added undo test for n > 1

Author: kr-2003

lib/Interpreter/CppInterOp.cpp

@@ -3618,8 +3618,6 @@ namespace Cpp {
 
   int Undo(unsigned N) {
 #ifdef CPPINTEROP_USE_CLING
-    llvm::logAllUnhandledErrors(Undo(N), llvm::errs(),
-                                "Undo not implemented in Cling");
     return compat::Interpreter::kFailure;
 #else
     return getInterp().undo(N);

unittests/CppInterOp/FunctionReflectionTest.cpp

@@ -1261,7 +1261,28 @@ TEST(FunctionReflectionTest, UndoTest) {
   EXPECT_STREQ(cerrs.c_str(), "");
   Cpp::Undo();
   testing::internal::CaptureStderr();
+  Cpp::Process("int y = x;");
+  cerrs = testing::internal::GetCapturedStderr();
+  EXPECT_STREQ(
+      cerrs.c_str(),
+      "In file included from <<< inputs >>>:1:\ninput_line_2:1:9: error: use "
+      "of undeclared identifier 'x'\n    1 | int y = x;\n      |         "
+      "^\nFailed to parse via ::process:Parsing failed.\n");
+  testing::internal::CaptureStderr();
   Cpp::Process("int x = 10;");
   cerrs = testing::internal::GetCapturedStderr();
   EXPECT_STREQ(cerrs.c_str(), "");
+  testing::internal::CaptureStderr();
+  Cpp::Process("int y = 10;");
+  cerrs = testing::internal::GetCapturedStderr();
+  EXPECT_STREQ(cerrs.c_str(), "");
+  Cpp::Undo(2);
+  testing::internal::CaptureStderr();
+  Cpp::Process("int x = 20;");
+  cerrs = testing::internal::GetCapturedStderr();
+  EXPECT_STREQ(cerrs.c_str(), "");
+  testing::internal::CaptureStderr();
+  Cpp::Process("int y = 20;");
+  cerrs = testing::internal::GetCapturedStderr();
+  EXPECT_STREQ(cerrs.c_str(), "");
 }