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| author | bors <bors@rust-lang.org> | 2020-09-12 18:01:33 +0000 |
|---|---|---|
| committer | bors <bors@rust-lang.org> | 2020-09-12 18:01:33 +0000 |
| commit | 989190874fe2a0e9877ce4f02a6c60641e3d42a3 (patch) | |
| tree | cdc1dd5f294a9c7b29e5ea413f03aaf6e2caa833 /compiler/rustc_codegen_llvm/src/lib.rs | |
| parent | 7adeb2c795239e2e5ffbe4cd4672157c8e1b9277 (diff) | |
| parent | 14cc17759de0863e85eea46c0f5bfcc362d1bfe8 (diff) | |
| download | rust-989190874fe2a0e9877ce4f02a6c60641e3d42a3.tar.gz rust-989190874fe2a0e9877ce4f02a6c60641e3d42a3.zip | |
Auto merge of #76538 - fusion-engineering-forks:check-useless-unstable-trait-impl, r=lcnr
Warn for #[unstable] on trait impls when it has no effect.
Earlier today I sent a PR with an `#[unstable]` attribute on a trait `impl`, but was informed that this attribute has no effect there. (comment: https://github.com/rust-lang/rust/pull/76525#issuecomment-689678895, issue: https://github.com/rust-lang/rust/issues/55436)
This PR adds a warning for this situation. Trait `impl` blocks with `#[unstable]` where both the type and the trait are stable will result in a warning:
```
warning: An `#[unstable]` annotation here has no effect. See issue #55436 <https://github.com/rust-lang/rust/issues/55436> for more information.
--> library/std/src/panic.rs:235:1
|
235 | #[unstable(feature = "integer_atomics", issue = "32976")]
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
```
---
It detects three problems in the existing code:
1. A few `RefUnwindSafe` implementations for the atomic integer types in `library/std/src/panic.rs`. Example:
https://github.com/rust-lang/rust/blob/d92155bf6ae0b7d79fc83cbeeb0cc0c765353471/library/std/src/panic.rs#L235-L236
2. An implementation of `Error` for `LayoutErr` in `library/std/srd/error.rs`:
https://github.com/rust-lang/rust/blob/d92155bf6ae0b7d79fc83cbeeb0cc0c765353471/library/std/src/error.rs#L392-L397
3. `From` implementations for `Waker` and `RawWaker` in `library/alloc/src/task.rs`. Example:
https://github.com/rust-lang/rust/blob/d92155bf6ae0b7d79fc83cbeeb0cc0c765353471/library/alloc/src/task.rs#L36-L37
Case 3 interesting: It has a bound with an `#[unstable]` trait (`W: Wake`), so appears to have much effect on stable code. It does however break similar blanket implementations. It would also have immediate effect if `Wake` was implemented for any stable type. (Which is not the case right now, but there are no warnings in place to prevent it.) Whether this case is a problem or not is not clear to me. If it isn't, adding a simple `c.visit_generics(..);` to this PR will stop the warning for this case.
Diffstat (limited to 'compiler/rustc_codegen_llvm/src/lib.rs')
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