| Age | Commit message (Collapse) | Author | Lines |
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Make `Default` const and add some `const Default` impls
Full list of `impl const Default` types:
- ()
- bool
- char
- std::ascii::Char
- usize
- u8
- u16
- u32
- u64
- u128
- i8
- i16
- i32
- i64
- i128
- f16
- f32
- f64
- f128
- std::marker::PhantomData<T>
- Option<T>
- std::iter::Empty<T>
- std::ptr::Alignment
- &[T]
- &mut [T]
- &str
- &mut str
- String
- Vec<T>
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Fix in std::String docs
This PR removes the word “else” from the sentence ('something else similar') in the String documentation to improve clarity.
Fixes rust-lang/rust#143579.
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Full list of `impl const Default` types:
- ()
- bool
- char
- Cell
- std::ascii::Char
- usize
- u8
- u16
- u32
- u64
- u128
- i8
- i16
- i32
- i64
- i128
- f16
- f32
- f64
- f128
- std::marker::PhantomData<T>
- Option<T>
- std::iter::Empty<T>
- std::ptr::Alignment
- &[T]
- &mut [T]
- &str
- &mut str
- String
- Vec<T>
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Let String pass #[track_caller] to its Vec calls
I've added `#[track_caller]` to `String` methods that delegate to `Vec` methods that already have `#[track_caller]`.
I've also added `#[track_caller]` to methods that have `assert!` or `panic!` due to invalid inputs.
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r=tgross35
Use a distinct `ToString` implementation for `u128` and `i128`
Part of https://github.com/rust-lang/rust/issues/135543.
Follow-up of rust-lang/rust#136264.
When working on https://github.com/rust-lang/rust/pull/142098, I realized that `i128` and `u128` could also benefit from a distinct `ToString` implementation so here it.
The last commit is just me realizing that I forgot to add the format tests for `usize` and `isize`.
Here is the bench comparison:
| bench name | last nightly | with this PR | diff |
|-|-|-|-|
| bench_i128 | 29.25 ns/iter (+/- 0.66) | 17.52 ns/iter (+/- 0.7) | -40.1% |
| bench_u128 | 34.06 ns/iter (+/- 0.21) | 16.1 ns/iter (+/- 0.6) | -52.7% |
I used this code to test:
```rust
#![feature(test)]
extern crate test;
use test::{Bencher, black_box};
#[inline(always)]
fn convert_to_string<T: ToString>(n: T) -> String {
n.to_string()
}
macro_rules! decl_benches {
($($name:ident: $ty:ident,)+) => {
$(
#[bench]
fn $name(c: &mut Bencher) {
c.iter(|| convert_to_string(black_box({ let nb: $ty = 20; nb })));
}
)+
}
}
decl_benches! {
bench_u128: u128,
bench_i128: i128,
}
```
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Optimize `ToString` implementation for integers
Part of https://github.com/rust-lang/rust/issues/135543.
Follow-up of https://github.com/rust-lang/rust/pull/133247 and https://github.com/rust-lang/rust/pull/128204.
The benchmark results are:
| name| 1.87.0-nightly (3ea711f17 2025-03-09) | With this PR | diff |
|-|-|-|-|
| bench_i16 | 32.06 ns/iter (+/- 0.12) | 17.62 ns/iter (+/- 0.03) | -45% |
| bench_i32 | 31.61 ns/iter (+/- 0.04) | 15.10 ns/iter (+/- 0.06) | -52% |
| bench_i64 | 31.71 ns/iter (+/- 0.07) | 15.02 ns/iter (+/- 0.20) | -52% |
| bench_i8 | 13.21 ns/iter (+/- 0.14) | 14.93 ns/iter (+/- 0.16) | +13% |
| bench_u16 | 31.20 ns/iter (+/- 0.06) | 16.14 ns/iter (+/- 0.11) | -48% |
| bench_u32 | 33.27 ns/iter (+/- 0.05) | 16.18 ns/iter (+/- 0.10) | -51% |
| bench_u64 | 31.44 ns/iter (+/- 0.06) | 16.62 ns/iter (+/- 0.21) | -47% |
| bench_u8 | 10.57 ns/iter (+/- 0.30) | 13.00 ns/iter (+/- 0.43) | +22% |
More information about it in [the original comment](https://github.com/rust-lang/rust/pull/136264#discussion_r1987542954).
r? `@workingjubilee`
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Bump boostrap compiler to new beta
try-job: `*msvc*`
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Improve performance of `String` methods by avoiding unnecessary memcpy
for the character bytes, with added codegen check to ensure compliance.
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This feature was approved for stabilization in
https://github.com/rust-lang/rust/issues/129041#issuecomment-2508940661
so this change stabilizes it.
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For the tests that make use of internal implementation details, we
include the module to test using #[path] in alloctests now.
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library: Use `size_of` from the prelude instead of imported
Use `std::mem::{size_of, size_of_val, align_of, align_of_val}` from the prelude instead of importing or qualifying them.
These functions were added to all preludes in Rust 1.80.
try-job: test-various
try-job: x86_64-gnu
try-job: x86_64-msvc-1
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Use `std::mem::{size_of, size_of_val, align_of, align_of_val}` from the
prelude instead of importing or qualifying them.
These functions were added to all preludes in Rust 1.80.
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Stabilize `string_extend_from_within`
FCP'd here: https://github.com/rust-lang/rust/issues/103806#issuecomment-2674989531.
Closes #103806.
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Update `String::from_raw_parts` safety requirements
These have become out of sync with `Vec::from_raw_part`'s safety requirements, and are likely to diverge again. I think it's safest to just point at `Vec`'s requirements.
https://github.com/rust-lang/rust/issues/119206#issuecomment-2180116680
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Co-authored-by: Amanieu d'Antras <amanieu@gmail.com>
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Impl TryFrom<Vec<u8>> for String
I think this is useful enough to have :)
As a general question, is there any policy around adding "missing" trait implementations? (like adding `AsRef<T> for T` for std types), I mostly stumble upon them when using a lot of "impl Trait in argument position" like (`foo: impl Into<String>`)
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Add `MAX_LEN_UTF8` and `MAX_LEN_UTF16` Constants
This pull request adds the `MAX_LEN_UTF8` and `MAX_LEN_UTF16` constants as per #45795, gated behind the `char_max_len` feature.
The constants are currently applied in the `alloc`, `core` and `std` libraries.
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Signed-off-by: tison <wander4096@gmail.com>
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This is the only trait specializable outside of the standard library.
Before stabilizing specialization we will probably want to remove
support for this. It was originally made specializable to allow a more
efficient ToString in libproc_macro back when this way the only way to
get any data out of a TokenStream. We now support getting individual
tokens, so proc macros no longer need to call it as often.
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This allows to build custom `std::Formatter`s at runtime.
Also added some related enums and two related methods on `std::Formatter`.
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optimize str.replace
Adds a fast path for str.replace for the ascii to ascii case. This allows for autovectorizing the code. Also should this instead be done with specialization? This way we could remove one branch. I think it is the kind of branch that is easy to predict though.
Benchmark for the fast path (replace all "a" with "b" in the rust wikipedia article, using criterion) :
| N | Speedup | Time New (ns) | Time Old (ns) |
|----------|---------|---------------|---------------|
| 2 | 2.03 | 13.567 | 27.576 |
| 8 | 1.73 | 17.478 | 30.259 |
| 11 | 2.46 | 18.296 | 45.055 |
| 16 | 2.71 | 17.181 | 46.526 |
| 37 | 4.43 | 18.526 | 81.997 |
| 64 | 8.54 | 18.670 | 159.470 |
| 200 | 9.82 | 29.634 | 291.010 |
| 2000 | 24.34 | 81.114 | 1974.300 |
| 20000 | 30.61 | 598.520 | 18318.000 |
| 1000000 | 29.31 | 33458.000 | 980540.000 |
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liballoc: introduce String, Vec const-slicing
This change `const`-qualifies many methods on `Vec` and `String`, notably `as_slice`, `as_str`, `len`. These changes are made behind the unstable feature flag `const_vec_string_slice`.
## Motivation
This is to support simultaneous variance over ownership and constness. I have an enum type that may contain either `String` or `&str`, and I want to produce a `&str` from it in a possibly-`const` context.
```rust
enum StrOrString<'s> {
Str(&'s str),
String(String),
}
impl<'s> StrOrString<'s> {
const fn as_str(&self) -> &str {
match self {
// In a const-context, I really only expect to see this variant, but I can't switch the implementation
// in some mode like #[cfg(const)] -- there has to be a single body
Self::Str(s) => s,
// so this is a problem, since it's not `const`
Self::String(s) => s.as_str(),
}
}
}
```
Currently `String` and `Vec` don't support this, but can without functional changes. Similar logic applies for `len`, `capacity`, `is_empty`.
## Changes
The essential thing enabling this change is that `Unique::as_ptr` is `const`. This lets us convert `RawVec::ptr` -> `Vec::as_ptr` -> `Vec::as_slice` -> `String::as_str`.
I had to move the `Deref` implementations into `as_{str,slice}` because `Deref` isn't `#[const_trait]`, but I would expect this change to be invisible up to inlining. I moved the `DerefMut` implementations as well for uniformity.
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This change `const`-qualifies many methods on Vec and String, notably
`as_slice`, `as_str`, `len`. These changes are made behind the unstable
feature flag `const_vec_string_slice` with the following tracking issue:
https://github.com/rust-lang/rust/issues/129041
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Avoid re-validating UTF-8 in `FromUtf8Error::into_utf8_lossy`
Part of the unstable feature `string_from_utf8_lossy_owned` - #129436
Refactor `FromUtf8Error::into_utf8_lossy` to copy valid UTF-8 bytes into the buffer, avoiding double validation of bytes.
Add tests that mirror the `String::from_utf8_lossy` tests.
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Refactor `into_utf8_lossy` to copy valid UTF-8 bytes into the buffer,
avoiding double validation of bytes.
Add tests that mirror the `String::from_utf8_lossy` tests
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instead of path
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items instead of paths
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