{"ast_node_type":"function","tokens":[{"end":70,"kind":"keyword","start":0,"text":"fn"}]}
    fn str_from_to(&self, start: BytePos, end: BytePos) -> &'src str {
    /// Slice of the source text spanning from `start` up to but excluding `end`.
        &self.src[self.src_index(start)..self.src_index(end)]