https://github.com/akashagrwl created
https://github.com/llvm/llvm-project/pull/210254
Sema::isMemberAccessibleForDeletion treats AR_delayed as unreachable, but
CheckAccess returns AR_delayed whenever it runs inside an enclosing
delayed-diagnostics scope. That happens when deletion checking runs
synchronously while parsing a later declaration -- e.g. while explaining why a
defaulted operator<=> is deleted for an expression in that declaration's
initializer. The caller cannot consume a delayed diagnostic, so letting
CheckAccess delay always hits
llvm_unreachable("cannot delay =delete computation") and crashes.
Force an immediate answer by wrapping the CheckAccess call in
DelayedDiagnostics.pushUndelayed()/popUndelayed() via llvm::scope_exit,
mirroring the existing Sema::CheckEnableIf pattern in SemaOverload.cpp.
Co-authored - Claude-Sonnet
>From feef97bd46edced72a58f904d4807c2196fa2afb Mon Sep 17 00:00:00 2001
From: Akash Agrawal <[email protected]>
Date: Thu, 16 Jul 2026 23:06:52 -0700
Subject: [PATCH] [Clang][Sema] Don't delay the access check when computing
implicit deletion
Sema::isMemberAccessibleForDeletion treats AR_delayed as unreachable, but
CheckAccess returns AR_delayed whenever it runs inside an enclosing
delayed-diagnostics scope. That happens when deletion checking runs
synchronously while parsing a later declaration -- e.g. while explaining why a
defaulted operator<=> is deleted for an expression in that declaration's
initializer. The caller cannot consume a delayed diagnostic, so letting
CheckAccess delay always hits
llvm_unreachable("cannot delay =delete computation") and crashes.
Force an immediate answer by wrapping the CheckAccess call in
DelayedDiagnostics.pushUndelayed()/popUndelayed() via llvm::scope_exit,
mirroring the existing Sema::CheckEnableIf pattern in SemaOverload.cpp.
---
clang/lib/Sema/SemaAccess.cpp | 11 +++++++++++
clang/test/SemaCXX/cxx20-default-compare.cpp | 18 ++++++++++++++++++
2 files changed, 29 insertions(+)
diff --git a/clang/lib/Sema/SemaAccess.cpp b/clang/lib/Sema/SemaAccess.cpp
index 17415b4185eff..f2e19488a6ee2 100644
--- a/clang/lib/Sema/SemaAccess.cpp
+++ b/clang/lib/Sema/SemaAccess.cpp
@@ -21,6 +21,7 @@
#include "clang/Sema/DelayedDiagnostic.h"
#include "clang/Sema/Initialization.h"
#include "clang/Sema/Lookup.h"
+#include "llvm/ADT/ScopeExit.h"
using namespace clang;
using namespace sema;
@@ -1612,6 +1613,16 @@ bool Sema::isMemberAccessibleForDeletion(CXXRecordDecl
*NamingClass,
// Suppress diagnostics.
Entity.setDiag(Diag);
+ // Deletion checking can run while we are inside an enclosing
+ // delayed-diagnostics scope (e.g. when parsing a later declaration whose
+ // initializer requires explaining why a defaulted comparison operator is
+ // deleted). CheckAccess would then return AR_delayed, but the result must be
+ // known immediately here. Force an undelayed check, mirroring CheckEnableIf.
+ llvm::scope_exit UndelayDiags(
+ [&, CurrentState(DelayedDiagnostics.pushUndelayed())] {
+ DelayedDiagnostics.popUndelayed(CurrentState);
+ });
+
switch (CheckAccess(*this, Loc, Entity)) {
case AR_accessible: return true;
case AR_inaccessible: return false;
diff --git a/clang/test/SemaCXX/cxx20-default-compare.cpp
b/clang/test/SemaCXX/cxx20-default-compare.cpp
index 3e4673c31e489..cb2886608d6f6 100644
--- a/clang/test/SemaCXX/cxx20-default-compare.cpp
+++ b/clang/test/SemaCXX/cxx20-default-compare.cpp
@@ -65,3 +65,21 @@ struct MutCheck : MutOnly {
// bool operator==(this MutCheck, MutCheck) = default;
};
}
+
+namespace delayed_deletion_check {
+// Explaining why a defaulted comparison operator is deleted can run while we
+// are parsing a later declaration, i.e. inside an enclosing
delayed-diagnostics
+// scope. The access check for the deleted-ness computation must produce an
+// immediate answer rather than being delayed. Previously this crashed.
+struct HasPrivateSpaceship {
+private:
+ std::strong_ordering operator<=>(const HasPrivateSpaceship &) const; //
expected-note 2 {{declared private here}}
+};
+
+struct S {
+ HasPrivateSpaceship member; // expected-note 2 {{because it would invoke a
private 'operator<=>' member of 'delayed_deletion_check::HasPrivateSpaceship'
to compare member 'member'}}
+ auto operator<=>(const S &) const = default; // expected-warning
{{explicitly defaulted three-way comparison operator is implicitly deleted}}
expected-note {{replace 'default' with 'delete'}} expected-note {{explicitly
defaulted function was implicitly deleted here}}
+};
+
+bool b = (S{} < S{}); // expected-error {{object of type 'S' cannot be
compared because its 'operator<=>' is implicitly deleted}}
+}
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