syntax_data: {"ast_node_type":"other","tokens":[{"end":78,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:         //   it's clearer that it's intended as a dummy value, and more likely
context_before:         //   present, it's better to use `sym::dummy` than `sym::empty`, because
context_after:         //   to be detected if it accidentally does get used.