23.1.1

New error codes:

• Y052: Disallow default values in global or class namespaces where the assignment does not have a type annotation. Stubs should be explicit about the type of all variables in the stub; without type annotations, the type checker is forced to make inferences, which may have unpredictable consequences. Enum members are excluded from this check, as are various special assignments such as __all__ and __match_args__.

Other changes:

• Disallow numeric default values where len(str(default)) > 7. If a function has a default value where the string representation is greater than 7 characters, it is likely to be an implementation detail or a constant that varies depending on the system you're running on, such as sys.maxsize.
• Disallow str or bytes defaults where the default is >50 characters long, for similar reasons.
• Allow ast.Attribute nodes as default values for a small number of special cases, such as sys.maxsize and sys.executable.
• Fewer Y020 false positives are now emitted when encountering default values in stub files.