Add slice::remainder
This adds a remainder function to the Slice iterator, so that a caller can access unused
elements if iteration stops.
Addresses #91733
Make some `usize`-typed masks definitions agnostic to the size of `usize`
Some masks where defined as
```rust
const NONASCII_MASK: usize = 0x80808080_80808080u64 as usize;
```
where it was assumed that `usize` is never wider than 64, which is currently true.
To make those constants valid in a hypothetical 128-bit target, these constants have been redefined in an `usize`-width-agnostic way
```rust
const NONASCII_MASK: usize = usize::from_ne_bytes([0x80; size_of::<usize>()]);
```
There are already some cases where Rust anticipates the possibility of supporting 128-bit targets, such as not implementing `From<usize>` for `u64`.
docs: add link from zip to unzip
The docs for `Iterator::unzip` explain that it is kind of an inverse operation to `Iterator::zip` and guide the reader to the `zip` docs, but the `zip` docs don't let the user know that they can undo the `zip` operation with `unzip`. This change modifies the docs to help the user find `unzip`.
Create (unstable) 2024 edition
[On Zulip](https://rust-lang.zulipchat.com/#narrow/stream/213817-t-lang/topic/Deprecating.20macro.20scoping.20shenanigans/near/272860652), there was a small aside regarding creating the 2024 edition now as opposed to later. There was a reasonable amount of support and no stated opposition.
This change creates the 2024 edition in the compiler and creates a prelude for the 2024 edition. There is no current difference between the 2021 and 2024 editions. Cargo and other tools will need to be updated separately, as it's not in the same repository. This change permits the vast majority of work towards the next edition to proceed _now_ instead of waiting until 2024.
For sanity purposes, I've merged the "hello" UI tests into a single file with multiple revisions. Otherwise we'd end up with a file per edition, despite them being essentially identical.
````@rustbot```` label +T-lang +S-waiting-on-review
Not sure on the relevant team, to be honest.
Stabilize `derive_default_enum`
This stabilizes `#![feature(derive_default_enum)]`, as proposed in [RFC 3107](https://github.com/rust-lang/rfcs/pull/3107) and tracked in #87517. In short, it permits you to `#[derive(Default)]` on `enum`s, indicating what the default should be by placing a `#[default]` attribute on the desired variant (which must be a unit variant in the interest of forward compatibility).
```````@rustbot``````` label +S-waiting-on-review +T-lang
Some masks where defined as
```rust
const NONASCII_MASK: usize = 0x80808080_80808080u64 as usize;
```
where it was assumed that `usize` is never wider than 64, which is currently true.
To make those constants valid in a hypothetical 128-bit target, these constants have been redefined in an `usize`-width-agnostic way
```rust
const NONASCII_MASK: usize = usize::from_ne_bytes([0x80; size_of::<usize>()]);
```
There are already some cases where Rust anticipates the possibility of supporting 128-bit targets, such as not implementing `From<usize>` for `u64`.
The docs for `Iterator::unzip` explain that it is kind of an inverse operation to `Iterator::zip` and guide the reader to the `zip` docs, but the `zip` docs don't let the user know that they can undo the `zip` operation with `unzip`. This change modifies the docs to help the user find `unzip`.
Implement tuples using recursion
Because it is c00l3r™, requires less repetition and can be used as a reference for external people.
This change is non-essential and I am not sure about potential performance impacts so feel free to close this PR if desired.
r? `@petrochenkov`
Faster parsing for lower numbers for radix up to 16 (cont.)
( Continuation of https://github.com/rust-lang/rust/pull/83371 )
With LingMan's change I think this is potentially ready.
Clarify str::from_utf8_unchecked's invariants
Specifically, make it clear that it is immediately UB to pass ill-formed UTF-8 into the function. The previous wording left space to interpret that the UB only occurred when calling another function, which "assumes that `&str`s are valid UTF-8."
This does not change whether str being UTF-8 is a safety or a validity invariant. (As per previous discussion, it is a safety invariant, not a validity invariant.) It just makes it clear that valid UTF-8 is a precondition of str::from_utf8_unchecked, and that emitting an Abstract Machine fault (e.g. UB or a sanitizer error) on invalid UTF-8 is a valid thing to do.
If user code wants to create an unsafe `&str` pointing to ill-formed UTF-8, it must be done via transmutes. Also, just, don't.
Zulip discussion: https://rust-lang.zulipchat.com/#narrow/stream/136281-t-lang.2Fwg-unsafe-code-guidelines/topic/str.3A.3Afrom_utf8_unchecked.20Safety.20requirement
Update binary_search example to instead redirect to partition_point
Inspired by discussion in the tracking issue for `Result::into_ok_or_err`: https://github.com/rust-lang/rust/issues/82223#issuecomment-1067098167
People are surprised by us not providing a `Result<T, T> -> T` conversion, and the main culprit for this confusion seems to be the `binary_search` API. We should instead redirect people to the equivalent API that implicitly does that `Result<T, T> -> T` conversion internally which should obviate the need for the `into_ok_or_err` function and give us time to work towards a more general solution that applies to all enums rather than just `Result` such as making or_patterns usable for situations like this via postfix `match`.
I choose to duplicate the example rather than simply moving it from `binary_search` to partition point because most of the confusion seems to arise when people are looking at `binary_search`. It makes sense to me to have the example presented immediately rather than requiring people to click through to even realize there is an example. If I had to put it in only one place I'd leave it in `binary_search` and remove it from `partition_point` but it seems pretty obviously relevant to `partition_point` so I figured the best option would be to duplicate it.
Specifically, make it clear that it is immediately UB to pass ill-formed UTF-8 into the function. The previous wording left space to interpret that the UB only occurred when calling another function, which "assumes that `&str`s are valid UTF-8."
This does not change whether str being UTF-8 is a safety or a validity invariant. (As per previous discussion, it is a safety invariant, not a validity invariant.) It just makes it clear that valid UTF-8 is a precondition of str::from_utf8_unchecked, and that emitting an Abstract Machine fault (e.g. UB or a sanitizer error) on invalid UTF-8 is a valid thing to do.
If user code wants to create an unsafe `&str` pointing to ill-formed UTF-8, it must be done via transmutes. Also, just, don't.
Avoid duplication of doc comments in `std::char` constants and functions
For those consts and functions, only the summary is kept and a reference to the `char` associated const/method is included.
Additionaly, re-exported functions have been converted to function definitions that call the previously re-exported function. This makes it easier to add a deprecated attribute to these functions in the future.
Use bitwise XOR in to_ascii_uppercase
This saves an instruction compared to the previous approach, which
was to unset the fifth bit with bitwise OR.
Comparison of generated assembly on x86: https://godbolt.org/z/GdfvdGs39
This can also affect autovectorization, saving SIMD instructions as well: https://godbolt.org/z/cnPcz75T9
Not sure if `u8::to_ascii_lowercase` should also be changed, since using bitwise OR for that function does not require an extra bitwise negate since the code is setting a bit rather than unsetting a bit. `char::to_ascii_uppercase` already uses XOR, so no change seems to be required there.
Left overs of #95761
These are just nits. Feel free to close this PR if all modifications are not worth merging.
* `#![feature(decl_macro)]` is not needed anymore in `rustc_expand`
* `tuple_impls` does not require `$Tuple:ident`. I guess it is there to enhance readability?
r? ```@petrochenkov```
Make non-power-of-two alignments a validity error in `Layout`
Inspired by the zulip conversation about how `Layout` should better enforce `size <= isize::MAX as usize`, this uses an N-variant enum on N-bit platforms to require at the validity level that the existing invariant of "must be a power of two" is upheld.
This was MIRI can catch it, and means there's a more-specific type for `Layout` to store than just `NonZeroUsize`.
It's left as `pub(crate)` here; a future PR could consider giving it a tracking issue for non-internal usage.
Inspired by the zulip conversation about how `Layout` should better enforce `size < isize::MAX as usize`, this uses an N-variant enum on N-bit platforms to require at the validity level that the existing invariant of "must be a power of two" is upheld.
This was MIRI can catch it, and means there's a more-specific type for `Layout` to store than just `NonZeroUsize`.
