Clarify non-exact length in the Iterator::take documentation
There's an example which demonstrates incomplete length case, but it'd be best to explain it right from the start.
Document panicking cases for integer division and remainder
This PR documents the cases when integer division and remainder operations panic. These operations panic in two cases: division by zero and overflow.
It's surprising that these operations always panic on overflow, unlike most other arithmetic operations, which panic on overflow only when `debug_assertions` is enabled. The panic on overflow for the remainder is also surprising because a return value of `0` would be reasonable in this case. ("Overflow" occurs only for `MIN % -1`.) Since the panics on overflow are somewhat surprising, they should be documented.
I guess it's worth asking: is panic on overflow (even when `debug_assertions` is disabled) the intended behavior? If not, what's the best way forward?
Add license metadata for std dependencies
These five crates are in the dependency tree of `std` but lack license metadata:
- `alloc`
- `core`
- `panic_abort`
- `panic_unwind`
- `unwind`
Querying the dependency tree of `std` is a useful thing to be able to do, since these crates will typically be linked into Rust binaries. Tools show the license fields missing, as seen in https://github.com/rust-lang/rust/issues/67014#issuecomment-782704534. This PR adds the license field for the five crates, based on the license of the `std` package and this repo as a whole. I also added the `repository` and `descriptions` fields, since those seem useful. For `description`, I copied text from top-level comments for the respective modules - except for `unwind` which has none.
I also note that https://github.com/rust-lang/rust/pull/73530 attempted to add license metadata for all crates in this repo, but was rejected because there was question about some of them. I hope that this smaller change, focusing only on the runtime dependencies, will be easier to review.
cc `@Mark-Simulacrum` `@Lokathor`
Fix inequality in docs for div_euclid
This commit fixes the statement of the inequality that the Euclidean remainder satisfies. (The remainder is guaranteed to be less than abs(rhs), not rhs.) It also rewords the documentation to make it a little easier to read.
(You might wonder why I've written `abs(rhs)` instead of `rhs.abs()`. Two reasons: first, the `rem_euclid` docs use `abs(rhs)` instead of `rhs.abs()`, and second, the absolute value here is the mathematical absolute value, not the the `.abs()` operation which may overflow.)
Implement TrustedLen and TrustedRandomAccess for Range<integer>, array::IntoIter, VecDequeue's iterators
This should make some `FromIterator` and `.zip()` specializations applicable in a few more cases.
``@rustbot`` label libs-impl
Make NonNull::as_ref (and friends) return refs with unbound lifetimes
# Rationale:
1. The documentation for all of these functions claims that this is what the functions already do, as they all come with this comment:
> You must enforce Rust's aliasing rules, *since the returned lifetime 'a is arbitrarily chosen* and does not necessarily reflect the actual lifetime of the data...
So I think it's just a bug that they weren't this way already. Note that had it not been for this part, I wouldn't be making this PR, so if we decide we won't take this change, I'll follow it up with a docs PR to fix this.
2. This is how the equivalent raw pointer functions behave.
They also take `self` and not `&self`/`&mut self`, but that can't be changed compatibly at this point. This is the next best thing.
3. Without this fix, often code that uses these methods will find it has to expand the lifetime of the result.
(I can't speak for others but even in unsafe-heavy code, needing to do this unexpectedly is a huge red flag -- if Rust thinks something should have a specific lifetime, I assume it's for a reason)
### Can this cause existing code to be unsound?
I'm confident this can't cause new unsoundness since the reference exists for at most its lifetime, but you get a borrow checker error if you do something that would require/allow the reference to exist past its lifetime.
Additionally, the aliasing rules of a reference only applies while the reference exists.
This *must* be the case, as it is required by the rules used by safe code. (That said, the documentation in this file sort of contradicts it, but I think it's just ambiguity between the lifetime `'a` in `&'a T` and lifetime of the `&'a T` reference itself...)
We are increasing the lifetime of these references, but they should already have hard bounds on that lifetime, or they'd have borrow checker errors.
(CC ``@RalfJung`` because I have gone and done the mistake where I say something definitive about aliasing in Rust which is honestly outside the group of things I should make definitive comments about).
# Caveats
1. This is insta-stable (except for on the unstable functions ofc). I don't think there's any other alternative.
2. I don't believe this is a breaking change in practice. In theory someone could be assigning `NonNull::as_ref` to a function pointer of type `fn(&NonNull<T>) -> &T`. Now they'd need to use a slightly different function pointer type which is (probably) incompatible. This seems pathological, but I guess crater could be used if there are concerns.
3. This has no tests. The old version didn't either that I saw. I could add some stuff that fails to compile without it, if that would be useful.
4. Sometimes the NLL borrow checker gives up and decides lifetimes live till the end of the scope, as opposed to the range where they're used. If this change can cause this to happen more, then my soundness rationale is wrong, and it's likely breaking.
In practice this seems super unlikely.
Anyway. That was a lot of typing.
Fixes https://github.com/rust-lang/rust/issues/80183
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
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.
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.
Add `reverse` search alias for Iterator::rev()
When searching for "reverse" in rustdoc you can't find the rev method on Iterator so here is a search alias for that.
Don't implement mem::replace with mem::swap.
`swap` is a complicated operation, so this changes the implementation of `replace` to use `read` and `write` instead.
See https://github.com/rust-lang/rust/pull/83019.
I wrote there:
> Implementing the simpler operation (replace) with the much more complicated operation (swap) doesn't make a whole lot of sense. `replace` is just read+write, and the primitive for moving out of a `&mut`. `swap` is for doing that to *two* `&mut` at the same time, which is both more niche and more complicated (as shown by `swap_nonoverlapping_bytes`).
This could be especially interesting for `Option<VeryLargeStruct>::take()`, since swapping such a large structure with `swap_nonoverlapping_bytes` is going to be much less efficient than `ptr::write()`'ing a `None`.
But also for small values where `swap` just reads/writes using temporary variable, this makes a `replace` or `take` operation simpler:
convert slice doc link to intra-doc links
Continuing where #80189 stopped, with `core::slice`.
I had an issue with two dead links in my doc when implementing `Deref<Target = [T]>` for one of my type. This means that [`binary_search_by_key`](https://doc.rust-lang.org/nightly/std/primitive.slice.html#method.binary_search_by_key) was available, but not [`sort_by_key`](https://doc.rust-lang.org/nightly/std/primitive.slice.html#method.sort_by_key) even though it was linked in it's doc (same issue with [`as_ptr`](https://doc.rust-lang.org/nightly/std/primitive.slice.html#method.as_ptr) and [`as_mut_pbr`](https://doc.rust-lang.org/nightly/std/primitive.slice.html#method.as_mut_ptr)). It becomes available if I implement `DerefMut`, as it needs an `&mut self`.
<details>
<summary>Code that will have dead links in its doc</summary>
```rust
pub struct A;
pub struct B;
impl std::ops::Deref for B{
type Target = [A];
fn deref(&self) -> &Self::Target {
&A
}
}
```
</details>
I removed the link to `sort_by_key` from `binary_search_by_key` doc as I didn't find a nice way to have a live link:
- `binary_search_by_key` is in `core`
- `sort_by_key` is in `alloc`
- intra-doc link `slice::sort_by_key` doesn't work, as `alloc` is not available when `core` is being build (the warning can't be ignored: ```error[E0710]: an unknown tool name found in scoped lint: `rustdoc::broken_intra_doc_links` ```)
- keeping the link as an anchor `#method.sort_by_key` meant a dead link
- an absolute link would work but doesn't feel right...
