{"ast_node_type":"variable","tokens":[{"end":91,"kind":"keyword","start":0,"text":"let"}]}
    let pred = ty::TraitPredicate { trait_ref, polarity: ty::PredicatePolarity::Negative };
        ty::TraitRef::new(tcx, tcx.require_lang_item(hir::LangItem::Copy, DUMMY_SP), [ty]);
    let obligation = traits::Obligation {