Implementation of the `expect` attribute (RFC 2383)
This is an implementation of the `expect` attribute as described in [RFC-2383](https://rust-lang.github.io/rfcs/2383-lint-reasons.html). The attribute allows the suppression of lint message by expecting them. Unfulfilled lint expectations (meaning no expected lint was caught) will emit the `unfulfilled_lint_expectations` lint at the `expect` attribute.
### Example
#### input
```rs
// required feature flag
#![feature(lint_reasons)]
#[expect(unused_mut)] // Will warn about an unfulfilled expectation
#[expect(unused_variables)] // Will be fulfilled by x
fn main() {
let x = 0;
}
```
#### output
```txt
warning: this lint expectation is unfulfilled
--> $DIR/trigger_lint.rs:3:1
|
LL | #[expect(unused_mut)] // Will warn about an unfulfilled expectation
| ^^^^^^^^^^
|
= note: `#[warn(unfulfilled_lint_expectations)]` on by default
```
### Implementation
This implementation introduces `Expect` as a new lint level for diagnostics, which have been expected. All lint expectations marked via the `expect` attribute are collected in the [`LintLevelsBuilder`] and assigned an ID that is stored in the new lint level. The `LintLevelsBuilder` stores all found expectations and the data needed to emit the `unfulfilled_lint_expectations` in the [`LintLevelsMap`] which is the result of the [`lint_levels()`] query.
The [`rustc_errors::HandlerInner`] is the central error handler in rustc and handles the emission of all diagnostics. Lint message with the level `Expect` are suppressed during this emission, while the expectation ID is stored in a set which marks them as fulfilled. The last step is then so simply check if all expectations collected by the [`LintLevelsBuilder`] in the [`LintLevelsMap`] have been marked as fulfilled in the [`rustc_errors::HandlerInner`]. Otherwise, a new lint message will be emitted.
The implementation of the `LintExpectationId` required some special handling to make it stable between sessions. Lints can be emitted during [`EarlyLintPass`]es. At this stage, it's not possible to create a stable identifier. The level instead stores an unstable identifier, which is later converted to a stable `LintExpectationId`.
### Followup TO-DOs
All open TO-DOs have been marked with `FIXME` comments in the code. This is the combined list of them:
* [ ] The current implementation doesn't cover cases where the `unfulfilled_lint_expectations` lint is actually expected by another `expect` attribute.
* This should be easily possible, but I wanted to get some feedback before putting more work into this.
* This could also be done in a new PR to not add to much more code to this one
* [ ] Update unstable documentation to reflect this change.
* [ ] Update unstable expectation ids in [`HandlerInner::stashed_diagnostics`](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_errors/struct.HandlerInner.html#structfield.stashed_diagnostics)
### Open questions
I also have a few open questions where I would like to get feedback on:
1. The RFC discussion included a suggestion to change the `expect` attribute to something else. (Initiated by `@Ixrec` [here](https://github.com/rust-lang/rfcs/pull/2383#issuecomment-378424091), suggestion from `@scottmcm` to use `#[should_lint(...)]` [here](https://github.com/rust-lang/rfcs/pull/2383#issuecomment-378648877)). No real conclusion was drawn on that point from my understanding. Is this still open for discussion, or was this discarded with the merge of the RFC?
2. How should the expect attribute deal with the new `force-warn` lint level?
---
This approach was inspired by a discussion with `@LeSeulArtichaut.`
RFC tracking issue: #54503
Mentoring/Implementation issue: #85549
[`LintLevelsBuilder`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_lint/levels/struct.LintLevelsBuilder.html
[`LintLevelsMap`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_middle/lint/struct.LintLevelMap.html
[`lint_levels()`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_middle/ty/context/struct.TyCtxt.html#method.lint_levels
[`rustc_errors::HandlerInner`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_errors/struct.HandlerInner.html
[`EarlyLintPass`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_lint/trait.EarlyLintPass.html
remove obligation dedup from `impl_or_trait_obligations`
Looking at the examples from #38528 they all seem to compile fine even without this and it seems like this might be unnecessary effort
Miri/CTFE: properly treat overflow in (signed) division/rem as UB
To my surprise, it looks like LLVM treats overflow of signed div/rem as UB. From what I can tell, MIR `Div`/`Rem` directly lowers to the corresponding LLVM operation, so to make that correct we also have to consider these overflows UB in the CTFE/Miri interpreter engine.
r? `@oli-obk`
Rollup of 8 pull requests
Successful merges:
- #93562 (Update the documentation for `{As,Into,From}Raw{Fd,Handle,Socket}`.)
- #94101 (rustdoc: add test cases for hidden enum variants)
- #94484 (8 - Make more use of `let_chains`)
- #94522 (Remove out-of-context line at end of E0284 message)
- #94534 (Re-export (unstable) core::ffi types from std::ffi)
- #94536 (Move transmute_undefined_repr back to nursery again)
- #94537 (Use ? operator in one instance instead of manual match)
- #94544 (Add some examples to comments in mbe code)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
Remove out-of-context line at end of E0284 message
Removed the last line of E0284 message because it was out of context (probably kept by accident when changing whole error message).
Update the documentation for `{As,Into,From}Raw{Fd,Handle,Socket}`.
This change weakens the descriptions of the
`{as,into,from}_raw_{fd,handle,socket}` descriptions from saying that
they *do* express ownership relations to say that they are *typically used*
in ways that express ownership relations. This is needed since, for
example, std's own [`RawFd`] implements `{As,From,Into}Fd` without any of
the ownership relationships.
This adds proper `# Safety` comments to `from_raw_{fd,handle,socket}`,
adds the requirement that raw handles be not opened with the
`FILE_FLAG_OVERLAPPED` flag, and merges the `OwnedHandle::from_raw_handle`
comment into the main `FromRawHandle::from_raw_handle` comment.
And, this changes `HandleOrNull` and `HandleOrInvalid` to not implement
`FromRawHandle`, since they are intended for limited use in FFI situations,
and not for generic use, and they have constraints that are stronger than
the those of `FromRawHandle`.
[`RawFd`]: https://doc.rust-lang.org/stable/std/os/unix/io/type.RawFd.html
There may eventually be something to say about `FILE_FLAG_OVERLAPPED` here,
however this appears to be independent of the other changes in this PR,
so remove them from this PR so that it can be discussed separately.
Restore the local filter on mono item sorting
In `CodegenUnit::items_in_deterministic_order`, there's a comment that
only local HirIds should be taken into account, but #90408 removed the
`as_local` call that sets others to None. Restoring that check fixes the
s390x hangs seen in [RHBZ 2058803].
[RHBZ 2058803]: https://bugzilla.redhat.com/show_bug.cgi?id=2058803
Documentation was missed when demoting Windows XP to no_std only
After a quick discussion on #81250 which removed special casing for mutexes added [here](10b103af48) to support Windows XP, we can't say that the standard library can build for it.
This change modifies the tier 3 non-ARM targets to show the standard library will no longer build for these and there is no work being done to change that.
Improve allowness of the unexpected_cfgs lint
This pull-request improve the allowness (`#[allow(...)]`) of the `unexpected_cfgs` lint.
Before this PR only crate level `#![allow(unexpected_cfgs)]` worked, now with this PR it also work when put around `cfg!` or if it is in a upper level. Making it work ~for the attributes `cfg`, `cfg_attr`, ...~ for the same level is awkward as the current code is design to give "Some parent node that is close to this macro call" (cf. https://doc.rust-lang.org/nightly/nightly-rustc/rustc_expand/base/struct.ExpansionData.html) meaning that allow on the same line as an attribute won't work. I'm note even sure if this would be possible.
Found while working on https://github.com/rust-lang/rust/pull/94298.
r? ````````@petrochenkov````````
Adt copy suggestions
Previously we've only suggested adding `Copy` bounds when the type being moved/copied is a type parameter (generic). With this PR we also suggest adding bounds when a type
- Can be copy
- All predicates that need to be satisfied for that are based on type params
i.e. we will suggest `T: Copy` for `Option<T>`, but won't suggest anything for `Option<String>`.
An example:
```rust
fn duplicate<T>(t: Option<T>) -> (Option<T>, Option<T>) {
(t, t)
}
```
New error (current compiler doesn't provide `help`:):
```text
error[E0382]: use of moved value: `t`
--> t.rs:2:9
|
1 | fn duplicate<T>(t: Option<T>) -> (Option<T>, Option<T>) {
| - move occurs because `t` has type `Option<T>`, which does not implement the `Copy` trait
2 | (t, t)
| - ^ value used here after move
| |
| value moved here
|
help: consider restricting type parameter `T`
|
1 | fn duplicate<T: Copy>(t: Option<T>) -> (Option<T>, Option<T>) {
| ++++++
```
Fixes#93623
r? ``````````@estebank``````````
``````````@rustbot`````````` label +A-diagnostics +A-suggestion-diagnostics +C-enhancement
----
I'm not at all sure if this is the right implementation for this kind of suggestion, but it seems to work :')
Rename `BorrowedFd::borrow_raw_fd` to `BorrowedFd::borrow_raw`.
Also, rename `BorrowedHandle::borrow_raw_handle` and
`BorrowedSocket::borrow_raw_socket` to `BorrowedHandle::borrow_raw` and
`BorrowedSocket::borrow_raw`.
This is just a minor rename to reduce redundancy in the user code calling
these functions, and to eliminate an inessential difference between
`BorrowedFd` code and `BorrowedHandle`/`BorrowedSocket` code.
While here, add a simple test exercising `BorrowedFd::borrow_raw_fd`.
r? ``````@joshtriplett``````
Add documentation about `BorrowedFd::to_owned`.
Following up on #88564, this adds documentation explaining why
`BorrowedFd::to_owned` returns another `BorrowedFd` rather than an
`OwnedFd`. And similar for `BorrowedHandle` and `BorrowedSocket`.
r? `````@joshtriplett`````
There's still open discussion if this lint is ready to be enabled by
default. We want to give us more time to figure this out and prevent
this lint from getting to stable as an enabled-by-default lint.
Error if submodule fetch fails.
In CI, if fetching a submodule fails, the script would exit successfully. Later parts of the build will fail due to the missing files, but it is a bit confusing, and I think it would be better to error out earlier.
The reason is that in bash, `wait` without arguments will exit 0 even if a background job exits with an error. The solution here is to wait on each individual job, which will return the exit code of the job.
This was encountered in #92177.
* Add UI tests with macros for the `expect` attribute (RFC-2383)
* Addressed review comments - mostly UI test updates (RFC-2383)
* Documented lint level attribute on macro not working bug (RFC-2383)
See `rust#87391`
