added undo command for repl

Author: kr-2003

include/clang/Interpreter/CppInterOp.h

@@ -785,6 +785,11 @@ namespace Cpp {
                                    unsigned complete_line = 1U,
                                    unsigned complete_column = 1U);
 
+  /// Reverts the last N operations performed by the interpreter.
+  ///\param[in] N The number of operations to undo. Defaults to 1.
+  ///\returns 0 on success, non-zero on failure.
+  CPPINTEROP_API int Undo(unsigned N = 1);
+
 } // end namespace Cpp
 
 #endif // CPPINTEROP_CPPINTEROP_H

lib/Interpreter/CppInterOp.cpp

@@ -3672,4 +3672,6 @@ namespace Cpp {
                          complete_column);
   }
 
+  int Undo(unsigned N) { return getInterp().undo(N); }
+
   } // end namespace Cpp

lib/Interpreter/CppInterOpInterpreter.h

@@ -429,6 +429,21 @@ class Interpreter {
     return ret; // TODO: Implement
   }
 
+  CompilationResult undo(unsigned N = 1) {
+#ifdef CPPINTEROP_USE_CLING
+    llvm::logAllUnhandledErrors(Undo(N), llvm::errs(),
+                                "Undo not implemented in Cling");
+    return kFailure;
+#else
+    if (llvm::Error Err = Undo(N)) {
+      llvm::logAllUnhandledErrors(std::move(Err), llvm::errs(),
+                                  "Failed to undo via ::undo: or something");
+      return kFailure;
+    }
+    return kSuccess;
+#endif
+  }
+
 }; // Interpreter
 } // namespace Cpp
 

unittests/CppInterOp/FunctionReflectionTest.cpp

@@ -1517,3 +1517,17 @@ TEST(FunctionReflectionTest, Destruct) {
   output = testing::internal::GetCapturedStdout();
   EXPECT_EQ(output, "Destructor Executed");
 }
+
+TEST(FunctionReflectionTest, UndoTest) {
+  Cpp::CreateInterpreter();
+  std::string cerrs;
+  testing::internal::CaptureStderr();
+  Cpp::Process("int x = 5;");
+  cerrs = testing::internal::GetCapturedStderr();
+  EXPECT_STREQ(cerrs.c_str(), "");
+  Cpp::Undo();
+  testing::internal::CaptureStderr();
+  Cpp::Process("int x = 10;");
+  cerrs = testing::internal::GetCapturedStderr();
+  EXPECT_STREQ(cerrs.c_str(), "");
+}