<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/143668>143668</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            clang-repl %undo message is misleading when there is nothing left to undo
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            new issue
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          DavidSpickett
      </td>
    </tr>
</table>

<pre>
    This is the smallest problem but it might be a good first time contributor issue so I'm reporting it anyway.

Start clang-repl and immediately `%undo`:
```
C:\Users\tcwg\llvm-worker\lldb-aarch64-windows\build>.\bin\clang-repl
clang-repl> %undo
error: Operation failed. Too many undos
```
Would be nice if this could tell it had reached the top (or bottom?) of the undo stack and customise the error to say that instead.
```
error: Operation failed. No input left to undo.
```
Here's a longer example that shows building a set of lines and undo-ing back to the beginning:
```
C:\Users\tcwg\llvm-worker\lldb-aarch64-windows\build>.\bin\clang-repl
clang-repl> int i = 1;
clang-repl> int j = i + 1;
clang-repl> %undo
clang-repl> int k = j + 1;
In file included from <<< inputs >>>:1:
input_line_3:1:9: error: use of undeclared identifier 'j'
    1 | int k = j + 1;
      | ^
error: Parsing failed.
clang-repl> %undo
clang-repl> int l = i + 1;
input_line_4:1:9: error: use of undeclared identifier 'i'
    1 | int l = i + 1;
      |         ^
error: Parsing failed.
clang-repl> %undo
error: Operation failed. Too many undos
clang-repl>
```
</pre>
<img width="1" height="1" alt="" src="http://email.email.llvm.org/o/eJzEVc1u4zYQfhr6MrAhUZa0PujgODG6l7bAbtHjghJH0iQUKZCjuH77grTTuNm0wOayAgGRHM7P981wqEKgwSI2orwT5f1KLTw639yrZ9JfZuqekHnVOn1uvo4UgALwiBAmZQwGhtm71uAE7cJADBMNI0OLoGBwTkNPPjAwTQids-ypXdh5oBAWhODgs5D1BB5n55nsEE0oez6p80Zke5Htv7DyDJ1Rdlh7nA0oq4GmCTUpRnMGUWVClovVLs6KqBMnl5HtD3GrPPwR0AdRHrg7DaI8GPM8rU_OP6FPK92ulfLdWG3XJ7LaneLZdiGjRfGwiXOyojy8hiGy_c2ieICXGLI9eu-8KPbw24xeMTkLvSKDegNfnYNJ2TPEo-FNpH-6xejInKUOgXrgSHeXdhmNidSMSoNH1Y2oUxbYzSDkJ-ehdcxuEsVRyB24PkmjFwisuqfEWrcEdhMFTMIUJrCDoM7Ao2IgGxiV3ryJ63_w_OqA7LwwGOw52ooe3-r_gh6FrAMoMM4O6AH_UtNs8OI1jO4UIHEd868gIEcAhiyGFHc0uo6yNiJhl8JvcSBryQ4_L-VkGQhEcQ-5KO7eFT8mMYGQd-8fei2b75WfkvLjrfJnCz0ZBLKdWTRq6L2bQBSHy7hkI4AoHl7GPr8QlCTfIqnfiuvuLib1n-wuASPti9XYGeVRA2m0TD2hByHrRyFrke0BAHIQ9eG_QoT0xQOifLgtn9-VDzGL1-L5ISrM9zzeANp-CBC9B-gdR6-AXr4PA_uR1vAvG7cVvtJNoXfFTq2wyevtriqKbVmvxqbOVdWrbptlqlBY53Whyi7Lqu0Oy75s6xU1MpNlVuV5tsvrot60eVZ1PXbY1rhTfSu2GU6KzCZelo3zwyr16SbfFlX1aWVUiyakd0JKi6dLFxdSxmfDN-mGtcsQxDYzFDi8mmFig81NF79yAhOGoAaMr8pEwaBKTeA0oo233CeBdTzG3dsms1q8aUbmOcTylkchjwPxuLSbzk1CHqPn6289e_eIHQt5TPEGIY9XQM-N_DsAAP__axg0jw">