change behavior of Union w.r.t. Any; update docstrings

Author: ilevkivskyi

python2/test_typing.py

@@ -201,10 +201,6 @@ 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)
 
     def test_union_object(self):
         u = Union[object]
@@ -214,12 +210,6 @@ 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

@@ -431,9 +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__ = ()
@@ -602,16 +606,6 @@ 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?).
@@ -650,14 +644,11 @@ 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)
@@ -730,7 +721,7 @@ 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 +202,6 @@ 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)
 
     def test_union_object(self):
         u = Union[object]
@@ -215,12 +211,6 @@ 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

@@ -378,9 +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__ = ()
@@ -545,16 +549,6 @@ 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?).
@@ -592,14 +586,11 @@ 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)
@@ -665,7 +656,7 @@ 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__ = ()