From 936ebbea9deac86b5aa6ddc681eb60987578f624 Mon Sep 17 00:00:00 2001
From: Chris Wesseling <Chris.Wesseling@cwi.nl>
Date: Fri, 26 Nov 2021 16:44:16 +0100
Subject: [PATCH 1/4] Vendor typing._SpecialForm to fool typing._type_check

Adds a local copy of _SpecialForm in our namespace, so
typing._type_check won't raise TypeError. (#964)
---
 .../src/test_typing_extensions.py             |  6 ++
 typing_extensions/src/typing_extensions.py    | 64 +++++++++++++------
 2 files changed, 49 insertions(+), 21 deletions(-)

diff --git a/typing_extensions/src/test_typing_extensions.py b/typing_extensions/src/test_typing_extensions.py
index 2fc5b3f2..731f9731 100644
--- a/typing_extensions/src/test_typing_extensions.py
+++ b/typing_extensions/src/test_typing_extensions.py
@@ -2199,6 +2199,12 @@ def test_no_isinstance(self):
         with self.assertRaises(TypeError):
             issubclass(int, Self)
 
+    def test_alias(self):
+        TupleSelf = Tuple[Self, Self]
+        class Alias:
+            def return_tuple(self) -> TupleSelf:
+                return (self, self)
+
 class AllTests(BaseTestCase):
 
     def test_typing_extensions_includes_standard(self):
diff --git a/typing_extensions/src/typing_extensions.py b/typing_extensions/src/typing_extensions.py
index 15fec259..13bf7df7 100644
--- a/typing_extensions/src/typing_extensions.py
+++ b/typing_extensions/src/typing_extensions.py
@@ -2048,40 +2048,61 @@ def __eq__(self, other):
 
     TypeGuard = _TypeGuard(_root=True)
 
+if not hasattr(typing, "Self") and sys.version_info[:2] >= (3, 7):
+    # Vendored from cpython typing._SpecialFrom
+    class _SpecialForm(typing._Final, _root=True):
+        __slots__ = ('_name', '__doc__', '_getitem')
 
-if hasattr(typing, "Self"):
-    Self = typing.Self
+        def __init__(self, getitem):
+            self._getitem = getitem
+            self._name = getitem.__name__
+            self.__doc__ = getitem.__doc__
+
+        def __getattr__(self, item):
+            if item in {'__name__', '__qualname__'}:
+                return self._name
+
+            raise AttributeError(item)
+
+        def __mro_entries__(self, bases):
+            raise TypeError(f"Cannot subclass {self!r}")
 
-elif sys.version_info[:2] >= (3, 9):
-    class _SelfForm(typing._SpecialForm, _root=True):
         def __repr__(self):
-            return 'typing_extensions.' + self._name
+            return 'typing.' + self._name
 
-    @_SelfForm
-    def Self(self, params):
-        """Used to spell the type of "self" in classes.
+        def __reduce__(self):
+            return self._name
 
-        Example::
+        def __call__(self, *args, **kwds):
+            raise TypeError(f"Cannot instantiate {self!r}")
 
-          from typing import Self
+        def __or__(self, other):
+            return Union[self, other]
 
-          class ReturnsSelf:
-              def parse(self, data: bytes) -> Self:
-                  ...
-                  return self
+        def __ror__(self, other):
+            return Union[other, self]
 
-        """
+        def __instancecheck__(self, obj):
+            raise TypeError(f"{self} cannot be used with isinstance()")
 
-        raise TypeError(f"{self} is not subscriptable")
+        def __subclasscheck__(self, cls):
+            raise TypeError(f"{self} cannot be used with issubclass()")
+
+        @typing._tp_cache
+        def __getitem__(self, parameters):
+            return self._getitem(self, parameters)
+
+if hasattr(typing, "Self"):
+    Self = typing.Self
 
 elif sys.version_info[:2] >= (3, 7):
-    class _SelfForm(typing._SpecialForm, _root=True):
+    class _SelfForm(_SpecialForm, _root=True):
         def __repr__(self):
             return 'typing_extensions.' + self._name
 
-    Self = _SelfForm(
-        "Self",
-        doc="""Used to spell the type of "self" in classes.
+    @_SelfForm
+    def Self(self, params):
+        """Used to spell the type of "self" in classes.
 
         Example::
 
@@ -2093,7 +2114,8 @@ def parse(self, data: bytes) -> Self:
                   return self
 
         """
-    )
+
+        raise TypeError(f"{self} is not subscriptable")
 else:
     class _Self(typing._FinalTypingBase, _root=True):
         """Used to spell the type of "self" in classes.

From 8f8c7930d33e7c966beea308b97669376c893348 Mon Sep 17 00:00:00 2001
From: Chris Wesseling <chris.wesseling@xs4all.nl>
Date: Fri, 26 Nov 2021 21:04:41 +0100
Subject: [PATCH 2/4] Fix module name in __repr__

Co-authored-by: James Hilton-Balfe <50501825+Gobot1234@users.noreply.github.com>
---
 typing_extensions/src/typing_extensions.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/typing_extensions/src/typing_extensions.py b/typing_extensions/src/typing_extensions.py
index 13bf7df7..8a909960 100644
--- a/typing_extensions/src/typing_extensions.py
+++ b/typing_extensions/src/typing_extensions.py
@@ -2068,7 +2068,7 @@ def __mro_entries__(self, bases):
             raise TypeError(f"Cannot subclass {self!r}")
 
         def __repr__(self):
-            return 'typing.' + self._name
+            return f'typing_extensions.{self._name}'
 
         def __reduce__(self):
             return self._name

From 4c221928281d78050dbdbbfba9daa4f3f07ee44b Mon Sep 17 00:00:00 2001
From: Chris Wesseling <chris.wesseling@xs4all.nl>
Date: Fri, 26 Nov 2021 21:33:48 +0100
Subject: [PATCH 3/4] Fix NameError

---
 typing_extensions/src/typing_extensions.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/typing_extensions/src/typing_extensions.py b/typing_extensions/src/typing_extensions.py
index 8a909960..c7b59f67 100644
--- a/typing_extensions/src/typing_extensions.py
+++ b/typing_extensions/src/typing_extensions.py
@@ -2077,10 +2077,10 @@ def __call__(self, *args, **kwds):
             raise TypeError(f"Cannot instantiate {self!r}")
 
         def __or__(self, other):
-            return Union[self, other]
+            return typing.Union[self, other]
 
         def __ror__(self, other):
-            return Union[other, self]
+            return typing.Union[other, self]
 
         def __instancecheck__(self, obj):
             raise TypeError(f"{self} cannot be used with isinstance()")

From e8b1c13dea7383f60034cac645d9bdb852b171a4 Mon Sep 17 00:00:00 2001
From: Chris Wesseling <chris.wesseling@xs4all.nl>
Date: Sun, 28 Nov 2021 17:56:04 +0100
Subject: [PATCH 4/4] Simplify flow

---
 typing_extensions/src/typing_extensions.py | 14 ++++----------
 1 file changed, 4 insertions(+), 10 deletions(-)

diff --git a/typing_extensions/src/typing_extensions.py b/typing_extensions/src/typing_extensions.py
index c7b59f67..9f1c7aa3 100644
--- a/typing_extensions/src/typing_extensions.py
+++ b/typing_extensions/src/typing_extensions.py
@@ -2048,7 +2048,9 @@ def __eq__(self, other):
 
     TypeGuard = _TypeGuard(_root=True)
 
-if not hasattr(typing, "Self") and sys.version_info[:2] >= (3, 7):
+if hasattr(typing, "Self"):
+    Self = typing.Self
+elif sys.version_info[:2] >= (3, 7):
     # Vendored from cpython typing._SpecialFrom
     class _SpecialForm(typing._Final, _root=True):
         __slots__ = ('_name', '__doc__', '_getitem')
@@ -2092,15 +2094,7 @@ def __subclasscheck__(self, cls):
         def __getitem__(self, parameters):
             return self._getitem(self, parameters)
 
-if hasattr(typing, "Self"):
-    Self = typing.Self
-
-elif sys.version_info[:2] >= (3, 7):
-    class _SelfForm(_SpecialForm, _root=True):
-        def __repr__(self):
-            return 'typing_extensions.' + self._name
-
-    @_SelfForm
+    @_SpecialForm
     def Self(self, params):
         """Used to spell the type of "self" in classes.