fix minor mistake in comments describing VecDeque resizing
Avoiding confusion where one of the items in the deque seems to disappear in two of the three cases
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 more niches to rawvec
Previously RawVec only had a single niche in its `NonNull` pointer. With this change it now has `isize::MAX` niches since half the value-space of the capacity field is never needed, we can't have a capacity larger than isize::MAX.
adds a column number to `dbg!()`
this would be very nice to have for a few reasons:
1. the rfc, when deciding not to add column numbers to macro, failed to acknowledge any potential ambiguous cases -- such as the one provided in #114910 -- which do exist
2. would be able to consistently and easily jump directly to the `dbg!()` regardless of the sutation
3. takes up, at a maximum, 3 characters of _horizontal_ screen space
fixes#114910
[std] Add xcoff in object's feature list
object-0.32.0 has supported XCOFF format. And backtrace in submodule has been updated to support XCOFF and AIX. Add `xcoff` to supported feature list to make backtrace built on AIX.
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.
Collect lang items from AST, get rid of `GenericBound::LangItemTrait`
r? `@cjgillot`
cc #115178
Looking forward, the work to remove `QPath::LangItem` will also be significantly more difficult, but I plan on doing it as well. Specifically, we have to change:
1. A lot of `rustc_ast_lowering` for things like expr `..`
2. A lot of astconv, since we actually instantiate lang and non-lang paths quite differently.
3. A ton of diagnostics and clippy lints that are special-cased via `QPath::LangItem`
Meanwhile, it was pretty easy to remove `GenericBound::LangItemTrait`, so I just did that here.
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
Rollup of 3 pull requests
Successful merges:
- #116888 (Add discussion that concurrent access to the environment is unsafe)
- #118888 (Uplift `TypeAndMut` and `ClosureKind` to `rustc_type_ir`)
- #118929 (coverage: Tidy up early parts of the instrumentor pass)
r? `@ghost`
`@rustbot` modify labels: rollup
Add discussion that concurrent access to the environment is unsafe
The bug report #27970 has existed for 8 years, the actual bug dates back to Rust pre-1.0. I documented it since it's in the interest of the user to be aware of it. The note can be removed once #27970 is fixed.
Fix cases where std accidentally relied on inline(never)
This PR increases the power of `-Zcross-crate-inline-threshold=always` so that it applies through `#[inline(never)]`. Note that though this is called "cross-crate-inlining" in this case especially it is _just_ lazy per-CGU codegen. The MIR inliner and LLVM still respect the attribute as much as they ever have.
Trying to bootstrap with the new `-Zcross-crate-inline-threshold=always` change revealed two bugs:
We have special intrinsics `assert_inhabited`, `assert_zero_valid`, and `assert_mem_uniniitalized_valid` which codegen backends will lower to nothing or a call to `panic_nounwind`. Since we may not have any call to `panic_nounwind` in MIR but emit one anyway, we need to specially tell `MirUsedCollector` about this situation.
`#[lang = "start"]` is special-cased already so that `MirUsedCollector` will collect it, but then when we make it cross-crate-inlinable it is only assigned to a CGU based on whether `MirUsedCollector` saw a call to it, which of course we didn't.
---
I started looking into this because https://github.com/rust-lang/rust/pull/118683 revealed a case where we were accidentally relying on a function being `#[inline(never)]`, and cranking up cross-crate-inlinability seems like a way to find other situations like that.
r? `@nnethercote` because I don't like what I'm doing to the CGU partitioning code here but I can't come up with something much better
