[clang][Interp] Handle CXXDefaultInitExpr of composite type

Author: tbaederr

clang/lib/AST/Interp/ByteCodeExprGen.cpp

@@ -2916,11 +2916,7 @@ template <class Emitter>
 bool ByteCodeExprGen<Emitter>::VisitCXXDefaultInitExpr(
     const CXXDefaultInitExpr *E) {
   SourceLocScope<Emitter> SLS(this, E);
-  if (Initializing)
-    return this->visitInitializer(E->getExpr());
-
-  assert(classify(E->getType()));
-  return this->visit(E->getExpr());
+  return this->delegate(E->getExpr());
 }
 
 template <class Emitter>

clang/test/AST/Interp/records.cpp

@@ -1264,3 +1264,24 @@ namespace {
   static_assert(true_type::value, "");
   static_assert(true_type::value, "");
 }
+
+#if __cplusplus >= 202002L
+namespace {
+  /// Used to crash because the CXXDefaultInitExpr is of compound type.
+  struct A {
+    int &x;
+    constexpr ~A() { --x; }
+  };
+  struct B {
+    int &x;
+    const A &a = A{x};
+  };
+  constexpr int a() {
+    int x = 1;
+    int f = B{x}.x;
+    B{x}; // both-warning {{expression result unused}}
+
+    return 1;
+  }
+}
+#endif