[clang][Interp] Visit LabelStmt sub statements

Author: tbaederr

clang/lib/AST/Interp/ByteCodeStmtGen.cpp

@@ -292,8 +292,9 @@ bool ByteCodeStmtGen<Emitter>::visitStmt(const Stmt *S) {
   case Stmt::GCCAsmStmtClass:
   case Stmt::MSAsmStmtClass:
   case Stmt::GotoStmtClass:
-  case Stmt::LabelStmtClass:
     return this->emitInvalid(S);
+  case Stmt::LabelStmtClass:
+    return this->visitStmt(cast<LabelStmt>(S)->getSubStmt());
   default: {
     if (auto *Exp = dyn_cast<Expr>(S))
       return this->discard(Exp);

clang/test/AST/Interp/cxx23.cpp

@@ -157,3 +157,16 @@ namespace VirtualBases {
     D d;
   }
 }
+
+namespace LabelGoto {
+  constexpr int foo() { // all20-error {{never produces a constant expression}}
+    a: // all20-warning {{use of this statement in a constexpr function is a C++23 extension}}
+    goto a; // all20-note 2{{subexpression not valid in a constant expression}} \
+            // ref23-note {{subexpression not valid in a constant expression}} \
+            // expected23-note {{subexpression not valid in a constant expression}}
+
+    return 1;
+  }
+  static_assert(foo() == 1, ""); // all-error {{not an integral constant expression}} \
+                                 // all-note {{in call to}}
+}