Mention "null pointer optimization" in option docs.
I had seen people discuss "null pointer optimization," but when I tried to find official documentation (using Google), the `std::option` page didn't show up, because it doesn't use that term. Hopefully adding the term will help others find it in the future.
Revert "Auto merge of #83770 - the8472:tra-extend, r=Mark-Simulacrum"
Due to a performance regression that didn't show up in the original perf run
this reverts commit 9111b8ae97 (#83770), reversing
changes made to 9a700d2947.
Since since is expected to have the inverse impact it should probably be rollup=never.
r? `@Mark-Simulacrum`
Make `Step` trait safe to implement
This PR makes a few modifications to the `Step` trait that I believe better position it for stabilization in the short term. In particular,
1. `unsafe trait TrustedStep` is introduced, indicating that the implementation of `Step` for a given type upholds all stated invariants (which have remained unchanged). This is gated behind a new `trusted_step` feature, as stabilization is realistically blocked on min_specialization.
2. The `Step` trait is internally specialized on the `TrustedStep` trait, which avoids a serious performance regression.
3. `TrustedLen` is implemented for `T: TrustedStep` as the latter's invariants subsume the former's.
4. The `Step` trait is no longer `unsafe`, as the invariants must not be relied upon by unsafe code (unless the type implements `TrustedStep`).
5. `TrustedStep` is implemented for all types that implement `Step` in the standard library and compiler.
6. The `step_trait_ext` feature is merged into the `step_trait` feature. I was unable to find any reasoning for the features being split; the `_unchecked` methods need not necessarily be stabilized at the same time, but I think it is useful to have them under the same feature flag.
All existing implementations of `Step` will be broken, as it is not possible to `unsafe impl` a safe trait. Given this trait only exists on nightly, I feel this breakage is acceptable. The blanket `impl<T: Step> TrustedLen for T` will likely cause some minor breakage, but this should be covered by the equivalent impl for `TrustedStep`.
Hopefully these changes are sufficient to place `Step` in decent position for stabilization, which would allow user-defined types to be used with `a..b` syntax.
Mention workaround for floats in Iterator::{min, max}
`Iterator::{min, max}` can't be used with iterators of floats due to NaN issues. This suggests a workaround in the documentation of those functions.
Remove Iterator #[rustc_on_unimplemented]s that no longer apply.
Now that `IntoIterator` is implemented for arrays, all the `rustc_on_unimplemented` for arrays of ranges (e.g. `for _ in [1..3] {}`) no longer apply, since they are now valid Rust.
Separated these from #85670, because we should discuss a potential new (clippy?) lint for these.
Until Rust 1.52, `for _ in [1..3] {}` produced:
```
error[E0277]: `[std::ops::Range<{integer}>; 1]` is not an iterator
--> src/main.rs:2:14
|
2 | for _ in [1..3] {}
| ^^^^^^ if you meant to iterate between two values, remove the square brackets
|
= help: the trait `std::iter::Iterator` is not implemented for `[std::ops::Range<{integer}>; 1]`
= note: `[start..end]` is an array of one `Range`; you might have meant to have a `Range` without the brackets: `start..end`
= note: required by `std::iter::IntoIterator::into_iter`
```
But in Rust 1.53 and later, it compiles fine. It iterates over the array by value, for one iteration with the element `1..3`.
This is probably a mistake, which is no longer caught. Should we have a lint for it? Should Clippy have a lint for it?
cc ```@estebank``` ```@flip1995```
cc https://github.com/rust-lang/rust/issues/84513
While stdlib implementations of the unchecked methods require unchecked
math, there is no reason to gate it behind this for external users. The
reasoning for a separate `step_trait_ext` feature is unclear, and as
such has been merged as well.
Add `TrustedRandomAccess` specialization for `Vec::extend()`
This should do roughly the same as the `TrustedLen` specialization but result in less IR by using `__iterator_get_unchecked`
instead of `Iterator::for_each`
Conflicting specializations are manually prioritized by grouping them under yet another helper trait.
Fix typo in core::array::IntoIter comment
Saw a small typo reading some internal comments and decided to just throw this up to fix it for future readers.
Remove num_as_ne_bytes feature
From the discussion in #76976, it is determined that eventual results of the safe transmute work as a more general mechanism will let these conversions happen in safe code without needing specialized methods.
Merging this PR closes#76976 and resolves#64464. Several T-libs members have raised their opinion that it doesn't pull its weight as a standalone method, and so we should not track it as a specific thing to add.
fix `matches!` and `assert_matches!` on edition 2021
Previously this code failed to compile on edition 2021. [(Playground)](https://play.rust-lang.org/?version=nightly&mode=debug&edition=2021&gist=53960f2f051f641777b9e458da747707)
```rust
fn main() {
matches!((), ());
}
```
```
Compiling playground v0.0.1 (/playground)
error: `$pattern:pat` may be followed by `|`, which is not allowed for `pat` fragments
|
= note: allowed there are: `=>`, `,`, `=`, `if` or `in`
error: aborting due to previous error
error: could not compile `playground`
To learn more, run the command again with --verbose.
```
Demote `ControlFlow::{from|into}_try` to `pub(crate)`
They have mediocre names and non-obvious semantics, so personally I don't think they're worth trying to stabilize, and thus might as well just be internal (they're used for convenience in iterator adapters), not something shown in the rustdocs.
I don't think anyone actually wanted to use them outside `core` -- they just got made public-but-unstable along with the whole type in https://github.com/rust-lang/rust/pull/76204 that promoted `LoopState` from an internal type to the exposed `ControlFlow` type.
cc https://github.com/rust-lang/rust/issues/75744, the tracking issue they mention.
cc https://github.com/rust-lang/rust/pull/85608, the PR where I'm proposing stabilizing the type.
Fix pointer provenance in <[T]>::copy_within
Previously the `self.as_mut_ptr()` invalidated the pointer created by the first `self.as_ptr()`. This also triggered miri when run with `-Zmiri-track-raw-pointers`
Better English for documenting when to use unimplemented!()
I don't think "plan of using" is correct here. I considered "plan on using" but eventually decided "plan to use" is better.
Bump bootstrap compiler to beta 1.53.0
This PR bumps the bootstrap compiler to version 1.53.0 beta, as part of our usual release process (this was supposed to be Wednesday's step, but creating the beta release took longer than expected).
The PR also includes the "Bootstrap: skip rustdoc fingerprint for building docs" commit, see the reasoning [on Zulip](https://zulip-archive.rust-lang.org/241545trelease/88450153betabootstrap.html).
r? `@Mark-Simulacrum`
Extend `rustc_on_implemented` to improve more `?` error messages
`_Self` could match the generic definition; this adds that functionality for matching the generic definition of type parameters too.
Your advice welcome on the wording of all these messages, and which things belong in the message/label/note.
r? `@estebank`
fix pad_integral example
pad_integral's parameter `is_nonnegative - whether the original integer was either positive or zero`, but in example it checked as `self.nb > 0`, so it previously printed `-0` for `format!("{}", Foo::new(0)`, what is wrong.
Extremely outdated; not only are traits implemented on arrays of arbitrary length, those implementations are documented on the primitive type, not in this module.
Rollup of 8 pull requests
Successful merges:
- #84717 (impl FromStr for proc_macro::Literal)
- #85169 (Add method-toggle to <details> for methods)
- #85287 (Expose `Concurrent` (private type in public i'face))
- #85315 (adding time complexity for partition_in_place iter method)
- #85439 (Add diagnostic item to `CStr`)
- #85464 (Fix UB in documented example for `ptr::swap`)
- #85470 (Fix invalid CSS rules for a:hover)
- #85472 (CTFE Machine: do not expose Allocation)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
Avoid zero-length memcpy in formatting
This has two separate and somewhat orthogonal commits. The first change adjusts the ToString general impl for all types that implement Display; it no longer uses the full format machinery, rather directly falling onto a `std::fmt::Display::fmt` call. The second change directly adjusts the general core::fmt::write function which handles the production of format_args! to avoid zero-length push_str calls.
Both changes target the fact that push_str will still call memmove internally (or a similar function), as it doesn't know the length of the passed string. For zero-length strings in particular, this is quite expensive, and even for very short (several bytes long) strings, this is also expensive. Future work in this area may wish to have us fallback to write_char or similar, which may be cheaper on the (typically) short strings between the interpolated pieces in format_args!.
adding time complexity for partition_in_place iter method
I feel that one thing missing from rust docs compared to cpp references is existence of time complexity for all methods and functions. While it would be humongous task to include it for everything in single go, it is still doable if we as community keep on adding it in relevant places as and when we find them.
This PR adds the time complexity for partition_in_place method in iter.
