isInstance does not work on Typeable with base-4.8 anymore
> :set -XTemplateHaskell > :m +Data.Typeable > :m +Language.Haskell.TH --- With GHC 7.8 or earlier versions of GHC (I only tried with GHC 7.6, but my friends tried on 7.8 and earlier versions) > $(isInstance ''Typeable [ConT ''Char] >>= stringE.show) "True" --- With GHC 7.10.1 > $(isInstance ''Typeable [ConT ''Char] >>= stringE.show) "False"
I have noticed that standalone derivings of Typeable instances in Data.Typeable are disappared magically in base-4.8 of GHC 7.10,also one cannot query the instances of it by using
:i Typeable in GHCi, however, obviously, I can use
typeOf function in base-4.8 to get the TypeRep of Char.
The problem is that
isInstance in template-haskell library doesn't know Char and many other types are instances of Typeable anymore.