Rollup of 6 pull requests #139169
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Rollup of 6 pull requests #139169
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I saw someone post a code sample that contained these two attributes, which immediately made me suspicious. My suspicions were confirmed when I did a small test and checked the compiler source code to confirm that in these cases, `#[inline]` is indeed ignored (because you can't exactly `LocalCopy`an unmangled symbol since that would lead to duplicate symbols, and doing a mix of an unmangled `GloballyShared` and mangled `LocalCopy` instantiation is too complicated for our current instatiation mode logic, which I don't want to change right now). So instead, emit the usual unused attribute lint with a message saying that the attribute is ignored in this position. I think this is not 100% true, since I expect LLVM `inlinehint` to still be applied to such a function, but that's not why people use this attribute, they use it for the `LocalCopy` instantiation mode, where it doesn't work.
…=lcnr
Prefer built-in sized impls (and only sized impls) for rigid types always
This PR changes the confirmation of `Sized` obligations to unconditionally prefer the built-in impl, even if it has nested obligations. This also changes all other built-in impls (namely, `Copy`/`Clone`/`DiscriminantKind`/`Pointee`) to *not* prefer built-in impls over param-env impls. This aligns the old solver with the behavior of the new solver.
---
In the old solver, we register many builtin candidates with the `BuiltinCandidate { has_nested: bool }` candidate kind. The precedence this candidate takes over other candidates is based on the `has_nested` field. We only prefer builtin impls over param-env candidates if `has_nested` is `false`
https://github.com/rust-lang/rust/blob/2b4694a69804f89ff9d47d1a427f72c876f7f44c/compiler/rustc_trait_selection/src/traits/select/mod.rs#L1804-L1866
Preferring param-env candidates when the builtin candidate has nested obligations *still* ends up leading to detrimental inference guidance, like:
```rust
fn hello<T>() where (T,): Sized {
let x: (_,) = Default::default();
// ^^ The `Sized` obligation on the variable infers `_ = T`.
let x: (i32,) = x;
// We error here, both a type mismatch and also b/c `T: Default` doesn't hold.
}
```
Therefore this PR adjusts the candidate precedence of `Sized` obligations by making them a distinct candidate kind and unconditionally preferring them over all other candidate kinds.
Special-casing `Sized` this way is necessary as there are a lot of traits with a `Sized` super-trait bound, so a `&'a str: From<T>` where-bound results in an elaborated `&'a str: Sized` bound. People tend to not add explicit where-clauses which overlap with builtin impls, so this tends to not be an issue for other traits.
We don't know of any tests/crates which need preference for other builtin traits. As this causes builtin impls to diverge from user-written impls we would like to minimize the affected traits. Otherwise e.g. moving impls for tuples to std by using variadic generics would be a breaking change. For other builtin impls it's also easier for the preference of builtin impls over where-bounds to result in issues.
---
There are two ways preferring builtin impls over where-bounds can be incorrect and undesirable:
- applying the builtin impl results in undesirable region constraints. E.g. if only `MyType<'static>` implements `Copy` then a goal like `(MyType<'a>,): Copy` would require `'a == 'static` so we must not prefer it over a `(MyType<'a>,): Copy` where-bound
- this is mostly not an issue for `Sized` as all `Sized` impls are builtin and don't add any region constraints not already required for the type to be well-formed
- however, even with `Sized` this is still an issue if a nested goal also gets proven via a where-bound: [playground](https://play.rust-lang.org/?version=stable&mode=debug&edition=2024&gist=30377da5b8a88f654884ab4ebc72f52b)
- if the builtin impl has associated types, we should not prefer it over where-bounds when normalizing that associated type. This can result in normalization adding more region constraints than just proving trait bounds. rust-lang#133044
- not an issue for `Sized` as it doesn't have associated types.
r? lcnr
…r=fmease Fix closure recovery for missing block when return type is specified Firstly, fix the `is_array_like_block` condition to make sure we're actually recovering a mistyped *block* rather than some other delimited expression. This fixes rust-lang#138748. Secondly, split out the recovery of missing braces on a closure body into a separate recovery. Right now, the suggestion `"you might have meant to write this as part of a block"` originates from `suggest_fixes_misparsed_for_loop_head`, which feels kinda brittle and coincidental since AFAICT that recovery wasn't ever really intended to fix this. We also can make this `MachineApplicable` in this case. Fixes rust-lang#138748 r? `@fmease` or reassign if you're busy/don't wanna review this
…ethlin Emit `unused_attributes` for `#[inline]` on exported functions I saw someone post a code sample that contained these two attributes, which immediately made me suspicious. My suspicions were confirmed when I did a small test and checked the compiler source code to confirm that in these cases, `#[inline]` is indeed ignored (because you can't exactly `LocalCopy`an unmangled symbol since that would lead to duplicate symbols, and doing a mix of an unmangled `GloballyShared` and mangled `LocalCopy` instantiation is too complicated for our current instatiation mode logic, which I don't want to change right now). So instead, emit the usual unused attribute lint with a message saying that the attribute is ignored in this position. I think this is not 100% true, since I expect LLVM `inlinehint` to still be applied to such a function, but that's not why people use this attribute, they use it for the `LocalCopy` instantiation mode, where it doesn't work. r? saethlin as the instantiation guy Procedurally, I think this should be fine to merge without any lang involvement, as this only does a very minor extension to an existing lint.
… r=oli-obk
Encode synthetic by-move coroutine body with a different `DefPathData`
See the included test. In the first revision rpass1, we have an async closure `{closure#0}` which has a coroutine as a child `{closure#0}::{closure#0}`. We synthesize a by-move coroutine body, which is `{closure#0}::{closure#1}` which depends on the mir_built query, which depends on the typeck query.
In the second revision rpass2, we've replaced the coroutine-closure by a closure with two children closure. Notably, the def path of the second child closure is the same as the synthetic def id from the last revision: `{closure#0}::{closure#1}`. When type-checking this closure, we end up trying to compute its def_span, which tries to fetch it from the incremental cache; this will try to force the dependencies from the last run, which ends up forcing the mir_built query, which ends up forcing the typeck query, which ends up with a query cycle.
The problem here is that we really should never have used the same `DefPathData` for the synthetic by-move coroutine body, since it's not a closure. Changing the `DefPathData` will mean that we can see that the def ids are distinct, which means we won't try to look up the closure's def span from the incremental cache, which will properly skip replaying the node's dependencies and avoid a query cycle.
Fixes rust-lang#139142
Remove mention of `exhaustive_patterns` from `never` docs
The example shows an exhaustive match:
```rust
#![feature(exhaustive_patterns)]
use std::str::FromStr;
let Ok(s) = String::from_str("hello");
```
But rust-lang#119612 moved this functionality to `#
rustbot
added
A-attributes
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@bprs r+ rollup=never p=5 |
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@bors r+ rollup=never p=5 |
bors
added
S-waiting-on-bors
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☀️ Test successful - checks-actions |
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📌 Perf builds for each rolled up PR:
previous master: ab5b1be771 In the case of a perf regression, run the following command for each PR you suspect might be the cause: |
What is this?This is an experimental post-merge analysis report that shows differences in test outcomes between the merged PR and its parent PR.Comparing ab5b1be (parent) -> 0b45675 (this PR) Test differencesShow 531 test diffsStage 1
Stage 2
Additionally, 448 doctest diffs were found. These are ignored, as they are noisy. Job group index
Job duration changes
How to interpret the job duration changes?Job durations can vary a lot, based on the actual runner instance |
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Finished benchmarking commit (0b45675): comparison URL. Overall result: ❌ regressions - no action needed@rustbot label: -perf-regression Instruction countThis is the most reliable metric that we have; it was used to determine the overall result at the top of this comment. However, even this metric can sometimes exhibit noise.
Max RSS (memory usage)Results (primary -1.6%, secondary -0.3%)This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.
CyclesResults (secondary 6.1%)This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.
Binary sizeThis benchmark run did not return any relevant results for this metric. Bootstrap: 773.745s -> 773.955s (0.03%) |
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Successful merges:
unused_attributesfor#[inline]on exported functions #138842 (Emitunused_attributesfor#[inline]on exported functions)DefPathData#139153 (Encode synthetic by-move coroutine body with a differentDefPathData)exhaustive_patternsfromneverdocs #139157 (Remove mention ofexhaustive_patternsfromneverdocs)r? @ghost
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