Address review partially

* Add tests for callable typevar substitution * Update docstrings and news Co-Authored-By: Guido van Rossum <gvanrossum@users.noreply.github.com>
python · gvanrossum · Dec 13, 2020 · Oct 31, 2020 · Oct 31, 2020 · Oct 31, 2020
commit 598d29bc0ce52c78e4bc723749911ed8ec86d384
diff --git a/Lib/_collections_abc.py b/Lib/_collections_abc.py
@@ -414,8 +414,13 @@ def __subclasshook__(cls, C):
 
 
 class _CallableGenericAlias(GenericAlias):
-    """ Internal class specifically for consistency between the ``__args__`` of
-    ``collections.abc.Callable``'s and ``typing.Callable``'s ``GenericAlias``.
+    """ Represent `Callable[argtypes, resulttype]`.
+
+    This sets ``__args__`` to a tuple containing the flattened``argtypes``
+    followed by ``resulttype``.
+
+    Example: ``Callable[[int, str], float]`` sets ``__args__`` to
+    ``(int, str, float)``.
     """
     __slots__ = ()
     def __new__(cls, origin, args):
@@ -463,7 +468,7 @@ def __repr__(self):
 
     def __reduce__(self):
         args = self.__args__
-        if not (len(args) == 2 and args[0] is ...):
+        if not (len(args) == 2 and args[0] is Ellipsis):
             args = list(args[:-1]), args[-1]
         return _CallableGenericAlias, (Callable, args)
 
@@ -480,7 +485,7 @@ def _type_repr(obj):
         if obj.__module__ == 'builtins':
             return obj.__qualname__
         return f'{obj.__module__}.{obj.__qualname__}'
-    if obj is ...:
+    if obj is Ellipsis:
         return '...'
     if isinstance(obj, FunctionType):
         return obj.__name__

diff --git a/Lib/test/test_genericalias.py b/Lib/test/test_genericalias.py
@@ -321,6 +321,12 @@ def test_abc_callable(self):
             self.assertEqual(alias.__args__, loaded.__args__)
             self.assertEqual(alias.__parameters__, loaded.__parameters__)
 
+        with self.subTest("Testing TypeVar substitution"):
+            C1 = Callable[[int, T], T]
+            self.assertEqual(C1[str], Callable[[int, str], str])
+            C2 = Callable[[K, T], V]
+            self.assertEqual(C2[int, float, str], Callable[[int, float], str])
+
         # bpo-42195
         with self.subTest("Testing collections.abc.Callable's consistency "
                           "with typing.Callable"):

diff --git a/Misc/NEWS.d/next/Core and Builtins/2020-11-20-00-57-47.bpo-42195.HeqcpS.rst b/Misc/NEWS.d/next/Core and Builtins/2020-11-20-00-57-47.bpo-42195.HeqcpS.rst
@@ -1,5 +1,5 @@
 The ``__args__`` of the parameterized generics for :data:`typing.Callable`
-and :class:`collections.abc.Callable` are now consistent.  Said ``__args__`` 
+and :class:`collections.abc.Callable` are now consistent.  The ``__args__`` 
 for :class:`collections.abc.Callable` are now flattened while 
 :data:`typing.Callable`'s have not changed.  To allow this change, 
 :class:`types.GenericAlias` can now be subclassed.  Patch by Ken Jin.  

diff --git a/Objects/genericaliasobject.c b/Objects/genericaliasobject.c
@@ -564,7 +564,6 @@ static PyGetSetDef ga_properties[] = {
     {0}
 };
 
-// Helper to create inheritable or non-inheritable gaobjects
 static inline gaobject *
 create_ga(PyTypeObject *type, PyObject *origin, PyObject *args) {
     if (!PyTuple_Check(args)) {