[FR] Improve literal_eval type definition

[sk-]

ast.literal_eval can only return Dict, Set, Tuple, int, str, bool, float, complex and None. However its return type is set as Any.

The problem with that type definition is that mypy (with warn_return_any) complains when you compare against Any, and the following code:

def comparator(value: str) -> bool:
    return ast.literal_eval(value) == expected_value

raises

Returning Any from function declared to return "bool"

[hauntsaninja]

Generally speaking, Union return types are problematic. For more discussion, see https://github.com/python/typeshed/blob/master/CONTRIBUTING.md#conventions I don't think literal_eval is an exception here, anecdotally and based on https://grep.app/search?q=literal_eval%28&filter[lang][0]=Python

[srittau]

Another example where something like python/typing#566 could help, but at the moment there is not much we can do in typeshed, unfortunately.