying const traits with relative ease. This means it has to go from the standard library, as well.
I have taken the initial step of just removing these impls from alloc, as removing them from core is a much more tangled task. In addition, all of these implementations are one more-or-less logically-connected group, so reverting their deconstification as a group seems like it will also be sensible.
r? `@fee1-dead`
Change advance(_back)_by to return the remainder instead of the number of processed elements
When advance_by can't advance the iterator by the number of requested elements it now returns the amount by which it couldn't be advanced instead of the amount by which it did.
This simplifies adapters like chain, flatten or cycle because the remainder doesn't have to be calculated as the difference between requested steps and completed steps anymore.
Additionally switching from `Result<(), usize>` to `Result<(), NonZeroUsize>` reduces the size of the result and makes converting from/to a usize representing the number of remaining steps cheap.
A successful advance is now signalled by returning `0` and other values now represent the remaining number
of steps that couldn't be advanced as opposed to the amount of steps that have been advanced during a partial advance_by.
This simplifies adapters a bit, replacing some `match`/`if` with arithmetic. Whether this is beneficial overall depends
on whether `advance_by` is mostly used as a building-block for other iterator methods and adapters or whether
we also see uses by users where `Result` might be more useful.
Stabilize `nonnull_slice_from_raw_parts`
FCP is done: https://github.com/rust-lang/rust/issues/71941#issuecomment-1100910416
Note that this doesn't const-stabilize `NonNull::slice_from_raw_parts` as `slice_from_raw_parts_mut` isn't const-stabilized yet. Given #67456 and #57349, it's not likely available soon, meanwhile, stabilizing only the feature makes some sense, I think.
Closes#71941
Implement Default for some alloc/core iterators
Add `Default` impls to the following collection iterators:
* slice::{Iter, IterMut}
* binary_heap::IntoIter
* btree::map::{Iter, IterMut, Keys, Values, Range, IntoIter, IntoKeys, IntoValues}
* btree::set::{Iter, IntoIter, Range}
* linked_list::IntoIter
* vec::IntoIter
and these adapters:
* adapters::{Chain, Cloned, Copied, Rev, Enumerate, Flatten, Fuse, Rev}
For iterators which are generic over allocators it only implements it for the global allocator because we can't conjure an allocator from nothing or would have to turn the allocator field into an `Option` just for this change.
These changes will be insta-stable.
ACP: https://github.com/rust-lang/libs-team/issues/77
Remove the assume(!is_null) from Vec::as_ptr
At a guess, this code is leftover from LLVM was worse at keeping track of the niche information here. In any case, we don't need this anymore: Removing this `assume` doesn't get rid of the `nonnull` attribute on the return type.
Introduce `Rc::into_inner`, as a parallel to `Arc::into_inner`
Unlike `Arc`, `Rc` doesn't have the same race condition to avoid, but
maintaining an equivalent API still makes it easier to work with both
`Rc` and `Arc`.
Unlike `Arc`, `Rc` doesn't have the same race condition to avoid, but
maintaining an equivalent API still makes it easier to work with both
`Rc` and `Arc`.
Rollup of 9 pull requests
Successful merges:
- #104363 (Make `unused_allocation` lint against `Box::new` too)
- #106633 (Stabilize `nonzero_min_max`)
- #106844 (allow negative numeric literals in `concat!`)
- #108071 (Implement goal caching with the new solver)
- #108542 (Force parentheses around `match` expression in binary expression)
- #108690 (Place size limits on query keys and values)
- #108708 (Prevent overflow through Arc::downgrade)
- #108739 (Prevent the `start_bx` basic block in codegen from having two `Builder`s at the same time)
- #108806 (Querify register_tools and post-expansion early lints)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
Make `unused_allocation` lint against `Box::new` too
Previously it only linted against `box` syntax, which likely won't ever be stabilized, which is pretty useless. Even now I'm not sure if it's a meaningful lint, but it's at least something 🤷
This means that code like the following will be linted against:
```rust
Box::new([1, 2, 3]).len();
f(&Box::new(1)); // where f : &i32 -> ()
```
The lint works by checking if a `Box::new` (or `box`) expression has an a borrow adjustment, meaning that the code that first stores the box in a variable won't be linted against:
```rust
let boxed = Box::new([1, 2, 3]); // no lint
boxed.len();
```
Fix `vec_deque::Drain` FIXME
In my original `VecDeque` rewrite, I didn't use `VecDeque::slice_ranges` in `Drain::as_slices`, even though that's basically the exact use case for `slice_ranges`. The reason for this was that a `VecDeque` wrapped in a `Drain` actually has its length set to `drain_start`, so that there's no potential use after free if you `mem::forget` the `Drain`. I modified `slice_ranges` to accept an explicit `len` parameter instead, which it now uses to bounds check the given range. This way, `Drain::as_slices` can use `slice_ranges` internally instead of having to basically just copy paste the `slice_ranges` code. Since `slice_ranges` is just an internal helper function, this shouldn't change the user facing behavior in any way.
Remove or document uses of #[rustc_box] in library
r? `@thomcc`
Only one of these uses is tested for in the rustc-perf benchmark suite. The impact there on compile time is somewhat dramatic, but I am inclined to make this change as a simplification to the library and wait for people to complain if it explodes their compilation time. I think in the absence of data or reports from users about what code paths really matter, if we are optimizing for compilation time, it's hard to argue against using `#[rustc_box]` everywhere we currently call `Box::new`.
This adds both a test specific to #108453 as well as an exhaustive test
that goes through all possible combinations of head index, length and target capacity
for a deque with capacity 16.
Implement more methods for `vec_deque::IntoIter`
This implements a couple `Iterator` methods on `vec_deque::IntoIter` (`(try_)fold`, `(try_)rfold` `advance_(back_)by`, `next_chunk`, `count` and `last`) to allow these to be more efficient than their default implementations, also allowing many other `Iterator` methods that use these under the hood to take advantage of these manual implementations. `vec::IntoIter` has similar implementations for many of these methods. This PR does not yet implement `TrustedRandomAccess` and friends, as I'm not very familiar with the required safety guarantees.
r? `@the8472` (since you also took over my last PR)
Use associated items of `char` instead of freestanding items in `core::char`
The associated functions and constants on `char` have been stable since 1.52 and the freestanding items have soft-deprecated since 1.62 (https://github.com/rust-lang/rust/pull/95566). This PR ~~marks them as "deprecated in future", similar to the integer and floating point modules (`core::{i32, f32}` etc)~~ replaces all uses of `core::char::*` with `char::*` to prepare for future deprecation of `core::char::*`.
simplify layout calculations in rawvec
The use of `Layout::array` was introduced in #83706 which lead to a [perf regression](https://github.com/rust-lang/rust/pull/83706#issuecomment-1048377719).
This PR basically reverts that change since rust currently only supports stride == size types, but to be on the safe side it leaves a const-assert there to make sure this gets caught if those assumptions ever change.
Stabilize feature `cstr_from_bytes_until_nul`
This PR seeks to stabilize `cstr_from_bytes_until_nul`.
Partially addresses #95027
This function has only been on nightly for about 10 months, but I think it is simple enough that there isn't harm discussing stabilization. It has also had at least a handful of mentions on both the user forum and the discord, so it seems like it's already in use or at least known.
This needs FCP still.
Comment on potential discussion points:
- eventual conversion of `CStr` to be a single thin pointer: this function will still be useful to provide a safe way to create a `CStr` after this change.
- should this return a length too, to address concerns about the `CStr` change? I don't see it as being particularly useful, and it seems less ergonomic (i.e. returning `Result<(&CStr, usize), FromBytesUntilNulError>`). I think users that also need this length without the additional `strlen` call are likely better off using a combination of other methods, but this is up for discussion
- `CString::from_vec_until_nul`: this is also useful, but it doesn't even have a nightly implementation merged yet. I propose feature gating that separately, as opposed to blocking this `CStr` implementation on that
Possible alternatives:
A user can use `from_bytes_with_nul` on a slice up to `my_slice[..my_slice.iter().find(|c| c == 0).unwrap()]`. However; that is significantly less ergonomic, and is a bit more work for the compiler to optimize compared the direct `memchr` call that this wraps.
## New stable API
```rs
// both in core::ffi
pub struct FromBytesUntilNulError(());
impl CStr {
pub const fn from_bytes_until_nul(
bytes: &[u8]
) -> Result<&CStr, FromBytesUntilNulError>
}
```
cc ```@ericseppanen``` original author, ```@Mark-Simulacrum``` original reviewer, ```@m-ou-se``` brought up some issues on the thin pointer CStr
```@rustbot``` modify labels: +T-libs-api +needs-fcp
