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Fall back to being const-unstable when undeclared #93666

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Fall back to being const-unstable when undeclared #93666

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25 changes: 6 additions & 19 deletions compiler/rustc_const_eval/src/transform/check_consts/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -86,7 +86,7 @@ pub fn rustc_allow_const_fn_unstable(tcx: TyCtxt<'_>, def_id: DefId, feature_gat
// functions are subject to more stringent restrictions than "const-unstable" functions: They
// cannot use unstable features and can only call other "const-stable" functions.
pub fn is_const_stable_const_fn(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
use attr::{ConstStability, Stability, StabilityLevel};
use attr::{ConstStability, StabilityLevel};

// A default body marked const is not const-stable because const
// trait fns currently cannot be const-stable. We shouldn't
Expand All @@ -98,22 +98,9 @@ pub fn is_const_stable_const_fn(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
// Const-stability is only relevant for `const fn`.
assert!(tcx.is_const_fn_raw(def_id));

// Functions with `#[rustc_const_unstable]` are const-unstable.
match tcx.lookup_const_stability(def_id) {
Some(ConstStability { level: StabilityLevel::Unstable { .. }, .. }) => return false,
Some(ConstStability { level: StabilityLevel::Stable { .. }, .. }) => return true,
None => {}
}

// Functions with `#[unstable]` are const-unstable.
//
// FIXME(ecstaticmorse): We should keep const-stability attributes wholly separate from normal stability
// attributes. `#[unstable]` should be irrelevant.
if let Some(Stability { level: StabilityLevel::Unstable { .. }, .. }) =
tcx.lookup_stability(def_id)
{
return false;
}

true
// A function is only const-stable if it has `#[rustc_const_stable]`.
matches!(
tcx.lookup_const_stability(def_id),
Some(ConstStability { level: StabilityLevel::Stable { .. }, .. })
)
}