Method try_from_borrowed_object

crates/vm/src/sliceable.rs:261–285

(
        vm: &VirtualMachine,
        obj: &PyObject,
        type_name: &str,
    )

impl SequenceIndex {
    pub fn try_from_borrowed_object(
        vm: &VirtualMachine,
        obj: &PyObject,
        type_name: &str,
    ) -> PyResult<Self> {
        if let Some(i) = obj.downcast_ref::<PyInt>() {
            // TODO: number protocol
            i.try_to_primitive(vm)
                .map_err(|_| vm.new_index_error("cannot fit 'int' into an index-sized integer"))
                .map(Self::Int)
        } else if let Some(slice) = obj.downcast_ref::<PySlice>() {
            slice.to_saturated(vm).map(Self::Slice)
        } else if let Some(i) = obj.try_index_opt(vm) {
            // TODO: __index__ for indices is no more supported?
            i?.try_to_primitive(vm)
                .map_err(|_| vm.new_index_error("cannot fit 'int' into an index-sized integer"))
                .map(Self::Int)
        } else {
            Err(vm.new_type_error(format!(
                "{} indices must be integers or slices or classes that override __index__ operator, not '{}'",
                type_name,
                obj.class()
            )))
        }
    }
}

pub trait SequenceIndexOp {