Move Solo to base, if possible
Being in the ghc-prim package, the Solo documentation can't link to Applicative or traverse. If it's possible to move its definition to Data.Tuple without undue difficulty, then we should do so.
Being in the ghc-prim package, the Solo documentation can't link to Applicative or traverse. If it's possible to move its definition to Data.Tuple without undue difficulty, then we should do so.