Method call

crates/stdlib/src/json.rs:634–658

(zelf: &Py<Self>, (pystr, char_idx): Self::Args, vm: &VirtualMachine)

    impl Callable for JsonScanner {
        type Args = (PyStrRef, isize);
        fn call(zelf: &Py<Self>, (pystr, char_idx): Self::Args, vm: &VirtualMachine) -> PyResult {
            if char_idx < 0 {
                return Err(vm.new_value_error("idx cannot be negative"));
            }
            let char_idx = char_idx as usize;
            let pystr = pystr.try_into_utf8(vm)?;
            let s = pystr.as_str();

            // Calculate byte index from char index (O(char_idx) but only at entry point)
            let byte_idx = if char_idx == 0 {
                0
            } else {
                match s.char_indices().nth(char_idx) {
                    Some((byte_i, _)) => byte_i,
                    None => {
                        // char_idx is beyond the string length
                        return PyIterReturn::StopIteration(Some(vm.ctx.new_int(char_idx).into()))
                            .to_pyresult(vm);
                    }
                }
            };

            zelf.parse(pystr, char_idx, byte_idx, zelf.to_owned().into(), vm)
                .and_then(|x| x.to_pyresult(vm))
        }
    }

    fn encode_string(s: &str, ascii_only: bool) -> String {