{"ast_node_type":"struct","tokens":[{"end":108,"kind":"keyword","start":0,"text":"//"}]}
    // FIXME(dingxiangfei2009): Investigate the set of attributes on target struct to be propagated to impls
    // Declare helper function that adds implementation blocks.
    let attrs = thin_vec![cx.attr_word(sym::automatically_derived, span),];