Make no_mangle on foreign items explicit instead of implicit
for a followup PR I'm working on I need some foreign items to mangle. I could add a new attribute: `no_no_mangle` or something silly like that but by explicitly putting `no_mangle` in the codegen fn attrs of foreign items we can default it to `no_mangle` and then easily remove it when we don't want it.
I guess you'd know about this r? `@bjorn3.` Shouldn't be too hard to review :)
Builds on rust-lang/rust#144655 which should merge first.
fix: re-enable self-assignment
## Description
Re-enables the self-assignment detection that was previously disabled due to unrelated regressions. The fix detects useless assignments like `x = x` and `foo.field = foo.field`.
## History
The original regressions (rust-lang/rust#81626, rust-lang/rust#81658) were specifically about false positives in write-only field detection, not self-assignment detection. Belows are brief history for the rule that I understand.
- Self-assignment detection was originally implemented in rust-lang/rust#87129 to address rust-lang/rust#75356
- The implementation was disabled alongside the revert of rust-lang/rust#81473's "write-only fields" detection
- rust-lang/rust#81473 was reverted via rust-lang/rust#86212 and rust-lang/rust#83171 due to false positives in write-only field detection (rust-lang/rust#81626, rust-lang/rust#81658)
- The self-assignment detection feature got removed, even though it wasn't the reason for the problems
This PR only re-enables the self-assignment checks, which are orthogonal to the problematic write-only field analysis.
## Changes
- Removed `#[allow(dead_code)]` from `compiler/rustc_passes/src/dead.rs` file
- `handle_assign` and
- `check_for_self_assign`
- Added `ExprKind::Assign` handling in `visit_expr` to call both methods
- Updated test expectations in `tests/ui/lint/dead-code/self-assign.rs`
Port `#[allow_internal_unsafe]` to the new attribute system (attempt 2)
This is a slightly modified version of ae1487aa9922de7642c448cc0908584026699e1c, which caused a performance regression (reverted in https://github.com/rust-lang/rust/pull/145086#issue-3303428759). The diff between this PR and the previous one can be seen in 027a1def.
r? ```````@jdonszelmann``````` 💖
Implement `stability_implications` without a visitor.
Since https://github.com/rust-lang/rust/pull/143845, the `Annotator` visitor was a no-op when the crate is not staged_api. This PR avoids using a visitor altogether, making `stability_implications` truly a no-op in most cases.
Simplify dead code lint
This PR scratches a few itches I had when looking at that code.
The perf improvement comes from keeping the `scanned` set through several marking phases. This pretty much divides by 2 the number of HIR traversals.
Disabling loading of pretty printers in the debugger itself is more
reliable. Before this commit the .gdb_debug_scripts section couldn't be
included in dylibs or rlibs as otherwise there is no way to disable the
section anymore without recompiling the entire standard library.
Mitigate `#[align]` name resolution ambiguity regression with a rename
Mitigates beta regression rust-lang/rust#143834 after a beta backport.
### Background on the beta regression
The name resolution regression arises due to rust-lang/rust#142507 adding a new feature-gated built-in attribute named `#[align]`. However, unfortunately even [introducing new feature-gated unstable built-in attributes can break user code](https://www.github.com/rust-lang/rust/issues/134963) such as
```rs
macro_rules! align {
() => {
/* .. */
};
}
pub(crate) use align; // `use` here becomes ambiguous
```
### Mitigation approach
This PR renames `#[align]` to `#[rustc_align]` to mitigate the beta regression by:
1. Undoing the introduction of a new built-in attribute with a common name, i.e. `#[align]`.
2. Renaming `#[align]` to `#[rustc_align]`. The renamed attribute being `rustc_align` will not introduce new stable breakages, as attributes beginning with `rustc` are reserved and perma-unstable. This does mean existing nightly code using `fn_align` feature will additionally need to specify `#![feature(rustc_attrs)]`.
This PR is very much a short-term mitigation to alleviate time pressure from having to fully fix the current limitation of inevitable name resolution regressions that would arise from adding any built-in attributes. Long-term solutions are discussed in [#t-lang > namespacing macro attrs to reduce conflicts with new adds](https://rust-lang.zulipchat.com/#narrow/channel/213817-t-lang/topic/namespacing.20macro.20attrs.20to.20reduce.20conflicts.20with.20new.20adds/with/529249622).
### Alternative mitigation options
[Various mitigation options were considered during the compiler triage meeting](https://github.com/rust-lang/rust/issues/143834#issuecomment-3084415277), and those consideration are partly reproduced here:
- Reverting the PR doesn't seem very minimal/trivial, and carries risks of its own.
- Rename to a less-common but aim-to-stabilization name is itself not safe nor convenient, because (1) that risks introducing new regressions (i.e. ambiguity against the new name), and (2) lang would have to FCP the new name hastily for the mitigation to land timely and have a chance to be backported. This also makes the path towards stabilization annoying.
- Rename the attribute to a rustc attribute, which will be perma-unstable and does not cause new ambiguities in stable code.
- This alleviates the time pressure to address *this* regression, or for lang to have to rush an FCP for some new name that can still break user code.
- This avoids backing out a whole implementation.
### Review advice
This PR is best reviewed commit-by-commit.
- Commit 1 adds a test `tests/ui/attributes/fn-align-nameres-ambiguity-143834.rs` which demonstrates the current name resolution regression re. `align`. This test fails against current master.
- Commit 2 carries out the renames and test reblesses. Notably, commit 2 will cause `tests/ui/attributes/fn-align-nameres-ambiguity-143834.rs` to change from fail (nameres regression) to pass.
This PR, if the approach still seems acceptable, will need a beta-backport to address the beta regression.
From `#[align]` -> `#[rustc_align]`. Attributes starting with `rustc`
are always perma-unstable and feature-gated by `feature(rustc_attrs)`.
See regression RUST-143834.
For the underlying problem where even introducing new feature-gated
unstable built-in attributes can break user code such as
```rs
macro_rules! align {
() => {
/* .. */
};
}
pub(crate) use align; // `use` here becomes ambiguous
```
refer to RUST-134963.
Since the `#[align]` attribute is still feature-gated by
`feature(fn_align)`, we can rename it as a mitigation. Note that
`#[rustc_align]` will obviously mean that current unstable user code
using `feature(fn_aling)` will need additionally `feature(rustc_attrs)`,
but this is a short-term mitigation to buy time, and is expected to be
changed to a better name with less collision potential.
See
<https://rust-lang.zulipchat.com/#narrow/channel/238009-t-compiler.2Fmeetings/topic/.5Bweekly.5D.202025-07-17/near/529290371>
where mitigation options were considered.
Split-up stability_index query
This PR aims to move deprecation and stability processing away from the monolithic `stability_index` query, and directly implement `lookup_{deprecation,stability,body_stability,const_stability}` queries.
The basic idea is to:
- move per-attribute sanity checks into `check_attr.rs`;
- move attribute compatibility checks into the `MissingStabilityAnnotations` visitor;
- progressively dismantle the `Annotator` visitor and the `stability_index` query.
The first commit contains functional change, and now warns when `#[automatically_derived]` is applied on a non-trait impl block. The other commits should not change visible behaviour.
Perf in https://github.com/rust-lang/rust/pull/143845#issuecomment-3066308630 shows small but consistent improvement, except for unused-warnings case. That case being a stress test, I'm leaning towards accepting the regression.
This PR changes `check_attr`, so has a high conflict rate on that file. This should not cause issues for review.
Jakub Beránek