pub fn const_kind(&self) -> hir::ConstContext {
self.const_kind.expect("`const_kind` must not be called on a non-const fn")
}
+
+ pub fn is_const_stable_const_fn(&self) -> bool {
+ self.const_kind == Some(hir::ConstContext::ConstFn)
+ && self.tcx.features().staged_api
+ && is_const_stable(self.tcx, self.def_id.to_def_id())
+ }
}
/// Returns `true` if this `DefId` points to one of the official `panic` lang items.
attr::allow_internal_unstable(&tcx.sess, attrs)
.map_or(false, |mut features| features.any(|name| name == feature_gate))
}
+
+// Returns `true` if the given `const fn` is "const-stable".
+//
+// Const-stability is only relevant for `const fn` within a `staged_api` crate. Only "const-stable"
+// functions can be called in a const-context by users of the stable compiler. "const-stable"
+// 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(tcx: TyCtxt<'tcx>, def_id: DefId) -> bool {
+ use attr::{ConstStability, Stability, StabilityLevel};
+
+ // 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
+}
Status::Allowed => return,
Status::Unstable(gate) if ccx.tcx.features().enabled(gate) => {
- let unstable_in_stable = ccx.const_kind() == hir::ConstContext::ConstFn
- && ccx.tcx.features().enabled(sym::staged_api)
- && !ccx.tcx.has_attr(ccx.def_id.to_def_id(), sym::rustc_const_unstable)
+ let unstable_in_stable = ccx.is_const_stable_const_fn()
&& !super::allow_internal_unstable(ccx.tcx, ccx.def_id.to_def_id(), gate);
if unstable_in_stable {
/// Returns `true` if we should use the more precise live drop checker that runs after drop
/// elaboration.
-pub fn checking_enabled(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> bool {
+pub fn checking_enabled(ccx: &ConstCx<'_, '_>) -> bool {
// Const-stable functions must always use the stable live drop checker.
- if tcx.features().staged_api && !tcx.has_attr(def_id.to_def_id(), sym::rustc_const_unstable) {
+ if ccx.is_const_stable_const_fn() {
return false;
}
- tcx.features().const_precise_live_drops
+ ccx.tcx.features().const_precise_live_drops
}
/// Look for live drops in a const context.
return;
}
- if !checking_enabled(tcx, def_id) {
+ let ccx = ConstCx { body, tcx, def_id, const_kind, param_env: tcx.param_env(def_id) };
+ if !checking_enabled(&ccx) {
return;
}
- let ccx = ConstCx { body, tcx, def_id, const_kind, param_env: tcx.param_env(def_id) };
-
let mut visitor = CheckLiveDrops { ccx: &ccx, qualifs: Qualifs::default() };
visitor.visit_body(body);