bpo-43224: Unpack concrete tuple types into a sequence of types

G[*tuple[int, str]] == G[int, str]
python · Mar 21, 2022 · bc310d5 · bc310d5
1 parent 5c3201e
commit bc310d5
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Showing 4 changed files with 32 additions and 15 deletions.
diff --git a/Lib/test/test_genericalias.py b/Lib/test/test_genericalias.py
@@ -174,13 +174,13 @@ class MyList(list):
                 tuple[int]
             )
         ]
-        self.assertEqual(repr(x1), 'tuple[*tuple[int]]')
+        self.assertEqual(repr(x1), 'tuple[int]')
         x2 = tuple[
             tuple(  # Ditto TODO
                 tuple[int, str]
             )
         ]
-        self.assertEqual(repr(x2), 'tuple[*tuple[int, str]]')
+        self.assertEqual(repr(x2), 'tuple[int, str]')
         x3 = tuple[
             tuple(  # Ditto TODO
                 tuple[int, ...]
@@ -418,21 +418,17 @@ def __new__(cls, *args, **kwargs):
         with self.assertRaises(TypeError):
             Bad(list, int, bad=int)
 
-    def test_iter_creates_starred_tuple(self):
-        t = tuple[int, str]
-        iter_t = iter(t)
-        x = next(iter_t)
-        self.assertEqual(repr(x), '*tuple[int, str]')
+    def test_unpack_concrete_tuple_type(self):
+        self.assertEqual([*tuple[()]], [])
+        self.assertEqual([*tuple[int]], [int])
+        self.assertEqual([*tuple[int, str]], [int, str])
+        self.assertEqual([*tuple[int, str, float]], [int, str, float])
 
-    def test_calling_next_twice_raises_stopiteration(self):
-        t = tuple[int, str]
-        iter_t = iter(t)
-        next(iter_t)
-        with self.assertRaises(StopIteration):
-            next(iter_t)
+    def test_unpack_unbounded_tuple_type(self):
+        self.assertEqual(repr([*tuple[int, ...]]), '[*tuple[int, ...]]')
 
     def test_del_iter(self):
-        t = tuple[int, str]
+        t = tuple[int, ...]
         iter_x = iter(t)
         del iter_x
 

diff --git a/Lib/test/test_typing.py b/Lib/test/test_typing.py
@@ -408,6 +408,15 @@ def test_cannot_be_called(self):
         with self.assertRaises(TypeError):
             Unpack()
 
+    def test_unpack_concrete_tuple_type(self):
+        self.assertEqual([*Tuple[()]], [])
+        self.assertEqual([*Tuple[int]], [int])
+        self.assertEqual([*Tuple[int, str]], [int, str])
+        self.assertEqual([*Tuple[int, str, float]], [int, str, float])
+
+    def test_unpack_unbounded_tuple_type(self):
+        self.assertEqual(repr([*Tuple[int, ...]]), '[*typing.Tuple[int, ...]]')
+
 
 class TypeVarTupleTests(BaseTestCase):
 

diff --git a/Lib/typing.py b/Lib/typing.py
@@ -1398,6 +1398,10 @@ def __mro_entries__(self, bases):
         return (self.__origin__,)
 
     def __iter__(self):
+        if (self.__origin__ is tuple and
+            not (len(self.__args__) == 2 and self.__args__[1] is ...)):
+            yield from self.__args__
+            return
         yield Unpack[self]
 
 

diff --git a/Objects/genericaliasobject.c b/Objects/genericaliasobject.c
@@ -667,7 +667,15 @@ static PyTypeObject Py_GenericAliasIterType = {
 };
 
 static PyObject *
-ga_iter(PyObject *self) {
+ga_iter(PyObject *self)
+{
+    gaobject *alias = (gaobject *)self;
+    if (alias->origin == (PyObject *)&PyTuple_Type &&
+        !(PyTuple_GET_SIZE(alias->args) == 2 &&
+          PyTuple_GET_ITEM(alias->args, 1) == Py_Ellipsis))
+    {
+        return PyObject_GetIter(alias->args);
+    }
     gaiterobject *gi = PyObject_GC_New(gaiterobject, &Py_GenericAliasIterType);
     if (gi == NULL) {
         return NULL;