yesodweb/persistent — comment on commit e88300b42c489019131c3ae26333db218f6317b9
File: persistent/Database/Persist/Store.hs line 375
By snoyberg:

This is the point at which we should check for a PersistText/PersistByteString and try to do a JSON parse.

I'm not sure about OverlappingInstances here, maybe we should drop the String instance.