syntax_data: {"ast_node_type":"other","tokens":[{"end":34,"kind":"keyword","start":0,"text":"seen_tys:"}]}
source_snippet:     seen_tys: FxHashSet<Ty<'tcx>>,
context_before:     query_ty: Ty<'tcx>,
context_after:     /// A stack of types left to process, and the recursion depth when we