check_consts: fix error requesting feature gate when that gate is not actually needed

1 files changed, 23 insertions, 10 deletions

diff --git a/compiler/rustc_const_eval/src/check_consts/check.rs b/compiler/rustc_const_eval/src/check_consts/check.rs
index c3efca28c68..ffe32acb316 100644
--- a/compiler/rustc_const_eval/src/check_consts/check.rs
+++ b/compiler/rustc_const_eval/src/check_consts/check.rs
@@ -272,9 +272,18 @@ impl<'mir, 'tcx> Checker<'mir, 'tcx> {
     /// context.
     pub fn check_op_spanned<O: NonConstOp<'tcx>>(&mut self, op: O, span: Span) {
         let gate = match op.status_in_item(self.ccx) {
-            Status::Unstable { gate, safe_to_expose_on_stable, is_function_call }
-                if self.tcx.features().enabled(gate) =>
-            {
+            Status::Unstable {
+                gate,
+                safe_to_expose_on_stable,
+                is_function_call,
+                gate_already_checked,
+            } if gate_already_checked || self.tcx.features().enabled(gate) => {
+                if gate_already_checked {
+                    assert!(
+                        !safe_to_expose_on_stable,
+                        "setting `gate_already_checked` without `safe_to_expose_on_stable` makes no sense"
+                    );
+                }
                 // Generally this is allowed since the feature gate is enabled -- except
                 // if this function wants to be safe-to-expose-on-stable.
                 if !safe_to_expose_on_stable
@@ -745,7 +754,7 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                             self.check_op(ops::IntrinsicUnstable {
                                 name: intrinsic.name,
                                 feature,
-                                const_stable: is_const_stable,
+                                const_stable_indirect: is_const_stable,
                             });
                         }
                         Some(ConstStability { level: StabilityLevel::Stable { .. }, .. }) => {
@@ -800,6 +809,12 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
 
                         // We only honor `span.allows_unstable` aka `#[allow_internal_unstable]` if
                         // the callee is safe to expose, to avoid bypassing recursive stability.
+                        // This is not ideal since it means the user sees an error, not the macro
+                        // author, but that's also the case if one forgets to set
+                        // `#[allow_internal_unstable]` in the first place. Note that this cannot be
+                        // integrated in the check below since we want to enforce
+                        // `callee_safe_to_expose_on_stable` even if
+                        // `!self.enforce_recursive_const_stability()`.
                         if (self.span.allows_unstable(feature)
                             || implied_feature.is_some_and(|f| self.span.allows_unstable(f)))
                             && callee_safe_to_expose_on_stable
@@ -830,15 +845,13 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                                     && issue == NonZero::new(27812)
                                     && self.tcx.sess.opts.unstable_opts.force_unstable_if_unmarked
                             };
-                        // We do *not* honor this if we are in the "danger zone": we have to enforce
-                        // recursive const-stability and the callee is not safe-to-expose. In that
-                        // case we need `check_op` to do the check.
-                        let danger_zone = !callee_safe_to_expose_on_stable
-                            && self.enforce_recursive_const_stability();
-                        if danger_zone || !feature_enabled {
+                        // Even if the feature is enabled, we still need check_op to double-check
+                        // this if the callee is not safe to expose on stable.
+                        if !feature_enabled || !callee_safe_to_expose_on_stable {
                             self.check_op(ops::FnCallUnstable {
                                 def_id: callee,
                                 feature,
+                                feature_enabled,
                                 safe_to_expose_on_stable: callee_safe_to_expose_on_stable,
                             });
                         }