{"ast_node_type":"other","tokens":[{"end":51,"kind":"keyword","start":0,"text":"G:"}]}
    G: FnMut(ty::Region<'tcx>) -> ty::Region<'tcx>,
    F: FnMut(Ty<'tcx>) -> Ty<'tcx>,
    H: FnMut(ty::Const<'tcx>) -> ty::Const<'tcx>,