Refactor PySetterValue handling in object and type modules

- Update object_set_dict to use new PySetterValue variants
- Modify getset.rs to handle PySetterValue::Delete
- Add delete_dict method to PyObject
- Adjust type.rs to use new PySetterValue semantics

vm/src/builtins/object.rs

@@ -495,13 +495,14 @@ pub fn object_get_dict(obj: PyObjectRef, vm: &VirtualMachine) -> PyResult<PyDict
     obj.dict()
         .ok_or_else(|| vm.new_attribute_error("This object has no __dict__".to_owned()))
 }
+
 pub fn object_set_dict(obj: PyObjectRef, dict: PySetterValue<PyDictRef>, vm: &VirtualMachine) -> PyResult<()> {
     match dict {
-        PySetterValue::Some(dict) => {
+        PySetterValue::Assign(dict) => {
             obj.set_dict(dict)
                 .map_err(|_| vm.new_attribute_error("This object has no __dict__".to_owned()))
         }
-        PySetterValue::None => {
+        PySetterValue::Delete => {
             obj.delete_dict()
                 .map_err(|_| vm.new_attribute_error("This object has no deletable __dict__".to_owned()))
         }

vm/src/builtins/type.rs

@@ -1288,7 +1288,7 @@ fn subtype_set_dict(obj: PyObjectRef, value: PyObjectRef, vm: &VirtualMachine) -
             descr_set(&descr, obj, PySetterValue::Assign(value), vm)
         }
         None => {
-            object::object_set_dict(obj, value.try_into_value(vm)?, vm)?;
+            object::object_set_dict(obj, PySetterValue::Delete, vm)?;
             Ok(())
         }
     }

vm/src/function/getset.rs

@@ -36,8 +36,10 @@ where
 {
     #[inline]
     fn from_setter_value(vm: &VirtualMachine, obj: PySetterValue) -> PyResult<Self> {
-        let obj = obj.ok_or_else(|| vm.new_type_error("can't delete attribute".to_owned()))?;
-        T::try_from_object(vm, obj)
+        match obj {
+            PySetterValue::Assign(obj) => T::try_from_object(vm, obj),
+            PySetterValue::Delete => T::try_from_object(vm, vm.ctx.none()),
+        }
     }
 }
 

vm/src/object/core.rs

@@ -717,6 +717,19 @@ impl PyObject {
         }
     }
 
+    pub fn delete_dict(&self) -> Result<(), ()> {
+        match self.instance_dict() {
+            Some(_) => {
+                unsafe {
+                    let ptr = self as *const _ as *mut PyObject;
+                    (*ptr).0.dict = None;
+                }
+                Ok(())
+            }
+            None => Err(()),
+        }
+    }
+
     #[inline(always)]
     pub fn payload_if_subclass<T: crate::PyPayload>(&self, vm: &VirtualMachine) -> Option<&T> {
         if self.class().fast_issubclass(T::class(&vm.ctx)) {