This allows the optimizer to turn certain iterator pipelines such as
```rust
let vec = vec![0usize; 100];
vec.into_iter().map(|e| e as isize).collect::<Vec<_>>()
```
into a noop.
The optimization only applies when iterator sources are `T: Copy`
since `impl TrustedRandomAccess for IntoIter<T>`.
No such requirement applies to the output type (`Iterator::Item`).
Fix overflowing length in Vec<ZST> to VecDeque
`Vec` can hold up to `usize::MAX` ZST items, but `VecDeque` has a lower
limit to keep its raw capacity as a power of two, so we should check
that in `From<Vec<T>> for VecDeque<T>`. We can also simplify the
capacity check for the remaining non-ZST case.
Before this fix, the new test would fail on the length:
```
thread 'collections::vec_deque::tests::test_from_vec_zst_overflow' panicked at 'assertion failed: `(left == right)`
left: `0`,
right: `9223372036854775808`', library/alloc/src/collections/vec_deque/tests.rs:474:5
note: panic did not contain expected string
panic message: `"assertion failed: `(left == right)`\n left: `0`,\n right: `9223372036854775808`"`,
expected substring: `"capacity overflow"`
```
That was a result of `len()` using a mask `& (size - 1)` with the
improper length. Now we do get a "capacity overflow" panic as soon as
that `VecDeque::from(vec)` is attempted.
Fixes#80167.
Add `as_str` method for split whitespace str iterators
This PR adds `as_str` methods to `SplitWhitespace` and `SplitAsciiWhitespace`
str iterators. The methods return the remainder, similar to `as_str` methods on
`Chars` and other split iterators. This PR is a continuation of https://github.com/rust-lang/rust/pull/75265, which added `as_str` for all other str split iterators.
The feature gate for new methods is `#![feature(str_split_whitespace_as_str)]`.
`SplitWhitespace` and `SplitAsciiWhitespace` use iterators under the hood, so to implement `as_str` it's required to either
1. Make fields of some iterators `pub(crate)`
2. Add getter methods (like `into_inner`, `inner`, `inner_mut`...) to some (all) iterators
3. Completely rewrite `SplitWhitespace` and `SplitAsciiWhitespace`
This PR uses the 1. approach since it's easier to implement and requires fewer changes (and no changes to the public API). If you think that's not the right way, please, tell me.
r? `@m-ou-se`
Fix typo/inaccuracy in the documentation of Iterator::skip_while
One of the examples used to say “this leads to a possibly confusing situation, where the type of the closure is a double reference” while _actually_ referring to the type of the closure _argument_.
This PR just changes a single word in documentation.
`````@rustbot````` modify labels: A-iterators, T-doc, T-lang
Deprecate std::os::haiku::raw, which accidentally wasn't deprecated
In early 2016, all `std::os::*::raw` modules [were deprecated](aa23c98450) in accordance with [RFC 1415](https://github.com/rust-lang/rfcs/blob/master/text/1415-trim-std-os.md). However, at this same time support for Haiku was being added to libstd, landing shortly after the aforementioned commit, and due to some crossed wires a `std::os::haiku::raw` module was added and was not marked as deprecated.
I have been in correspondence with the author of the Haiku patch, ````@nielx,```` who has confirmed that this was simply an oversight and that the definitions from the libc crate should be preferred instead.
Clarify docs for Read::read's return value
Right now the docs for `Read::read`'s return value are phrased in a way that makes it easy for the reader to assume that the return value is never larger than the passed buffer. This PR clarifies that this is a requirement for implementations of the trait, but that callers have to expect a buggy yet safe implementation failing to do so, especially if unchecked accesses to the buffer are done afterwards.
I fell into this trap recently, and when I noticed, I looked at the docs again and had the feeling that I might not have been the first one to miss this.
The same issue of trusting the return value of `read` was also present in std itself for about 2.5 years and only fixed recently, see #80895.
I hope that clarifying the docs might help others to avoid this issue.
Reuse `std::sys::unsupported::pipe` on `hermit`
Pipes are not supported on `hermit` and `hermit/pipe.rs` is identical to `unsupported/pipe.rs`. This PR reduces duplication between the two by doing the following on `hermit`:
```rust
#[path = "../unsupported/pipe.rs"]
pub mod pipe;
```
Implement String::remove_matches
Closes#50206.
I lifted the function help from `@frewsxcv's` original PR (#50015), hope they don't mind.
I'm also wondering whether it would be useful for `remove_matches` to collect up the removed substrings into a `Vec` and return them, right now they're just overwritten by the copy and lost.
One of the examples used to say “this leads to a possibly confusing situation,
where the type of the closure is a double reference” while _actually_ referring to
the type of the closure _argument_.
Add more links between hash and btree collections
- 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
See also https://github.com/rust-lang/rust/pull/81989#issuecomment-783920840.
Vec::dedup_by optimization
Now `Vec::dedup_by` drops items in-place as it goes through them.
From my benchmarks, it is around 10% faster when T is small, with no major regression when otherwise.
I used `ptr::copy` instead of conditional `ptr::copy_nonoverlapping`, because the latter had some weird performance issues on my ryzen laptop (it was 50% slower on it than on intel/sandybridge laptop)
It would be good if someone was able to reproduce these results.
`Vec` can hold up to `usize::MAX` ZST items, but `VecDeque` has a lower
limit to keep its raw capacity as a power of two, so we should check
that in `From<Vec<T>> for VecDeque<T>`. We can also simplify the
capacity check for the remaining non-ZST case.
Before this fix, the new test would fail on the length:
```
thread 'collections::vec_deque::tests::test_from_vec_zst_overflow' panicked at 'assertion failed: `(left == right)`
left: `0`,
right: `9223372036854775808`', library/alloc/src/collections/vec_deque/tests.rs:474:5
note: panic did not contain expected string
panic message: `"assertion failed: `(left == right)`\n left: `0`,\n right: `9223372036854775808`"`,
expected substring: `"capacity overflow"`
```
That was a result of `len()` using a mask `& (size - 1)` with the
improper length. Now we do get a "capacity overflow" panic as soon as
that `VecDeque::from(vec)` is attempted.
Deprecate `intrinsics::drop_in_place` and `collections::Bound`, which accidentally weren't deprecated
Fixes#82080.
I've taken the liberty of updating the `since` values to 1.52, since an unobservable deprecation isn't much of a deprecation (even the detailed release notes never bothered to mention these deprecations).
As mentioned in the issue I'm *pretty* sure that using a type alias for `Bound` is semantically equivalent to the re-export; [the reference implies](https://doc.rust-lang.org/reference/items/type-aliases.html) that type aliases only observably differ from types when used on unit structs or tuple structs, whereas `Bound` is an enum.
Add a check for ASCII characters in to_upper and to_lower
This extra check has better performance. See discussion here:
https://internals.rust-lang.org/t/to-upper-speed/13896
Thanks to `@gilescope` for helping discover and test this.
Deprecate RustcEncodable and RustcDecodable.
We can't remove the `RustcEncodable` and `RustcDecodable` derive macros from the prelude, but we can deprecate them.
Added `try_exists()` method to `std::path::Path`
This method is similar to the existing `exists()` method, except it
doesn't silently ignore the errors, leading to less error-prone code.
This change intentionally does NOT touch the documentation of `exists()`
nor recommend people to use this method while it's unstable.
Such changes are reserved for stabilization to prevent confusing people.
Apart from that it avoids conflicts with #80979.
`@joshtriplett` requested this PR in [internals discussion](https://internals.rust-lang.org/t/the-api-of-path-exists-encourages-broken-code/13817/25?u=kixunil)
Add a `min_type_alias_impl_trait` feature gate
This new feature gate only permits type alias impl trait to be constrained by function and trait method return types. All other possible constraining sites like const/static types, closure return types and binding types are now forbidden and gated under the `type_alias_impl_trait` and `impl_trait_in_bindings` feature gates (which are both marked as incomplete, as they have various ways to ICE the compiler or cause query cycles where they shouldn't).
r? `@nikomatsakis`
This is best reviewed commit-by-commit
