def is_special_target(right: ProperType) -> bool:
"""Whitelist some special cases for use in isinstance() with improper types."""
if isinstance(right, CallableType) and right.is_type_obj():
if right.type_object().fullname() == 'builtins.tuple':
# Used with Union[Type, Tuple[Type, ...]].
return True
if right.type_object().fullname() in ('mypy.types.Type',
'mypy.types.ProperType',
'mypy.types.TypeAliasType'):
# Special case: things like assert isinstance(typ, ProperType) are always OK.
return True
if right.type_object().fullname() in ('mypy.types.UnboundType',
'mypy.types.TypeVarType',
'mypy.types.RawExpressionType',
'mypy.types.EllipsisType',
'mypy.types.StarType',
'mypy.types.TypeList',
'mypy.types.CallableArgument',
'mypy.types.PartialType',
'mypy.types.ErasedType'):
# Special case: these are not valid targets for a type alias and thus safe.
# TODO: introduce a SyntheticType base to simplify this?
return True
elif isinstance(right, TupleType):
return all(is_special_target(t) for t in get_proper_types(right.items))
return False
def is_dangerous_target(typ: ProperType) -> bool:
"""Is this a dangerous target (right argument) for an isinstance() check?"""
if isinstance(typ, TupleType):
return any(is_dangerous_target(get_proper_type(t)) for t in typ.items)
if isinstance(typ, CallableType) and typ.is_type_obj():
return typ.type_object().has_base('mypy.types.Type')
return False