syntax_data: {"ast_node_type":"other","tokens":[{"end":28,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:         // position past it.
context_before:         // position that belongs to it, as opposed to hashing the first
context_after:         let Some((file, line_lo, col_lo, line_hi, col_hi)) = ctx.span_data_to_lines_and_cols(&span)