[clang] c295f05 - [clang-repl] Improve error message on failed undos (#149396)

[via cfe-commits]

Author: Aaron Danen
Date: 2025-07-23T10:13:11+01:00
New Revision: c295f050633ba4feb3e2ed74811b9c9d7add758d

URL: https://github.com/llvm/llvm-project/commit/c295f050633ba4feb3e2ed74811b9c9d7add758d
DIFF: https://github.com/llvm/llvm-project/commit/c295f050633ba4feb3e2ed74811b9c9d7add758d.diff

LOG: [clang-repl] Improve error message on failed undos (#149396)

Updated error message logic for undo function. Throws different errors
for the case of there being nothing to undo, and for the case of
requesting more undos than there are operations to undo.

Fixes https://github.com/llvm/llvm-project/issues/143668

Added: 
    

Modified: 
    clang/lib/Interpreter/Interpreter.cpp
    clang/unittests/Interpreter/InterpreterTest.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/Interpreter/Interpreter.cpp b/clang/lib/Interpreter/Interpreter.cpp
index db6a2bb914f43..9b714860c4145 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()))

diff  --git a/clang/unittests/Interpreter/InterpreterTest.cpp b/clang/unittests/Interpreter/InterpreterTest.cpp
index 2ba15cbd37093..768058b954d49 100644
--- a/clang/unittests/Interpreter/InterpreterTest.cpp
+++ b/clang/unittests/Interpreter/InterpreterTest.cpp
@@ -160,12 +160,12 @@ TEST_F(InterpreterTest, UndoCommand) {
 
   // Fail to undo.
   auto Err1 = Interp->Undo();
-  EXPECT_EQ("Operation failed. Too many undos",
+  EXPECT_EQ("Operation failed. No input left to undo",
             llvm::toString(std::move(Err1)));
   auto Err2 = Interp->Parse("int foo = 42;");
   EXPECT_TRUE(!!Err2);
   auto Err3 = Interp->Undo(2);
-  EXPECT_EQ("Operation failed. Too many undos",
+  EXPECT_EQ("Operation failed. Wanted to undo 2 inputs, only have 1.",
             llvm::toString(std::move(Err3)));
 
   // Succeed to undo.