Remove Sentinel import code

No longer needed due to a correctly implemented reduce method.

Simplifies code and makes syntax more predictable.

Author: HexDecimal

doc/index.rst

@@ -1067,17 +1067,6 @@ Sentinel objects
       >>> class MyClass:
       ...     MISSING = Sentinel('MyClass.MISSING')
 
-   Calling the Sentinel class follows these rules for the return value:
-
-   1. If *name* and *module_name* were used in a previous call then return the same
-      object as that previous call.
-      This preserves the identity of the sentinel.
-   2. Otherwise if *module_name.name* already exists then return that object
-      even if that object is not a :class:`typing_extensions.Sentinel` type.
-      This enables forward compatibility with sentinel types from other libraries
-      (the inverse may not be true.)
-   3. Otherwise a new :class:`typing_extensions.Sentinel` is returned.
-
    .. versionadded:: 4.14.0
 
       See :pep:`661`

src/test_typing_extensions.py

@@ -9316,14 +9316,6 @@ def test_sentinel_copy(self):
         self.assertIs(self.SENTINEL, copy.copy(self.SENTINEL))
         self.assertIs(self.SENTINEL, copy.deepcopy(self.SENTINEL))
 
-    def test_sentinel_import(self):
-        self.assertIs(Sentinel("TestSentinels"), TestSentinels)
-        self.assertIs(Sentinel._import_sentinel("TestSentinels.SENTINEL", __name__), TestSentinels.SENTINEL)
-        self.assertIs(Sentinel._import_sentinel("nonexistent", __name__), None)
-        self.assertIs(Sentinel._import_sentinel("TestSentinels.nonexistent", __name__), None)
-        self.assertIs(Sentinel._import_sentinel("nonexistent", ""), None)
-        self.assertIs(Sentinel._import_sentinel("nonexistent", "nonexistent.nonexistent.nonexistent"), None)
-
     def test_sentinel_picklable_qualified(self):
         for proto in range(pickle.HIGHEST_PROTOCOL + 1):
             self.assertIs(self.SENTINEL, pickle.loads(pickle.dumps(self.SENTINEL, protocol=proto)))

src/typing_extensions.py

@@ -4211,31 +4211,13 @@ def __new__(
         if sentinel is not None:
             return sentinel
 
-        # Import sentinel at module_name.name
-        sentinel = cls._import_sentinel(name, module_name)
-        if sentinel is not None:
-            return _sentinel_registry.setdefault(registry_key, sentinel)
-
         # Create initial or anonymous sentinel
         sentinel = super().__new__(cls)
         sentinel._name = name
         sentinel.__module__ = module_name  # Assign which module defined this instance
         sentinel._repr = repr if repr is not None else name
         return _sentinel_registry.setdefault(registry_key, sentinel)
 
-    @staticmethod
-    def _import_sentinel(name: str, module_name: str):
-        """Return object `name` imported from `module_name`, otherwise return None."""
-        if not module_name:
-            return None
-        try:
-            module = importlib.import_module(module_name)
-            return operator.attrgetter(name)(module)
-        except ImportError:
-            return None
-        except AttributeError:
-            return None
-
     def __repr__(self) -> str:
         return self._repr