[web-devel] Automatically making every Cereal.Serialize instance of PersistField - bad idea?

With a bit of code, you can save a lot of effort if you add new types to Persistent: instance Cereal.Serialize a => PersistField a where toPersistValue a = PersistByteString $ Cereal.encode a fromPersistValue (PersistByteString b) = Cereal.decode b fromPersistValue _ = Left "bad type for cereal encoded data" sqlType _ = SqlBlob isNullable _ = False BUT, this requires UndecidableInstances. Is this a bad idea? mc