<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/147020>147020</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [mlir] Error message for optional properties is confusing
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            mlir
      </td>
    </tr>

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

    <tr>
      <th>Reporter</th>
      <td>
          peledins-zimperium
      </td>
    </tr>
</table>

<pre>
    I had to look up source code for this error message:
```
          return emitError(loc, "only properties with default values "
 "that can be optionally parsed "
 "can be used to anchor an optional group");
```
to understand that "optionally parsed" means that it must have the optional parser enabled.

I think a better error message would be:
```
          return emitError(loc, "only properties with `defaultValue` "
 "that also have `optionalParser` "
 "can be used to anchor an optional group");
```
</pre>
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