Method co_positions

crates/vm/src/builtins/code.rs:953–1070

(&self, vm: &VirtualMachine)

    #[pymethod]
    pub fn co_positions(&self, vm: &VirtualMachine) -> PyResult<PyObjectRef> {
        // Return an iterator over (line, end_line, column, end_column) tuples for each instruction
        let linetable = self.code.linetable.as_ref();
        let mut positions = Vec::new();

        if !linetable.is_empty() {
            let mut reader = LineTableReader::new(linetable);
            let mut line = self.code.first_line_number.map_or(0, |n| n.get() as i32);

            while !reader.at_end() {
                let first_byte = match reader.read_byte() {
                    Some(b) => b,
                    None => break,
                };

                if (first_byte & 0x80) == 0 {
                    break; // Invalid linetable
                }

                let code = (first_byte >> 3) & 0x0f;
                let length = ((first_byte & 0x07) + 1) as i32;

                let kind = match PyCodeLocationInfoKind::from_code(code) {
                    Some(k) => k,
                    None => break, // Invalid code
                };

                let (line_delta, end_line_delta, column, end_column): (
                    i32,
                    i32,
                    Option<i32>,
                    Option<i32>,
                ) = match kind {
                    PyCodeLocationInfoKind::None => {
                        // No location - all values are None
                        (0, 0, None, None)
                    }
                    PyCodeLocationInfoKind::Long => {
                        // Long form
                        let delta = reader.read_signed_varint();
                        let end_line_delta = reader.read_varint() as i32;

                        let col = reader.read_varint();
                        let column = if col == 0 {
                            None
                        } else {
                            Some((col - 1) as i32)
                        };

                        let end_col = reader.read_varint();
                        let end_column = if end_col == 0 {
                            None
                        } else {
                            Some((end_col - 1) as i32)
                        };

                        // endline = line + end_line_delta (will be computed after line update)
                        (delta, end_line_delta, column, end_column)