Follow up for #283 (response to comments) including change in Union[X, Any]

python2/test_typing.py

@@ -201,10 +201,13 @@ def test_subclass_error(self):
  def test_union_any(self):
  u = Union[Any]
  self.assertEqual(u, Any)
- u = Union[int, Any]
- self.assertEqual(u, Any)
- u = Union[Any, int]
- self.assertEqual(u, Any)
+ u1 = Union[int, Any]
+ u2 = Union[Any, int]
+ u3 = Union[Any, object]
+ self.assertEqual(u1, u2)
+ self.assertNotEqual(u1, Any)
+ self.assertNotEqual(u2, Any)
+ self.assertNotEqual(u3, Any)
 
  def test_union_object(self):
  u = Union[object]
@@ -214,12 +217,6 @@ def test_union_object(self):
  u = Union[object, int]
  self.assertEqual(u, object)
 
- def test_union_any_object(self):
- u = Union[object, Any]
- self.assertEqual(u, Any)
- u = Union[Any, object]
- self.assertEqual(u, Any)
-
  def test_unordered(self):
  u1 = Union[int, float]
  u2 = Union[float, int]

python2/typing.py

@@ -149,7 +149,7 @@ def __new__(cls, *args, **kwds):
  isinstance(args[1], tuple)):
  # Close enough.
  raise TypeError("Cannot subclass %r" % cls)
- return object.__new__(cls)
+ return super(_TypingBase, cls).__new__(cls)
 
  # Things that are not classes also need these.
  def _eval_type(self, globalns, localns):
@@ -168,7 +168,11 @@ def __call__(self, *args, **kwds):
 
 
 class _FinalTypingBase(_TypingBase):
- """Mix-in class to prevent instantiation."""
+ """Mix-in class to prevent instantiation.
+
+ Prevents instantiation unless _root=True is given in class call.
+ It is used to create pseudo-singleton instances Any, Union, Tuple, etc.
+ """
 
  __slots__ = ()
 
@@ -256,7 +260,7 @@ def __init__(self, name, type_var, impl_type, type_checker):
  assert isinstance(name, basestring), repr(name)
  assert isinstance(impl_type, type), repr(impl_type)
  assert not isinstance(impl_type, TypingMeta), repr(impl_type)
- assert isinstance(type_var, (type, _TypingBase))
+ assert isinstance(type_var, (type, _TypingBase)), repr(type_var)
  self.name = name
  self.type_var = type_var
  self.impl_type = impl_type
@@ -427,9 +431,13 @@ def __new__(cls, name, bases, namespace):
 class _Any(_FinalTypingBase):
  """Special type indicating an unconstrained type.
 
- - Any object is an instance of Any.
- - Any class is a subclass of Any.
- - As a special case, Any and object are subclasses of each other.
+ - Any is compatible with every type.
+ - Any assumed to have all methods.
+ - All values assumed to be instances of Any.
+
+ Note that all the above statements are true from the point of view of
+ static type checkers. At runtime, Any should not be used with instance
+ or class checks.
  """
  __metaclass__ = AnyMeta
  __slots__ = ()
@@ -598,16 +606,10 @@ class Manager(Employee): pass
  Union[Manager, int, Employee] == Union[int, Employee]
  Union[Employee, Manager] == Employee
 
- - Corollary: if Any is present it is the sole survivor, e.g.::
-
- Union[int, Any] == Any
-
  - Similar for object::
 
  Union[int, object] == object
 
- - To cut a tie: Union[object, Any] == Union[Any, object] == Any.
-
  - You cannot subclass or instantiate a union.
 
  - You cannot write Union[X][Y] (what would it mean?).
@@ -646,14 +648,11 @@ def __new__(cls, parameters=None, *args, **kwds):
  assert not all_params, all_params
  # Weed out subclasses.
  # E.g. Union[int, Employee, Manager] == Union[int, Employee].
- # If Any or object is present it will be the sole survivor.
- # If both Any and object are present, Any wins.
- # Never discard type variables, except against Any.
+ # If object is present it will be sole survivor among proper classes.
+ # Never discard type variables.
  # (In particular, Union[str, AnyStr] != AnyStr.)
  all_params = set(params)
  for t1 in params:
- if t1 is Any:
- return Any
  if not isinstance(t1, type):
  continue
  if any(isinstance(t2, type) and issubclass(t1, t2)
@@ -726,7 +725,7 @@ def __new__(cls, name, bases, namespace):
 class _Optional(_FinalTypingBase):
  """Optional type.
 
- Optional[X] is equivalent to Union[X, type(None)].
+ Optional[X] is equivalent to Union[X, None].
  """
 
  __metaclass__ = OptionalMeta

src/test_typing.py

@@ -202,10 +202,13 @@ def test_subclass_error(self):
  def test_union_any(self):
  u = Union[Any]
  self.assertEqual(u, Any)
- u = Union[int, Any]
- self.assertEqual(u, Any)
- u = Union[Any, int]
- self.assertEqual(u, Any)
+ u1 = Union[int, Any]
+ u2 = Union[Any, int]
+ u3 = Union[Any, object]
+ self.assertEqual(u1, u2)
+ self.assertNotEqual(u1, Any)
+ self.assertNotEqual(u2, Any)
+ self.assertNotEqual(u3, Any)
 
  def test_union_object(self):
  u = Union[object]
@@ -215,12 +218,6 @@ def test_union_object(self):
  u = Union[object, int]
  self.assertEqual(u, object)
 
- def test_union_any_object(self):
- u = Union[object, Any]
- self.assertEqual(u, Any)
- u = Union[Any, object]
- self.assertEqual(u, Any)
-
  def test_unordered(self):
  u1 = Union[int, float]
  u2 = Union[float, int]

src/typing.py

@@ -143,7 +143,6 @@ class _TypingBase(metaclass=TypingMeta, _root=True):
 
  __slots__ = ()
 
-
  def __init__(self, *args, **kwds):
  pass
 
@@ -158,7 +157,7 @@ def __new__(cls, *args, **kwds):
  isinstance(args[1], tuple)):
  # Close enough.
  raise TypeError("Cannot subclass %r" % cls)
- return object.__new__(cls)
+ return super().__new__(cls)
 
  # Things that are not classes also need these.
  def _eval_type(self, globalns, localns):
@@ -177,7 +176,11 @@ def __call__(self, *args, **kwds):
 
 
 class _FinalTypingBase(_TypingBase, _root=True):
- """Mix-in class to prevent instantiation."""
+ """Mix-in class to prevent instantiation.
+
+ Prevents instantiation unless _root=True is given in class call.
+ It is used to create pseudo-singleton instances Any, Union, Tuple, etc.
+ """
 
  __slots__ = ()
 
@@ -273,7 +276,7 @@ def __init__(self, name, type_var, impl_type, type_checker):
  assert isinstance(name, str), repr(name)
  assert isinstance(impl_type, type), repr(impl_type)
  assert not isinstance(impl_type, TypingMeta), repr(impl_type)
- assert isinstance(type_var, (type, _TypingBase))
+ assert isinstance(type_var, (type, _TypingBase)), repr(type_var)
  self.name = name
  self.type_var = type_var
  self.impl_type = impl_type
@@ -375,9 +378,13 @@ def _type_repr(obj):
 class _Any(_FinalTypingBase, _root=True):
  """Special type indicating an unconstrained type.
 
- - Any object is an instance of Any.
- - Any class is a subclass of Any.
- - As a special case, Any and object are subclasses of each other.
+ - Any is compatible with every type.
+ - Any assumed to have all methods.
+ - All values assumed to be instances of Any.
+
+ Note that all the above statements are true from the point of view of
+ static type checkers. At runtime, Any should not be used with instance
+ or class checks.
  """
 
  __slots__ = ()
@@ -502,7 +509,7 @@ def inner(*args, **kwds):
  try:
  return cached(*args, **kwds)
  except TypeError:
- pass # Do not duplicate real errors.
+ pass # All real errors (not unhashable args) are raised below.
  return func(*args, **kwds)
  return inner
 
@@ -542,16 +549,10 @@ class Manager(Employee): pass
  Union[Manager, int, Employee] == Union[int, Employee]
  Union[Employee, Manager] == Employee
 
- - Corollary: if Any is present it is the sole survivor, e.g.::
-
- Union[int, Any] == Any
-
  - Similar for object::
 
  Union[int, object] == object
 
- - To cut a tie: Union[object, Any] == Union[Any, object] == Any.
-
  - You cannot subclass or instantiate a union.
 
  - You cannot write Union[X][Y] (what would it mean?).
@@ -589,14 +590,11 @@ def __new__(cls, parameters=None, *args, _root=False):
  assert not all_params, all_params
  # Weed out subclasses.
  # E.g. Union[int, Employee, Manager] == Union[int, Employee].
- # If Any or object is present it will be the sole survivor.
- # If both Any and object are present, Any wins.
- # Never discard type variables, except against Any.
+ # If object is present it will be sole survivor among proper classes.
+ # Never discard type variables.
  # (In particular, Union[str, AnyStr] != AnyStr.)
  all_params = set(params)
  for t1 in params:
- if t1 is Any:
- return Any
  if not isinstance(t1, type):
  continue
  if any(isinstance(t2, type) and issubclass(t1, t2)
@@ -662,7 +660,7 @@ def __subclasscheck__(self, cls):
 class _Optional(_FinalTypingBase, _root=True):
  """Optional type.
 
- Optional[X] is equivalent to Union[X, type(None)].
+ Optional[X] is equivalent to Union[X, None].
  """
 
  __slots__ = ()