Understanding Pycharm inferred type hinting

Question

I would like to understand what is going on in PyCharm with Inferred type in the Quick Documentation window.

Using the function below, I see the following in Quick Documentation:

Argument host appears as Optional[str] as I expect it to, but auth and version only show str | None str | None . Technically (I believe) both are correct, but why the discrepancy between these similar arguments?

You'll notice I tried altering the type hint for version just to see if that made any difference.

Am I missing something about how type hinting works?
Is there some way I can get Optional[str] to display for auth and version ?

def getBaseUrl(service, host=None, auth=None, version=None):
    """
    Defaulted arguments will automatically fetch the values from config 

    :param str service: wms, wfs
    :param str or None host:    [internal | external | {user submitted host}] -
                                internal and external will use the config file to automatically determine
                                anything else will be assumed as a server address including possible port.
    :param str or None auth:    basic, digest, oauth 
                                anything else will raise exception
    :param version: eg wms_v1, wfs_v1
    :type version:  str or None
    :return: base url for use in the gis Webservice
    """
    assert service.lower() == 'wms' or service.lower() == 'wfs', "Unsupported service: %s" % service

    internalhost = cfg.get('GIS', 'internalhost')
    externalhost = cfg.get('GIS', 'externalhost')

    if host is None:
        host = cfg.get('GIS', 'host')
    if version is None:
        version = cfg.get(service, 'version')

    if host == "internal":
        host = "{host}".format(host=internalhost)

    elif host == 'external':
        host = "{host}".format(host=externalhost)

    else:
        host = "{host}".format(host=host)

    return buildBaseUrl(host=host, version=version, auth=auth, service=service)

Answer 1

Looks like this is indeed a bug with Pycharm. To be fixed in 2016.2 release.

https://youtrack.jetbrains.com/issue/PY-17705