The root cause was fixed upstream in LLVM main. This adds a reminder to revert the workaround once the LLVM rustc depends on is new enough. Since I'm not sure how such optimizations get routed to LLVM releases, I used the conservative assumption that it will only show up with LLVM 13.
fix Miri errors in libcore doctests
Now that Miri can run doctests, it found some issues in the libcore doctests:
* The `AtomicPtr` tests accessed dangling memory! `AtomicPtr::new(&mut 10);` makes the `10` a temporary that is deallocated after the end of this expression.
* The tests for `set_ptr_value` used `&array[0] as *const _` to get a pointer to the array; this needs to be `array.as_ptr()` instead (Cc https://github.com/rust-lang/unsafe-code-guidelines/issues/134).
* I reduced a buffer size in a `MaybeUninit` test to make it less slow in Miri, and added a spin loop hint to fix a diverging loop in Miri.
Don't tell users to use a nightly flag on the stable channel
When a crate requires a newer edition, currently rustc tells users to use `-Z unstable-options`. This is not ideal, because:
* This flag doesn't work on the stable channel, so solution to one error only causes another error, which is frustrating.
* Directs users towards the nightly channel, which is not necessarily the correct solution. Once the next edition is released, this message will be mostly seen by users of out-of-date stable Rust versions who merely need to update their Rust to the latest stable.
Avoid `;` -> `,` recovery and unclosed `}` recovery from being too verbose
Those two recovery attempts have a very bad interaction that causes too
unnecessary output. Add a simple gate to avoid interpreting a `;` as a
`,` when there are unclosed braces.
Fix#83498.
Categorize and explain target features support
There are 3 different uses of the `-C target-feature` args passed to rustc:
1. All of the features are passed to LLVM, which uses them to configure code-generation. This is sort-of stabilized since 1.0 though LLVM does change/add/remove target features regularly.
2. Target features which are in [the compiler's allowlist](69e1d22ddb/compiler/rustc_codegen_ssa/src/target_features.rs (L12-L34)) can be used in `cfg!(target_feature)` etc. These may have different names than in LLVM and are renamed before passing them to LLVM.
3. Target features which are in the allowlist and which are stabilized or feature-gate-enabled can be used in `#[target_feature]`.
It can be confusing that `rustc --print target-features` just prints out the LLVM features without separating out the rustc features or even mentioning that the dichotomy exists.
This improves the situation by separating out the rustc and LLVM target features and adding a brief explanation about the difference.
Abbreviated Example Output:
```
$ rustc --print target-features
Features supported by rustc for this target:
adx - Support ADX instructions.
aes - Enable AES instructions.
...
xsaves - Support xsaves instructions.
crt-static - Enables libraries with C Run-time Libraries(CRT) to be statically linked.
Code-generation features supported by LLVM for this target:
16bit-mode - 16-bit mode (i8086).
32bit-mode - 32-bit mode (80386).
...
x87 - Enable X87 float instructions.
xop - Enable XOP instructions.
Use +feature to enable a feature, or -feature to disable it.
For example, rustc -C target-cpu=mycpu -C target-feature=+feature1,-feature2
Code-generation features cannot be used in cfg or #[target_feature],
and may be renamed or removed in a future version of LLVM or rustc.
```
Motivated by #83975.
CC https://github.com/rust-lang/rust/issues/49653
Those two recovery attempts have a very bad interaction that causes too
unnecessary output. Add a simple gate to avoid interpreting a `;` as a
`,` when there are unclosed braces.
reduce threads spawned by ui-tests
The test harness already spawns enough tests to keep all cores busy.
Individual tests should keep their own threading to a minimum to avoid context switch overhead.
When running ui tests with lld enabled this shaves about 10% off that testsuite on my machine.
Resolves#81946
rustdoc: Don't generate blanket impls when running --show-coverage
`get_blanket_impls` is the slowest part of rustdoc, and the coverage pass
completely ignores blanket impls. This stops running it at all, and also
removes some unnecessary checks in `calculate_doc_coverage` that ignored
the impl anyway.
We don't currently measure --show-coverage in perf.rlo, but I tested
this locally on cargo and it brought the time down from 2.9 to 1.6
seconds.
This also adds back a commented-out test; Rustdoc has been able to deal with `impl trait` for almost a year now.
r? `@GuillaumeGomez`
get_blanket_impls is the slowest part of rustdoc, and the coverage pass
completely ignores blanket impls. This stops running it at all, and also
removes some unnecessary checks in `calculate_doc_coverage` that ignored
the impl anyway.
We don't currently measure --show-coverage in perf.rlo, but I tested
this locally on cargo and it brought the time down from 2.9 to 1.6
seconds.
Mention missing 1.38.0 change in RELEASES.md
Mention that doc comments on `pub use` statements are prepended to the documentation of the reexported item
Fixes#84007
the test harness already spawns enough tests for all cores, individual
tests should keep their own threading to a minimum to avoid context switch
overhead
some tests fail with 1 CGU, so explicit compile flags have been added
to keep their old behavior
Don't concatenate binders across types
Partially addresses #83737
There's actually two issues that I uncovered in #83737. The first is that we are concatenating bound vars across types, i.e. in
```
F: Fn(&()) -> &mut (dyn Future<Output = ()> + Unpin)
```
the bound vars on `Future` get set as `for<anon>` since those are the binders on `Fn(&()`. This is obviously wrong, since we should only concatenate directly nested trait refs. This is solved here by introducing a new `TraitRefBoundary` scope, that we put around the "syntactical" trait refs and basically don't allow concatenation across.
Now, this alone *shouldn't* be a super terrible problem. At least not until you consider the other issue, which is a much more elusive and harder to design a "perfect" fix. A repro can be seen in:
```
use core::future::Future;
async fn handle<F>(slf: &F)
where
F: Fn(&()) -> &mut (dyn for<'a> Future<Output = ()> + Unpin),
{
(slf)(&()).await;
}
```
Notice the `for<'a>` around `Future`. Here, `'a` is unused, so the `for<'a>` Binder gets changed to a `for<>` Binder in the generator witness, but the "local decl" still has it. This has heavy intersections with region anonymization and erasing. Luckily, it's not *super* common to find this unique set of circumstances. It only became apparently because of the first issue mentioned here. However, this *is* still a problem, so I'm leaving #83737 open.
r? `@nikomatsakis`
Merge idents when generating source content
The idea here is to not have a span for each part of a path. Currently, for `a:🅱️:c` we generate `<span>a</span>::<span>b</span>::<span>c</span>`, with this change, we will generate `<span>a:🅱️:c</span>`.
A nice "side-effect" is that it reduces the size of the output HTML too. :)
cc `@notriddle`
Stabilize `peekable_peek_mut`
Resolves#78302. Also adds some documentation on `std::iter::Iterator::peekable()` regarding the new method.
The feature was added in #77491 in Nov' 20, which is recently, but the feature seems reasonably small. Never did a stabilization-pr, excuse my ignorance if there is a protocol I'm not aware of.
Improve links in inline code in `core::pin`.
## Context
So I recently opened #80720. That PR uses HTML-based `<code>foo</code>` syntax in place of `` `foo` `` for some inline code. It looks like usage of `<code>` tags in doc comments is without precedent in the standard library, but the HTML-based syntax has an important advantage:
You can write something like
```
<code>[Box]<[Option]\<T>></code>
```
which becomes: <code>[Box]<[Option]\<T>></code>, whereas with ordinary backtick syntax, you cannot create links for a substring of an inline code block.
## Problem
I recalled (from my own experience) that a way to partially work around this limitation is to do something like
```
[`Box`]`<`[`Option`]`<T>>`
```
which looks like this: [`Box`]`<`[`Option`]`<T>>` _(admitted, it looks even worse on GitHub than in `rustdoc`’s CSS)_.
[Box]: https://doc.rust-lang.org/std/boxed/struct.Box.html "Box"
[`Box`]: https://doc.rust-lang.org/std/boxed/struct.Box.html "Box"
[Option]: https://doc.rust-lang.org/std/option/enum.Option.html "Option"
[`Option`]: https://doc.rust-lang.org/std/option/enum.Option.html "Option"
[Pin]: https://doc.rust-lang.org/std/pin/struct.Pin.html "Pin"
[&mut]: https://doc.rust-lang.org/std/primitive.reference.html "mutable reference"
So I searched the standard library and found that e.g. the [std::pin](https://doc.rust-lang.org/std/pin/index.html) module documentation uses this hack/workaround quite a bit, with types like <code>[Pin]<[Box]\<T>></code> or <code>[Pin]<[&mut] T>></code>. Although the way they look like in this sentence is what I would like them to look like, not what they currently look.
### Status Quo
Here’s a screenshot of what it currently looks like:
With a few HTML-style code blocks, we can fix all the spacing issues in the above screenshot that are due usage of this hack/workaround of putting multiple code blocks right next to each other being used.
### after d3915c555e:
There’s still a problem of inconsistency. Especially in a sentence such as
> A [`Pin<P>`][Pin] where `P: Deref` should be considered as a "`P`-style pointer" to _[...]_
looks weird with the variable `P` having different colors (and `Deref` has a different color from before where it was a link, too). Or compare the difference of <code>[Pin]<[Box]\<T>></code> vs [`Box<T>`][Box] where one time the variable is part of the link and the other time it isn’t.
_Note: Color differences show even **more strongly** when the ayu theme is used, while they are a bit less prominent in the light theme than they are in the dark theme, which is the one used for these screenshots._
This is why I’ve added the next commit
### after ceaeb249a3
pulling all the type parameters out of their links, and also the last commit with clearly visible changes
### after 87ac118ba3
where more links are added, removing e.g. the inconsistency with `Deref`’s color in e.g. `P: Deref` that I already mentioned above.
## Discussion
I am aware that this PR may very well be overkill. If for now only the first commit (plus the fix for the `Drop` link in e65385fbfa, the link titles 684edf7a70 as far as they apply, and a few of the line-break changes) are wanted, I can reduce this PR to just those changes. I personally find the rendered result with all these changes very nice though. On the other hand, all these `<code>` tags are not very nice in the source code, I’ll admit.
Perhaps alternative solutions could be preferred, such as `rustdoc` support for merging subsequent inline code blocks so that all the cases that currently use workarounds rendered as [`Box`]`<`[`Option`]`<T>>` automatically become <code>[Box]<[Option]\<T>></code> without any need for further changes. Even in this case, having a properly formatted, better looking example in the standard library docs could help motivate such a change to `rustdoc` by prodiving an example of the expected results and also the already existing alternative (i.e. using `<code>`). On the other hand, `` [`Box`]`<`[`Option`]`<T>>` `` isn’t particularly nice-looking source code either. I’m not even sure if I wouldn’t actually find the version `<code>[Box]<[Option]\<T>></code>` cleaner to read.
`@rustbot` modify labels: T-doc, T-rustdoc
