{"ast_node_type":"impl","tokens":[{"end":81,"kind":"keyword","start":0,"text":"predicates:"}]}
        predicates: impl DoubleEndedIterator<Item = (ty::Predicate<'tcx>, Span)>,
        closure_kind: hir::ClosureKind,
    ) -> (Option<ExpectedSig<'tcx>>, Option<ty::ClosureKind>) {