syntax_data: {"ast_node_type":"other","tokens":[{"end":39,"kind":"keyword","start":0,"text":"///"}]}
source_snippet:     /// - respect multi-byte characters
context_before:     ///   which means sm.span_to_snippet(next_point) will get `Err`
context_after:     pub fn next_point(&self, sp: Span) -> Span {