syntax_data: {"ast_node_type":"other","tokens":[{"end":14,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:             //
context_before:             // the [rustc dev guide][rd]
context_after:             // [rd]: https://rustc-dev-guide.rust-lang.org/borrow_check/region_inference/placeholders_and_universes.html