syntax_data: {"ast_node_type":"function","tokens":[{"end":57,"kind":"keyword","start":0,"text":"fn"}]}
source_snippet:     fn new(tcx: TyCtxt<'tcx>, item: LocalDefId) -> Self {
context_before: impl<'tcx> OpaqueTypeCollector<'tcx> {
context_after:         let mode = match tcx.def_kind(item) {