Function subs_tvars

crates/vm/src/builtins/genericalias.rs:358–402

(
    obj: PyObjectRef,
    params: &Py<PyTuple>,
    arg_items: &[PyObjectRef],
    vm: &VirtualMachine,
)

}

fn subs_tvars(
    obj: PyObjectRef,
    params: &Py<PyTuple>,
    arg_items: &[PyObjectRef],
    vm: &VirtualMachine,
) -> PyResult {
    obj.get_attr(identifier!(vm, __parameters__), vm)
        .ok()
        .and_then(|sub_params| {
            PyTupleRef::try_from_object(vm, sub_params)
                .ok()
                .filter(|sub_params| !sub_params.is_empty())
                .map(|sub_params| {
                    let mut sub_args = Vec::new();

                    for arg in sub_params.iter() {
                        if let Some(idx) = tuple_index(params.as_slice(), arg) {
                            let param = &params[idx];
                            let substituted_arg = &arg_items[idx];

                            // Check if this is a TypeVarTuple (has tp_iter)
                            if param.class().slots.iter.load().is_some()
                                && substituted_arg.try_to_ref::<PyTuple>(vm).is_ok()
                            {
                                // TypeVarTuple case - extend with tuple elements
                                if let Ok(tuple) = substituted_arg.try_to_ref::<PyTuple>(vm) {
                                    for elem in tuple {
                                        sub_args.push(elem.clone());
                                    }
                                    continue;
                                }
                            }

                            sub_args.push(substituted_arg.clone());
                        } else {
                            sub_args.push(arg.clone());
                        }
                    }

                    let sub_args: PyObjectRef = PyTuple::new_ref(sub_args, &vm.ctx).into();
                    obj.get_item(&*sub_args, vm)
                })
        })
        .unwrap_or(Ok(obj))
}

// CPython's _unpack_args equivalent
fn unpack_args(item: PyObjectRef, vm: &VirtualMachine) -> PyResult<PyTupleRef> {