[clang][Interp] Reject void-typed InitListExprs

Author: tbaederr

clang/lib/AST/Interp/ByteCodeExprGen.cpp

@@ -1114,6 +1114,9 @@ bool ByteCodeExprGen<Emitter>::visitArrayElemInit(unsigned ElemIndex,
 
 template <class Emitter>
 bool ByteCodeExprGen<Emitter>::VisitInitListExpr(const InitListExpr *E) {
+  if (E->getType()->isVoidType())
+    return this->emitInvalid(E);
+
   // Handle discarding first.
   if (DiscardResult) {
     for (const Expr *Init : E->inits()) {

clang/test/AST/Interp/functions.cpp

@@ -611,3 +611,9 @@ namespace {
 
   static_assert((g<int>(), true), "");
 }
+
+namespace {
+  /// The InitListExpr here is of void type.
+  void bir [[clang::annotate("B", {1, 2, 3, 4})]] (); // both-error {{'annotate' attribute requires parameter 1 to be a constant expression}} \
+                                                      // both-note {{subexpression not valid in a constant expression}}
+}