bpo-44732: Rename types.Union to types.UnionType (#27342)

Co-authored-by: Łukasz Langa <lukasz@langa.pl>
Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>

Doc/library/stdtypes.rst

@@ -5040,16 +5040,16 @@ enables cleaner type hinting syntax compared to :data:`typing.Union`.
       TypeError: isinstance() argument 2 cannot contain a parameterized generic
 
 The user-exposed type for the union object can be accessed from
-:data:`types.Union` and used for :func:`isinstance` checks.  An object cannot be
+:data:`types.UnionType` and used for :func:`isinstance` checks.  An object cannot be
 instantiated from the type::
 
    >>> import types
-   >>> isinstance(int | str, types.Union)
+   >>> isinstance(int | str, types.UnionType)
    True
-   >>> types.Union()
+   >>> types.UnionType()
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
-   TypeError: cannot create 'types.Union' instances
+   TypeError: cannot create 'types.UnionType' instances
 
 .. note::
    The :meth:`__or__` method for type objects was added to support the syntax

Doc/library/types.rst

@@ -312,7 +312,7 @@ Standard names are defined for the following types:
       This type can now be subclassed.
 
 
-.. data:: Union
+.. data:: UnionType
 
    The type of :ref:`union type expressions<types-union>`.
 

Lib/test/test_typing.py

@@ -3090,7 +3090,7 @@ class GetUtilitiesTestCase(TestCase):
         self.assertIs(get_origin(Callable), collections.abc.Callable)
         self.assertIs(get_origin(list[int]), list)
         self.assertIs(get_origin(list), None)
-        self.assertIs(get_origin(list | str), types.Union)
+        self.assertIs(get_origin(list | str), types.UnionType)
         self.assertIs(get_origin(P.args), P)
         self.assertIs(get_origin(P.kwargs), P)
 

Lib/types.py

@@ -297,9 +297,8 @@ def coroutine(func):
 
     return wrapped
 
-
 GenericAlias = type(list[int])
-Union = type(int | str)
+UnionType = type(int | str)
 
 EllipsisType = type(Ellipsis)
 NoneType = type(None)

Lib/typing.py

@@ -175,7 +175,7 @@ def _type_check(arg, msg, is_argument=True, module=None):
         return arg
     if isinstance(arg, _SpecialForm) or arg in (Generic, Protocol):
         raise TypeError(f"Plain {arg} is not valid as type argument")
-    if isinstance(arg, (type, TypeVar, ForwardRef, types.Union, ParamSpec)):
+    if isinstance(arg, (type, TypeVar, ForwardRef, types.UnionType, ParamSpec)):
         return arg
     if not callable(arg):
         raise TypeError(f"{msg} Got {arg!r:.100}.")
@@ -215,7 +215,7 @@ def _collect_type_vars(types_, typevar_types=None):
     for t in types_:
         if isinstance(t, typevar_types) and t not in tvars:
             tvars.append(t)
-        if isinstance(t, (_GenericAlias, GenericAlias, types.Union)):
+        if isinstance(t, (_GenericAlias, GenericAlias, types.UnionType)):
             tvars.extend([t for t in t.__parameters__ if t not in tvars])
     return tuple(tvars)
 
@@ -268,7 +268,7 @@ def _remove_dups_flatten(parameters):
     # Flatten out Union[Union[...], ...].
     params = []
     for p in parameters:
-        if isinstance(p, (_UnionGenericAlias, types.Union)):
+        if isinstance(p, (_UnionGenericAlias, types.UnionType)):
             params.extend(p.__args__)
         elif isinstance(p, tuple) and len(p) > 0 and p[0] is Union:
             params.extend(p[1:])
@@ -322,13 +322,13 @@ def _eval_type(t, globalns, localns, recursive_guard=frozenset()):
     """
     if isinstance(t, ForwardRef):
         return t._evaluate(globalns, localns, recursive_guard)
-    if isinstance(t, (_GenericAlias, GenericAlias, types.Union)):
+    if isinstance(t, (_GenericAlias, GenericAlias, types.UnionType)):
         ev_args = tuple(_eval_type(a, globalns, localns, recursive_guard) for a in t.__args__)
         if ev_args == t.__args__:
             return t
         if isinstance(t, GenericAlias):
             return GenericAlias(t.__origin__, ev_args)
-        if isinstance(t, types.Union):
+        if isinstance(t, types.UnionType):
             return functools.reduce(operator.or_, ev_args)
         else:
             return t.copy_with(ev_args)
@@ -1038,7 +1038,7 @@ class _GenericAlias(_BaseGenericAlias, _root=True):
         for arg in self.__args__:
             if isinstance(arg, self._typevar_types):
                 arg = subst[arg]
-            elif isinstance(arg, (_GenericAlias, GenericAlias, types.Union)):
+            elif isinstance(arg, (_GenericAlias, GenericAlias, types.UnionType)):
                 subparams = arg.__parameters__
                 if subparams:
                     subargs = tuple(subst[x] for x in subparams)
@@ -1206,7 +1206,7 @@ class _UnionGenericAlias(_GenericAlias, _root=True):
         return Union[params]
 
     def __eq__(self, other):
-        if not isinstance(other, (_UnionGenericAlias, types.Union)):
+        if not isinstance(other, (_UnionGenericAlias, types.UnionType)):
             return NotImplemented
         return set(self.__args__) == set(other.__args__)
 
@@ -1810,7 +1810,7 @@ def _strip_annotations(t):
         if stripped_args == t.__args__:
             return t
         return GenericAlias(t.__origin__, stripped_args)
-    if isinstance(t, types.Union):
+    if isinstance(t, types.UnionType):
         stripped_args = tuple(_strip_annotations(a) for a in t.__args__)
         if stripped_args == t.__args__:
             return t
@@ -1841,8 +1841,8 @@ def get_origin(tp):
         return tp.__origin__
     if tp is Generic:
         return Generic
-    if isinstance(tp, types.Union):
-        return types.Union
+    if isinstance(tp, types.UnionType):
+        return types.UnionType
     return None
 
 
@@ -1866,7 +1866,7 @@ def get_args(tp):
                          or isinstance(res[0], (ParamSpec, _ConcatenateGenericAlias)))):
             res = (list(res[:-1]), res[-1])
         return res
-    if isinstance(tp, types.Union):
+    if isinstance(tp, types.UnionType):
         return tp.__args__
     return ()
 

Misc/NEWS.d/next/Core and Builtins/2021-07-26-15-27-03.bpo-44732.IxObt3.rst

@@ -0,0 +1 @@
+Rename ``types.Union`` to ``types.UnionType``.

Objects/unionobject.c

@@ -1,4 +1,4 @@
-// types.Union -- used to represent e.g. Union[int, str], int | str
+// types.UnionType -- used to represent e.g. Union[int, str], int | str
 #include "Python.h"
 #include "pycore_object.h"  // _PyObject_GC_TRACK/UNTRACK
 #include "pycore_unionobject.h"
@@ -414,7 +414,7 @@ union_parameters(PyObject *self, void *Py_UNUSED(unused))
 }
 
 static PyGetSetDef union_properties[] = {
-    {"__parameters__", union_parameters, (setter)NULL, "Type variables in the types.Union.", NULL},
+    {"__parameters__", union_parameters, (setter)NULL, "Type variables in the types.UnionType.", NULL},
     {0}
 };
 
@@ -424,7 +424,7 @@ static PyNumberMethods union_as_number = {
 
 PyTypeObject _PyUnion_Type = {
     PyVarObject_HEAD_INIT(&PyType_Type, 0)
-    .tp_name = "types.Union",
+    .tp_name = "types.UnionType",
     .tp_doc = "Represent a PEP 604 union type\n"
               "\n"
               "E.g. for int | str",