syntax_data: {"ast_node_type":"function","tokens":[{"end":91,"kind":"keyword","start":0,"text":"fn"}]}
source_snippet:     fn record_impl_from_cstore(&mut self, tcx: TyCtxt<'tcx>, parent: DefId, child: DefId) {
context_before:     /// Insert cached metadata mapping from a child impl back to its parent.
context_after:         if self.parent.insert(child, parent).is_some() {