[clang][Interp] Properly reject StmtExprs with Stmt result

Author: tbaederr

clang/lib/AST/Interp/Compiler.cpp

@@ -3194,13 +3194,9 @@ bool Compiler<Emitter>::VisitStmtExpr(const StmtExpr *E) {
     }
 
     assert(S == Result);
-    if (const Expr *ResultExpr = dyn_cast<Expr>(S)) {
-      if (DiscardResult)
-        return this->discard(ResultExpr);
+    if (const Expr *ResultExpr = dyn_cast<Expr>(S))
       return this->delegate(ResultExpr);
-    }
-
-    return this->visitStmt(S);
+    return this->emitUnsupported(E);
   }
 
   return BS.destroyLocals();

clang/test/AST/Interp/literals.cpp

@@ -1214,6 +1214,10 @@ namespace StmtExprs {
     return 76;
   }
   static_assert(foo() == 76, "");
+
+  namespace CrossFuncLabelDiff {
+    constexpr long a(bool x) { return x ? 0 : (long)&&lbl + (0 && ({lbl: 0;})); }
+  }
 }
 #endif