rust_2015 and rust_2018 are just re-exports of v1.
rust_2021 is a module that for now just re-exports everything from v1,
such that we can add more things later.
Expand FlattenCompat folds
The former `chain`+`chain`+`fold` implementation looked nice from a
functional-programming perspective, but it introduced unnecessary layers
of abstraction on every `flat_map`/`flatten` fold. It's straightforward
to just fold each part in turn, and this makes it look like a simplified
version of the existing `try_fold` implementation.
For the `iter::bench_flat_map*` benchmarks, I get a large improvement in
`bench_flat_map_chain_sum`, from 1,598,473 ns/iter to 499,889 ns/iter,
and the rest are unchanged.
`escape_unicode`, `escape_default`, `len_utf8`, `len_utf16`, to_ascii_lowercase`, `eq_ignore_ascii_case`
`u8` methods `to_ascii_lowercase`, `to_ascii_uppercase` also must be made const
u8 methods made const
Update methods.rs
Update mod.rs
Update methods.rs
Fix `since` in rustc_const_stable to next stable
Fix `since` in rustc_const_stable to next stable
Update methods.rs
Update mod.rs
Update the bootstrap compiler
This updates the bootstrap compiler, notably leaving out a change to enable semicolon in macro expressions lint, because stdarch still depends on the old behavior.
- Link from `core::hash` to `HashMap` and `HashSet`
- Link from HashMap and HashSet to the module-level documentation on
when to use the collection
- Link from several collections to Wikipedia articles on the general
concept
Slight perf improvement on char::to_ascii_lowercase
`char::to_ascii_lowercase()` was checking if it was ascii and then if it was in the right range. Instead propose to check once (I think removing a compare and a shift in the process: [godbolt](https://godbolt.org/z/e5Tora) ).
before:
```
test char::methods::bench_to_ascii_lowercase ... bench: 11,196 ns/iter (+/- 632)
test char::methods::bench_to_ascii_uppercase ... bench: 11,656 ns/iter (+/- 671)
```
after:
```
test char::methods::bench_to_ascii_lowercase ... bench: 9,612 ns/iter (+/- 979)
test char::methods::bench_to_ascii_uppercase ... bench: 8,241 ns/iter (+/- 701)
```
(calling u8::to_ascii_lowercase and letting that flip the 5th bit is also an option, but it's more instructions. I'm thinking for things around ascii and char we want to be as efficient as possible.)
Improve design of `assert_len`
It was discussed in the [tracking issue](https://github.com/rust-lang/rust/issues/76393#issuecomment-761765448) that `assert_len`'s name and usage are confusing. This PR improves them based on a suggestion by ``@scottmcm`` in that issue.
I also improved the documentation to make it clearer when you might want to use this method.
Old example:
```rust
let range = range.assert_len(slice.len());
```
New example:
```rust
let range = range.ensure_subset_of(..slice.len());
```
Fixes#81157
improve UnsafeCell docs
Sometimes [questions like this come up](https://rust-lang.zulipchat.com/#narrow/stream/136281-t-lang.2Fwg-unsafe-code-guidelines/topic/UnsafeCells.20as.20raw.20pointers) because the UnsafeCell docs say "it's the only legal way to obtain aliasable data that is considered mutable". That is not entirely correct, since raw pointers also provide that option. So I propose we focus the docs on the interaction of `UnsafeCell` and *shared references* specifically, which is really where they are needed.
Add internal `collect_into_array[_unchecked]` to remove duplicate code
Unlike the similar PRs #69985, #75644 and #79659, this PR only adds private functions and does not propose any new public API. The change is just for the purpose of avoiding duplicate code.
Many array methods already contained the same kind of code and there are still many array related methods to come (e.g. `Iterator::{chunks, map_windows, next_n, ...}`, `[T; N]::{cloned, copied, ...}`, ...) which all basically need this functionality. Writing custom `unsafe` code for each of those doesn't seem like a good idea. I added two functions in this PR (and not just the `unsafe` version) because I already know that I need the `Option`-returning version for `Iterator::map_windows`.
This is closely related to https://github.com/rust-lang/rust/issues/81615. I think that all options listed in that issue can be implemented using the function added in this PR. The only instance where `collect_array_into` might not be general enough is when the caller want to handle incomplete arrays manually. Currently, if `iter` yields fewer than `N` items, `None` is returned and the already yielded items are dropped. But as this is just a private function, it can be made more general in future PRs.
And while this was not the goal, this seems to lead to better assembly for `array::map`: https://rust.godbolt.org/z/75qKTa (CC ``@JulianKnodt)``
Let me know what you think :)
CC ``@matklad`` ``@bstrie``
Improve assert_eq! and assert_ne!
This PR improves `assert_eq!` and `assert_ne!` by moving the panicking code in an external function.
It does not change the fast path, but the move of the formatting in the cold path (the panic) may have a positive effect on in instruction cache use and with inlining.
Moreover, the use of trait objects instead of generic may improve compile times for `assert_eq!`-heavy code.
Godbolt link: ~~https://rust.godbolt.org/z/TYa9MT~~ \
Updated: https://rust.godbolt.org/z/bzE84x
simplify eat_digits
Simplify eat_digits by checking values in iterator, plus decrease function size, by returning unchecked slices.
https://godbolt.org/z/cxjav4
Add tests for Atomic*::fetch_{min,max}
This ensures that all atomic operations except for fences are tested. This has been useful to test my work on using atomic instructions for atomic operations in cg_clif instead of a global lock.
Ensure valid TraitRefs are created for GATs
This fixes `ProjectionTy::trait_ref` to use the correct substs. Places that need all of the substs have been updated to not use `trait_ref`.
r? ````@jackh726````
Implement RFC 2580: Pointer metadata & VTable
RFC: https://github.com/rust-lang/rfcs/pull/2580
~~Before merging this PR:~~
* [x] Wait for the end of the RFC’s [FCP to merge](https://github.com/rust-lang/rfcs/pull/2580#issuecomment-759145278).
* [x] Open a tracking issue: https://github.com/rust-lang/rust/issues/81513
* [x] Update `#[unstable]` attributes in the PR with the tracking issue number
----
This PR extends the language with a new lang item for the `Pointee` trait which is special-cased in trait resolution to implement it for all types. Even in generic contexts, parameters can be assumed to implement it without a corresponding bound.
For this I mostly imitated what the compiler was already doing for the `DiscriminantKind` trait. I’m very unfamiliar with compiler internals, so careful review is appreciated.
This PR also extends the standard library with new unstable APIs in `core::ptr` and `std::ptr`:
```rust
pub trait Pointee {
/// One of `()`, `usize`, or `DynMetadata<dyn SomeTrait>`
type Metadata: Copy + Send + Sync + Ord + Hash + Unpin;
}
pub trait Thin = Pointee<Metadata = ()>;
pub const fn metadata<T: ?Sized>(ptr: *const T) -> <T as Pointee>::Metadata {}
pub const fn from_raw_parts<T: ?Sized>(*const (), <T as Pointee>::Metadata) -> *const T {}
pub const fn from_raw_parts_mut<T: ?Sized>(*mut (),<T as Pointee>::Metadata) -> *mut T {}
impl<T: ?Sized> NonNull<T> {
pub const fn from_raw_parts(NonNull<()>, <T as Pointee>::Metadata) -> NonNull<T> {}
/// Convenience for `(ptr.cast(), metadata(ptr))`
pub const fn to_raw_parts(self) -> (NonNull<()>, <T as Pointee>::Metadata) {}
}
impl<T: ?Sized> *const T {
pub const fn to_raw_parts(self) -> (*const (), <T as Pointee>::Metadata) {}
}
impl<T: ?Sized> *mut T {
pub const fn to_raw_parts(self) -> (*mut (), <T as Pointee>::Metadata) {}
}
/// `<dyn SomeTrait as Pointee>::Metadata == DynMetadata<dyn SomeTrait>`
pub struct DynMetadata<Dyn: ?Sized> {
// Private pointer to vtable
}
impl<Dyn: ?Sized> DynMetadata<Dyn> {
pub fn size_of(self) -> usize {}
pub fn align_of(self) -> usize {}
pub fn layout(self) -> crate::alloc::Layout {}
}
unsafe impl<Dyn: ?Sized> Send for DynMetadata<Dyn> {}
unsafe impl<Dyn: ?Sized> Sync for DynMetadata<Dyn> {}
impl<Dyn: ?Sized> Debug for DynMetadata<Dyn> {}
impl<Dyn: ?Sized> Unpin for DynMetadata<Dyn> {}
impl<Dyn: ?Sized> Copy for DynMetadata<Dyn> {}
impl<Dyn: ?Sized> Clone for DynMetadata<Dyn> {}
impl<Dyn: ?Sized> Eq for DynMetadata<Dyn> {}
impl<Dyn: ?Sized> PartialEq for DynMetadata<Dyn> {}
impl<Dyn: ?Sized> Ord for DynMetadata<Dyn> {}
impl<Dyn: ?Sized> PartialOrd for DynMetadata<Dyn> {}
impl<Dyn: ?Sized> Hash for DynMetadata<Dyn> {}
```
API differences from the RFC, in areas noted as unresolved questions in the RFC:
* Module-level functions instead of associated `from_raw_parts` functions on `*const T` and `*mut T`, following the precedent of `null`, `slice_from_raw_parts`, etc.
* Added `to_raw_parts`
Add a `Result::into_ok_or_err` method to extract a `T` from `Result<T, T>`
When updating code to handle the semi-recent deprecation of `compare_and_swap` in favor of `compare_exchange`, which returns `Result<T, T>`, I wanted this. I've also wanted it with code using `slice::binary_search` before.
The name (and perhaps the documentation) is the hardest part here, but this name seems consistent with the other Result methods, and equivalently memorable.
Document that `assert!` format arguments are evaluated lazily
It can be useful to do some computation in `assert!` format arguments, in order to get better error messages. For example:
```rust
assert!(
some_condition,
"The state is invalid. Details: {}",
expensive_call_to_get_debugging_info(),
);
```
It seems like `assert!` only evaluates the format arguments if the assertion fails, which is useful but doesn't appear to be documented anywhere. This PR documents the behavior and adds some tests.
To digit simplification
I found out the other day that all the ascii digits have the first four bits as one would hope them to. (Eg. char `2` ends `0b0010`). There are two bits to indicate it's in the digit range ( `0b0011_0000`). If it is a true digit then all the higher bits aside from these two will be 0 (as ascii is the lowest part of the unicode u32 spectrum). So XORing with `0b11_0000` should mean we either get the number 0-9 or alternativly we get a larger number in the u32 space. If we get something that's not 0-9 then it will be discarded as it will be greater than the radix.
The code seems so fast though that there's quite a lot of noise in the benchmarks so it's not that easy to prove conclusively that it's faster as well as less instructions.
The non-fast path I was toying with as well wondering if we could do this as then we'd only have one return and less instructions still:
```
match self {
'a'..='z' => self as u32 - 'a' as u32 + 10,
'A'..='Z' => self as u32 - 'A' as u32 + 10,
_ => { radix = 10; self as u32 ^ ASCII_DIGIT_MASK},
}
```
Here's the [godbolt](https://godbolt.org/z/883c9n).
( H/T to ``@byteshadow`` for pointing out xor was what I needed)
It can be useful to do some computation in `assert!` format arguments, in order to get better error messages. For example:
```rust
assert!(
some_condition,
"The state is invalid. Details: {}",
expensive_call_to_get_debugging_info(),
);
```
It seems like `assert!` only evaluates the format arguments if the assertion fails, which is useful but doesn't appear to be documented anywhere. This PR documents the behavior and adds some tests.
The former `chain`+`chain`+`fold` implementation looked nice from a
functional-programming perspective, but it introduced unnecessary layers
of abstraction on every `flat_map`/`flatten` fold. It's straightforward
to just fold each part in turn, and this makes it look like a simplified
version of the existing `try_fold` implementation.
For the `iter::bench_flat_map*` benchmarks, I get a large improvement in
`bench_flat_map_chain_sum`, from 1,598,473 ns/iter to 499,889 ns/iter,
and the rest are unchanged.
This does not suggest adding such a function to the public API. This is
just for the purpose of avoiding duplicate code. Many array methods
already contained the same kind of code and there are still many array
related methods to come (e.g. `Iterator::{chunks, map_windows, next_n,
...}`) which all basically need this functionality. Writing custom
`unsafe` code for each of those seems not like a good idea.
The `may_have_side_effect` is an implementation detail of `TrustedRandomAccess`
trait. It describes if obtaining an iterator element may have side effects. It
is currently implemented as an associated function.
Turn `may_have_side_effect` into an associated constant. This makes the
value immediately available to the optimizer.
The use of module-level functions instead of associated functions
on `<*const T>` or `<*mut T>` follows the precedent of
`ptr::slice_from_raw_parts` and `ptr::slice_from_raw_parts_mut`.
Increment `self.index` before calling `Iterator::self.a.__iterator_ge…
…`t_unchecked` in `Zip` `TrustedRandomAccess` specialization
Otherwise if `Iterator::self.a.__iterator_get_unchecked` panics the
index would not have been incremented yet and another call to
`Iterator::next` would read from the same index again, which is not
allowed according to the API contract of `TrustedRandomAccess` for
`!Clone`.
Fixes https://github.com/rust-lang/rust/issues/81740
Only split doctest lang strings on `,`, ` `, and `\t`. Additionally, to
preserve backwards compatibility with pandoc-style langstrings, strip a
surrounding `{}`, and remove leading `.`s from each token.
Prior to this change, doctest lang strings were split on all
non-alphanumeric characters except `-` or `_`, which limited future
extensions to doctest lang string tokens, for example using `=` for
key-value tokens.
This is a breaking change, although it is not expected to be disruptive,
because lang strings using separators other than `,` and ` ` are not
very common
Bump stabilization version for const int methods
These methods missed the beta cutoff. See #80962 for details.
`@rustbot` modify labels to +A-const-fn, +A-intrinsics
r? `@m-ou-se`
Expand the docs for ops::ControlFlow a bit
Since I was writing some examples for an RFC anyway.
And I almost made the mistake of reordering the variants, so added a note and a test about that.
Stabilize remaining integer methods as `const fn`
This pull request stabilizes the following methods as `const fn`:
- `i*::checked_div`
- `i*::checked_div_euclid`
- `i*::checked_rem`
- `i*::checked_rem_euclid`
- `i*::div_euclid`
- `i*::overflowing_div`
- `i*::overflowing_div_euclid`
- `i*::overflowing_rem`
- `i*::overflowing_rem_euclid`
- `i*::rem_euclid`
- `i*::wrapping_div`
- `i*::wrapping_div_euclid`
- `i*::wrapping_rem`
- `i*::wrapping_rem_euclid`
- `u*::checked_div`
- `u*::checked_div_euclid`
- `u*::checked_rem`
- `u*::checked_rem_euclid`
- `u*::div_euclid`
- `u*::overflowing_div`
- `u*::overflowing_div_euclid`
- `u*::overflowing_rem`
- `u*::overflowing_rem_euclid`
- `u*::rem_euclid`
- `u*::wrapping_div`
- `u*::wrapping_div_euclid`
- `u*::wrapping_rem`
- `u*::wrapping_rem_euclid`
These can all be implemented on the current stable (1.49). There are two unstable details: const likely/unlikely and unchecked division/remainder. Both of these are for optimizations, and are in no way required to make the methods function; there is no exposure of these details publicly. Per comments below, it seems best practice is to stabilize the intrinsics. As such, `intrinsics::unchecked_div` and `intrinsics::unchecked_rem` have been stabilized as `const` as part of this pull request as well. The methods themselves remain unstable.
I believe part of the reason these were not stabilized previously was the behavior around division by 0 and modulo 0. After testing on nightly, the diagnostic for something like `const _: i8 = 5i8 % 0i8;` is similar to that of `const _: i8 = 5i8.rem_euclid(0i8);` (assuming the appropriate feature flag is enabled). As such, I believe these methods are ready to be stabilized as `const fn`.
This pull request represents the final methods mentioned in #53718. As such, this PR closes#53718.
`@rustbot` modify labels to +A-const-fn, +T-libs
expand/resolve: Turn `#[derive]` into a regular macro attribute
This PR turns `#[derive]` into a regular attribute macro declared in libcore and defined in `rustc_builtin_macros`, like it was previously done with other "active" attributes in https://github.com/rust-lang/rust/pull/62086, https://github.com/rust-lang/rust/pull/62735 and other PRs.
This PR is also a continuation of #65252, #69870 and other PRs linked from them, which layed the ground for converting `#[derive]` specifically.
`#[derive]` still asks `rustc_resolve` to resolve paths inside `derive(...)`, and `rustc_expand` gets those resolution results through some backdoor (which I'll try to address later), but otherwise `#[derive]` is treated as any other macro attributes, which simplifies the resolution-expansion infra pretty significantly.
The change has several observable effects on language and library.
Some of the language changes are **feature-gated** by [`feature(macro_attributes_in_derive_output)`](https://github.com/rust-lang/rust/issues/81119).
#### Library
- `derive` is now available through standard library as `{core,std}::prelude::v1::derive`.
#### Language
- `derive` now goes through name resolution, so it can now be renamed - `use derive as my_derive; #[my_derive(Debug)] struct S;`.
- `derive` now goes through name resolution, so this resolution can fail in corner cases. Crater found one such regression, where import `use foo as derive` goes into a cycle with `#[derive(Something)]`.
- **[feature-gated]** `#[derive]` is now expanded as any other attributes in left-to-right order. This allows to remove the restriction on other macro attributes following `#[derive]` (https://github.com/rust-lang/reference/issues/566). The following macro attributes become a part of the derive's input (this is not a change, non-macro attributes following `#[derive]` were treated in the same way previously).
- `#[derive]` is now expanded as any other attributes in left-to-right order. This means two derive attributes `#[derive(Foo)] #[derive(Bar)]` are now expanded separately rather than together. It doesn't generally make difference, except for esoteric cases. For example `#[derive(Foo)]` can now produce an import bringing `Bar` into scope, but previously both `Foo` and `Bar` were required to be resolved before expanding any of them.
- **[feature-gated]** `#[derive()]` (with empty list in parentheses) actually becomes useful. For historical reasons `#[derive]` *fully configures* its input, eagerly evaluating `cfg` everywhere in its target, for example on fields.
Expansion infra doesn't do that for other attributes, but now when macro attributes attributes are allowed to be written after `#[derive]`, it means that derive can *fully configure* items for them.
```rust
#[derive()]
#[my_attr]
struct S {
#[cfg(FALSE)] // this field in removed by `#[derive()]` and not observed by `#[my_attr]`
field: u8
}
```
- `#[derive]` on some non-item targets is now prohibited. This was accidentally allowed as noop in the past, but was warned about since early 2018 (#50092), despite that crater found a few such cases in unmaintained crates.
- Derive helper attributes used before their introduction are now reported with a deprecation lint. This change is long overdue (since macro modularization, https://github.com/rust-lang/rust/issues/52226#issuecomment-422605033), but it was hard to do without fixing expansion order for derives. The deprecation is tracked by #79202.
```rust
#[trait_helper] // warning: derive helper attribute is used before it is introduced
#[derive(Trait)]
struct S {}
```
Crater analysis: https://github.com/rust-lang/rust/pull/79078#issuecomment-731436821
Add a note about the correctness and the effect on unsafe code to the `ExactSizeIterator` docs
As it is a safe trait it does not provide any guarantee that the
returned length is correct and as such unsafe code must not rely on it.
That's why `TrustedLen` exists.
Fixes https://github.com/rust-lang/rust/issues/81739
Update LayoutError/LayoutErr stability attributes
`LayoutError` ended up not making it into 1.49.0, updating the stability attributes to reflect that.
I also pushed `LayoutErr` deprecation back a release to allow 2 releases before the deprecation comes into effect.
This change should be backported to beta.
Add lint for `panic!(123)` which is not accepted in Rust 2021.
This extends the `panic_fmt` lint to warn for all cases where the first argument cannot be interpreted as a format string, as will happen in Rust 2021.
It suggests to add `"{}",` to format the message as a string. In the case of `std::panic!()`, it also suggests the recently stabilized
`std::panic::panic_any()` function as an alternative.
It renames the lint to `non_fmt_panic` to match the lint naming guidelines.
This is part of #80162.
r? ```@estebank```
As it is a safe trait it does not provide any guarantee that the
returned length is correct and as such unsafe code must not rely on it.
That's why `TrustedLen` exists.
Fixes https://github.com/rust-lang/rust/issues/81739
Otherwise if `Iterator::self.a.__iterator_get_unchecked` panics the
index would not have been incremented yet and another call to
`Iterator::next` would read from the same index again, which is not
allowed according to the API contract of `TrustedRandomAccess` for
`!Clone`.
Fixes https://github.com/rust-lang/rust/issues/81740
Add some links to the cell docs.
This adds a few links to the cell module docs to make it a little easier to navigate to the types and functions it references.
Fix bug with assert!() calling the wrong edition of panic!().
The span of `panic!` produced by the `assert` macro did not carry the right edition. This changes `assert` to call the right version.
Also adds tests for the 2021 edition of panic and assert, that would've caught this.
Add doc aliases for "delete"
This patch adds doc aliases for "delete". The added aliases are supposed to reference usages `delete` in other programming languages.
- `HashMap::remove`, `BTreeMap::remove` -> `Map#delete` and `delete` keyword in JavaScript.
- `HashSet::remove`, `BTreeSet::remove` -> `Set#delete` in JavaScript.
- `mem::drop` -> `delete` keyword in C++.
- `fs::remove_file`, `fs::remove_dir`, `fs::remove_dir_all`-> `File#delete` in Java, `File#delete` and `Dir#delete` in Ruby.
Before this change, searching for "delete" in documentation returned no results.
Implement Rust 2021 panic
This implements the Rust 2021 versions of `panic!()`. See https://github.com/rust-lang/rust/issues/80162 and https://github.com/rust-lang/rfcs/pull/3007.
It does so by replacing `{std, core}::panic!()` by a bulitin macro that expands to either `$crate::panic::panic_2015!(..)` or `$crate::panic::panic_2021!(..)` depending on the edition of the caller.
This does not yet make std's panic an alias for core's panic on Rust 2021 as the RFC proposes. That will be a separate change: c5273bdfb2 That change is blocked on figuring out what to do with https://github.com/rust-lang/rust/issues/80846 first.
This patch adds doc aliases for "delete". The added aliases are
supposed to reference usages `delete` in other programming
languages.
- `HashMap::remove`, `BTreeMap::remove` -> `Map#delete` and `delete`
keyword in JavaScript.
- `HashSet::remove`, `BTreeSet::remove` -> `Set#delete` in JavaScript.
- `mem::drop` -> `delete` keyword in C++.
- `fs::remove_file`, `fs::remove_dir`, `fs::remove_dir_all`
-> `File#delete` in Java, `File#delete` and `Dir#delete` in Ruby.
Before this change, searching for "delete" in documentation
returned no results.
Optimize decimal formatting of 128-bit integers
## Description
This PR optimizes the `udivmod_1e19` function, which is used for formatting 128-bit integers, based on the algorithm provided in \[1\]. This optimization improves performance of formatting 128-bit integers, especially on 64-bit architectures. It also slightly reduces the output binary size.
## Assembler comparison
https://godbolt.org/z/YrG5zY
## Performance
#### previous results
```
test fmt::write_u128_max ... bench: 552 ns/iter (+/- 4)
test fmt::write_u128_min ... bench: 125 ns/iter (+/- 2)
```
#### new results
```
test fmt::write_u128_max ... bench: 205 ns/iter (+/- 13)
test fmt::write_u128_min ... bench: 129 ns/iter (+/- 5)
```
## Reference
\[1\] T. Granlund and P. Montgomery, “Division by Invariant Integers Using Multiplication” in Proc. of the SIGPLAN94 Conference on Programming Language Design and Implementation, 1994, pp. 61–72
Remove requirement that forces symmetric and transitive PartialEq impls to exist
### Counterexample of symmetry:
If you [have](https://docs.rs/proc-macro2/1.0.24/proc_macro2/struct.Ident.html#impl-PartialEq%3CT%3E) an impl like:
```rust
impl<T> PartialEq<T> for Ident
where
T: ?Sized + AsRef<str>
```
then Rust will not even allow the symmetric impl to exist.
```console
error[E0210]: type parameter `T` must be covered by another type when it appears before the first local type (`Ident`)
--> src/main.rs:9:6
|
9 | impl<T> PartialEq<Ident> for T where T: ?Sized + AsRef<str> {
| ^ type parameter `T` must be covered by another type when it appears before the first local type (`Ident`)
|
= note: implementing a foreign trait is only possible if at least one of the types for which it is implemented is local, and no uncovered type parameters appear before that first local type
= note: in this case, 'before' refers to the following order: `impl<..> ForeignTrait<T1, ..., Tn> for T0`, where `T0` is the first and `Tn` is the last
```
<br>
### Counterexample of transitivity:
Consider these two existing impls from `regex` and `clap`:
```rust
// regex
/// An inline representation of `Option<char>`.
pub struct Char(u32);
impl PartialEq<char> for Char {
fn eq(&self, other: &char) -> bool {
self.0 == *other as u32
}
}
```
```rust
// clap
pub(crate) enum KeyType {
Short(char),
Long(OsString),
Position(u64),
}
impl PartialEq<char> for KeyType {
fn eq(&self, rhs: &char) -> bool {
match self {
KeyType::Short(c) => c == rhs,
_ => false,
}
}
}
```
It's nice to be able to add `PartialEq<proc_macro::Punct> for char` in libproc_macro (https://github.com/rust-lang/rust/pull/80595), but it makes no sense to force an `impl PartialEq<Punct> for Char` and `impl PartialEq<Punct> for KeyType` in `regex` and `clap` in code that otherwise has nothing to do with proc macros.
<br>
`@rust-lang/libs`
Stabilize `core::slice::fill_with`
_Tracking issue: https://github.com/rust-lang/rust/issues/79221_
This stabilizes the `slice_fill_with` feature for Rust 1.51, following the stabilization of `slice_fill` in 1.50. This was requested by libs team members in https://github.com/rust-lang/rust/pull/79213.
This PR also adds the "memset" alias for `slice::fill_with`, mirroring the alias set on the `slice::fill` sibling API. This will ensure someone looking for "memset" will find both variants.
r? `@Amanieu`
Stabilize by-value `[T; N]` iterator `core::array::IntoIter`
Tracking issue: https://github.com/rust-lang/rust/issues/65798
This is unblocked now that `min_const_generics` has been stabilized in https://github.com/rust-lang/rust/pull/79135.
This PR does *not* include the corresponding `IntoIterator` impl, which is https://github.com/rust-lang/rust/pull/65819. Instead, an iterator can be constructed through the `new` method.
`new` would become unnecessary when `IntoIterator` is implemented and might be deprecated then, although it will stay stable.
Implement missing `AsMut<str>` for `str`
Allows `&mut str` to be taken by a Generic which requires `T` such that `T: AsMut<str>`. Motivating example:
```rust
impl<'i, T> From<T> for StructImmut<'i> where
T: AsRef<str> + 'i,
{
fn from(asref: T) -> Self {
let string: &str = asref.as_ref();
// ...
}
}
impl<'i, T> From<T> for StructMut<'i> where
T: AsMut<str> + 'i,
{
fn from(mut asmut: T) -> Self {
let string: &mut str = asmut.as_mut();
// ...
}
}
```
The Immutable form of this structure can be constructed by `StructImmut::from(s)` where `s` may be a `&String` or a `&str`, because `AsRef<str>` is implemented for `str`. However, the mutable form of the structure can be constructed in the same way **only** with a `&mut String`, and **not** with a `&mut str`.
This change does have some precedent, because as can be seen in [the Implementors](https://doc.rust-lang.org/std/convert/trait.AsMut.html#implementors), `AsMut<[T]>` is implemented for `[T]` as well as for `Vec<T>`, but `AsMut<str>` is implemented only for `String`. This would complete the symmetry.
As a trait implementation, this should be immediately stable.
Slight simplification of chars().count()
Slight simplification: No need to call len(), we can just count the number of non continuation bytes.
I can't see any reason not to do this, can you?
Stabilize `unsigned_abs`
Resolves#74913.
This PR stabilizes the `i*::unsigned_abs()` method, which returns the absolute value of an integer _as its unsigned equivalent_. This has the advantage that it does not overflow on `i*::MIN`.
I have gone ahead and used this in a couple locations throughout the repository.
Stabilize raw ref macros
This stabilizes `raw_ref_macros` (https://github.com/rust-lang/rust/issues/73394), which is possible now that https://github.com/rust-lang/rust/issues/74355 is fixed.
However, as I already said in https://github.com/rust-lang/rust/issues/73394#issuecomment-751342185, I am not particularly happy with the current names of the macros. So I propose we also change them, which means I am proposing to stabilize the following in `core::ptr`:
```rust
pub macro const_addr_of($e:expr) {
&raw const $e
}
pub macro mut_addr_of($e:expr) {
&raw mut $e
}
```
The macro name change means we need another round of FCP. Cc `````@rust-lang/libs`````
Fixes#73394
Add `core::stream::Stream`
[[Tracking issue: #79024](https://github.com/rust-lang/rust/issues/79024)]
This patch adds the `core::stream` submodule and implements `core::stream::Stream` in accordance with [RFC2996](https://github.com/rust-lang/rfcs/pull/2996). The RFC hasn't been merged yet, but as requested by the libs team in https://github.com/rust-lang/rfcs/pull/2996#issuecomment-725696389 I'm filing this PR to get the ball rolling.
## Documentatation
The docs in this PR have been adapted from [`std::iter`](https://doc.rust-lang.org/std/iter/index.html), [`async_std::stream`](https://docs.rs/async-std/1.7.0/async_std/stream/index.html), and [`futures::stream::Stream`](https://docs.rs/futures/0.3.8/futures/stream/trait.Stream.html). Once this PR lands my plan is to follow this up with PRs to add helper methods such as `stream::repeat` which can be used to document more of the concepts that are currently missing. That will allow us to cover concepts such as "infinite streams" and "laziness" in more depth.
## Feature gate
The feature gate for `Stream` is `stream_trait`. This matches the `#[lang = "future_trait"]` attribute name. The intention is that only the APIs defined in RFC2996 will use this feature gate, with future additions such as `stream::repeat` using their own feature gates. This is so we can ensure a smooth path towards stabilizing the `Stream` trait without needing to stabilize all the APIs in `core::stream` at once. But also don't start expanding the API until _after_ stabilization, as was the case with `std::future`.
__edit:__ the feature gate has been changed to `async_stream` to match the feature gate proposed in the RFC.
## Conclusion
This PR introduces `core::stream::{Stream, Next}` and re-exports it from `std` as `std::stream::{Stream, Next}`. Landing `Stream` in the stdlib has been a mult-year process; and it's incredibly exciting for this to finally happen!
---
r? `````@KodrAus`````
cc/ `````@rust-lang/wg-async-foundations````` `````@rust-lang/libs`````
Make more traits of the From/Into family diagnostic items
Following traits are now diagnostic items:
- `From` (unchanged)
- `Into`
- `TryFrom`
- `TryInto`
This also adds symbols for those items:
- `into_trait`
- `try_from_trait`
- `try_into_trait`
Related: https://github.com/rust-lang/rust-clippy/pull/6620#discussion_r562482587
Add `unwrap_unchecked()` methods for `Option` and `Result`
In particular:
- `unwrap_unchecked()` for `Option`.
- `unwrap_unchecked()` and `unwrap_err_unchecked()` for `Result`.
These complement other `*_unchecked()` methods in `core` etc.
Currently there are a couple of places it may be used inside rustc (`LinkedList`, `BTree`). It is also easy to find other repositories with similar functionality.
Fixes#48278.
Prevent query cycles in the MIR inliner
r? `@eddyb` `@wesleywiser`
cc `@rust-lang/wg-mir-opt`
The general design is that we have a new query that is run on the `validated_mir` instead of on the `optimized_mir`. That query is forced before going into the optimization pipeline, so as to not try to read from a stolen MIR.
The query should not be cached cross crate, as you should never call it for items from other crates. By its very design calls into other crates can never cause query cycles.
This is a pessimistic approach to inlining, since we strictly have more calls in the `validated_mir` than we have in `optimized_mir`, but that's not a problem imo.
More clear documentation for NonNull<T>
Rephrase and hopefully clarify the discussion of covariance in `NonNull<T>` documentation.
I'm very much not an expert so someone should definitely double check the correctness of what I'm saying. At the same time, the new language makes more sense to me, so hopefully it also is more logical to others whose knowledge of covariance basically begins and ends with the [Rustonomicon chapter](https://doc.rust-lang.org/nomicon/subtyping.html).
Related to #48929.
This is a temporary change only, as we wait to resolve dynamic dispatch issues. The `Stream::next` method and corresponding documentation are expected to be fully restored once we have a path to proceed.
Ref: https://github.com/rust-lang/rfcs/pull/2996#issuecomment-757386206
update docs
Change branching in `iter.skip()`
Optimize branching in `Skip`, which was brought up in #80416.
This assumes that if `next` is called, it's likely that there will be more calls to `next`, and the branch for skip will only be hit once thus it's unlikely to take that path. Even w/o the `unlikely` intrinsic, it compiles more efficiently, I believe because the path where `next` is called is always taken.
It should be noted there are very few places in the compiler where `Skip` is used, so probably won't have a noticeable perf impact.
[New impl](https://godbolt.org/z/85rdj4)
[Old impl](https://godbolt.org/z/Wc74rh)
[Some additional asm examples](https://godbolt.org/z/feKzoz) although they really don't have a ton of difference between them.
Following traits are now diagnostic items:
- `From` (unchanged)
- `Into`
- `TryFrom`
- `TryInto`
This also adds symbols for those items:
- `into_trait`
- `try_from_trait`
- `try_into_trait`
Expand docs on Iterator::intersperse
Unstable feature in #79524. This expands on the docs to bring them more in line with how other methods of `Iterator` are demonstrated.
Stability oddity with const intrinsics
cc `@RalfJung`
In https://github.com/rust-lang/rust/pull/80699#discussion_r551495670 `@usbalbin` realized we accepted some intrinsics as `const` without a `#[rustc_const_(un)stable]` attribute. I did some digging, and that example works because intrinsics inherit their stability from their parents... including `#[rustc_const_(un)stable]` attributes. While we may want to fix that (not sure, wasn't there just a MCPed PR that caused this on purpose?), we definitely want tests for it, thus this PR adding tests and some fun tracing statements.
Add NonZeroUn::is_power_of_two
This saves instructions on both new and old machines <https://rust.godbolt.org/z/4fjTMz>
- On the default x64 target (with no fancy instructions available) it saves a few instructions by not needing to also check for zero.
- On newer targets (with BMI1) it uses `BLSR` for super-short assembly.
This can be used for things like checks against alignments stored in `NonZeroUsize`.
Add `as_rchunks` (and friends) to slices
`@est31` mentioned (https://github.com/rust-lang/rust/issues/76354#issuecomment-717027175) that, for completeness, there needed to be an `as_chunks`-like method that chunks from the end (with the remainder at the beginning) like `rchunks` does.
So here's a PR for `as_rchunks: &[T] -> (&[T], &[[T; N]])` and `as_rchunks_mut: &mut [T] -> (&mut [T], &mut [[T; N]])`.
But as I was doing this and copy-pasting `from_raw_parts` calls, I thought that I should extract that into an unsafe method. It started out a private helper, but it seemed like `as_chunks_unchecked` could be reasonable as a "real" method, so I added docs and made it public. Let me know if you think it doesn't pull its weight.
Rollup of 17 pull requests
Successful merges:
- #78455 (Introduce {Ref, RefMut}::try_map for optional projections in RefCell)
- #80144 (Remove giant badge in README)
- #80614 (Explain why borrows can't be held across yield point in async blocks)
- #80670 (TrustedRandomAaccess specialization composes incorrectly for nested iter::Zips)
- #80681 (Clarify what the effects of a 'logic error' are)
- #80764 (Re-stabilize Weak::as_ptr and friends for unsized T)
- #80901 (Make `x.py --color always` apply to logging too)
- #80902 (Add a regression test for #76281)
- #80941 (Do not suggest invalid code in pattern with loop)
- #80968 (Stabilize the poll_map feature)
- #80971 (Put all feature gate tests under `feature-gates/`)
- #81021 (Remove doctree::Import)
- #81040 (doctest: Reset errors before dropping the parse session)
- #81060 (Add a regression test for #50041)
- #81065 (codegen_cranelift: Fix redundant semicolon warn)
- #81069 (Add sample code for Rc::new_cyclic)
- #81081 (Add test for #34792)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
TrustedRandomAaccess specialization composes incorrectly for nested iter::Zips
I found this while working on improvements for TRA.
After partially consuming a Zip adapter and then wrapping it into another Zip where the adapters use their `TrustedRandomAccess` specializations leads to the outer adapter returning elements which should have already been consumed.
If the optimizer gets tripped up by the addition this might affect performance for chained `zip()` iterators even when the inner one is not partially advanced but it would require more extensive fixes to `TrustedRandomAccess` to communicate those offsets earlier.
Included test fails on nightly, [playground link](https://play.rust-lang.org/?version=nightly&mode=debug&edition=2018&gist=24fa1edf8a104ff31f5a24830593b01f)
implement ptr::write without dedicated intrinsic
This makes `ptr::write` more consistent with `ptr::write_unaligned`, `ptr::read`, `ptr::read_unaligned`, all of which are implemented in terms of `copy_nonoverlapping`.
This means we can also remove `move_val_init` implementations in codegen and Miri, and its special handling in the borrow checker.
Also see [this Zulip discussion](https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/ptr.3A.3Aread.20vs.20ptr.3A.3Awrite).
Fix formatting specifiers doc links
d36e3e23a8 seems to have inadvertently changed many of these links to point to `core::fmt` instead of `std::fmt`. The information about formatting specifiers is only documented in [`std::fmt`](https://doc.rust-lang.org/std/fmt/); [`core::fmt`](https://doc.rust-lang.org/core/fmt/) is empty. 3baf6a4a74 seems to have already fixed a couple of these links to point back to `std::fmt`.
Deprecate atomic::spin_loop_hint in favour of hint::spin_loop
For https://github.com/rust-lang/rust/issues/55002
We wanted to leave `atomic::spin_loop_hint` alone when stabilizing `hint::spin_loop` so folks had some time to migrate. This now deprecates `atomic_spin_loop_hint`.
Add Iterator::intersperse_with
This is a follow-up to #79479, tracking in #79524, as discussed https://github.com/rust-lang/rust/pull/79479#issuecomment-752671731.
~~Note that I had to manually implement `Clone` and `Debug` because `derive` insists on placing a `Clone`-bound on the struct-definition, which is too narrow. There is a long-standing issue # for this somewhere around here :-)~~
Also, note that I refactored the guts of `Intersperse` into private functions and re-used them in `IntersperseWith`, so I also went light on duplicating all the tests.
If this is suitable to be merged, the tracking issue should be updated, since it only mentions `intersperse`.
Happy New Year!
r? ``@m-ou-se``
Add as_ref and as_mut methods for Bound
Add as_ref and as_mut method for std::ops::range::Bound, patterned off
of the methods of the same name on Option.
I'm not quite sure what the process is for introducing new feature gates (this is my first contribution) so I've left these ungated, but happy to do whatever is necessary to gate them.
These tests invoke the various op traits using all accepted types they
are implemented for as well as for references to those types.
This fixes#49660 and ensures the following implementations exist:
* `Add`, `Sub`, `Mul`, `Div`, `Rem`
* `T op T`, `T op &T`, `&T op T` and `&T op &T`
* for all integer and floating point types
* `AddAssign`, `SubAssign`, `MulAssign`, `DivAssign`, `RemAssign`
* `&mut T op T` and `&mut T op &T`
* for all integer and floating point types
* `Neg`
* `op T` and `op &T`
* for all signed integer and floating point types
* `Not`
* `op T` and `op &T`
* for `bool`
* `BitAnd`, `BitOr`, `BitXor`
* `T op T`, `T op &T`, `&T op T` and `&T op &T`
* for all integer types and bool
* `BitAndAssign`, `BitOrAssign`, `BitXorAssign`
* `&mut T op T` and `&mut T op &T`
* for all integer types and bool
* `Shl`, `Shr`
* `L op R`, `L op &R`, `&L op R` and `&L op &R`
* for all pairs of integer types
* `ShlAssign`, `ShrAssign`
* `&mut L op R`, `&mut L op &R`
* for all pairs of integer types
Rework diagnostics for wrong number of generic args (fixes#66228 and #71924)
This PR reworks the `wrong number of {} arguments` message, so that it provides more details and contextual hints.
Stabilize split_inclusive
### Contents of this MR
This stabilises:
* `slice::split_inclusive`
* `slice::split_inclusive_mut`
* `str::split_inclusive`
Closes#72360.
### A possible concern
The proliferation of `split_*` methods is not particularly pretty. The existence of `split_inclusive` seems to invite the addition of `rsplit_inclusive`, `splitn_inclusive`, etc. We could instead have a more general API, along these kinds of lines maybe:
```
pub fn split_generic('a,P,H>(&'a self, pat: P, how: H) -> ...
where P: Pattern
where H: SplitHow;
pub fn split_generic_mut('a,P,H>(&'a mut self, pat: P, how: H) -> ...
where P: Pattern
where H: SplitHow;
trait SplitHow {
fn reverse(&self) -> bool;
fn inclusive -> bool;
fn limit(&self) -> Option<usize>;
}
pub struct SplitFwd;
...
pub struct SplitRevInclN(pub usize);
```
But maybe that is worse.
### Let us defer that? ###
This seems like a can of worms. I think we can defer opening it now; if and when we have something more general, these two methods can become convenience aliases. But I thought I would mention it so the lang API team can consider it and have an opinion.
Add `MaybeUninit` method `array_assume_init`
When initialising an array element-by-element, the conversion to the initialised array is done through `mem::transmute`, which is both ugly and does not work with const generics (see #61956). This PR proposes the associated method `array_assume_init`, matching the style of `slice_assume_init_*`:
```rust
unsafe fn array_assume_init<T, const N: usize>(array: [MaybeUninit<T>; N]) -> [T; N];
```
Example:
```rust
let mut array: [MaybeUninit<i32>; 3] = MaybeUninit::uninit_array();
array[0].write(0);
array[1].write(1);
array[2].write(2);
// SAFETY: Now safe as we initialised all elements
let array: [i32; 3] = unsafe {
MaybeUninit::array_assume_init(array)
};
```
Things I'm unsure about:
* Should this be a method of array instead?
* Should the function be const?
std/core docs: fix wrong link in PartialEq
PartialEq doc was attempting to link to ``[`Eq`]`` but instead we got a link to `` `eq` ``. Disambiguate with `trait@Eq`.
You can see the bad link [here](https://doc.rust-lang.org/std/cmp/trait.PartialEq.html) (Second sentence, "floating point types implement PartialEq but not Eq").
These methods work very similarly to `Option`'s methods `as_ref` and
`as_mut`. They are useful in several situation, particularly when
calling other array methods (like `map`) on the result. Unfortunately,
we can't easily call them `as_ref` and `as_mut` as that would shadow
those methods on slices, thus being a breaking change (that is likely
to affect a lot of code).
In particular:
- `unwrap_unchecked()` for `Option`.
- `unwrap_unchecked()` and `unwrap_err_unchecked()` for `Result`.
These complement other `*_unchecked()` methods in `core` etc.
Currently there are a couple of places it may be used inside rustc
(`LinkedList`, `BTree`). It is also easy to find other repositories
with similar functionality.
Fixes#48278.
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Implement From<char> for u64 and u128.
With this PR you can write
```
let u = u64::from('👤');
let u = u128::from('👤');
```
Previously, you could already write `as` conversions ([Playground link](https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=cee18febe28e69024357d099f07ca081)):
```
// Lossless conversions
dbg!('👤' as u32); // Prints 128100
dbg!('👤' as u64); // Prints 128100
dbg!('👤' as u128); // Prints 128100
// truncates, thus no `From` impls.
dbg!('👤' as u8); // Prints 100
dbg!('👤' as u16); // Prints 62564
// These `From` impls already exist.
dbg!(u32::from('👤')); // Prints 128100
dbg!(u64::from(u32::from('👤'))); // Prints 128100
```
The idea is from ``@gendx`` who opened [this Internals thread](https://internals.rust-lang.org/t/implement-from-char-for-u64/13454), and ``@withoutboats`` responded that someone should open a PR for it.
Some people mentioned `From<char>` impls for `f32` and `f64`, but that doesn't seem correct to me, so I didn't include them here.
I don't know what the feature should be named. Must it be registered somewhere, like unstable features?
r? ``@withoutboats``
I split the example into two: one that fails to compile, and one that
works. I also made them identical except for the addition of `by_ref`
so we don't confuse readers with random differences.
Stabilize slice::strip_prefix and slice::strip_suffix
These two methods are useful. The corresponding methods on `str` are already stable.
I believe that stablising these now would not get in the way of, in the future, extending these to take a richer pattern API a la `str`'s patterns.
Tracking PR: #73413. I also have an outstanding PR to improve the docs for these two functions and the corresponding ones on `str`: #75078
I have tried to follow the [instructions in the dev guide](https://rustc-dev-guide.rust-lang.org/stabilization_guide.html#stabilization-pr). The part to do with `compiler/rustc_feature` did not seem applicable. I assume that's because these are just library features, so there is no corresponding machinery in rustc.
Change:
```
`parse` can parse any type that...
```
to:
```
`parse` can parse into any type that...
```
Word `into` added to be more precise and in coherence with other parts of the doc.
Add more code spans to docs in intrinsics.rs
I have added some more code spans in core/src/intrinsics.rs, changing some `=` to `==`, etc. I also changed the wording in some sections.
After partially consuming a Zip adapter and then wrapping it into
another Zip where the adapters use their TrustedRandomAccess specializations
leads to the outer adapter returning elements which should have already been
consumed.
remove allow(incomplete_features) from std
cc https://github.com/rust-lang/rust/pull/80349#issuecomment-753357123
> Now I am somewhat concerned that the standard library uses some of these features...
I think it is theoretically ok to use incomplete features in the standard library or the compiler if we know that there is an already working subset and we explicitly document what we have to be careful about. Though at that point it is probably better to try and split the incomplete feature into two separate ones, similar to `min_specialization`.
Will be interesting once `feature(const_evaluatable_checked)` works well enough to imo be used in the compiler but not yet well enough to be removed from `INCOMPLETE_FEATURES`.
r? `@RalfJung`
Add docs note about `Any::type_id` on smart pointers
Fixes#79868.
There's an issue I've run into a couple times while using values of type `Box<dyn Any>` - essentially, calling `value.type_id()` doesn't dereference to the trait object, but uses the implementation of `Any` for `Box<dyn Any>`, giving us the `TypeId` of the container instead of the object inside it.
I couldn't find any notes about this in the documentation and - while it could be inferred from existing knowledge of Rust and the blanket implemenation of `Any` - I think it'd be nice to have a note about it in the documentation for the `any` module.
Anyways, here's a first draft of a section about it. I'm happy to revise wording :)
The return of the GroupBy and GroupByMut iterators on slice
According to https://github.com/rust-lang/rfcs/pull/2477#issuecomment-742034372, I am opening this PR again, this time I implemented it in safe Rust only, it is therefore much easier to read and is completely safe.
This PR proposes to add two new methods to the slice, the `group_by` and `group_by_mut`. These two methods provide a way to iterate over non-overlapping sub-slices of a base slice that are separated by the predicate given by the user (e.g. `Partial::eq`, `|a, b| a.abs() < b.abs()`).
```rust
let slice = &[1, 1, 1, 3, 3, 2, 2, 2];
let mut iter = slice.group_by(|a, b| a == b);
assert_eq!(iter.next(), Some(&[1, 1, 1][..]));
assert_eq!(iter.next(), Some(&[3, 3][..]));
assert_eq!(iter.next(), Some(&[2, 2, 2][..]));
assert_eq!(iter.next(), None);
```
[An RFC](https://github.com/rust-lang/rfcs/pull/2477) was open 2 years ago but wasn't necessary.
Remove all doc_comment!{} hacks by using #[doc = expr] where needed.
This replaces about 200 cases of
`````rust
doc_comment! {
concat!("The smallest value that can be represented by this integer type.
# Examples
Basic usage:
```
", $Feature, "assert_eq!(", stringify!($SelfT), "::MIN, ", stringify!($Min), ");",
$EndFeature, "
```"),
#[stable(feature = "assoc_int_consts", since = "1.43.0")]
pub const MIN: Self = !0 ^ ((!0 as $UnsignedT) >> 1) as Self;
}
`````
by
```rust
/// The smallest value that can be represented by this integer type.
///
/// # Examples
///
/// Basic usage:
///
/// ```
#[doc = concat!("assert_eq!(", stringify!($SelfT), "::MIN, ", stringify!($Min), ");")]
/// ```
#[stable(feature = "assoc_int_consts", since = "1.43.0")]
pub const MIN: Self = !0 ^ ((!0 as $UnsignedT) >> 1) as Self;
```
---
**Note:** For a usable diff, make sure to enable 'ignore whitspace': https://github.com/rust-lang/rust/pull/79150/files?diff=unified&w=1
Rollup of 9 pull requests
Successful merges:
- #78934 (refactor: removing library/alloc/src/vec/mod.rs ignore-tidy-filelength)
- #79479 (Add `Iterator::intersperse`)
- #80128 (Edit rustc_ast::ast::FieldPat docs)
- #80424 (Don't give an error when creating a file for the first time)
- #80458 (Some Promotion Refactoring)
- #80488 (Do not create dangling &T in Weak<T>::drop)
- #80491 (Miri: make size/align_of_val work for dangling raw ptrs)
- #80495 (Rename kw::Invalid -> kw::Empty)
- #80513 (Add regression test for #80062)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
Add "chr" as doc alias to char::from_u32
Many programming languages provide a function called `chr` - Perl, Python, PHP, Visual Basic, SQL. This change makes `char::from_u32` easier to discover in the documentation.
`ord` is not added as its name conflicts with `Ord` trait, and it's not exactly clear what it could point to (`<u32 as From<char>>::from`?). I don't think it's exactly necessary, as `char::from_u32` documentation page says you can do reverse conversion with `as` operator anyway.
Add "length" as doc alias to len methods
Currently when searching for `length` there are no results: https://doc.rust-lang.org/std/?search=length. This makes `len` methods appear when searching for `length`.
Add `impl Div<NonZeroU{0}> for u{0}` which cannot panic
Dividing an unsigned int by a `NonZeroUxx` requires a user to write (for example, in [this SO question](https://stackoverflow.com/questions/64855738/how-to-inform-the-optimizer-that-nonzerou32get-will-never-return-zero)):
```
pub fn safe_div(x: u32, y: std::num::NonZeroU32) -> u32 {
x / y.get()
}
```
which generates a panicking-checked-div [assembly](https://godbolt.org/#g:!((g:!((g:!((h:codeEditor,i:(fontScale:14,j:1,lang:rust,selection:(endColumn:2,endLineNumber:6,positionColumn:2,positionLineNumber:6,selectionStartColumn:2,selectionStartLineNumber:6,startColumn:2,startLineNumber:6),source:%27pub+fn+div(x:+u32,+y:+u32)+-%3E+u32+%7B%0A++++x+/+y%0A%7D%0Apub+fn+safe_div(x:+u32,+y:+std::num::NonZeroU32)+-%3E+u32+%7B%0A++++x+/+y.get()+//+an+unchecked+division+expected%0A%7D%27),l:%275%27,n:%270%27,o:%27Rust+source+%231%27,t:%270%27)),k:50,l:%274%27,n:%270%27,o:%27%27,s:0,t:%270%27),(g:!((h:compiler,i:(compiler:r1470,filters:(b:%270%27,binary:%271%27,commentOnly:%270%27,demangle:%270%27,directives:%270%27,execute:%271%27,intel:%270%27,libraryCode:%271%27,trim:%271%27),fontScale:14,j:1,lang:rust,libs:!(),options:%27-O%27,selection:(endColumn:1,endLineNumber:1,positionColumn:1,positionLineNumber:1,selectionStartColumn:1,selectionStartLineNumber:1,startColumn:1,startLineNumber:1),source:1),l:%275%27,n:%270%27,o:%27rustc+1.47.0+(Editor+%231,+Compiler+%231)+Rust%27,t:%270%27)),k:50,l:%274%27,n:%270%27,o:%27%27,s:0,t:%270%27)),l:%272%27,n:%270%27,o:%27%27,t:%270%27)),version:4).
Avoiding the `panic` currently requires `unsafe` code.
This PR adds an `impl Div<NonZeroU{0}> for u{0}` (and `impl Rem<NonZeroU{0}> for u{0}`) which calls the `unchecked_div` (and `unchecked_rem`) intrinsic without any additional checks,
making the following code compile:
```
pub fn safe_div(x: u32, y: std::num::NonZeroU32) -> u32 {
x / y
}
pub fn safe_rem(x: u32, y: std::num::NonZeroU32) -> u32 {
x % y
}
```
The doc is set to match the regular div impl [docs](https://doc.rust-lang.org/beta/src/core/ops/arith.rs.html#460).
I've marked these as stable because (as I understand it) trait impls are automatically stable. I'm happy to change it to unstable if needed.
Following `@dtolnay` template from a similar issue:
this adds the following **stable** impls, which rely on dividing unsigned integers by nonzero integers being well defined and previously would have involved unsafe code to encode that knowledge:
```
impl Div<NonZeroU8> for u8 {
type Output = u8;
}
impl Rem<NonZeroU8> for u8 {
type Output = u8;
}
```
and equivalent for u16, u32, u64, u128, usize, but **not** for i8, i16, i32, i64, i128, isize (since -1/MIN is undefined).
r? `@dtolnay`
We hope later to extend `core::str::Pattern` to slices too, perhaps as
part of stabilising that. We want to minimise the amount of type
inference breakage when we do that, so we don't want to stabilise
strip_prefix and strip_suffix taking a simple `&[T]`.
@KodrAus suggested the approach of introducing a new perma-unstable
trait, which reduces this future inference break risk.
I found it necessary to make two impls of this trait, as the unsize
coercion don't apply when hunting for trait implementations.
Since SlicePattern's only method returns a reference, and the whole
trait is just a wrapper for slices, I made the trait type be the
non-reference type [T] or [T;N] rather than the reference. Otherwise
the trait would have a lifetime parameter.
I marked both the no-op conversion functions `#[inline]`. I'm not
sure if that is necessary but it seemed at the very least harmless.
Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>
Stabilize `core::slice::fill`
Tracking issue https://github.com/rust-lang/rust/issues/70758
Stabilizes the `core::slice::fill` API in Rust 1.50, adding a `memset` doc alias so people coming from C/C++ looking for this operation can find it in the docs. This API hasn't seen any changes since we changed the signature in https://github.com/rust-lang/rust/pull/71165/, and it seems like the right time to propose stabilization. Thanks!
r? `@m-ou-se`
Deprecate atomic compare_and_swap method
Finish implementing [RFC 1443](https://github.com/rust-lang/rfcs/blob/master/text/1443-extended-compare-and-swap.md) (https://github.com/rust-lang/rfcs/pull/1443).
It was decided to deprecate `compare_and_swap` [back in Rust 1.12 already](https://github.com/rust-lang/rust/issues/31767#issuecomment-215903038). I can't find any info about that decision being reverted. My understanding is just that it has been forgotten. If there has been a decision on keeping `compare_and_swap` then it's hard to find, and even if this PR does not go through it can act as a place where people can find out about the decision being reverted.
Atomic operations are hard to understand, very hard. And it does not help that there are multiple similar methods to do compare and swap with. They are so similar that for a reader it might be hard to understand the difference. This PR aims to make that simpler by finally deprecating `compare_and_swap` which is essentially just a more limited version of `compare_exchange`. The documentation is also updated (according to the RFC text) to explain the differences a bit better.
Even if we decide to not deprecate `compare_and_swap`. I still think the documentation for the atomic operations should be improved to better describe their differences and similarities. And the documentation can be written nicer than the PR currently proposes, but I wanted to start somewhere. Most of it is just copied from the RFC.
The documentation for `compare_exchange` and `compare_exchange_weak` indeed describe how they work! The problem is that they are more complex and harder to understand than `compare_and_swap`. So for someone who does not fully grasp this they might fall back to using `compare_and_swap`. Making the documentation outline the similarities and differences might build a bridge for people so they can cross over to the more powerful and sometimes more efficient operations.
The conversions I do to avoid the `std` internal deprecation errors are very straight forward `compare_and_swap -> compare_exchange` changes where the orderings are just using the mapping in the new documentation. Only in one place did I use `compare_exchange_weak`. This can probably be improved further. But the goal here was not for those operations to be perfect. Just to not get worse and to allow the deprecation to happen.
Added [T; N]::zip()
This is my first PR to rust so I hope I have done everything right, or at least close :)
---
This is PR adds the array method `[T; N]::zip()` which, in my mind, is a natural extension to #75212.
My implementation of `zip()` is mostly just a modified copy-paste of `map()`. Should I keep the comments? Also am I right in assuming there should be no way for the `for`-loop to panic, thus no need for the dropguard seen in the `map()`-function?
The doc comment is in a similar way a slightly modified copy paste of [`Iterator::zip()`](https://doc.rust-lang.org/beta/std/iter/trait.Iterator.html#method.zip)
`@jplatte` mentioned in [#75490](https://github.com/rust-lang/rust/pull/75490#issuecomment-677790758) `zip_with()`,
> zip and zip_with seem like they would be useful :)
is this something I should add (assuming there is interest for this PR at all :))
Fix memory leak in test "mem::uninit_write_slice_cloned_no_drop"
This fixes#80116. I replaced the `Rc` based method I was using with a type that panics when dropped.
Move {f32,f64}::clamp to core.
`clamp` was recently stabilized (tracking issue: https://github.com/rust-lang/rust/issues/44095). But although `Ord::clamp` was added in `core` (because `Ord` is in `core`), the versions for the `f32` and `f64` primitives were added in `std` (together with `floor`, `sin`, etc.), not in `core` (together with `min`, `max`, `from_bits`, etc.).
This change moves them to `core`, such that `clamp` on floats is available in `no_std` programs as well.
Integer types have a `count_ones` method that end up calling
`intrinsics::ctpop`.
On some architectures, that intrinsic is translated as a corresponding
CPU instruction know as "popcount" or "popcnt".
This PR makes it so that searching for those names in rustdoc shows those methods.
CC https://blog.rust-lang.org/2020/11/19/Rust-1.48.html#adding-search-aliases
MaybeUninit::copy/clone_from_slice
This PR adds 2 new methods to MaybeUninit under the feature of `maybe_uninit_write_slice`: `copy_from_slice` and `clone_from_slice`.
These are useful for initializing uninitialized buffers (such as the one returned by `Vec::spare_capacity_mut` for example) with initialized data.
The methods behave similarly to the methods on slices, but the destination is uninitialized and they return the destination slice as an initialized slice.
std::iter: document iteration over `&T` and `&mut T`
A colleague of mine is new to Rust, and mentioned that it was “slightly
confusing” to figure out what `&mut` does in iterating over `&mut foo`:
```rust
for value in &mut self.my_vec {
// ...
}
```
My colleague had read the `std::iter` docs and not found the answer
there. There is a brief section at the top about “the three forms of
iteration”, which mentions `iter_mut`, but it doesn’t cover the purpose
of `&mut coll` for a collection `coll`. This patch adds an explanatory
section to the docs. I opted to create a new section so that it can
appear after the note that `impl<I: Iterator> IntoIterator for I`, and
it’s nice for the existing “three forms of iteration” to appear near the
top.
Test Plan:
Ran `./x.py doc library/core`, and the result looked good, including
links. Manually copy-pasted the two doctests into the playground and ran
them.
wchargin-branch: doc-iter-by-reference
Add some core::cmp::Ordering helpers
...to allow easier equal-to-or-greater-than and less-than-or-equal-to
comparisons.
Prior to Rust 1.42 a greater-than-or-equal-to comparison might be written
either as a match block, or a traditional conditional check like this:
```rust
if cmp == Ordering::Equal || cmp == Ordering::Greater {
// Do something
}
```
Which requires two instances of `cmp`. Don't forget that while `cmp` here
is very short, it could be something much longer in real use cases.
From Rust 1.42 a nicer alternative is possible:
```rust
if matches!(cmp, Ordering::Equal | Ordering::Greater) {
// Do something
}
```
The commit adds another alternative which may be even better in some cases:
```rust
if cmp.is_equal_or_greater() {
// Do something
}
```
The earlier examples could be cleaner than they are if the variants of
`Ordering` are imported such that `Equal`, `Greater` and `Less` can be
referred to directly, but not everyone will want to do that.
The new solution can shorten lines, help avoid logic mistakes, and avoids
having to import `Ordering` / `Ordering::*`.
...to allow easier greater-than-or-equal-to and less-than-or-equal-to
comparisons, and variant checking without needing to import the enum,
similar to `Option::is_none()` / `Option::is_some()`, in situations where
you are dealing with an `Ordering` value. (Simple `PartialOrd` / `Ord`
based evaluation may not be suitable for all situations).
Prior to Rust 1.42 a greater-than-or-equal-to comparison might be written
either as a match block, or a traditional conditional check like this:
```rust
if cmp == Ordering::Equal || cmp == Ordering::Greater {
// Do something
}
```
Which requires two instances of `cmp`. Don't forget that while `cmp` here
is very short, it could be something much longer in real use cases.
From Rust 1.42 a nicer alternative is possible:
```rust
if matches!(cmp, Ordering::Equal | Ordering::Greater) {
// Do something
}
```
The commit adds another alternative which may be even better in some cases:
```rust
if cmp.is_ge() {
// Do something
}
```
The earlier examples could be cleaner than they are if the variants of
`Ordering` are imported such that `Equal`, `Greater` and `Less` can be
referred to directly, but not everyone will want to do that.
The new solution can shorten lines, help avoid logic mistakes, and avoids
having to import `Ordering` / `Ordering::*`.
Constier maybe uninit
I was playing around trying to make `[T; N]::zip()` in #79451 be `const fn`. One of the things I bumped into was `MaybeUninit::assume_init`. Is there any reason for the intrinsic `assert_inhabited<T>()` and therefore `MaybeUninit::assume_init` not being `const`?
---
I have as best as I could tried to follow the instruction in [library/core/src/intrinsics.rs](https://github.com/rust-lang/rust/blob/master/library/core/src/intrinsics.rs#L11). I have no idea what I am doing but it seems to compile after some slight changes after the copy paste. Is this anywhere near how this should be done?
Also any ideas for name of the feature gate? I guess `const_maybe_assume_init` is quite misleading since I have added some more methods. Should I add test? If so what should be tested?
Rollup of 12 pull requests
Successful merges:
- #79732 (minor stylistic clippy cleanups)
- #79750 (Fix trimming of lint docs)
- #79777 (Remove `first_merge` from liveness debug logs)
- #79795 (Privatize some of libcore unicode_internals)
- #79803 (Update xsv to prevent random CI failures)
- #79810 (Account for gaps in def path table during decoding)
- #79818 (Fixes to Rust coverage)
- #79824 (Strip prefix instead of replacing it with empty string)
- #79826 (Simplify visit_{foreign,trait}_item)
- #79844 (Move RWUTable to a separate module)
- #79861 (Update LLVM submodule)
- #79862 (Remove tab-lock and replace it with ctrl+up/down arrows to switch between search result tabs)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
Privatize some of libcore unicode_internals
My understanding is that these API are perma unstable, so it doesn't
make sense to pollute docs & IDE completion[1] with them.
[1]: https://github.com/rust-analyzer/rust-analyzer/issues/6738
Use more std:: instead of core:: in docs for consistency
``@rustbot`` label T-doc
Some cleanup work to use `std::` instead of `core::` in docs as much as possible. This helps with terminology and consistency, especially for newcomers from other languages that have often heard of `std` to describe the standard library but not of `core`.
Edit: I also added more intra doc links when I saw the opportunity.
Avoid panic_bounds_check in fmt::write.
Writing any fmt::Arguments would trigger the inclusion of usize formatting and padding code in the resulting binary, because indexing used in fmt::write would generate code using panic_bounds_check, which prints the index and length.
These bounds checks are not necessary, as fmt::Arguments never contains any out-of-bounds indexes.
This change replaces them with unsafe get_unchecked, to reduce the amount of generated code, which is especially important for embedded targets.
---
Demonstration of the size of and the symbols in a 'hello world' no_std binary:
<details>
<summary>Source code</summary>
```rust
#![feature(lang_items)]
#![feature(start)]
#![no_std]
use core::fmt;
use core::fmt::Write;
#[link(name = "c")]
extern "C" {
#[allow(improper_ctypes)]
fn write(fd: i32, s: &str) -> isize;
fn exit(code: i32) -> !;
}
struct Stdout;
impl fmt::Write for Stdout {
fn write_str(&mut self, s: &str) -> fmt::Result {
unsafe { write(1, s) };
Ok(())
}
}
#[start]
fn main(_argc: isize, _argv: *const *const u8) -> isize {
let _ = writeln!(Stdout, "Hello World");
0
}
#[lang = "eh_personality"]
fn eh_personality() {}
#[panic_handler]
fn panic(_: &core::panic::PanicInfo) -> ! {
unsafe { exit(1) };
}
```
</details>
Before:
```
text data bss dec hex filename
6059 736 8 6803 1a93 before
```
```
0000000000001e00 T <T as core::any::Any>::type_id
0000000000003dd0 D core::fmt::num::DEC_DIGITS_LUT
0000000000001ce0 T core::fmt::num:👿:<impl core::fmt::Display for u64>::fmt
0000000000001ce0 T core::fmt::num:👿:<impl core::fmt::Display for usize>::fmt
0000000000001370 T core::fmt::write
0000000000001b30 t core::fmt::Formatter::pad_integral::write_prefix
0000000000001660 T core::fmt::Formatter::pad_integral
0000000000001350 T core::ops::function::FnOnce::call_once
0000000000001b80 t core::ptr::drop_in_place
0000000000001120 t core::ptr::drop_in_place
0000000000001c50 t core::iter::adapters::zip::Zip<A,B>::new
0000000000001c90 t core::iter::adapters::zip::Zip<A,B>::new
0000000000001b90 T core::panicking::panic_bounds_check
0000000000001c10 T core::panicking::panic_fmt
0000000000001130 t <&mut W as core::fmt::Write>::write_char
0000000000001200 t <&mut W as core::fmt::Write>::write_fmt
0000000000001250 t <&mut W as core::fmt::Write>::write_str
```
After:
```
text data bss dec hex filename
3068 600 8 3676 e5c after
```
```
0000000000001360 T core::fmt::write
0000000000001340 T core::ops::function::FnOnce::call_once
0000000000001120 t core::ptr::drop_in_place
0000000000001620 t core::iter::adapters::zip::Zip<A,B>::new
0000000000001660 t core::iter::adapters::zip::Zip<A,B>::new
0000000000001130 t <&mut W as core::fmt::Write>::write_char
0000000000001200 t <&mut W as core::fmt::Write>::write_fmt
0000000000001250 t <&mut W as core::fmt::Write>::write_str
```
Part of #68490.
Care has been taken to leave the old consts where appropriate, for testing backcompat regressions, module shadowing, etc. The intrinsics docs were accidentally referring to some methods on f64 as std::f64, which I changed due to being contrary with how we normally disambiguate the shadow module from the primitive. In one other place I changed std::u8 to std::ops since it was just testing path handling in macros.
For places which have legitimate uses of the old consts, deprecated attributes have been optimistically inserted. Although currently unnecessary, they exist to emphasize to any future deprecation effort the necessity of these specific symbols and prevent them from being accidentally removed.
Rename `optin_builtin_traits` to `auto_traits`
They were originally called "opt-in, built-in traits" (OIBITs), but
people realized that the name was too confusing and a mouthful, and so
they were renamed to just "auto traits". The feature flag's name wasn't
updated, though, so that's what this PR does.
There are some other spots in the compiler that still refer to OIBITs,
but I don't think changing those now is worth it since they are internal
and not particularly relevant to this PR.
Also see <https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/opt-in.2C.20built-in.20traits.20(auto.20traits).20feature.20name>.
r? `@oli-obk` (feel free to re-assign if you're not the right reviewer for this)
Proposal to add Peekable::peek_mut
A "peekable" iterator has a `peek()`-method which provides an immutable reference to the next item. We currently do not have a method to modify that item, which we could easily add via a `peek_mut()`. See the test for a use-case (alike to my original use case), where a "pristine" iterator is passed on after modifying its state via `peek_mut()`.
If there is interest in this, I can expand on the tests and docs.
Document unsafety in core::slice::memchr
Contributes to #66219
Note sure if that's good enough, especially for the `align_to` call.
The docs only mention transmuting and I don't think that everything related to reference lifetimes and state validity mentioned in the [nomicon](https://doc.rust-lang.org/nomicon/transmutes.html) are relevant here.
They were originally called "opt-in, built-in traits" (OIBITs), but
people realized that the name was too confusing and a mouthful, and so
they were renamed to just "auto traits". The feature flag's name wasn't
updated, though, so that's what this PR does.
There are some other spots in the compiler that still refer to OIBITs,
but I don't think changing those now is worth it since they are internal
and not particularly relevant to this PR.
Also see <https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/opt-in.2C.20built-in.20traits.20(auto.20traits).20feature.20name>.
Qualify `panic!` as `core::panic!` in non-built-in `core` macros
Fixes#78333.
-----
Otherwise code like this
#![no_implicit_prelude]
fn main() {
::std::todo!();
::std::unimplemented!();
}
will fail to compile, which is unfortunate and presumably unintended.
This changes many invocations of `panic!` in a `macro_rules!` definition
to invocations of `$crate::panic!`, which makes the invocations hygienic.
Note that this does not make the built-in macro `assert!` hygienic.
A colleague of mine is new to Rust, and mentioned that it was “slightly
confusing” to figure out what `&mut` does in iterating over `&mut foo`:
```rust
for value in &mut self.my_vec {
// ...
}
```
My colleague had read the `std::iter` docs and not found the answer
there. There is a brief section at the top about “the three forms of
iteration”, which mentions `iter_mut`, but it doesn’t cover the purpose
of `&mut coll` for a collection `coll`. This patch adds an explanatory
section to the docs. I opted to create a new section so that it can
appear after the note that `impl<I: Iterator> IntoIterator for I`, and
it’s nice for the existing “three forms of iteration” to appear near the
top.
Implementation note: I haven’t linkified the references to `HashSet` and
`HashMap`, since those are in `std` and these docs are in `core`;
linkifying them gave an “unresolved link” rustdoc error.
Test Plan:
Ran `./x.py doc library/core`, and the result looked good. Manually
copy-pasted the two doctests into the playground and ran them.
wchargin-branch: doc-iter-by-reference
wchargin-source: 0f35369a8a735868621166608797744e97536792
Otherwise code like this
#![no_implicit_prelude]
fn main() {
::std::todo!();
::std::unimplemented!();
}
will fail to compile, which is unfortunate and presumably unintended.
This changes many invocations of `panic!` in a `macro_rules!` definition
to invocations of `$crate::panic!`, which makes the invocations hygienic.
Note that this does not make the built-in macro `assert!` hygienic.
Impl Default for PhantomPinned
`PhantomPinned` is just a marker type, with an obvious default value (the only value). So I can't think of a reason not to do this. Sure, it's used in exotic situations with unsafe code. But the people writing that code can decide for themselves if they can derive `Default`, and in many situations the derived impl will make sense:
```rust
#[derive(Default)]
struct NeedsPin {
marker: PhantomPinned,
buf: [u8; 1024],
ptr_to_data: Option<*const u8>,
}
```
Also stabilize constctlz for const ctlz_nonzero.
The public methods stabilized const by this commit are:
* `{i*,u*}::checked_pow`
* `{i*,u*}::saturating_pow`
* `{i*,u*}::wrapping_pow`
* `{i*,u*}::overflowing_pow`
* `{i*,u*}::pow`
* `u*::next_power_of_two`
* `u*::checked_next_power_of_two`
* `u*::wrapping_next_power_of_two` (the method itself is still unstable)
Stabilize refcell_take
Tracking Issue: #71395
``@KodrAus`` nominated this for FCP, so here's a PR!
I've never made a stabilization PR, so please mention if there's anything I can improve, thanks.
Stabilize alloc::Layout const functions
Stabilizes #67521. In particular the following stable methods are stabilized as `const fn`:
* `size`
* `align`
* `from_size_align`
Stabilizing `size` and `align` should not be controversial as they are simple (usize and NonZeroUsize) fields and I don't think there's any reason to make them not const compatible in the future. That being true, the other methods are trivially `const`. The only other issue being returning a `Result` from a `const fn` but this has been made more usable by recent stabilizations.
Split each iterator adapter and source into individual modules
This PR creates individual modules for each iterator adapter and iterator source.
This is done to enhance the readability of corresponding modules (`adapters/mod.rs` and `sources.rs`) which were hard to navigate and read because of lots of repeated lines (e.g.: `adapters/mod.rs` was 3k lines long). This is also in line with some adapters which already had their own modules (`Flatten`, `FlatMap`, `Chain`, `Zip`, `Fuse`).
This PR also makes `Take`s adapter fields private (I have no idea why they were `pub(super)` before).
r? ``@LukasKalbertodt``
Add f{32,64}::is_subnormal
The docs recommend that you use dedicated methods instead of calling `classify` directly, although there isn't actually a way of checking if a number is subnormal without calling classify. There are dedicated methods for all other forms, excluding `is_zero` (which is just `== 0.0` anyway).
Stabilize clamp
Tracking issue: https://github.com/rust-lang/rust/issues/44095
Clamp has been merged and unstable for about a year and a half now. How do we feel about stabilizing this?
More consistently use spaces after commas in lists in docs
This PR changes instances of lists that didn't use spaces after commas, like `vec![1,2,3]`, to `vec![1, 2, 3]` to be more consistent with idiomatic Rust style (the way these were looks strange to me, especially because there are often lists that *do* use spaces after the commas later in the same code block 😬).
I noticed one of these in an example in the stdlib docs and went looking for more, but as far as I can see, I'm only changing those spots in user-facing documentation or rustc output, and the changes make no semantic difference.
clarify rules for ZST Boxes
LLVM's rules around `getelementptr inbounds` with offset 0 are a bit annoying, and as a consequence we have no choice but say that a `Box<()>` pointing to previously allocated memory that has since been freed is UB. Clarify the docs to reflect this.
This is based on conversations on the LLVM mailing list.
* Here's my initial mail: https://lists.llvm.org/pipermail/llvm-dev/2019-February/130452.html
* The first email of the March part of that thread: https://lists.llvm.org/pipermail/llvm-dev/2019-March/130831.html
* First email of the April part: https://lists.llvm.org/pipermail/llvm-dev/2019-April/131693.html
The conclusion for me at least was that `getelementptr inbounds` with offset 0 is *not* the identity function, but can sometimes return `poison` even when the input is a regular pointer -- specifically, it returns `poison` when this pointer points into something that LLVM "knows has been deallocated", i.e., a former LLVM-managed allocation. It is however the identity function on pointers obtained by casting integers.
Note that there [are formal proposals](https://people.mpi-sws.org/~jung/twinsem/twinsem.pdf) for LLVM semantics where `getelementptr inbounds` with offset 0 isn't quite the identity function but never returns `poison` (it affects the provenance of the pointer but in a way that doesn't matter if this pointer is never used for memory accesses), and indeed this is likely necessary to consistently describe LLVM semantics. But with the informal LLVM LangRef that we have right now, and with LLVM devs insisting otherwise, it seems unwise to rely on this.
Add lint for panic!("{}")
This adds a lint that warns about `panic!("{}")`.
`panic!(msg)` invocations with a single argument use their argument as panic payload literally, without using it as a format string. The same holds for `assert!(expr, msg)`.
This lints checks if `msg` is a string literal (after expansion), and warns in case it contained braces. It suggests to insert `"{}", ` to use the message literally, or to add arguments to use it as a format string.
This lint is also a good starting point for adding warnings about `panic!(not_a_string)` later, once [`panic_any()`](https://github.com/rust-lang/rust/pull/74622) becomes a stable alternative.
Make as{_mut,}_slice on array::IntoIter public
The functions are useful in cases where you want to move data out of the IntoIter in bulk, by transmute_copy'ing the slice and then forgetting the IntoIter.
In the compiler, this is useful for providing a sped up IntoIter implementation. One can alternatively provide a separate allocate_array function but one can avoid duplicating some logic by passing everything through the generic iterator using interface.
As per suggestion in https://github.com/rust-lang/rust/pull/78569/files#r526506964
Clarify availability of atomic operations
This was noticed while we were updating the embedded rust book: https://github.com/rust-embedded/book/pull/273/files
These targets do natively have atomic load/stores, but do not support CAS operations.
This macro is used in expression position (a match arm), and only
compiles because of #33953
Regardless of what happens with that issue, this makes the
usage of the macro less confusing at the call site.
add trailing_zeros and leading_zeros to non zero types
as a way towards being able to use the optimized intrinsics ctlz_nonzero and cttz_nonzero from stable.
have not crated any tracking issue if this is not a solution that is wanted
Rename/Deprecate LayoutErr in favor of LayoutError
Implements rust-lang/wg-allocators#73.
This patch renames LayoutErr to LayoutError, and uses a type alias to support users using the old name.
The new name will be instantly stable in release 1.49 (current nightly), the type alias will become deprecated in release 1.51 (so that when the current nightly is 1.51, 1.49 will be stable).
This is the only error type in `std` that ends in `Err` rather than `Error`, if this PR lands all stdlib error types will end in `Error` 🥰
Test structural matching for all range types
As of #70166 all range types (`core::ops::Range` etc.) can be structurally matched upon, and by extension used in const generics. In reference to the fact that this is a publicly observable property of these types, and thus falls under the Rust stability guarantees of the standard library, a regression test was added in #70283.
This regression test was implemented by me by testing for the ability to use the range types within const generics, but that is not the actual property the std guarantees now (const generics is still unstable). This PR addresses that situation by adding extra tests for the range types that directly test whether they can be structurally matched upon.
Note: also adds the otherwise unrelated test `test_range_to_inclusive` for completeness with the other range unit tests
Duration::zero() -> Duration::ZERO
In review for #72790, whether or not a constant or a function should be favored for `#![feature(duration_zero)]` was seen as an open question. In https://github.com/rust-lang/rust/issues/73544#issuecomment-691701670 an invitation was opened to either stabilize the methods or propose a switch to the constant value, supplemented with reasoning. Followup comments suggested community preference leans towards the const ZERO, which would be reason enough.
ZERO also "makes sense" beside existing associated consts for Duration. It is ever so slightly awkward to have a series of constants specifying 1 of various units but leave 0 as a method, especially when they are side-by-side in code. It seems unintuitive for the one non-dynamic value (that isn't from Default) to be not-a-const, which could hurt discoverability of the associated constants overall. Elsewhere in `std`, methods for obtaining a constant value were even deprecated, as seen with [std::u32::min_value](https://doc.rust-lang.org/std/primitive.u32.html#method.min_value).
Most importantly, ZERO costs less to use. A match supports a const pattern, but const fn can only be used if evaluated through a const context such as an inline `const { const_fn() }` or a `const NAME: T = const_fn()` declaration elsewhere. Likewise, while https://github.com/rust-lang/rust/issues/73544#issuecomment-691949373 notes `Duration::zero()` can optimize to a constant value, "can" is not "will". Only const contexts have a strong promise of such. Even without that in mind, the comment in question still leans in favor of the constant for simplicity. As it costs less for a developer to use, may cost less to optimize, and seems to have more of a community consensus for it, the associated const seems best.
r? ```@LukasKalbertodt```
Refactor IntErrorKind to avoid "underflow" terminology
This PR is a continuation of #76455
# Changes
- `Overflow` renamed to `PosOverflow` and `Underflow` renamed to `NegOverflow` after discussion in #76455
- Changed some of the parsing code to return `InvalidDigit` rather than `Empty` for strings "+" and "-". https://users.rust-lang.org/t/misleading-error-in-str-parse-for-int-types/49178
- Carry the problem `char` with the `InvalidDigit` variant.
- Necessary changes were made to the compiler as it depends on `int_error_matching`.
- Redid tests to match on specific errors.
r? ```@KodrAus```
Stabilize `Poll::is_ready` and `is_pending` as const
Insta-stabilize the methods `is_ready` and `is_pending` of `std::task::Poll` as const, in the same way as [PR#76198](https://github.com/rust-lang/rust/pull/76198).
Possible because of the recent stabilization of const control flow.
Part of #76225.
Partially fix#55002, deprecate in another release
Co-authored-by: Ashley Mannix <kodraus@hey.com>
Update stable version for stabilize_spin_loop
Co-authored-by: Joshua Nelson <joshua@yottadb.com>
Use better example for spinlock
As suggested by KodrAus
Remove renamed_spin_loop already available in master
Fix spin loop example
`crate::` -> `core::`
It looks weird to have `crate::` in the link text and we use the actual
crate name everywhere else.
If anyone is curious, I used this Vim command to update all the links:
%s/\(\s\)\[`crate::\(.*\)`\]/\1[`core::\2`](crate::\2)/g
Add fetch_update methods to AtomicBool and AtomicPtr
These methods were stabilized for the integer atomics in #71843, but the methods were not added for the non-integer atomics `AtomicBool` and `AtomicPtr`.
Point out that total_cmp is no strict superset of partial comparison
Partial comparison and total_cmp are not equal. This helps
preventing the mistake of creating float wrappers that
base their Ord impl on total_cmp and their PartialOrd impl on
the PartialOrd impl of the float type. PartialOrd and Ord
[are required to agree with each other](https://doc.rust-lang.org/std/cmp/trait.Ord.html#how-can-i-implement-ord).
Trivial fixes to bitwise operator documentation
Added fixes to documentation of `BitAnd`, `BitOr`, `BitXor` and
`BitAndAssign`, where the documentation for implementation on
`Vector<bool>` was using logical operators in place of the bitwise
operators.
r? @steveklabnik
Closes#78619
Clarify handling of final line ending in str::lines()
I found the description as it stands a bit confusing. I've added a bit more explanation to make it clear that a trailing line ending does not produce a final empty line.
These methods were stabilized for the integer atomics in #71843, but the methods
were not added for the non-integer atomics `AtomicBool` and `AtomicPtr`.
Partial comparison and total_cmp are not equal. This helps
preventing the mistake of creating float wrappers that
base their Ord impl on total_cmp and their PartialOrd impl on
the PartialOrd impl of the float type. PartialOrd and Ord
are required to agree with each other.
fix various aliasing issues in the standard library
This fixes various cases where the standard library either used raw pointers after they were already invalidated by using the original reference again, or created raw pointers for one element of a slice and used it to access neighboring elements.
Fix doc links to std::fmt
`std::format` and `core::write` macros' docs linked to `core::fmt` for format string reference, even though only `std::fmt` has format string documentation (and the link titles were `std::fmt`)
Added fixes to documentation of `BitAnd`, `BitOr`, `BitXor` and
`BitAndAssign`, where the documentation for implementation on
`Vector<bool>` was using logical operators in place of the bitwise
operators.
r? @steveklabnik
cc #78619
I found the description as it stands a bit confusing. I've added a bit more explanation to make it clear that a trailing line ending does not produce a final empty line.
std::format and core::write macros' docs linked to core::fmt for format string reference, even though only std::fmt has format string documentation and the link titles were std::fmt.
Improve documentation for slice strip_* functions
Prompted by the stabilisation tracking issue #73413 I looked at the docs for `strip_prefix` and `strip_suffix` for both `str` and `slice`, and I felt they could be slightly improved.
Thanks for your attention.
Separate unsized locals
Closes#71694
Takes over again #72029 and #74971
cc @RalfJung @oli-obk @pnkfelix @eddyb as they've participated in previous reviews of this PR.
The lint checks arguments in calls to `transmute` or functions that have
`Pointer` as a trait bound and displays a warning if the argument is a function
reference. Also checks for `std::fmt::Pointer::fmt` to handle formatting macros
although it doesn't depend on the exact expansion of the macro or formatting
internals. `std::fmt::Pointer` and `std::fmt::Pointer::fmt` were also added as
diagnostic items and symbols.
Add [T]::as_chunks(_mut)
Allows getting the slices directly, rather than just through an iterator as in `array_chunks(_mut)`. The constructors for those iterators are then written in terms of these methods, so the iterator constructors no longer have any `unsafe` of their own.
Unstable, of course. #74985
Optimise align_offset for stride=1 further
`stride == 1` case can be computed more efficiently through `-p (mod
a)`. That, then translates to a nice and short sequence of LLVM
instructions:
%address = ptrtoint i8* %p to i64
%negptr = sub i64 0, %address
%offset = and i64 %negptr, %a_minus_one
And produces pretty much ideal code-gen when this function is used in
isolation.
Typical use of this function will, however, involve use of
the result to offset a pointer, i.e.
%aligned = getelementptr inbounds i8, i8* %p, i64 %offset
This still looks very good, but LLVM does not really translate that to
what would be considered ideal machine code (on any target). For example
that's the codegen we obtain for an unknown alignment:
; x86_64
dec rsi
mov rax, rdi
neg rax
and rax, rsi
add rax, rdi
In particular negating a pointer is not something that’s going to be
optimised for in the design of CISC architectures like x86_64. They
are much better at offsetting pointers. And so we’d love to utilize this
ability and produce code that's more like this:
; x86_64
lea rax, [rsi + rdi - 1]
neg rsi
and rax, rsi
To achieve this we need to give LLVM an opportunity to apply its
various peep-hole optimisations that it does during DAG selection. In
particular, the `and` instruction appears to be a major inhibitor here.
We cannot, sadly, get rid of this load-bearing operation, but we can
reorder operations such that LLVM has more to work with around this
instruction.
One such ordering is proposed in #75579 and results in LLVM IR that
looks broadly like this:
; using add enables `lea` and similar CISCisms
%offset_ptr = add i64 %address, %a_minus_one
%mask = sub i64 0, %a
%masked = and i64 %offset_ptr, %mask
; can be folded with `gepi` that may follow
%offset = sub i64 %masked, %address
…and generates the intended x86_64 machine code.
One might also wonder how the increased amount of code would impact a
RISC target. Turns out not much:
; aarch64 previous ; aarch64 new
sub x8, x1, #1 add x8, x1, x0
neg x9, x0 sub x8, x8, #1
and x8, x9, x8 neg x9, x1
add x0, x0, x8 and x0, x8, x9
(and similarly for ppc, sparc, mips, riscv, etc)
The only target that seems to do worse is… wasm32.
Onto actual measurements – the best way to evaluate snipets like these
is to use llvm-mca. Much like Aarch64 assembly would allow to suspect,
there isn’t any performance difference to be found. Both snippets
execute in same number of cycles for the CPUs I tried. On x86_64,
we get throughput improvement of >50%!
Fixes#75579
Properly define va_arg and va_list for aarch64-apple-darwin
From [Apple][]:
> Because of these changes, the type `va_list` is an alias for `char*`,
> and not for the struct type in the generic procedure call standard.
With this change `/x.py test --stage 1 src/test/ui/abi/variadic-ffi`
passes.
Fixes#78092
[Apple]: https://developer.apple.com/documentation/xcode/writing_arm64_code_for_apple_platforms
transmute_copy: explain that alignment is handled correctly
The doc comment currently is somewhat misleading because if it actually transmuted `&T` to `&U`, a higher-aligned `U` would be problematic.
replace `#[allow_internal_unstable]` with `#[rustc_allow_const_fn_unstable]` for `const fn`s
`#[allow_internal_unstable]` is currently used to side-step feature gate and stability checks.
While it was originally only meant to be used only on macros, its use was expanded to `const fn`s.
This pr adds stricter checks for the usage of `#[allow_internal_unstable]` (only on macros) and introduces the `#[rustc_allow_const_fn_unstable]` attribute for usage on `const fn`s.
This pr does not change any of the functionality associated with the use of `#[allow_internal_unstable]` on macros or the usage of `#[rustc_allow_const_fn_unstable]` (instead of `#[allow_internal_unstable]`) on `const fn`s (see https://github.com/rust-lang/rust/issues/69399#issuecomment-712911540).
Note: The check for `#[rustc_allow_const_fn_unstable]` currently only validates that the attribute is used on a function, because I don't know how I would check if the function is a `const fn` at the place of the check. I therefore openend this as a 'draft pull request'.
Closesrust-lang/rust#69399
r? @oli-obk
Fix const core::panic!(non_literal_str).
Invocations of `core::panic!(x)` where `x` is not a string literal expand to `panic!("{}", x)`, which is not understood by the const panic logic right now. This adds `panic_str` as a lang item, and modifies the const eval implementation to hook into this item as well.
This fixes the issue mentioned here: https://github.com/rust-lang/rust/issues/51999#issuecomment-687604248
r? `@RalfJung`
`@rustbot` modify labels: +A-const-eval
change the order of type arguments on ControlFlow
This allows ControlFlow<BreakType> which is much more ergonomic for common iterator combinator use cases.
Addresses one component of #75744
Check for exhaustion in RangeInclusive::contains and slicing
When a range has finished iteration, `is_empty` returns true, so it
should also be the case that `contains` returns false.
Fixes#77941.
add `insert` to `Option`
This removes a cause of `unwrap` and code complexity.
This allows replacing
```
option_value = Some(build());
option_value.as_mut().unwrap()
```
with
```
option_value.insert(build())
```
It's also useful in contexts not requiring the mutability of the reference.
Here's a typical cache example:
```
let checked_cache = cache.as_ref().filter(|e| e.is_valid());
let content = match checked_cache {
Some(e) => &e.content,
None => {
cache = Some(compute_cache_entry());
// unwrap is OK because we just filled the option
&cache.as_ref().unwrap().content
}
};
```
It can be changed into
```
let checked_cache = cache.as_ref().filter(|e| e.is_valid());
let content = match checked_cache {
Some(e) => &e.content,
None => &cache.insert(compute_cache_entry()).content,
};
```
*(edited: I removed `insert_with`)*
This removes a cause of `unwrap` and code complexity.
This allows replacing
```
option_value = Some(build());
option_value.as_mut().unwrap()
```
with
```
option_value.insert(build())
```
or
```
option_value.insert_with(build)
```
It's also useful in contexts not requiring the mutability of the reference.
Here's a typical cache example:
```
let checked_cache = cache.as_ref().filter(|e| e.is_valid());
let content = match checked_cache {
Some(e) => &e.content,
None => {
cache = Some(compute_cache_entry());
// unwrap is OK because we just filled the option
&cache.as_ref().unwrap().content
}
};
```
It can be changed into
```
let checked_cache = cache.as_ref().filter(|e| e.is_valid());
let content = match checked_cache {
Some(e) => &e.content,
None => &cache.insert_with(compute_cache_entry).content,
};
```
Doc formating consistency between slice sort and sort_unstable, and big O notation consistency
Updated documentation for slice sorting methods to be consistent between stable and unstable versions, which just ended up being minor formatting differences.
I also went through and updated any doc comments with big O notation to be consistent with #74010 by italicizing them rather than having them in a code block.
Implement TryFrom between NonZero types.
This will instantly be stable, as trait implementations for stable types and traits can not be `#[unstable]`.
Closes#77258.
@rustbot modify labels: +T-libs
Duration::ZERO composes better with match and various other things,
at the cost of an occasional parens, and results in less work for the
optimizer, so let's use that instead.
This expands time's test suite to use more and in more places the
range of methods and constants added to Duration in recent
proposals for the sake of testing more API surface area and
improving legibility.
Improve wording of "cannot multiply" type error
For example, if you had this code:
fn foo(x: i32, y: f32) -> f32 {
x * y
}
You would get this error:
error[E0277]: cannot multiply `f32` to `i32`
--> src/lib.rs:2:7
|
2 | x * y
| ^ no implementation for `i32 * f32`
|
= help: the trait `Mul<f32>` is not implemented for `i32`
However, that's not usually how people describe multiplication. People
usually describe multiplication like how the division error words it:
error[E0277]: cannot divide `i32` by `f32`
--> src/lib.rs:2:7
|
2 | x / y
| ^ no implementation for `i32 / f32`
|
= help: the trait `Div<f32>` is not implemented for `i32`
So that's what this change does. It changes this:
error[E0277]: cannot multiply `f32` to `i32`
--> src/lib.rs:2:7
|
2 | x * y
| ^ no implementation for `i32 * f32`
|
= help: the trait `Mul<f32>` is not implemented for `i32`
To this:
error[E0277]: cannot multiply `i32` by `f32`
--> src/lib.rs:2:7
|
2 | x * y
| ^ no implementation for `i32 * f32`
|
= help: the trait `Mul<f32>` is not implemented for `i32`
Add Pin::static_ref, static_mut.
This adds `Pin::static_ref` and `Pin::static_mut`, which convert a static reference to a pinned static reference.
Static references are effectively already pinned, as what they refer to has to live forever and can never be moved.
---
Context: I want to update the `sys` and `sys_common` mutexes/rwlocks/condvars to use `Pin<&self>` in their functions, instead of only warning in the unsafety comments that they may not be moved. That should make them a little bit less dangerous to use. Putting such an object in a `static` (e.g. through `sys_common::StaticMutex`) fulfills the requirements about never moving it, but right now there's no safe way to get a `Pin<&T>` to a `static`. This solves that.
Writing any fmt::Arguments would trigger the inclusion of usize
formatting and padding code in the resulting binary, because indexing
used in fmt::write would generate code using panic_bounds_check, which
prints the index and length.
These bounds checks are not necessary, as fmt::Arguments never contains
any out-of-bounds indexes.
This change replaces them with unsafe get_unchecked, to reduce the
amount of generated code, which is especially important for embedded
targets.
Move `slice::check_range` to `RangeBounds`
Since this method doesn't take a slice anymore (#76662), it makes more sense to define it on `RangeBounds`.
Questions:
- Should the new method be `assert_len` or `assert_length`?
For example, if you had this code:
fn foo(x: i32, y: f32) -> f32 {
x * y
}
You would get this error:
error[E0277]: cannot multiply `f32` to `i32`
--> src/lib.rs:2:7
|
2 | x * y
| ^ no implementation for `i32 * f32`
|
= help: the trait `Mul<f32>` is not implemented for `i32`
However, that's not usually how people describe multiplication. People
usually describe multiplication like how the division error words it:
error[E0277]: cannot divide `i32` by `f32`
--> src/lib.rs:2:7
|
2 | x / y
| ^ no implementation for `i32 / f32`
|
= help: the trait `Div<f32>` is not implemented for `i32`
So that's what this change does. It changes this:
error[E0277]: cannot multiply `f32` to `i32`
--> src/lib.rs:2:7
|
2 | x * y
| ^ no implementation for `i32 * f32`
|
= help: the trait `Mul<f32>` is not implemented for `i32`
To this:
error[E0277]: cannot multiply `i32` by `f32`
--> src/lib.rs:2:7
|
2 | x * y
| ^ no implementation for `i32 * f32`
|
= help: the trait `Mul<f32>` is not implemented for `i32`
Deny broken intra-doc links in linkchecker
Since rustdoc isn't warning about these links, check for them manually.
This also fixes the broken links that popped up from the lint.
Add `str::{Split,RSplit,SplitN,RSplitN,SplitTerminator,RSplitTerminator,SplitInclusive}::as_str` methods
tl;dr this allows viewing unyelded part of str-split-iterators, like so:
```rust
let mut split = "Mary had a little lamb".split(' ');
assert_eq!(split.as_str(), "Mary had a little lamb");
split.next();
assert_eq!(split.as_str(), "had a little lamb");
split.by_ref().for_each(drop);
assert_eq!(split.as_str(), "");
```
--------------
This PR adds semi-identical `as_str` methods to most str-split-iterators with signatures like `&'_ Split<'a, P: Pattern<'a>> -> &'a str` (Note: output `&str` lifetime is bound to the `'a`, not the `'_`). The methods are similar to [`Chars::as_str`]
`SplitInclusive::as_str` is under `"str_split_inclusive_as_str"` feature gate, all other methods are under `"str_split_as_str"` feature gate.
Before this PR you had to sum `len`s of all yielded parts or collect into `String` to emulate `as_str`.
[`Chars::as_str`]: https://doc.rust-lang.org/core/str/struct.Chars.html#method.as_str
Replace absolute paths with relative ones
Modern compilers allow reaching external crates
like std or core via relative paths in modules
outside of lib.rs and main.rs.
Stabilize slice_partition_at_index
This stabilizes slice_partition_at_index, including renaming `partition_at_index*` -> `select_nth_unstable*`.
Closes#55300
r? `@Amanieu`
The stabilisation issue, #73413, has an open item for documentation.
I looked at the docs and it is all there, but I felt it could do with
some minor wording improvement.
I looked at the `str::strip_prefix` docs for a template. (That
resulted in me slightly changing that doc too.)
I de-linkified `None` and `Some`, as I felt that rather noisy.. I
searched stdlib, and these don't seem to be usually linkified.
Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>
"Some is returned with <some value>" is an awkward construction.
The use of the passive voice is a bit odd, and doesn't seem like the
house style.
So say instead "returns X, wrapped in `Some`", for which there is some
other precedent in stdlib.
Instead of repeating "with the prefix removed", say "after the
prefix". This is a bit clearer that the original is not modified.
Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>
This stabilizes the functionality in slice_partition_at_index,
but under the names `select_nth_unstable*`. The functions
`partition_at_index*` are left as deprecated, to be removed in
a later release.
Closes#55300
Allow generic parameters in intra-doc links
Fixes#62834.
---
The contents of the generics will be mostly ignored (except for warning
if fully-qualified syntax is used, which is currently unsupported in
intra-doc links - see issue #74563).
* Allow links like `Vec<T>`, `Result<T, E>`, and `Option<Box<T>>`
* Allow links like `Vec::<T>::new()`
* Warn on
* Unbalanced angle brackets (e.g. `Vec<T` or `Vec<T>>`)
* Missing type to apply generics to (`<T>` or `<Box<T>>`)
* Use of fully-qualified syntax (`<Vec as IntoIterator>::into_iter`)
* Invalid path separator (`Vec:<T>:new`)
* Too many angle brackets (`Vec<<T>>`)
* Empty angle brackets (`Vec<>`)
Note that this implementation *does* allow some constructs that aren't
valid in the actual Rust syntax, for example `Box::<T>new()`. That may
not be supported in rustdoc in the future; it is an implementation
detail.
Give `impl Trait` in a `const fn` its own feature gate
...previously it was gated under `#![feature(const_fn)]`.
I think we actually want to do this in all const-contexts? If so, this should be `#![feature(const_impl_trait)]` instead. I don't think there's any way to make use of `impl Trait` within a `const` initializer.
cc #77463
r? `@oli-obk`
Eliminate bounds checking in slice::Windows
This is how `<core::slice::Windows as Iterator>::next` looks right now:
```rust
fn next(&mut self) -> Option<&'a [T]> {
if self.size > self.v.len() {
None
} else {
let ret = Some(&self.v[..self.size]);
self.v = &self.v[1..];
ret
}
}
```
The line with `self.v = &self.v[1..];` relies on assumption that `self.v` is definitely not empty at this point. Else branch is taken when `self.size <= self.v.len()`, so `self.v` can be empty if `self.size` is zero. In practice, since `Windows` is never created directly but rather trough `[T]::windows` which panics when `size` is zero, `self.size` is never zero. However, the compiler doesn't know about this check, so it keeps the code which checks bounds and panics.
Using `NonZeroUsize` lets the compiler know about this invariant and reliably eliminate bounds checking without `unsafe` on `-O2`. Here is assembly of `Windows<'a, u32>::next` before and after this change ([goldbolt](https://godbolt.org/z/xrefzx)):
<details>
<summary>Before</summary>
```
example::next:
push rax
mov rcx, qword ptr [rdi + 8]
mov rdx, qword ptr [rdi + 16]
cmp rdx, rcx
jbe .LBB0_2
xor eax, eax
pop rcx
ret
.LBB0_2:
test rcx, rcx
je .LBB0_5
mov rax, qword ptr [rdi]
mov rsi, rax
add rsi, 4
add rcx, -1
mov qword ptr [rdi], rsi
mov qword ptr [rdi + 8], rcx
pop rcx
ret
.LBB0_5:
lea rdx, [rip + .L__unnamed_1]
mov edi, 1
xor esi, esi
call qword ptr [rip + core::slice::slice_index_order_fail@GOTPCREL]
ud2
.L__unnamed_2:
.ascii "./example.rs"
.L__unnamed_1:
.quad .L__unnamed_2
.asciz "\f\000\000\000\000\000\000\000\016\000\000\000\027\000\000"
```
</details>
<details>
<summary>After</summary>
```
example::next:
mov rcx, qword ptr [rdi + 8]
mov rdx, qword ptr [rdi + 16]
cmp rdx, rcx
jbe .LBB0_2
xor eax, eax
ret
.LBB0_2:
mov rax, qword ptr [rdi]
lea rsi, [rax + 4]
add rcx, -1
mov qword ptr [rdi], rsi
mov qword ptr [rdi + 8], rcx
ret
```
</details>
Note the lack of call to `core::slice::slice_index_order_fail` in second snippet.
#### Possible reasons _not_ to merge this PR:
* this changes the error message on panic in `[T]::windows`. However, AFAIK this messages are not covered by backwards compatibility policy.
Implement advance_by, advance_back_by for iter::Chain
Part of #77404.
This PR does two things:
- implement `Chain::advance[_back]_by` in terms of `advance[_back]_by` on `self.a` and `advance[_back]_by` on `self.b`
- change `Chain::nth[_back]` to use `advance[_back]_by` on `self.a` and `nth[_back]` on `self.b`
This ensures that `Chain::nth` can take advantage of an efficient `nth` implementation on the second iterator, in case it doesn't implement `advance_by`.
cc `@scottmcm` in case you want to review this
Use more intra-doc-links in `core::fmt`
This is a follow-up to #75819, which encountered some broken links due to #75176, so this PR contains the links that are blocked on #75176.
r? @jyn514
Allows getting the slices directly, rather than just through an iterator as in `array_chunks(_mut)`. The constructors for those iterators are then written in terms of these methods, so the iterator constructors no longer have any `unsafe` of their own.
Hint the maximum length permitted by invariant of slices
One of the safety invariants of references, and in particular of references to slices, is that they may not cover more than `isize::MAX` bytes. The unsafe `from_raw_parts` constructors of slices explicitly requires the caller to guarantee this fact. Violating it would also be UB with regards to the semantics of generated llvm code.
This effectively bounds the length of a (non-ZST) slice from above by a compile time constant. But when the length is loaded from a function argument it appears llvm is not aware of this requirement. The additional value range assertions allow some further elision of code branches, including overflow checks, especially in the presence of artithmetic on the indices.
This may have a performance impact, adding more code to a common method but allowing more optimization. I'm not quite sure, is the Rust side of const-prop strong enough to elide the irrelevant match branches?
Fixes: #67186
Uses assume to check the length against a constant upper bound. The
inlined result then informs the optimizer of the sound value range.
This was tried with unreachable_unchecked before which introduces a
branch. This has the advantage of not being executed in sound code but
complicates basic blocks. It resulted in ~2% increased compile time in
some worst cases.
Add a codegen test for the assumption, testing the issue from #67186
Implement as_ne_bytes() for integers and floats
This is related to issue #64464.
I am pretty sure that these functions are actually const-ify-able, and technically as_bits() can also be implemented for floats, but I might need some comments on both.
Use less divisions in display u128/i128
This PR is an absolute mess, and I need to test if it improves the speed of fmt::Display for u128/i128, but I think it's correct.
It hopefully is more efficient by cutting u128 into at most 2 u64s, and also chunks by 1e16 instead of just 1e4.
Also I specialized the implementations for uints to always be non-false because it bothered me that it was checked at all
Do not merge until I benchmark it and also clean up the god awful mess of spaghetti.
Based on prior work in #44583
cc: `@Dylan-DPC`
Due to work on `itoa` and suggestion in original issue:
r? `@dtolnay`
Stabilize slice_ptr_range.
This has been unstable for almost a year now. Time to stabilize?
Closes#65807.
@rustbot modify labels: +T-libs +A-raw-pointers +A-slice +needs-fcp
This commit entroduces `core::str::SplitInclusive::as_str` method similar to
`core::str::Split::as_str`, but under different gate -
"str_split_inclusive_as_str" (this is done so because `SplitInclusive` is
itself unstable).
This commit introduses 2 methods under "str_split_as_str" gate with common
signature of `&Split<'a, _> -> &'a str'`. Both of them work like
`Chars::as_str` - return unyield part of the inner string.
Refactor memchr to allow optimization
Closes#75659
The implementation already uses naive search if the slice if short enough, but the case is complicated enough to not be optimized away. This PR refactors memchr so that it exists early when the slice is short enough.
Codegen-wise, as shown in #75659, memchr was not inlined previously so the only way I could find to test this is to check if there is no memchr call. Let me know if there is a more robust solution here.
Add Iterator::advance_by and DoubleEndedIterator::advance_back_by
This PR adds the iterator method
```rust
fn advance_by(&mut self, n: usize) -> Result<(), usize>
```
that advances the iterator by `n` elements, returning `Ok(())` if this succeeds or `Err(len)` if the length of the iterator was less than `n`.
Currently `Iterator::nth` is the method to override for efficiently advancing an iterator by multiple elements at once. `advance_by` is superior for this purpose because
- it's simpler to implement: instead of advancing the iterator and producing the next element you only need to advance the iterator
- it composes better: iterators like `Chain` and `FlatMap` can implement `advance_by` in terms of `advance_by` on their inner iterators, but they cannot implement `nth` in terms of `nth` on their inner iterators (see #60395)
- the default implementation of `nth` can trivially be implemented in terms of `advance_by` and `next`, which this PR also does
This PR also adds `DoubleEndedIterator::advance_back_by` for all the same reasons.
I'll make a tracking issue if it's decided this is worth merging. Also let me know if anything can be improved, this went through several iterations so there might very well still be room for improvement (especially in the doc comments). I've written overrides of these methods for most iterators that already override `nth`/`nth_back`, but those still need tests so I'll add them in a later PR.
cc @cuviper @scottmcm @Amanieu
Split core/str/mod.rs to smaller files
Note for reviewer:
* I split to multiple commits for easier reviewing, but I could git squash them all to one if requested.
* Recommend pulling this change locally and using advanced git diff viewer or this command:
```bash
git show --reverse --color-moved=dimmed-zebra --color-moved-ws=ignore-all-space master..
```
---
I split `core/str/mod.rs` to these modules:
* `converts`: Contains helper functions to convert from bytes to str.
* `error`: For error structs like Utf8Error.
* `iter`: For iterators of many str methods.
* `traits`: For indexing operations and build in traits on str.
* `validations`: For functions validating utf8 --- This name is awkward, maybe utf8.rs is better.
Add zero padding
Add benchmarks for fmt u128
This tests both when there is the max amount of work(all characters used)
And least amount of work(1 character used)
Add doc alias for iterator fold
fold is known in python and javascript as reduce,
not sure about inject but it was written in doc there.
This was my first confusion when coming into rust, I somehow cannot find where is reduce, sometimes I still forget that it is known as `fold`.
Remove `#[rustc_allow_const_fn_ptr]` and add `#![feature(const_fn_fn_ptr_basics)]`
`rustc_allow_const_fn_ptr` was a hack to work around the lack of an escape hatch for the "min `const fn`" checks in const-stable functions. Now that we have co-opted `allow_internal_unstable` for this purpose, we no longer need a bespoke attribute.
Now this functionality is gated under `const_fn_fn_ptr_basics` (how concise!), and `#[allow_internal_unstable(const_fn_fn_ptr_basics)]` replaces `#[rustc_allow_const_fn_ptr]`. `const_fn_fn_ptr_basics` allows function pointer types to appear in the arguments and locals of a `const fn` as well as function pointer casts to be performed inside a `const fn`. Both of these were allowed in constants and statics already. Notably, this does **not** allow users to invoke function pointers in a const context. Presumably, we will use a nicer name for that (`const_fn_ptr`?).
r? @oli-obk
UI to unit test for those using Cell/RefCell/UnsafeCell
Helps with #76268.
I'm working on all files using `Cell` and moving them to unit tests when possible.
r? @matklad
This was a hack to work around the lack of an escape hatch for the "min
`const fn`" checks in const-stable functions. Now that we have co-opted
`allow_internal_unstable` for this purpose, we no longer need the
bespoke attribute.
Add `#![feature(const_fn_floating_point_arithmetic)]`
cc #76618
This is a template for splitting up `const_fn` into granular feature gates. I think this will make it easier, both for us and for users, to track stabilization of each individual feature. We don't *have* to do this, however. We could also keep stabilizing things out from under `const_fn`.
cc @rust-lang/wg-const-eval
r? @oli-obk
Explicitly document the size guarantees that Option makes.
Triggered by a discussion on wg-unsafe-code-guidelines about which layouts of `Option<T>` one can guarantee are optimised to a single pointer.
CC @RalfJung
It's possible for method resolution to pick this method over a lower
priority stable method, causing compilation errors. Since this method
is permanently unstable, give it a name that is very unlikely to be used
in user code.
Make [].as_[mut_]ptr_range() (unstably) const.
Gated behind `const_ptr_offset`, as suggested by https://github.com/rust-lang/rust/issues/65807#issuecomment-697229404
This also marks `[].as_mut_ptr()` as const, because it's used by `as_mut_ptr_range`. I gated it behind the same feature, because I figured it's not worth adding a separate tracking issue for const `as_mut_ptr`.
Use `Self` in docs when possible
Fixes#76542.
I used `rg '\s*//[!/]\s+fn [\w_]+\(&?self, ' .` in `library/` to find instances, I found some with that and some by manually checking.
@rustbot modify labels: C-enhancement T-doc
add array::from_ref
mirrors the methods in `std::slice` with the same name.
I guess this method previously didn't exist as there was close to no reason to create an array of size `1`.
This will change due to const generics in the near future.
revert const_type_id stabilization
This reverts #72488, which is currently on beta and scheduled to stabilize in `1.47.0`, based on https://github.com/rust-lang/rust/pull/75923#issuecomment-696676511
It turns out we might not be quite ready to stabilize `TypeId` in const contexts before having a chance to rework its internals. Since `TypeId` is a bit of an oddity we want to be careful about how those internals are currently being relied on while making changes. That will be easier to do without having to also consider compile-time contexts.
r? `@eddyb`
Add #[track_caller] to more panicking Cell functions
Continuation of #74526
Adds the #[track_caller] attribute to almost all panicking Cell
functions. The ones that borrow two Cells in their function
body are spared, because the panic location helps pinpoint
which of the two borrows failed. You'd need to have
full debuginfo and backtraces enabled together with column
info in order to be able to discern the cases.
Column info in debuginfo is only available on non-Windows platforms.
Add cfg(target_has_atomic_equal_alignment) and use it for Atomic::from_mut.
Fixes some platform-specific problems with #74532 by using the actual alignment of the types instead of hardcoding a few `target_arch`s.
r? @RalfJung
Continuation of #74526
Adds the #[track_caller] attribute to almost all panicking Cell
functions. The ones that borrow two Cells in their function
body are spared, because the panic location helps pinpoint
which of the two borrows failed. You'd need to have
full debuginfo and backtraces enabled together with column
info in order to be able to discern the cases.
Column info is only available on non-Windows platforms.
Make some methods of `Pin` unstable const
Make the following methods unstable const under the `const_pin` feature:
- `new`
- `new_unchecked`
- `into_inner`
- `into_inner_unchecked`
- `get_ref`
- `into_ref`
- `get_mut`
- `get_unchecked_mut`
Of these, `into_inner` and `into_inner_unchecked` require the unstable `const_precise_live_drops`.
Also adds tests for these methods in a const context.
Tracking issue: #76654
r? @ecstatic-morse
Don't recommend ManuallyDrop to customize drop order
See
https://internals.rust-lang.org/t/need-for-controlling-drop-order-of-fields/12914/21
for the discussion.
TL;DR: ManuallyDrop is unsafe and footguny, but you can just ask the compiler to do all the work for you by re-ordering declarations.
Specifically, the original example from the docs is much better written as
```rust
struct Peach;
struct Banana;
struct Melon;
struct FruitBox {
melon: Melon,
// XXX: mind the relative drop order of the fields below
peach: Peach,
banana: Banana,
}
```
Revert adding Atomic::from_mut.
This reverts #74532, which made too many assumptions about platforms, breaking some things.
Will need to be added later with a better way of gating on proper alignment, without hardcoding cfg(target_arch)s.
---
To be merged if fixing from_mut (#76965) takes too long.
r? @ghost
Add non-`unsafe` `.get_mut()` for `Unsafecell`
- Tracking issue: https://github.com/rust-lang/rust/issues/76943
As discussed in: https://internals.rust-lang.org/t/add-non-unsafe-get-mut-for-unsafecell/12407
- ### [Rendered documentation](https://modest-dubinsky-1f9f47.netlify.app/core/cell/struct.unsafecell)
This PR tries to move the sound `&mut UnsafeCell<T> -> &mut T` projection that all the "downstream" constructions were already relying on, up to the root abstraction, where it rightfully belongs, and officially blessing it.
- this **helps reduce the amount of `unsafe` snippets out there** (_c.f._, the second commit of this PR: 09503fd1b3)
The fact that this getter is now expose for `UnsafeCell<T>` itself, will also help convey the idea that **`UnsafeCell` is not magical _w.r.t._ `&mut` accesses**, contrary to what some people incorrectly think.
- Even the standard library itself at some point had such a confusion, _c.f._ this comment where there is a mention of multi-threaded (and thus _shared_) access despite dealing with exclusive references over unique ownership: 59fb88d061/library/core/src/cell.rs (L498-L499)
r? @RalfJung
Use intra-doc links in core/src/iter when possible
Helps with #75080.
I also updated lots of links to use `fn()` instead of `fn` when possible.
@rustbot modify labels: T-doc A-intra-doc-links
r? @jyn514
Stabilize some Option methods as const
Stabilize the following methods of `Option` as const:
- `is_some`
- `is_none`
- `as_ref`
These methods are currently const under the unstable feature `const_option` (tracking issue: #67441).
I believe these methods to be eligible for stabilization because of the stabilization of #49146 (Allow if and match in constants) and the trivial implementations, see also: [PR#75463](https://github.com/rust-lang/rust/pull/75463).
Related: #76225
Remove MMX from Rust
Follow-up to https://github.com/rust-lang/stdarch/pull/890
This removes most of MMX from Rust (tests pass with small changes), keeping stable `is_x86_feature_detected!("mmx")` working.
Stabilize the following methods of `Option` as const:
- `is_some`
- `is_none`
- `as_ref`
Possible because of stabilization of #49146 (Allow if and match in constants).
Rollup of 15 pull requests
Successful merges:
- #76732 (Add docs for `BasicBlock`)
- #76832 (Let backends define custom targets)
- #76866 (Remove unused feature gates from library/ crates)
- #76875 (Move to intra-doc links in library/alloc/src/collections/binary_heap.rs)
- #76876 (Move to intra-doc links in collections/btree/map.rs and collections/linked_list.rs)
- #76877 (Move to intra-doc links in collections/vec_deque.rs and collections/vec_deque/drain.rs)
- #76878 (Move the version number to a plaintext file)
- #76883 (README.md: Remove prompts from code blocks)
- #76887 (Add missing examples on HashSet iter types)
- #76890 (use matches!() macro for simple if let conditions)
- #76891 (don't take `TyCtxt` by reference)
- #76910 (transmute: use diagnostic item)
- #76924 (Add tracking issue for feature(unix_socket_peek))
- #76926 (BTreeMap: code readability tweaks)
- #76940 (Don't allow implementing trait directly on type-alias-impl-trait)
Failed merges:
r? `@ghost`
transmute: use diagnostic item
closes#66075, we now have no remaining uses of `match_def_path` in the compiler while some uses still remain in `clippy`.
cc @RalfJung
Remove unused feature gates from library/ crates
Removes some unused feature gates from library crates. It's likely not a complete list as I only tested a subset for which it's more likely that it is unused.
Stabilize some Result methods as const
Stabilize the following methods of Result as const:
- `is_ok`
- `is_err`
- `as_ref`
A test is also included, analogous to the test for `const_option`.
These methods are currently const under the unstable feature `const_result` (tracking issue: #67520).
I believe these methods to be eligible for stabilization because of the stabilization of #49146 (Allow if and match in constants) and the trivial implementations, see also: [PR#75463](https://github.com/rust-lang/rust/pull/75463) and [PR#76135](https://github.com/rust-lang/rust/pull/76135).
Note: these methods are the only methods currently under the `const_result` feature, thus this PR results in the removal of the feature.
Related: #76225
This made too many assumptions about platforms, breaking some things.
Will need to be added later with a better way of gating on proper
alignment, without hardcoding cfg(target_arch)s.
Add associated constant `BITS` to all integer types
Recently I've regularly come across this snippet (in a few different crates, including `core` and `std`):
```rust
std::mem::size_of<usize>() * 8
```
I think it's time for a `usize::BITS`.
do not inline black_box when building for Miri
We cannot do the assembly trick in Miri, but let's at least make sure MIR inlining does not circumvent the black_box.
Also use black_box instead of local optimization barriers in a few const tests.
Add array_windows fn
This mimicks the functionality added by array_chunks, and implements a const-generic form of
`windows`. It makes egregious use of `unsafe`, but by necessity because the array must be
re-interpreted as a slice of arrays, and unlike array_chunks this cannot be done by casting the
original array once, since each time the index is advanced it needs to move one element, not
`N`.
I'm planning on adding more tests, but this should be good enough as a premise for the functionality.
Notably: should there be more functions overwritten for the iterator implementation/in general?
~~I've marked the issue as #74985 as there is no corresponding exact issue for `array_windows`, but it's based of off `array_chunks`.~~
Edit: See Issue #75027 created by @lcnr for tracking issue
~~Do not merge until I add more tests, please.~~
r? @lcnr
Updated issue to #75027
Update to rm oob access
And hopefully fix docs as well
Fixed naming conflict in test
Fix test which used 1-indexing
Nth starts from 0, woops
Fix a bunch of off by 1 errors
See https://play.rust-lang.org/?version=nightly&mode=debug&edition=2018&gist=757b311987e3fae1ca47122969acda5a
Add even more off by 1 errors
And also write `next` and `next_back` in terms of `nth` and `nth_back`.
Run fmt
Fix forgetting to change fn name in test
add nth_back test & document unsafe
Remove as_ref().unwrap()
Documented occurrences of unsafe, noting what invariants are maintained
Fix liballoc test suite for Miri
Mostly, fix the regression introduced by https://github.com/rust-lang/rust/pull/75207 that caused slices (i.e., references) to be created to invalid memory or memory that has aliasing pointers that we want to keep valid. @dylni this changes the type of `check_range` to only require the length, not the full reference to the slice, which indeed is all the information this function requires.
Also reduce the size of a test introduced in https://github.com/rust-lang/rust/pull/70793 to make it not take 3 minutes in Miri.
This makes https://github.com/RalfJung/miri-test-libstd work again.
Make all methods of `Duration` unstably const
Make the following methods of `Duration` unstable const under `duration_const_2`:
- `from_secs_f64`
- `from_secs_f32`
- `mul_f64`
- `mul_f32`
- `div_f64`
- `div_f32`
This results in all methods of `Duration` being (unstable) const.
Moved the tests to `library` as part of #76268.
Possible because of #72449, which made the relevant `f32` and `f64` methods const.
Tracking issue: #72440
r? @ecstatic-morse
Make some Ordering methods const
Resubmission of [PR#75463](https://github.com/rust-lang/rust/pull/75463) as per [PR#76172](https://github.com/rust-lang/rust/pull/76172).
Constify the following methods of `core::cmp::Ordering`:
- `reverse`
- `then`
Insta-stabilizes these methods as const under the `const_ordering` feature, as their implementation is a trivial match and the recent stabilization of #49146 (Allow `if` and `match` in constants).
Note: the `const_ordering` feature has never actually been used as these methods have not been `#[rustc_const_unstable]`.
Tracking issue: #76113
Note when a a move/borrow error is caused by a deref coercion
Fixes#73268
When a deref coercion occurs, we may end up with a move error if the
base value has been partially moved out of. However, we do not indicate
anywhere that a deref coercion is occuring, resulting in an error
message with a confusing span.
This PR adds an explicit note to move errors when a deref coercion is
involved. We mention the name of the type that the deref-coercion
resolved to, as well as the `Deref::Target` associated type being used.
Split `core::slice` to smaller mods
Unfortunately the `#[lang = "slice"]` is too big (3003 lines), I cannot split it further.
Note for reviewer:
* I split to multiple commits for easier reviewing, but I could git squash them all to one if requested.
* Recommend pulling this change locally and using advanced git diff viewer or this command:
```
git show --reverse --color-moved=dimmed-zebra master..
```
---
I split core/slice/mod.rs to these modules:
* `ascii`: For operations on `[u8]`.
* `cmp`: For comparison operations on `[T]`, like PartialEq and SliceContains impl.
* `index`: For indexing operations like Index/IndexMut and SliceIndex.
* `iter`: For Iterator definitions and implementation on `[T]`.
- `macros`: For iterator! and forward_iterator! macros.
* `raw`: For free function to create `&[T]` or `&mut [T]` from pointer + length or a reference.
The heapsort wrapper in mod.rs is removed in favor of reexport from `sort::heapsort`.
Remove internal and unstable MaybeUninit::UNINIT.
Looks like it is no longer necessary, as `uninit_array()` can be used instead in the few cases where it was needed.
(I wanted to just add `#[doc(hidden)]` to remove clutter from the documentation, but looks like it can just be removed entirely.)
Make the following methods unstable const under the `const_pin` feature:
- `new`
- `new_unchecked`
- `into_inner`
- `into_inner_unchecked`
- `get_ref`
- `into_ref`
Also adds tests for these methods in a const context.
Tracking issue: #76654
Make the following methods of `Duration` unstable const under `duration_const_2`:
- `from_secs_f64`
- `from_secs_f32`
- `mul_f64`
- `mul_f32`
- `div_f64`
- `div_f32`
This results in all methods of `Duration` being (unstable) const.
Also adds tests for these methods in a const context, moved the test to `library` as part of #76268.
Possible because of #72449, which made the relevant `f32` and `f64` methods const.
Tracking issue: #72440
Add MaybeUninit::assume_init_drop.
`ManuallyDrop`'s documentation tells the user to use `MaybeUninit` instead when handling uninitialized data. However, the main functionality of `ManuallyDrop` (`drop`) is not available directly on `MaybeUninit`. Adding it makes it easier to switch from one to the other.
I re-used the `maybe_uninit_extra` feature and tracking issue number (#63567), since it seems very related. (And to avoid creating too many features tracking issues for `MaybeUninit`.)
Add saturating methods for `Duration`
In some project, I needed a `saturating_add` method for `Duration`. I implemented it myself but i thought it would be a nice addition to the standard library as it matches closely with the integers types.
3 new methods have been introduced and are gated by the new `duration_saturating_ops` unstable feature:
* `Duration::saturating_add`
* `Duration::saturating_sub`
* `Duration::saturating_mul`
If have left the tracking issue to `none` for now as I want first to understand if those methods would be acceptable at all. If agreed, I'll update the PR with the tracking issue.
Further more, to match the behavior of integers types, I introduced 2 associated constants:
* `Duration::MIN`: this one is somehow a duplicate from `Duration::zero()` method, but at the time this method was added, `MIN` was rejected as it was considered a different semantic (see https://github.com/rust-lang/rust/pull/72790#issuecomment-636511743).
* `Duration::MAX`
Both have been gated by the already existing unstable feature `duration_constants`, I can introduce a new unstable feature if needed or just re-use the `duration_saturating_ops`.
We might have to decide whether:
* `MIN` should be replaced by `ZERO`?
* associated constants over methods?
Add `slice::array_chunks_mut`
This follows `array_chunks` from #74373 with a mutable version, `array_chunks_mut`. The implementation is identical apart from mutability. The new tests are adaptations of the `chunks_exact_mut` tests, plus an inference test like the one for `array_chunks`.
I reused the unstable feature `array_chunks` and tracking issue #74985, but I can separate that if desired.
r? `@withoutboats`
cc `@lcnr`
Stabilize core::future::{pending,ready}
This PR stabilizes `core::future::{pending,ready}`, tracking issue https://github.com/rust-lang/rust/issues/70921.
## Motivation
These functions have been on nightly for three months now, and have lived as part of the futures ecosystem for several years. In that time these functions have undergone several iterations, with [the `async-std` impls](https://docs.rs/async-std/1.6.2/async_std/future/index.html) probably diverging the most (using `async fn`, which in hindsight was a mistake).
It seems the space around these functions has been _thoroughly_ explored over the last couple of years, and the ecosystem has settled on the current shape of the functions. It seems highly unlikely we'd want to make any further changes to these functions, so I propose we stabilize.
## Implementation notes
This stabilization PR was fairly straightforward; this feature has already thoroughly been reviewed by the libs team already in https://github.com/rust-lang/rust/pull/70834. So all this PR does is remove the feature gate.
Fixes#73268
When a deref coercion occurs, we may end up with a move error if the
base value has been partially moved out of. However, we do not indicate
anywhere that a deref coercion is occuring, resulting in an error
message with a confusing span.
This PR adds an explicit note to move errors when a deref coercion is
involved. We mention the name of the type that the deref-coercion
resolved to, as well as the `Deref::Target` associated type being used.
Use intra-doc links in `core::ptr`
Part of #75080.
The only link that I did not change is a link to a function on the
`pointer` primitive because intra-doc links for the `pointer` primitive
don't work yet (see #63351).
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@rustbot modify labels: A-intra-doc-links T-doc
