Add documentation to more `From::from` implementations.
For users looking at documentation through IDE popups, this gives them relevant information rather than the generic trait documentation wording “Performs the conversion”. For users reading the documentation for a specific type for any reason, this informs them when the conversion may allocate or copy significant memory versus when it is always a move or cheap copy.
Notes on specific cases:
* The new documentation for `From<T> for T` explains that it is not a conversion at all.
* Also documented `impl<T, U> Into<U> for T where U: From<T>`, the other central blanket implementation of conversion.
* The new documentation for construction of maps and sets from arrays of keys mentions the handling of duplicates. Future work could be to do this for *all* code paths that convert an iterable to a map or set.
* I did not add documentation to conversions of a specific error type to a more general error type.
* I did not add documentation to unstable code.
This change was prepared by searching for the text "From<... for" and so may have missed some cases that for whatever reason did not match. I also looked for `Into` impls but did not find any worth documenting by the above criteria.
For users looking at documentation through IDE popups, this gives them
relevant information rather than the generic trait documentation wording
“Performs the conversion”. For users reading the documentation for a
specific type for any reason, this informs them when the conversion may
allocate or copy significant memory versus when it is always a move or
cheap copy.
Notes on specific cases:
* The new documentation for `From<T> for T` explains that it is not a
conversion at all.
* Also documented `impl<T, U> Into<U> for T where U: From<T>`, the other
central blanket implementation of conversion.
* I did not add documentation to conversions of a specific error type to
a more general error type.
* I did not add documentation to unstable code.
This change was prepared by searching for the text "From<... for" and so
may have missed some cases that for whatever reason did not match. I
also looked for `Into` impls but did not find any worth documenting by
the above criteria.
Add #[must_use] to remaining core functions
I've run out of compelling reasons to group functions together across crates so I'm just going to go module-by-module. This is everything remaining from the `core` crate.
Ignored by clippy for reasons unknown:
```rust
core::alloc::Layout unsafe fn for_value_raw<T: ?Sized>(t: *const T) -> Self;
core::any const fn type_name_of_val<T: ?Sized>(_val: &T) -> &'static str;
```
Ignored by clippy because of `mut`:
```rust
str fn split_at_mut(&mut self, mid: usize) -> (&mut str, &mut str);
```
<del>
Ignored by clippy presumably because a caller might want `f` called for side effects. That seems like a bad usage of `map` to me.
```rust
core::cell::Ref<'b, T> fn map<U: ?Sized, F>(orig: Ref<'b, T>, f: F) -> Ref<'b, T>;
core::cell::Ref<'b, T> fn map_split<U: ?Sized, V: ?Sized, F>(orig: Ref<'b, T>, f: F) -> (Ref<'b, U>, Ref<'b, V>);
```
</del>
Parent issue: #89692
r? ```@joshtriplett```
Add `Poll::ready` and revert stabilization of `task::ready!`
This PR adds an inherent `ready` method to `Poll` that can be used with the `?` operator as an alternative to the `task::ready!` macro:
```rust
let val = ready!(fut.poll(cx));
let val = fut.poll(cx).ready()?;
```
I think this form is a nice, non-breaking middle ground between changing the `impl Try for Poll`, and adding a separate macro. It looks better than `ready!` in my opinion, and it composes well:
```rust
let elem = ready!(fut.poll(cx)).pop().unwrap();
let elem = fut.poll(cx).ready()?.pop().unwrap();
```
The planned stabilization of `ready!` in 1.56 has been reverted because I think this alternate approach is worth considering.
r? rust-lang/libs
Add #[must_use] to from_value conversions
I added two methods to the list myself. Clippy did not flag them because they take `mut` args, but neither modifies their argument.
```rust
core::str const unsafe fn from_utf8_unchecked_mut(v: &mut [u8]) -> &mut str;
std::ffi::CString unsafe fn from_raw(ptr: *mut c_char) -> CString;
```
I put a custom note on `from_raw`:
```rust
#[must_use = "call `drop(from_raw(ptr))` if you intend to drop the `CString`"]
pub unsafe fn from_raw(ptr: *mut c_char) -> CString {
```
Parent issue: #89692
r? ``@joshtriplett``
----------
Fix spacing for links inside code blocks, and improve link tooltips in alloc::fmt
----------
Fix spacing for links inside code blocks, and improve link tooltips in alloc::{rc, sync}
----------
Fix spacing for links inside code blocks, and improve link tooltips in alloc::string
----------
Fix spacing for links inside code blocks in alloc::vec
----------
Fix spacing for links inside code blocks in core::option
----------
Fix spacing for links inside code blocks, and improve a few link tooltips in core::result
----------
Fix spacing for links inside code blocks in core::{iter::{self, iterator}, stream::stream, poll}
----------
Fix spacing for links inside code blocks, and improve a few link tooltips in std::{fs, path}
----------
Fix spacing for links inside code blocks in std::{collections, time}
----------
Fix spacing for links inside code blocks in and make formatting of `&str`-like types consistent in std::ffi::{c_str, os_str}
----------
Fix spacing for links inside code blocks, and improve link tooltips in std::ffi
----------
Fix spacing for links inside code blocks, and improve a few link tooltips
in std::{io::{self, buffered::{bufreader, bufwriter}, cursor, util}, net::{self, addr}}
----------
Fix typo in link to `into` for `OsString` docs
----------
Remove tooltips that will probably become redundant in the future
----------
Apply suggestions from code review
Replacing `…std/primitive.reference.html` paths with just `reference`
Co-authored-by: Joshua Nelson <github@jyn.dev>
----------
Also replace `…std/primitive.reference.html` paths with just `reference` in `core::pin`
Add examples to the various methods of `core::task::Poll`
This improves the documentation of the various methods of [`core::task::Poll`](https://doc.rust-lang.org/std/task/enum.Poll.html). These currently have fairly simple docs with no examples. This PR changes these methods to be closer to `core::option::Option` and adds usage examples (and importantly: tests!) to `Poll`'s methods.
cc/ `@rust-lang/wg-async-foundations`
## Screenshots
<details>
<summary>View generated rustdoc page</summary>
<image src="https://user-images.githubusercontent.com/2467194/123286616-59ee9b00-d50e-11eb-9e02-40269070f904.png" alt="Poll in core::task"></details>
No compiler changes as part of this -- just new unstable traits and impls thereof.
The goal here is to add the things that aren't going to break anything, to keep the feature implementation simpler in the next PR.
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.
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.
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.
Insta-stabilize the methods `is_ready` and `is_pending` of `Poll`.
Possible because of the recent stabilization of const control flow.
Also adds a test for these methods in a const context.
This commit adds new lang items which will be used in AST lowering once
`QPath::LangItem` is introduced.
Co-authored-by: Matthew Jasper <mjjasper1@gmail.com>
Signed-off-by: David Wood <david@davidtw.co>
