Bind method descriptor when __get__ owner is omitted (#8404)

`method_descriptor.__get__(obj)` raised a TypeError when the owner (the
optional second argument) was omitted, because the METHOD-flag branch
required the owner to be a type. Match CPython: a missing owner binds to
`obj`, while a non-type owner still raises "needs a type, not ...".

Assisted-by: Claude Code:claude-opus-4-8

Lib/test/test_types.py

@@ -660,7 +660,6 @@ class TypesTests(unittest.TestCase):
         self.assertIsInstance(int.from_bytes, types.BuiltinMethodType)
         self.assertIsInstance(int.__new__, types.BuiltinMethodType)
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; TypeError: descriptor 'read' needs a type, not 'StringIO', as arg 2
     def test_method_descriptor_crash(self):
         # gh-132747: The default __get__() implementation in C was unable
         # to handle a second argument of None when called from Python

crates/vm/src/builtins/descriptor.rs

@@ -79,7 +79,10 @@ impl GetDescriptor for PyMethodDescriptor {
         let bound = match obj {
             Some(obj) => {
                 if descr.method.flags.contains(PyMethodFlags::METHOD) {
-                    if cls.is_some_and(|c| c.fast_isinstance(vm.ctx.types.type_type)) {
+                    if cls
+                        .as_ref()
+                        .is_none_or(|c| c.fast_isinstance(vm.ctx.types.type_type))
+                    {
                         obj
                     } else {
                         return Err(vm.new_type_error(format!(