{"ast_node_type":"variable","tokens":[{"end":68,"kind":"keyword","start":0,"text":"let"}]}
    let typing_env = ty::TypingEnv::post_analysis(tcx, item_def_id);
fn dump_layout_of(tcx: TyCtxt<'_>, item_def_id: LocalDefId, attr: &Attribute) {
    let ty = tcx.type_of(item_def_id).instantiate_identity();