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lemma bar (r: Array α) (b: List α): r ++ b = { data := r.data ++ b }Even when importingStd.Data.List.Init.Lemmasas well. Is this the result of a missing lemma, or are there more tricks needed for these sorts of proofs? $\endgroup$rw [← Array.appendList_data], but is there an easier way that doesn't require me manually searching for lemmas? $\endgroup$congrproof seems to work with the symmetric goal,{ data := r.data ++ b } = r ++ b. That is a bit annoying, but good to know. $\endgroup$