None.__ne__(None) should be NotImplemented

evanrittenhouse · evanrittenhouse · commit ad59192529ef · 2023-11-26T10:49:26.000-06:00
diff --git a/extra_tests/snippets/builtin_none.py b/extra_tests/snippets/builtin_none.py
@@ -22,4 +22,4 @@ def none2():
 assert None.__eq__(3) is NotImplemented
 assert None.__ne__(3) is NotImplemented
 assert None.__eq__(None) is True
-# assert None.__ne__(None) is False  # changed in 3.12
+assert None.__ne__(None) is NotImplemented
diff --git a/vm/src/builtins/singletons.rs b/vm/src/builtins/singletons.rs
@@ -2,10 +2,12 @@ use super::{PyStrRef, PyType, PyTypeRef};
 use crate::{
     class::PyClassImpl,
     convert::ToPyObject,
+    function::PyComparisonValue,
     protocol::PyNumberMethods,
-    types::{AsNumber, Constructor, Representable},
-    Context, Py, PyObjectRef, PyPayload, PyResult, VirtualMachine,
+    types::{AsNumber, Comparable, Constructor, PyComparisonOp, Representable},
+    Context, Py, PyObject, PyObjectRef, PyPayload, PyResult, VirtualMachine,
 };
+use rustpython_vm::AsObject;
 
 #[pyclass(module = false, name = "NoneType")]
 #[derive(Debug)]
@@ -118,6 +120,22 @@ impl Representable for PyNotImplemented {
     }
 }
 
+impl Comparable for PyNone {
+    #[allow(unused_variables)]
+    fn cmp(
+        zelf: &Py<Self>,
+        other: &PyObject,
+        op: PyComparisonOp,
+        vm: &VirtualMachine,
+    ) -> PyResult<PyComparisonValue> {
+        if zelf.is(other) {
+            Ok(PyComparisonValue::Implemented(true))
+        } else {
+            Ok(PyComparisonValue::NotImplemented)
+        }
+    }
+}
+
 pub fn init(context: &Context) {
     PyNone::extend_class(context, context.types.none_type);
     PyNotImplemented::extend_class(context, context.types.not_implemented_type);
