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when an intrinsic has a const-stable fallback body, we can easily expose it on stable

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This commit is contained in:
Ralf Jung 2024-11-02 08:49:49 +01:00
parent 5069434c81
commit a741b33c14
5 changed files with 37 additions and 8 deletions
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16
compiler/rustc_const_eval/src/check_consts/check.rs
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@ -739,6 +739,12 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
// We use `intrinsic.const_stable` to determine if this can be safely exposed to
// stable code, rather than `const_stable_indirect`. This is to make
// `#[rustc_const_stable_indirect]` an attribute that is always safe to add.
// We also ask is_safe_to_expose_on_stable_const_fn; this determines whether the intrinsic
// fallback body is safe to expose on stable.
let is_const_stable = intrinsic.const_stable
|| (!intrinsic.must_be_overridden
&& tcx.is_const_fn(callee)
&& is_safe_to_expose_on_stable_const_fn(tcx, callee));
match tcx.lookup_const_stability(callee) {
None => {
// Non-const intrinsic.
@ -748,7 +754,7 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
// Intrinsic does not need a separate feature gate (we rely on the
// regular stability checker). However, we have to worry about recursive
// const stability.
if !intrinsic.const_stable && self.enforce_recursive_const_stability() {
if !is_const_stable && self.enforce_recursive_const_stability() {
self.dcx().emit_err(errors::UnmarkedIntrinsicExposed {
span: self.span,
def_path: self.tcx.def_path_str(callee),
@ -763,12 +769,14 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
self.check_op(ops::IntrinsicUnstable {
name: intrinsic.name,
feature,
const_stable: intrinsic.const_stable,
const_stable: is_const_stable,
});
}
Some(ConstStability { level: StabilityLevel::Stable { .. }, .. }) => {
// All good. But ensure this is indeed a const-stable intrinsic.
assert!(intrinsic.const_stable);
// All good. Note that a `#[rustc_const_stable]` intrinsic (meaning it
// can be *directly* invoked from stable const code) does not always
// have the `#[rustc_const_stable_intrinsic]` attribute (which controls
// exposing an intrinsic indirectly); we accept this call anyway.
}
}
// This completes the checks for intrinsics.