From 519b91e716661d64585a3ecc926ac6abcd2d243b Mon Sep 17 00:00:00 2001
From: Fidget-Spinner <28750310+Fidget-Spinner@users.noreply.github.com>
Date: Sat, 2 Jan 2021 17:05:20 +0800
Subject: [PATCH 1/9] tupleify everything

---
 Lib/test/test_genericalias.py | 18 ++++++++++++
 Objects/genericaliasobject.c  | 53 ++++++++++++++++++++++++-----------
 2 files changed, 55 insertions(+), 16 deletions(-)

diff --git a/Lib/test/test_genericalias.py b/Lib/test/test_genericalias.py
index fd024dcec8208b..fb2c42ffe50a79 100644
--- a/Lib/test/test_genericalias.py
+++ b/Lib/test/test_genericalias.py
@@ -391,5 +391,23 @@ def __call__(self):
             self.assertEqual(repr(C1), "collections.abc.Callable"
                                        "[typing.Concatenate[int, ~P], int]")
 
+    def test_tupleify(self):
+        # Converts all lists inside __args__ to tuple.
+        # For consistency with typing module which ensures
+        # most types are hashable.  Required since PEP 612
+        # introduces lists during substitution.
+
+        self.assertEqual(tuple[[]], tuple[(),])
+        self.assertEqual(tuple[int, [str, dict]], tuple[int, (str, dict)])
+        self.assertEqual(list[int, [str, [str, dict]]], list[int, (str, (str, dict))])
+        # Most likely to refleak due to nested list inside tuple.
+        self.assertEqual(list[int, (str, [str, dict])], list[int, (str, (str, dict))])
+
+        x = (int, str, [int, list])
+        self.assertEqual(list[x], list[int, str, (int, list)])
+        # Make sure the original tuple wasn't modified.
+        self.assertEqual(x, (int, str, [int, list]))
+
+
 if __name__ == "__main__":
     unittest.main()
diff --git a/Objects/genericaliasobject.c b/Objects/genericaliasobject.c
index 4cc82ffcdf39a3..570d831dfe21f4 100644
--- a/Objects/genericaliasobject.c
+++ b/Objects/genericaliasobject.c
@@ -4,6 +4,7 @@
 #include "pycore_object.h"
 #include "pycore_unionobject.h"   // _Py_union_as_number
 #include "structmember.h"         // PyMemberDef
+#include "pycore_tuple.h"         // _PyTuple_FromArray()
 
 typedef struct {
     PyObject_HEAD
@@ -225,6 +226,36 @@ tuple_add(PyObject *self, Py_ssize_t len, PyObject *item)
     return 0;
 }
 
+// Makes a deep copy of a tuple
+static inline PyObject *
+tuple_copy(PyObject *obj) {
+    return _PyTuple_FromArray(((PyTupleObject *)obj)->ob_item, Py_SIZE(obj));
+}
+
+// This converts all nested lists in args to a tuple (args should be a tuple).
+// Usually needed to help caching in other libraries.
+// Must be called on a copy of a tuple object, where the only reference is
+// owned by the caller.
+static inline void
+tupleify_lists(PyObject *args) {
+    Py_ssize_t len = PyTuple_GET_SIZE(args);
+    for (Py_ssize_t i = 0; i < len; ++i) {
+        PyObject *arg = PyTuple_GET_ITEM(args, i);
+        if (PyList_CheckExact(arg)) {
+            PyObject *new_arg = PyList_AsTuple(arg);
+            tupleify_lists(new_arg);
+            PyTuple_SET_ITEM(args, i, new_arg);
+            Py_DECREF(arg);
+        }
+        else if (PyTuple_CheckExact(arg)) {
+            // In case there are lists nested inside tuples.
+            // This works despite interned tuples because tuples containing
+            // lists aren't interned.
+            tupleify_lists(arg);
+        }
+    }
+}
+
 static PyObject *
 make_parameters(PyObject *args)
 {
@@ -306,14 +337,7 @@ 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);
         }
 
@@ -384,13 +408,7 @@ 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);
@@ -626,10 +644,13 @@ setup_ga(gaobject *alias, PyObject *origin, PyObject *args) {
     else {
         Py_INCREF(args);
     }
+    PyObject *new_args = tuple_copy(args);
+    tupleify_lists(new_args);
+    Py_DECREF(args);
 
     Py_INCREF(origin);
     alias->origin = origin;
-    alias->args = args;
+    alias->args = new_args;
     alias->parameters = NULL;
     alias->weakreflist = NULL;
     return 1;

From cb4e9af1818cb342fbb9573013e0d3fea154dbc0 Mon Sep 17 00:00:00 2001
From: Fidget-Spinner <28750310+Fidget-Spinner@users.noreply.github.com>
Date: Sat, 2 Jan 2021 17:42:35 +0800
Subject: [PATCH 2/9] update docs and add news

---
 Doc/library/stdtypes.rst                                   | 7 +++++++
 .../2021-01-02-17-37-08.bpo-41559.y2LoK8.rst               | 3 +++
 2 files changed, 10 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Core and Builtins/2021-01-02-17-37-08.bpo-41559.y2LoK8.rst

diff --git a/Doc/library/stdtypes.rst b/Doc/library/stdtypes.rst
index 2331849c02e982..a3bd02fb12e077 100644
--- a/Doc/library/stdtypes.rst
+++ b/Doc/library/stdtypes.rst
@@ -4946,6 +4946,13 @@ All parameterized generics implement special read-only attributes.
       >>> dict[str, list[int]].__args__
       (<class 'str'>, list[int])
 
+   .. versionchanged:: 3.9.2
+      ``__args__`` will convert all lists passed to the generic alias to tuples.
+      This aligns with the :mod:`typing` module which tries to ensure that
+      most types will be hashable for caching purposes.  Passing a list is valid
+      in certain scenarios from Python 3.10 and higher due to :pep:`612`.  An
+      exception to this behavior is the generic alias for
+      ``collections.abc.Callable``.
 
 .. attribute:: genericalias.__parameters__
 
diff --git a/Misc/NEWS.d/next/Core and Builtins/2021-01-02-17-37-08.bpo-41559.y2LoK8.rst b/Misc/NEWS.d/next/Core and Builtins/2021-01-02-17-37-08.bpo-41559.y2LoK8.rst
new file mode 100644
index 00000000000000..a8e72cb7cbb68d
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2021-01-02-17-37-08.bpo-41559.y2LoK8.rst	
@@ -0,0 +1,3 @@
+:ref:`Generic Alias <types-genericalias>` objects will now convert all lists
+received to tuples to aid caching in other libraries and prepare for
+:pep:`612` in Python 3.10.

From d4c9a59c241daab5b734de6029221a4fc54064b0 Mon Sep 17 00:00:00 2001
From: Fidget-Spinner <28750310+Fidget-Spinner@users.noreply.github.com>
Date: Sun, 3 Jan 2021 14:56:02 +0800
Subject: [PATCH 3/9] make tuple support less iffy

---
 Lib/test/test_genericalias.py |  8 ++++----
 Objects/genericaliasobject.c  | 15 ++++++---------
 2 files changed, 10 insertions(+), 13 deletions(-)

diff --git a/Lib/test/test_genericalias.py b/Lib/test/test_genericalias.py
index fb2c42ffe50a79..bb4bdc4bb57462 100644
--- a/Lib/test/test_genericalias.py
+++ b/Lib/test/test_genericalias.py
@@ -403,10 +403,10 @@ def test_tupleify(self):
         # Most likely to refleak due to nested list inside tuple.
         self.assertEqual(list[int, (str, [str, dict])], list[int, (str, (str, dict))])
 
-        x = (int, str, [int, list])
-        self.assertEqual(list[x], list[int, str, (int, list)])
-        # Make sure the original tuple wasn't modified.
-        self.assertEqual(x, (int, str, [int, list]))
+        x = (int, (int, [dict, float]))
+        self.assertEqual(list[x], list[int, (int, (dict, float))])
+        # Make sure the original tuple's list wasn't modified.
+        self.assertEqual(x, (int, (int, [dict, float])))
 
 
 if __name__ == "__main__":
diff --git a/Objects/genericaliasobject.c b/Objects/genericaliasobject.c
index 570d831dfe21f4..88c21662c0e3d2 100644
--- a/Objects/genericaliasobject.c
+++ b/Objects/genericaliasobject.c
@@ -226,7 +226,7 @@ tuple_add(PyObject *self, Py_ssize_t len, PyObject *item)
     return 0;
 }
 
-// Makes a deep copy of a tuple
+// Makes a shallow copy of a tuple
 static inline PyObject *
 tuple_copy(PyObject *obj) {
     return _PyTuple_FromArray(((PyTupleObject *)obj)->ob_item, Py_SIZE(obj));
@@ -241,18 +241,15 @@ tupleify_lists(PyObject *args) {
     Py_ssize_t len = PyTuple_GET_SIZE(args);
     for (Py_ssize_t i = 0; i < len; ++i) {
         PyObject *arg = PyTuple_GET_ITEM(args, i);
-        if (PyList_CheckExact(arg)) {
-            PyObject *new_arg = PyList_AsTuple(arg);
+        int is_list = PyList_CheckExact(arg);
+        int is_tuple = PyTuple_CheckExact(arg);
+        if (is_list || is_tuple) {
+            // In case there are lists nested inside tuples.
+            PyObject *new_arg = is_list ? PyList_AsTuple(arg) : tuple_copy(arg);
             tupleify_lists(new_arg);
             PyTuple_SET_ITEM(args, i, new_arg);
             Py_DECREF(arg);
         }
-        else if (PyTuple_CheckExact(arg)) {
-            // In case there are lists nested inside tuples.
-            // This works despite interned tuples because tuples containing
-            // lists aren't interned.
-            tupleify_lists(arg);
-        }
     }
 }
 

From cddc54b8c5a14df6b0c82add1c7388fb833886e9 Mon Sep 17 00:00:00 2001
From: Fidget-Spinner <28750310+Fidget-Spinner@users.noreply.github.com>
Date: Sat, 9 Jan 2021 11:12:59 +0800
Subject: [PATCH 4/9] apply suggestions by zackery

---
 Lib/test/test_genericalias.py |  4 ++++
 Objects/genericaliasobject.c  | 44 ++++++++++++++++++++++++++---------
 2 files changed, 37 insertions(+), 11 deletions(-)

diff --git a/Lib/test/test_genericalias.py b/Lib/test/test_genericalias.py
index bb4bdc4bb57462..1249b3f2256a40 100644
--- a/Lib/test/test_genericalias.py
+++ b/Lib/test/test_genericalias.py
@@ -408,6 +408,10 @@ def test_tupleify(self):
         # Make sure the original tuple's list wasn't modified.
         self.assertEqual(x, (int, (int, [dict, float])))
 
+        y = [int, str]
+        self.assertEqual(list[y], list[[int, str]])
+        self.assertEqual(y, [int, str])
+
 
 if __name__ == "__main__":
     unittest.main()
diff --git a/Objects/genericaliasobject.c b/Objects/genericaliasobject.c
index 22edc58c212a68..41cf0f7fa2c135 100644
--- a/Objects/genericaliasobject.c
+++ b/Objects/genericaliasobject.c
@@ -228,29 +228,49 @@ tuple_add(PyObject *self, Py_ssize_t len, PyObject *item)
 
 // Makes a shallow copy of a tuple
 static inline PyObject *
-tuple_copy(PyObject *obj) {
+tuple_copy(PyObject *obj)
+{
     return _PyTuple_FromArray(((PyTupleObject *)obj)->ob_item, Py_SIZE(obj));
 }
 
 // This converts all nested lists in args to a tuple (args should be a tuple).
 // Usually needed to help caching in other libraries.
-// Must be called on a copy of a tuple object, where the only reference is
-// owned by the caller.
-static inline void
+static inline PyObject *
 tupleify_lists(PyObject *args) {
     Py_ssize_t len = PyTuple_GET_SIZE(args);
+    PyObject *result = tuple_copy(args);
+    if (result == NULL) {
+        return NULL;
+    }
     for (Py_ssize_t i = 0; i < len; ++i) {
-        PyObject *arg = PyTuple_GET_ITEM(args, i);
+        PyObject *arg = PyTuple_GET_ITEM(result, i);
         int is_list = PyList_CheckExact(arg);
         int is_tuple = PyTuple_CheckExact(arg);
         if (is_list || is_tuple) {
             // In case there are lists nested inside tuples.
-            PyObject *new_arg = is_list ? PyList_AsTuple(arg) : tuple_copy(arg);
-            tupleify_lists(new_arg);
-            PyTuple_SET_ITEM(args, i, new_arg);
-            Py_DECREF(arg);
+            PyObject *new_arg = is_list ? PyList_AsTuple(arg) : arg;
+            if (new_arg == NULL) {
+                goto error;
+            }
+            PyObject *new_arg_tupled = tupleify_lists(new_arg);
+            if (new_arg_tupled == NULL) {
+                Py_DECREF(new_arg);
+                goto error;
+            }
+            Py_DECREF(new_arg);
+            PyTuple_SET_ITEM(result, i, new_arg_tupled);
+            // PyTuple_SET_ITEM doesn't DECREF existing item automatically.
+            if (is_list) {
+                Py_DECREF(arg);
+            }
+            continue;
+
+        error:
+            Py_DECREF(result);
+            return NULL;
         }
     }
+    return result;
 }
 
 static PyObject *
@@ -641,9 +661,11 @@ setup_ga(gaobject *alias, PyObject *origin, PyObject *args) {
     else {
         Py_INCREF(args);
     }
-    PyObject *new_args = tuple_copy(args);
-    tupleify_lists(new_args);
+    PyObject *new_args = tupleify_lists(args);
     Py_DECREF(args);
+    if (new_args == NULL) {
+        return 0;
+    }
 
     Py_INCREF(origin);
     alias->origin = origin;

From b365cc1d4ef01fc93fb11a991902004983f4316c Mon Sep 17 00:00:00 2001
From: Fidget-Spinner <28750310+Fidget-Spinner@users.noreply.github.com>
Date: Sat, 9 Jan 2021 11:37:15 +0800
Subject: [PATCH 5/9] fix order

---
 Objects/genericaliasobject.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/Objects/genericaliasobject.c b/Objects/genericaliasobject.c
index 41cf0f7fa2c135..20d9bb705c8211 100644
--- a/Objects/genericaliasobject.c
+++ b/Objects/genericaliasobject.c
@@ -252,6 +252,9 @@ tupleify_lists(PyObject *args) {
             if (new_arg == NULL) {
                 goto error;
             }
+            if (is_list) {
+                Py_DECREF(arg);
+            }
             PyObject *new_arg_tupled = tupleify_lists(new_arg);
             if (new_arg_tupled == NULL) {
                 Py_DECREF(new_arg);
@@ -259,10 +262,6 @@ tupleify_lists(PyObject *args) {
             }
             Py_DECREF(new_arg);
             PyTuple_SET_ITEM(result, i, new_arg_tupled);
-            // PyTuple_SET_ITEM doesn't DECREF existing item automatically.
-            if (is_list) {
-                Py_DECREF(arg);
-            }
             continue;
 
         error:

From e58597f0ef1e22ca120973c8bbf916848730691c Mon Sep 17 00:00:00 2001
From: Fidget-Spinner <28750310+Fidget-Spinner@users.noreply.github.com>
Date: Sun, 10 Jan 2021 23:36:04 +0800
Subject: [PATCH 6/9] Add recursion guards

---
 Objects/genericaliasobject.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/Objects/genericaliasobject.c b/Objects/genericaliasobject.c
index 20d9bb705c8211..4d5a8a53a2ff9c 100644
--- a/Objects/genericaliasobject.c
+++ b/Objects/genericaliasobject.c
@@ -253,9 +253,15 @@ tupleify_lists(PyObject *args) {
                 goto error;
             }
             if (is_list) {
+                // Discard old arg since AsTuple gives a new reference.
                 Py_DECREF(arg);
             }
+            if (Py_EnterRecursiveCall(" while converting lists to tuples in "
+                "GenericAlias' __args__")) {
+                goto error;
+            }
             PyObject *new_arg_tupled = tupleify_lists(new_arg);
+            Py_LeaveRecursiveCall();
             if (new_arg_tupled == NULL) {
                 Py_DECREF(new_arg);
                 goto error;

From bd57c35a7b1a804e60148e5dd7b4ebef8bedf7e0 Mon Sep 17 00:00:00 2001
From: Fidget-Spinner <28750310+Fidget-Spinner@users.noreply.github.com>
Date: Sun, 10 Jan 2021 23:40:10 +0800
Subject: [PATCH 7/9] remove redundant stuff

---
 Objects/genericaliasobject.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/Objects/genericaliasobject.c b/Objects/genericaliasobject.c
index 4d5a8a53a2ff9c..cd2efb510df241 100644
--- a/Objects/genericaliasobject.c
+++ b/Objects/genericaliasobject.c
@@ -262,11 +262,10 @@ tupleify_lists(PyObject *args) {
             }
             PyObject *new_arg_tupled = tupleify_lists(new_arg);
             Py_LeaveRecursiveCall();
+            Py_DECREF(new_arg);
             if (new_arg_tupled == NULL) {
-                Py_DECREF(new_arg);
                 goto error;
             }
-            Py_DECREF(new_arg);
             PyTuple_SET_ITEM(result, i, new_arg_tupled);
             continue;
 

From 0389d960f267f7dbc9d62a3fcb33f859767f7100 Mon Sep 17 00:00:00 2001
From: Fidget-Spinner <28750310+Fidget-Spinner@users.noreply.github.com>
Date: Fri, 5 Feb 2021 00:04:47 +0800
Subject: [PATCH 8/9] clean up code a little

---
 Objects/genericaliasobject.c | 51 +++++++++++++++++++-----------------
 1 file changed, 27 insertions(+), 24 deletions(-)

diff --git a/Objects/genericaliasobject.c b/Objects/genericaliasobject.c
index cd2efb510df241..79d7d494cd7b19 100644
--- a/Objects/genericaliasobject.c
+++ b/Objects/genericaliasobject.c
@@ -244,37 +244,40 @@ tupleify_lists(PyObject *args) {
     }
     for (Py_ssize_t i = 0; i < len; ++i) {
         PyObject *arg = PyTuple_GET_ITEM(result, i);
-        int is_list = PyList_CheckExact(arg);
-        int is_tuple = PyTuple_CheckExact(arg);
-        if (is_list || is_tuple) {
-            // In case there are lists nested inside tuples.
-            PyObject *new_arg = is_list ? PyList_AsTuple(arg) : arg;
+        if (arg == NULL) {
+            goto error;
+        }
+        PyObject *new_arg = NULL;
+        if (PyList_CheckExact(arg)) {
+            new_arg = PyList_AsTuple(arg);
             if (new_arg == NULL) {
                 goto error;
             }
-            if (is_list) {
-                // Discard old arg since AsTuple gives a new reference.
-                Py_DECREF(arg);
-            }
-            if (Py_EnterRecursiveCall(" while converting lists to tuples in "
-                "GenericAlias' __args__")) {
-                goto error;
-            }
-            PyObject *new_arg_tupled = tupleify_lists(new_arg);
-            Py_LeaveRecursiveCall();
-            Py_DECREF(new_arg);
-            if (new_arg_tupled == NULL) {
-                goto error;
-            }
-            PyTuple_SET_ITEM(result, i, new_arg_tupled);
+            Py_DECREF(arg);
+        }
+        else if (PyTuple_CheckExact(arg)) {
+            new_arg = arg;
+        }
+        else {
             continue;
-
-        error:
-            Py_DECREF(result);
-            return NULL;
         }
+        if (Py_EnterRecursiveCall(" while converting lists to tuples in "
+            "GenericAlias' __args__")) {
+            goto error;
+        }
+        PyObject *new_arg_tupled = tupleify_lists(new_arg);
+        Py_DECREF(new_arg);
+        Py_LeaveRecursiveCall();
+        if (new_arg_tupled == NULL) {
+            goto error;
+        }
+        PyTuple_SET_ITEM(result, i, new_arg_tupled);
     }
     return result;
+
+error:
+    Py_DECREF(result);
+    return NULL;
 }
 
 static PyObject *

From a97ff336e3e9e2282ad846ef8132fa3376c90159 Mon Sep 17 00:00:00 2001
From: Fidget-Spinner <28750310+Fidget-Spinner@users.noreply.github.com>
Date: Sat, 13 Feb 2021 13:32:51 +0800
Subject: [PATCH 9/9] simplify code and update news

---
 .../2021-01-02-17-37-08.bpo-41559.y2LoK8.rst           |  4 ++--
 Objects/genericaliasobject.c                           | 10 ++++------
 2 files changed, 6 insertions(+), 8 deletions(-)

diff --git a/Misc/NEWS.d/next/Core and Builtins/2021-01-02-17-37-08.bpo-41559.y2LoK8.rst b/Misc/NEWS.d/next/Core and Builtins/2021-01-02-17-37-08.bpo-41559.y2LoK8.rst
index a8e72cb7cbb68d..b981ce2655266e 100644
--- a/Misc/NEWS.d/next/Core and Builtins/2021-01-02-17-37-08.bpo-41559.y2LoK8.rst	
+++ b/Misc/NEWS.d/next/Core and Builtins/2021-01-02-17-37-08.bpo-41559.y2LoK8.rst	
@@ -1,3 +1,3 @@
 :ref:`Generic Alias <types-genericalias>` objects will now convert all lists
-received to tuples to aid caching in other libraries and prepare for
-:pep:`612` in Python 3.10.
+received to tuples to 1. work with ``typing.Union`` and ``typing.Optional``,
+2. aid caching in other libraries and 3. prepare for :pep:`612` in Python 3.10.
diff --git a/Objects/genericaliasobject.c b/Objects/genericaliasobject.c
index 79d7d494cd7b19..19192e5cb52400 100644
--- a/Objects/genericaliasobject.c
+++ b/Objects/genericaliasobject.c
@@ -234,7 +234,8 @@ tuple_copy(PyObject *obj)
 }
 
 // This converts all nested lists in args to a tuple (args should be a tuple).
-// Usually needed to help caching in other libraries.
+// Usually needed to work with typing.py's Union and Optional and help
+// caching in other libraries.
 static inline PyObject *
 tupleify_lists(PyObject *args) {
     Py_ssize_t len = PyTuple_GET_SIZE(args);
@@ -247,7 +248,7 @@ tupleify_lists(PyObject *args) {
         if (arg == NULL) {
             goto error;
         }
-        PyObject *new_arg = NULL;
+        PyObject *new_arg = arg;
         if (PyList_CheckExact(arg)) {
             new_arg = PyList_AsTuple(arg);
             if (new_arg == NULL) {
@@ -255,10 +256,7 @@ tupleify_lists(PyObject *args) {
             }
             Py_DECREF(arg);
         }
-        else if (PyTuple_CheckExact(arg)) {
-            new_arg = arg;
-        }
-        else {
+        else if (!PyTuple_CheckExact(arg)) {
             continue;
         }
         if (Py_EnterRecursiveCall(" while converting lists to tuples in "