Address review (and fix bug)

Author: AlexWaygood

Lib/test/test_typing.py

@@ -7519,7 +7519,7 @@ class GenericNamedTuple(NamedTuple, Generic[T]):
 
         self.assertEqual(CallNamedTuple.__orig_bases__, (NamedTuple,))
 
-    def test_setname_called_on_non_members(self):
+    def test_setname_called_on_values_in_class_dictionary(self):
         class Vanilla:
             def __set_name__(self, owner, name):
                 self.name = name
@@ -7533,6 +7533,15 @@ class Foo(NamedTuple):
         self.assertIsInstance(foo.attr, Vanilla)
         self.assertEqual(foo.attr.name, "attr")
 
+        class Bar(NamedTuple):
+            attr: Vanilla = Vanilla()
+
+        bar = Bar()
+        self.assertEqual(len(bar), 1)
+        self.assertIn('attr', Bar._fields)
+        self.assertIsInstance(bar.attr, Vanilla)
+        self.assertEqual(bar.attr.name, "attr")
+
     def test_setname_raises_the_same_as_on_other_classes(self):
         class CustomException(BaseException): pass
 

Lib/typing.py

@@ -2729,17 +2729,23 @@ def __new__(cls, typename, bases, ns):
         for key, val in ns.items():
             if key in _prohibited:
                 raise AttributeError("Cannot overwrite NamedTuple attribute " + key)
-            elif key not in _special and key not in nm_tpl._fields:
-                setattr(nm_tpl, key, val)
-                if hasattr(type(val), "__set_name__"):
+            elif key not in _special:
+                if key not in nm_tpl._fields:
+                    setattr(nm_tpl, key, val)
+                try:
+                    set_name = type(val).__set_name__
+                except AttributeError:
+                    pass
+                else:
                     try:
-                        type(val).__set_name__(val, nm_tpl, key)
+                        set_name(val, nm_tpl, key)
                     except BaseException as e:
                         e.add_note(
                             f"Error calling __set_name__ on {type(val).__name__!r} "
                             f"instance {key!r} in {typename!r}"
                         )
                         raise
+
         if Generic in bases:
             nm_tpl.__init_subclass__()
         return nm_tpl