1 files changed, 10 insertions, 2 deletions
diff --git a/clang/lib/Interpreter/Interpreter.cpp b/clang/lib/Interpreter/Interpreter.cpp
index db6a2bb..9b71486 100644
--- a/clang/lib/Interpreter/Interpreter.cpp
+++ b/clang/lib/Interpreter/Interpreter.cpp
@@ -761,10 +761,18 @@ Interpreter::getSymbolAddressFromLinkerName(llvm::StringRef Name) const {
 
 llvm::Error Interpreter::Undo(unsigned N) {
 
-  if (N > getEffectivePTUSize())
+  if (getEffectivePTUSize() == 0) {
     return llvm::make_error<llvm::StringError>("Operation failed. "
-                                               "Too many undos",
+                                               "No input left to undo",
                                                std::error_code());
+  } else if (N > getEffectivePTUSize()) {
+    return llvm::make_error<llvm::StringError>(
+        llvm::formatv(
+            "Operation failed. Wanted to undo {0} inputs, only have {1}.", N,
+            getEffectivePTUSize()),
+        std::error_code());
+  }
+
   for (unsigned I = 0; I < N; I++) {
     if (IncrExecutor) {
       if (llvm::Error Err = IncrExecutor->removeModule(PTUs.back()))