bpo-41559: Change PEP 612 implementation to pure Python (#25449)
diff --git a/Lib/_collections_abc.py b/Lib/_collections_abc.py
index 87302ac..dddf8a2 100644
--- a/Lib/_collections_abc.py
+++ b/Lib/_collections_abc.py
@@ -443,6 +443,18 @@ def __create_ga(cls, origin, args):
ga_args = args
return super().__new__(cls, origin, ga_args)
+ @property
+ def __parameters__(self):
+ params = []
+ for arg in self.__args__:
+ # Looks like a genericalias
+ if hasattr(arg, "__parameters__") and isinstance(arg.__parameters__, tuple):
+ params.extend(arg.__parameters__)
+ else:
+ if _is_typevarlike(arg):
+ params.append(arg)
+ return tuple(dict.fromkeys(params))
+
def __repr__(self):
if _has_special_args(self.__args__):
return super().__repr__()
@@ -458,16 +470,50 @@ def __reduce__(self):
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__
- # args[0] occurs due to things like Z[[int, str, bool]] from PEP 612
- if not isinstance(ga.__args__[0], tuple):
- t_result = ga.__args__[-1]
- t_args = ga.__args__[:-1]
- args = (t_args, t_result)
- return _CallableGenericAlias(Callable, args)
+ # rather than the default types.GenericAlias object. Most of the
+ # code is copied from typing's _GenericAlias and the builtin
+ # types.GenericAlias.
+ # A special case in PEP 612 where if X = Callable[P, int],
+ # then X[int, str] == X[[int, str]].
+ param_len = len(self.__parameters__)
+ if param_len == 0:
+ raise TypeError(f'There are no type or parameter specification'
+ f'variables left in {self}')
+ if (param_len == 1
+ and isinstance(item, (tuple, list))
+ and len(item) > 1) or not isinstance(item, tuple):
+ item = (item,)
+ item_len = len(item)
+ if item_len != param_len:
+ raise TypeError(f'Too {"many" if item_len > param_len else "few"}'
+ f' arguments for {self};'
+ f' actual {item_len}, expected {param_len}')
+ subst = dict(zip(self.__parameters__, item))
+ new_args = []
+ for arg in self.__args__:
+ if _is_typevarlike(arg):
+ arg = subst[arg]
+ # Looks like a GenericAlias
+ elif hasattr(arg, '__parameters__') and isinstance(arg.__parameters__, tuple):
+ subparams = arg.__parameters__
+ if subparams:
+ subargs = tuple(subst[x] for x in subparams)
+ arg = arg[subargs]
+ 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)):
+ 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
diff --git a/Lib/test/test_genericalias.py b/Lib/test/test_genericalias.py
index fd024dc..9f92739 100644
--- a/Lib/test/test_genericalias.py
+++ b/Lib/test/test_genericalias.py
@@ -353,6 +353,12 @@ def test_abc_callable(self):
self.assertEqual(repr(C4[dict]).split(".")[-1], "Callable[[int, dict], str]")
self.assertEqual(C4[dict], Callable[[int, dict], str])
+ # substitute a nested GenericAlias (both typing and the builtin
+ # version)
+ C5 = Callable[[typing.List[T], tuple[K, T], V], int]
+ self.assertEqual(C5[int, str, float],
+ Callable[[typing.List[int], tuple[str, int], float], int])
+
with self.subTest("Testing type erasure"):
class C1(Callable):
def __call__(self):
@@ -391,5 +397,16 @@ def __call__(self):
self.assertEqual(repr(C1), "collections.abc.Callable"
"[typing.Concatenate[int, ~P], int]")
+ with self.subTest("Testing TypeErrors"):
+ with self.assertRaisesRegex(TypeError, "variables left in"):
+ alias[int]
+ P = typing.ParamSpec('P')
+ C1 = Callable[P, T]
+ with self.assertRaisesRegex(TypeError, "many arguments for"):
+ C1[int, str, str]
+ with self.assertRaisesRegex(TypeError, "few arguments for"):
+ C1[int]
+
+
if __name__ == "__main__":
unittest.main()
diff --git a/Misc/NEWS.d/next/Library/2021-04-17-10-49-57.bpo-41559.caIwt9.rst b/Misc/NEWS.d/next/Library/2021-04-17-10-49-57.bpo-41559.caIwt9.rst
new file mode 100644
index 0000000..11db423
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2021-04-17-10-49-57.bpo-41559.caIwt9.rst
@@ -0,0 +1,6 @@
+:pep:`612` is now implemented purely in Python; builtin ``types.GenericAlias``
+objects no longer include ``typing.ParamSpec`` in ``__parameters__``
+(with the exception of ``collections.abc.Callable``\ 's ``GenericAlias``).
+This means previously invalid uses of ``ParamSpec`` (such as
+``list[P]``) which worked in earlier versions of Python 3.10 alpha,
+will now raise ``TypeError`` during substitution.
diff --git a/Objects/genericaliasobject.c b/Objects/genericaliasobject.c
index 8fae83b..756a7ce 100644
--- a/Objects/genericaliasobject.c
+++ b/Objects/genericaliasobject.c
@@ -156,25 +156,13 @@ ga_repr(PyObject *self)
return NULL;
}
-/* Checks if a variable number of names are from typing.py.
-* If any one of the names are found, return 1, else 0.
-**/
-static inline int
-is_typing_name(PyObject *obj, int num, ...)
+// isinstance(obj, TypeVar) without importing typing.py.
+// Returns -1 for errors.
+static int
+is_typevar(PyObject *obj)
{
- va_list names;
- va_start(names, num);
-
PyTypeObject *type = Py_TYPE(obj);
- int hit = 0;
- for (int i = 0; i < num; ++i) {
- if (!strcmp(type->tp_name, va_arg(names, const char *))) {
- hit = 1;
- break;
- }
- }
- va_end(names);
- if (!hit) {
+ if (strcmp(type->tp_name, "TypeVar") != 0) {
return 0;
}
PyObject *module = PyObject_GetAttrString((PyObject *)type, "__module__");
@@ -184,24 +172,9 @@ is_typing_name(PyObject *obj, int num, ...)
int res = PyUnicode_Check(module)
&& _PyUnicode_EqualToASCIIString(module, "typing");
Py_DECREF(module);
-
return res;
}
-// isinstance(obj, (TypeVar, ParamSpec)) without importing typing.py.
-// Returns -1 for errors.
-static inline int
-is_typevarlike(PyObject *obj)
-{
- return is_typing_name(obj, 2, "TypeVar", "ParamSpec");
-}
-
-static inline int
-is_paramspec(PyObject *obj)
-{
- return is_typing_name(obj, 1, "ParamSpec");
-}
-
// Index of item in self[:len], or -1 if not found (self is a tuple)
static Py_ssize_t
tuple_index(PyObject *self, Py_ssize_t len, PyObject *item)
@@ -236,7 +209,7 @@ make_parameters(PyObject *args)
Py_ssize_t iparam = 0;
for (Py_ssize_t iarg = 0; iarg < nargs; iarg++) {
PyObject *t = PyTuple_GET_ITEM(args, iarg);
- int typevar = is_typevarlike(t);
+ int typevar = is_typevar(t);
if (typevar < 0) {
Py_DECREF(parameters);
return NULL;
@@ -306,14 +279,7 @@ subs_tvars(PyObject *obj, PyObject *params, PyObject **argitems)
if (iparam >= 0) {
arg = argitems[iparam];
}
- // convert all the lists inside args to tuples to help
- // with caching in other libaries
- if (PyList_CheckExact(arg)) {
- arg = PyList_AsTuple(arg);
- }
- else {
- Py_INCREF(arg);
- }
+ Py_INCREF(arg);
PyTuple_SET_ITEM(subargs, i, arg);
}
@@ -348,19 +314,11 @@ ga_getitem(PyObject *self, PyObject *item)
int is_tuple = PyTuple_Check(item);
Py_ssize_t nitems = is_tuple ? PyTuple_GET_SIZE(item) : 1;
PyObject **argitems = is_tuple ? &PyTuple_GET_ITEM(item, 0) : &item;
- // A special case in PEP 612 where if X = Callable[P, int],
- // then X[int, str] == X[[int, str]].
- if (nparams == 1 && nitems > 1 && is_tuple &&
- is_paramspec(PyTuple_GET_ITEM(alias->parameters, 0))) {
- argitems = &item;
- }
- else {
- if (nitems != nparams) {
- return PyErr_Format(PyExc_TypeError,
- "Too %s arguments for %R",
- nitems > nparams ? "many" : "few",
- self);
- }
+ if (nitems != nparams) {
+ return PyErr_Format(PyExc_TypeError,
+ "Too %s arguments for %R",
+ nitems > nparams ? "many" : "few",
+ self);
}
/* Replace all type variables (specified by alias->parameters)
with corresponding values specified by argitems.
@@ -375,7 +333,7 @@ ga_getitem(PyObject *self, PyObject *item)
}
for (Py_ssize_t iarg = 0; iarg < nargs; iarg++) {
PyObject *arg = PyTuple_GET_ITEM(alias->args, iarg);
- int typevar = is_typevarlike(arg);
+ int typevar = is_typevar(arg);
if (typevar < 0) {
Py_DECREF(newargs);
return NULL;
@@ -384,13 +342,7 @@ ga_getitem(PyObject *self, PyObject *item)
Py_ssize_t iparam = tuple_index(alias->parameters, nparams, arg);
assert(iparam >= 0);
arg = argitems[iparam];
- // convert lists to tuples to help with caching in other libaries.
- if (PyList_CheckExact(arg)) {
- arg = PyList_AsTuple(arg);
- }
- else {
- Py_INCREF(arg);
- }
+ Py_INCREF(arg);
}
else {
arg = subs_tvars(arg, alias->parameters, argitems);