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Auto merge of #130689 - RalfJung:rustc_nonnull_optimization_guaranteed, r=jieyouxu

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fix rustc_nonnull_optimization_guaranteed docs

As far as I can tell, even back when this was [added](https://github.com/rust-lang/rust/pull/60300) it never *enabled* any optimizations. It just indicates that the FFI compat lint should accept those types for NPO.
This commit is contained in:
bors 2024-09-22 10:18:59 +00:00
commit 4ae36d906f
4 changed files with 8 additions and 4 deletions
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1
compiler/rustc_const_eval/src/interpret/call.rs
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@ -234,6 +234,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
// so we implement a type-based check that reflects the guaranteed rules for ABI compatibility.
if self.layout_compat(caller_abi.layout, callee_abi.layout)? {
// Ensure that our checks imply actual ABI compatibility for this concrete call.
// (This can fail e.g. if `#[rustc_nonnull_optimization_guaranteed]` is used incorrectly.)
assert!(caller_abi.eq_abi(callee_abi));
Ok(true)
} else {

6
compiler/rustc_feature/src/builtin_attrs.rs
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@ -859,8 +859,10 @@ pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
rustc_attr!(
rustc_nonnull_optimization_guaranteed, Normal, template!(Word), WarnFollowing,
EncodeCrossCrate::Yes,
"the `#[rustc_nonnull_optimization_guaranteed]` attribute is just used to enable \
niche optimizations in libcore and libstd and will never be stable",
"the `#[rustc_nonnull_optimization_guaranteed]` attribute is just used to document \
guaranteed niche optimizations in libcore and libstd and will never be stable\n\
(note that the compiler does not even check whether the type indeed is being non-null-optimized; \
it is your responsibility to ensure that the attribute is only used on types that are optimized)",
),
// ==========================================================================

2
tests/ui/feature-gates/feature-gate-rustc-attrs-1.rs
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@ -2,6 +2,6 @@
#[rustc_variance] //~ ERROR the `#[rustc_variance]` attribute is just used for rustc unit tests and will never be stable
#[rustc_error] //~ ERROR the `#[rustc_error]` attribute is just used for rustc unit tests and will never be stable
#[rustc_nonnull_optimization_guaranteed] //~ ERROR the `#[rustc_nonnull_optimization_guaranteed]` attribute is just used to enable niche optimizations in libcore and libstd and will never be stable
#[rustc_nonnull_optimization_guaranteed] //~ ERROR the `#[rustc_nonnull_optimization_guaranteed]` attribute is just used to document guaranteed niche optimizations in libcore and libstd and will never be stable
fn main() {}

3
tests/ui/feature-gates/feature-gate-rustc-attrs-1.stderr
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@ -16,7 +16,8 @@ LL | #[rustc_error]
= help: add `#![feature(rustc_attrs)]` to the crate attributes to enable
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
error[E0658]: the `#[rustc_nonnull_optimization_guaranteed]` attribute is just used to enable niche optimizations in libcore and libstd and will never be stable
error[E0658]: the `#[rustc_nonnull_optimization_guaranteed]` attribute is just used to document guaranteed niche optimizations in libcore and libstd and will never be stable
(note that the compiler does not even check whether the type indeed is being non-null-optimized; it is your responsibility to ensure that the attribute is only used on types that are optimized)
--> $DIR/feature-gate-rustc-attrs-1.rs:5:1
|
LL | #[rustc_nonnull_optimization_guaranteed]