1 files changed, 11 insertions, 1 deletions
diff --git a/Lib/_collections_abc.py b/Lib/_collections_abc.py
index 7c3faa6..e4eac79 100644
--- a/Lib/_collections_abc.py
+++ b/Lib/_collections_abc.py
@@ -434,7 +434,7 @@ class _CallableGenericAlias(GenericAlias):
             raise TypeError(
                 "Callable must be used as Callable[[arg, ...], result].")
         t_args, t_result = args
-        if isinstance(t_args, list):
+        if isinstance(t_args, (list, tuple)):
             ga_args = tuple(t_args) + (t_result,)
         # This relaxes what t_args can be on purpose to allow things like
         # PEP 612 ParamSpec.  Responsibility for whether a user is using
@@ -456,6 +456,16 @@ class _CallableGenericAlias(GenericAlias):
             args = list(args[:-1]), args[-1]
         return _CallableGenericAlias, (Callable, args)
 
+    def __getitem__(self, item):
+        # Called during TypeVar substitution, returns the custom subclass
+        # rather than the default types.GenericAlias object.
+        ga = super().__getitem__(item)
+        args = ga.__args__
+        t_result = args[-1]
+        t_args = args[:-1]
+        args = (t_args, t_result)
+        return _CallableGenericAlias(Callable, args)
+
 
 def _type_repr(obj):
     """Return the repr() of an object, special-casing types (internal helper).