Function _abc_register

crates/vm/src/stdlib/_abc.rs:214–242

(
        cls: PyObjectRef,
        subclass: PyObjectRef,
        vm: &VirtualMachine,
    )

    /// Internal ABC helper for subclass registration. Should be never used outside abc module.
    #[pyfunction]
    fn _abc_register(
        cls: PyObjectRef,
        subclass: PyObjectRef,
        vm: &VirtualMachine,
    ) -> PyResult<PyObjectRef> {
        // Type check
        if !subclass.class().fast_issubclass(vm.ctx.types.type_type) {
            return Err(vm.new_type_error("Can only register classes"));
        }

        // Check if already a subclass
        if subclass.is_subclass(&cls, vm)? {
            return Ok(subclass);
        }

        // Check for cycles
        if cls.is_subclass(&subclass, vm)? {
            return Err(vm.new_runtime_error("Refusing to create an inheritance cycle"));
        }

        // Add to registry
        let impl_data = get_impl(&cls, vm)?;
        add_to_weak_set(&impl_data.registry, &subclass, vm)?;

        // Invalidate negative cache
        increment_invalidation_counter();

        Ok(subclass)
    }

    /// Internal ABC helper for instance checks. Should be never used outside abc module.
    #[pyfunction]