{"ast_node_type":"variable","tokens":[{"end":78,"kind":"keyword","start":0,"text":"let"}]}
    let contravariant = terms_cx.arena.alloc(ConstantTerm(ty::Contravariant));
    let covariant = terms_cx.arena.alloc(ConstantTerm(ty::Covariant));
    let invariant = terms_cx.arena.alloc(ConstantTerm(ty::Invariant));