bpo-44801: Check arguments in substitution of ParamSpec in Callable (GH-27585)
(cherry picked from commit 3875a6954741065b136650db67ac533bc70a3eac)
Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
diff --git a/Lib/_collections_abc.py b/Lib/_collections_abc.py
index 33db9b2..87a9cd2 100644
--- a/Lib/_collections_abc.py
+++ b/Lib/_collections_abc.py
@@ -426,22 +426,16 @@ class _CallableGenericAlias(GenericAlias):
__slots__ = ()
def __new__(cls, origin, args):
- return cls.__create_ga(origin, args)
-
- @classmethod
- def __create_ga(cls, origin, args):
- if not isinstance(args, tuple) or len(args) != 2:
+ if not (isinstance(args, tuple) and len(args) == 2):
raise TypeError(
"Callable must be used as Callable[[arg, ...], result].")
t_args, t_result = args
- 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
- # Callable[...] properly is deferred to static type checkers.
- else:
- ga_args = args
- return super().__new__(cls, origin, ga_args)
+ if isinstance(t_args, list):
+ args = (*t_args, t_result)
+ elif not _is_param_expr(t_args):
+ raise TypeError(f"Expected a list of types, an ellipsis, "
+ f"ParamSpec, or Concatenate. Got {t_args}")
+ return super().__new__(cls, origin, args)
@property
def __parameters__(self):
@@ -456,7 +450,7 @@ def __parameters__(self):
return tuple(dict.fromkeys(params))
def __repr__(self):
- if _has_special_args(self.__args__):
+ if len(self.__args__) == 2 and _is_param_expr(self.__args__[0]):
return super().__repr__()
return (f'collections.abc.Callable'
f'[[{", ".join([_type_repr(a) for a in self.__args__[:-1]])}], '
@@ -464,7 +458,7 @@ def __repr__(self):
def __reduce__(self):
args = self.__args__
- if not _has_special_args(args):
+ if not (len(args) == 2 and _is_param_expr(args[0])):
args = list(args[:-1]), args[-1]
return _CallableGenericAlias, (Callable, args)
@@ -479,10 +473,11 @@ def __getitem__(self, item):
param_len = len(self.__parameters__)
if param_len == 0:
raise TypeError(f'{self} is not a generic class')
- if (param_len == 1
- and isinstance(item, (tuple, list))
- and len(item) > 1) or not isinstance(item, tuple):
+ if not isinstance(item, tuple):
item = (item,)
+ if (param_len == 1 and _is_param_expr(self.__parameters__[0])
+ and item and not _is_param_expr(item[0])):
+ item = (list(item),)
item_len = len(item)
if item_len != param_len:
raise TypeError(f'Too {"many" if item_len > param_len else "few"}'
@@ -492,7 +487,13 @@ def __getitem__(self, item):
new_args = []
for arg in self.__args__:
if _is_typevarlike(arg):
- arg = subst[arg]
+ if _is_param_expr(arg):
+ arg = subst[arg]
+ if not _is_param_expr(arg):
+ raise TypeError(f"Expected a list of types, an ellipsis, "
+ f"ParamSpec, or Concatenate. Got {arg}")
+ else:
+ arg = subst[arg]
# Looks like a GenericAlias
elif hasattr(arg, '__parameters__') and isinstance(arg.__parameters__, tuple):
subparams = arg.__parameters__
@@ -502,32 +503,31 @@ def __getitem__(self, item):
new_args.append(arg)
# args[0] occurs due to things like Z[[int, str, bool]] from PEP 612
- if not isinstance(new_args[0], (tuple, list)):
+ if not isinstance(new_args[0], list):
t_result = new_args[-1]
t_args = new_args[:-1]
new_args = (t_args, t_result)
return _CallableGenericAlias(Callable, tuple(new_args))
+
def _is_typevarlike(arg):
obj = type(arg)
# looks like a TypeVar/ParamSpec
return (obj.__module__ == 'typing'
and obj.__name__ in {'ParamSpec', 'TypeVar'})
-def _has_special_args(args):
- """Checks if args[0] matches either ``...``, ``ParamSpec`` or
+def _is_param_expr(obj):
+ """Checks if obj matches either a list of types, ``...``, ``ParamSpec`` or
``_ConcatenateGenericAlias`` from typing.py
"""
- if len(args) != 2:
- return False
- obj = args[0]
if obj is Ellipsis:
return True
+ if isinstance(obj, list):
+ return True
obj = type(obj)
names = ('ParamSpec', '_ConcatenateGenericAlias')
return obj.__module__ == 'typing' and any(obj.__name__ == name for name in names)
-
def _type_repr(obj):
"""Return the repr() of an object, special-casing types (internal helper).