syntax_data: {"ast_node_type":"other","tokens":[{"end":60,"kind":"keyword","start":0,"text":"///"}]}
source_snippet:     /// column offset when displayed, for a given `BytePos`.
context_before:     /// Looks up the file's (1-based) line number, (0-based `CharPos`) column offset, and (0-based)
context_after:     pub fn lookup_file_pos_with_col_display(&self, pos: BytePos) -> (usize, CharPos, usize) {