According to the documentation of "argparse.Action", a keyword 'bool' is not allowed for type argument, but it doesn't raise no errors.

One possible way to fix this issue is to check in the "argparse._ActionsContainer.add_argument" method.

This change maked the error message wrong if bool is rejected.

The corresponding current code in 3.2 and 3.3 is the same.

Thank you for your response.

My patch makes raise error by minimal change, but it may be better to raise NameError as in a case specifying "type=string" in 2.7.2.

Similar to the case "type=bool", specifications, such as "type=unicode" or "type=long", don't raise errors.
Because the set of problematic keywords are different between 2.7.x and 3.3.x, I have no idea to completely fix this problem.

I can't find anywhere in the documentation where type=bool, type=unicode or type=long are disallowed. They shouldn't be disallowed. If you want to pass type=bool, argparse should not stop you. And it currently doesn't:

>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('foo', type=bool)
>>> parser.parse_args([''])
Namespace(foo=False)
>>> parser.parse_args(['x'])
Namespace(foo=True)

>     - type -- The type which the command-line arguments should be converted
>         to, should be one of 'string', 'int', 'float', 'complex' or a
>         callable object that accepts a single string argument. If None,
>         'string' is assumed.

I misunderstood this sentence in the docstring of arcparse.Action because `bool` or `unicode` is not appeared in this list, which are callables.

So, I close this issue.