syntax_data: {"ast_node_type":"function","tokens":[{"end":97,"kind":"keyword","start":0,"text":"fn"}]}
source_snippet:     fn empty(cache: &'o ProvisionalEvaluationCache<'tcx>) -> TraitObligationStackList<'o, 'tcx> {
context_before: impl<'o, 'tcx> TraitObligationStackList<'o, 'tcx> {
context_after:         TraitObligationStackList { cache, head: None }