syntax_data: {"ast_node_type":"other","tokens":[{"end":95,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:                                           // freshening replaces all lifetimes with `ReErased`,
context_before:                                           // cache. Note that there is no 'fresh lifetime' flag -
context_after:                                           // which is different from how types/const are freshened.