syntax_data: {"ast_node_type":"other","tokens":[{"end":64,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:         //   `Option<Symbol>` when "no symbol" is a possibility.
context_before:         // - It should only be used when it genuinely means "empty symbol". Use
context_after:         // - For dummy symbols that are never used and absolutely must be