Invalid rule expression remained in the grammar 3.11.5

A reference to an invalid rule remained in the grammar specification 3.11.5:

default: '=' expression  | invalid_default

If this is meant to be a bug report, please open one at GitHub - python/cpython: The Python programming language .

No, this is just a documentation issue.

If you think the documentation needs to be fixed, you should still open an issue as Brett suggests.