Add tests for mutability checking

src/type_object.rs

@@ -22,6 +22,7 @@ pub unsafe trait PyObjectLayout<T: PyTypeInfo> {
     unsafe fn py_init(&mut self, _value: T) {}
     unsafe fn py_drop(&mut self, _py: Python) {}
     unsafe fn unchecked_ref(&self) -> &T;
+    #[allow(clippy::mut_from_ref)]
     unsafe fn unchecked_mut(&self) -> &mut T;
 }
 

tests/test_inheritance.rs

@@ -36,6 +36,14 @@ impl BaseClass {
     fn new() -> Self {
         BaseClass { val1: 10 }
     }
+    fn base_method(&self, x: usize) -> usize {
+        x * self.val1
+    }
+    fn base_set(&mut self, fn_: &pyo3::types::PyAny) -> PyResult<()> {
+        let value: usize = fn_.call0()?.extract()?;
+        self.val1 = value;
+        Ok(())
+    }
 }
 
 #[pyclass(extends=BaseClass)]
@@ -50,6 +58,13 @@ impl SubClass {
     fn new() -> (Self, BaseClass) {
         (SubClass { val2: 5 }, BaseClass { val1: 10 })
     }
+    fn sub_method(&self, x: usize) -> usize {
+        x * self.val2
+    }
+    fn sub_set_and_ret(&mut self, x: usize) -> usize {
+        self.val2 = x;
+        x
+    }
 }
 
 #[test]
@@ -61,6 +76,33 @@ fn inheritance_with_new_methods() {
     py_run!(py, inst, "assert inst.val1 == 10; assert inst.val2 == 5");
 }
 
+#[test]
+fn call_base_and_sub_methods() {
+    let gil = Python::acquire_gil();
+    let py = gil.python();
+    let obj = PyCell::new(py, SubClass::new()).unwrap();
+    py_run!(
+        py,
+        obj,
+        r#"
+    assert obj.base_method(10) == 100
+    assert obj.sub_method(10) == 50
+"#
+    );
+}
+
+#[test]
+fn mutation_fails() {
+    let gil = Python::acquire_gil();
+    let py = gil.python();
+    let obj = PyCell::new(py, SubClass::new()).unwrap();
+    let global = Some([("obj", obj)].into_py_dict(py));
+    let e = py
+        .run("obj.base_set(lambda: obj.sub_set_and_ret(1))", global, None)
+        .unwrap_err();
+    assert!(e.is_instance::<pyo3::pycell::PyBorrowMutError>(py))
+}
+
 #[pyclass]
 struct BaseClassWithResult {
     _val: usize,