Call descriptor __get__ attributes without pre-binding (#9043)

Extract the Python 3.14-compatible descriptor slot dispatch from #8954. Call the raw type attribute with descriptor, instance and owner, preserving ownership and recursion handling. Extend the existing Python snippet for staticmethod, classmethod, callable-object and ordinary __get__ replacements.

Assisted-by: OpenAI Codex:model identifier unavailable

crates/vm/src/types/slot.rs

@@ -779,13 +779,21 @@ fn descr_get_wrapper(
     cls: Option<&PyObject>,
     vm: &VirtualMachine,
 ) -> PyResult {
-    // A descriptor whose `__get__` is the descriptor itself resolves it by
-    // fetching `__get__` again, and none of that pushes a Python frame.
+    // slot_tp_descr_get calls the raw type attribute with all three arguments.
+    // Binding it first would omit self for builtin functions and incorrectly
+    // invoke the descriptor protocol of static/class/custom __get__ objects.
+    // Keep both the callable and self owned across user code that deletes them.
     vm.with_recursion(" while calling a Python object", || {
-        vm.call_special_method(
-            zelf,
-            identifier!(vm, __get__),
-            (obj.map(PyObject::to_owned), cls.map(PyObject::to_owned)),
+        let Some(get) = zelf.class().get_attr(identifier!(vm, __get__)) else {
+            return Ok(zelf.to_owned());
+        };
+        get.call(
+            (
+                zelf.to_owned(),
+                obj.map(PyObject::to_owned),
+                cls.map(PyObject::to_owned),
+            ),
+            vm,
         )
     })
 }

extra_tests/snippets/builtin_object.py

@@ -161,3 +161,35 @@ except RuntimeError as outer:
     with assert_raises(ValueError) as caught:
         RaisingAttributeHook().absent
     assert caught.exception.__context__ is outer
+
+
+# The descriptor slot calls the raw __get__ attribute without binding it first.
+class RawGetDescriptor:
+    __get__ = staticmethod(lambda *args: args)
+
+
+class RawGetOwner:
+    value = RawGetDescriptor()
+
+
+raw_descriptor = vars(RawGetOwner)["value"]
+raw_instance = RawGetOwner()
+assert raw_instance.value == (raw_descriptor, raw_instance, RawGetOwner)
+assert RawGetOwner.value == (raw_descriptor, None, RawGetOwner)
+
+
+class CallableGet:
+    def __get__(self, instance, owner):
+        raise AssertionError("__get__ must not be bound before the slot call")
+
+    def __call__(self, *args):
+        return args
+
+
+RawGetDescriptor.__get__ = CallableGet()
+assert raw_instance.value == (raw_descriptor, raw_instance, RawGetOwner)
+RawGetDescriptor.__get__ = classmethod(lambda *args: args)
+with assert_raises(TypeError):
+    raw_instance.value
+RawGetDescriptor.__get__ = lambda self, instance, owner: (self, instance, owner)
+assert raw_instance.value == (raw_descriptor, raw_instance, RawGetOwner)