Method retry_op_with_frozenset

crates/vm/src/builtins/set.rs:468–500

Run operation, on failure, if item is a set/set subclass, convert it into a frozenset and try the operation again. Propagates original error on failure to convert and restores item in KeyError on failure (remove).

(
        &self,
        item: &PyObject,
        vm: &VirtualMachine,
        op: F,
    )

    // into a frozenset and try the operation again. Propagates original error
    // on failure to convert and restores item in KeyError on failure (remove).
    fn retry_op_with_frozenset<T, F>(
        &self,
        item: &PyObject,
        vm: &VirtualMachine,
        op: F,
    ) -> PyResult<T>
    where
        F: Fn(&PyObject, &VirtualMachine) -> PyResult<T>,
    {
        op(item, vm).or_else(|original_err| {
            item.downcast_ref::<PySet>()
                // Keep original error around.
                .ok_or(original_err)
                .and_then(|set| {
                    op(
                        &PyFrozenSet {
                            inner: set.inner.copy(),
                            ..Default::default()
                        }
                        .into_pyobject(vm),
                        vm,
                    )
                    // If operation raised KeyError, report original set (set.remove)
                    .map_err(|op_err| {
                        if op_err.fast_isinstance(vm.ctx.exceptions.key_error) {
                            vm.new_key_error(item.to_owned())
                        } else {
                            op_err
                        }
                    })
                })
        })
    }
}

fn extract_set(obj: &PyObject) -> Option<&PySetInner> {