Add `IntoAsyncIterator`
This introduces the `IntoAsyncIterator` trait and uses it in the desugaring of the unstable `for await` loop syntax. This is mostly added for symmetry with `Iterator` and `IntoIterator`.
r? `@compiler-errors`
cc `@rust-lang/libs-api,` `@rust-lang/wg-async`
Add support for `for await` loops
This adds support for `for await` loops. This includes parsing, desugaring in AST->HIR lowering, and adding some support functions to the library.
Given a loop like:
```rust
for await i in iter {
...
}
```
this is desugared to something like:
```rust
let mut iter = iter.into_async_iter();
while let Some(i) = loop {
match core::pin::Pin::new(&mut iter).poll_next(cx) {
Poll::Ready(i) => break i,
Poll::Pending => yield,
}
} {
...
}
```
This PR also adds a basic `IntoAsyncIterator` trait. This is partly for symmetry with the way `Iterator` and `IntoIterator` work. The other reason is that for async iterators it's helpful to have a place apart from the data structure being iterated over to store state. `IntoAsyncIterator` gives us a good place to do this.
I've gated this feature behind `async_for_loop` and opened #118898 as the feature tracking issue.
r? `@compiler-errors`
do not allow ABI mismatches inside repr(C) types
In https://github.com/rust-lang/rust/pull/115476 we allowed ABI mismatches inside `repr(C)` types. This wasn't really discussed much; I added it because from how I understand calling conventions, this should actually be safe in practice. However I entirely forgot to actually allow this in Miri, and in the mean time I have learned that too much ABI compatibility can be a problem for CFI (it can reject fewer calls so that gives an attacker more room to play with).
So I propose we take back that part about ABI compatibility in `repr(C)`. It is anyway something that C and C++ do not allow, as far as I understand.
In the future we might want to introduce a class of ABI compatibilities where we say "this is a bug and it may lead to aborting the process, but it won't lead to arbitrary misbehavior -- worst case it'll just transmute the arguments from the caller type to the callee type". That would give CFI leeway to reject such calls without introducing the risk of arbitrary UB. (The UB can still happen if the transmute leads to bad results, of course, but it wouldn't be due to ABI weirdness.)
#115476 hasn't reached beta yet so if we land this before Dec 22nd we can just pretend this all never happened. ;) Otherwise we should do a beta backport (of the docs change at least).
Cc `@rust-lang/opsem` `@rust-lang/types`
Add ASCII whitespace trimming functions to `&str`
- Add `trim_ascii_start`, `trim_ascii_end`, and `trim_ascii` functions to `&str` for trimming ASCII whitespace
- Add `#[inline]` to `[u8]` `trim_ascii` functions
These functions are feature-gated by `#![feature(byte_slice_trim_ascii)]` #94035
Link to is_benchmark from the Ipv6Addr::is_global documentation
All other relevant is_* methods are mentioned in the list of addresses here, is_benchmarking has been the only one missing.
Make CStr documentation consistent ("nul" instead of "null")
"nul" is used in method names and appears more often in the documentation than "null", so make all instances "nul" to keep it consistent.
Stabilize `type_name_of_val`
Make the following API stable:
```rust
// in core::any
pub fn type_name_of_val<T: ?Sized>(_val: &T) -> &'static str
```
This is a convenience method to get the type name of a value, as opposed to `type_name` that takes a type as a generic.
Const stability is not added because this relies on `type_name` which is also not const. That has a blocking issue https://github.com/rust-lang/rust/issues/97156.
Wording was also changed to direct most of the details to `type_name` so we don't have as much duplicated documentation.
Fixes tracking issue #66359.
There were two main concerns in the tracking issue:
1. Naming: `type_name_of` and `type_name_of_val` seem like the only mentioned options. Differences in opinion here come from `std::mem::{size_of, align_of, size_of_val, align_of_val}`. This PR leaves the name as `type_name_of_val`, but I can change if desired since it is pretty verbose.
2. What this displays for `&dyn`: I don't think that having `type_name_of_val` function resolve those is worth the headache it would be, see https://github.com/rust-lang/rust/issues/66359#issuecomment-1718480774 for some workarounds. I also amended the docs wording to leave it open-ended, in case we have means to change that behavior in the future.
``@rustbot`` label -T-libs +T-libs-api +needs-fcp
r? libs-api
[`RFC 3086`] Attempt to try to resolve blocking concerns
Implements what is described at https://github.com/rust-lang/rust/issues/83527#issuecomment-1744822345 to hopefully make some progress.
It is unknown if such approach is or isn't desired due to the lack of further feedback, as such, it is probably best to nominate this PR to the official entities.
`@rustbot` labels +I-compiler-nominated
Add `trim_ascii_start`, `trim_ascii_end`, and `trim_ascii` functions to
`&str` for trimming ASCII whitespace under the `byte_slice_trim_ascii`
feature gate.
Add `inline` to `[u8]` `trim_ascii` functions
Add lint against ambiguous wide pointer comparisons
This PR is the resolution of https://github.com/rust-lang/rust/issues/106447 decided in https://github.com/rust-lang/rust/issues/117717 by T-lang.
## `ambiguous_wide_pointer_comparisons`
*warn-by-default*
The `ambiguous_wide_pointer_comparisons` lint checks comparison of `*const/*mut ?Sized` as the operands.
### Example
```rust
let ab = (A, B);
let a = &ab.0 as *const dyn T;
let b = &ab.1 as *const dyn T;
let _ = a == b;
```
### Explanation
The comparison includes metadata which may not be expected.
-------
This PR also drops `clippy::vtable_address_comparisons` which is superseded by this one.
~~One thing: is the current naming right? `invalid` seems a bit too much.~~
Fixes https://github.com/rust-lang/rust/issues/117717
guarantee that char and u32 are ABI-compatible
In https://github.com/rust-lang/rust/pull/116894 we added a guarantee that `char` has the same alignment as `u32`, but there is still one axis where these types could differ: function call ABI. So let's nail that down as well: in a function signature, `char` and `u32` are completely equivalent.
This is a new stable guarantee, so it will need t-lang approval.
detects redundant imports that can be eliminated.
for #117772 :
In order to facilitate review and modification, split the checking code and
removing redundant imports code into two PR.
Elaborate on ip_addr bit conversion endianness
Adds explanation of how endianness is handled when converting `Ipv4Addr` and `Ipv6Addr` to and from bits. This is intended to unblock stabilization of the affected methods.
Addresses #113744
Use OnceCell in cell module documentation
The spanning tree example in the std cell module implementation was created before `OnceCell` was added to Rust so it uses `RefCell`. However, in this case using `OnceCell` seems more appropriate and produces simpler code. As a bonus, this also means that all three cell types are presented in the examples of std cell module.
Add support for making lib features internal
We have the notion of an "internal" lang feature: a feature that is never intended to be stabilized, and using which can cause ICEs and other issues without that being considered a bug.
This extends that idea to lib features as well. It is an alternative to https://github.com/rust-lang/rust/pull/115623: instead of using an attribute to declare lib features internal, we simply do this based on the name. Everything ending in `_internals` or `_internal` is considered internal.
Then we rename `core_intrinsics` to `core_intrinsics_internal`, which fixes https://github.com/rust-lang/rust/issues/115597.
Make the following API stable:
// in core::any
pub fn type_name_of_val<T: ?Sized>(_val: &T) -> &'static str
Const stability is not added because this relies on `type_name` which is also
not const. That has a blocking issue.
Fixes#66359
