module TH_genExLib where

import Language.Haskell.TH

genAny :: Q Info -> Q [Dec]
genAny decl = do { d <- decl
                 ; case d of
                    ClassI (ClassD _ name _ _ decls) _ -> return [genAnyClass name decls]
                    _ -> error "genAny can be applied to classes only"
        }

genAnyClass :: Name -> [Dec] -> Dec
genAnyClass name decls
  = DataD [] anyName [] Nothing [constructor] []
  where
    anyName = mkName ("Any" ++ nameBase name ++ "1111")
    constructor = ForallC [PlainTV var_a SpecifiedSpec] [AppT (ConT name) (VarT var_a)] $
                  NormalC anyName
                                [(Bang NoSourceUnpackedness NoSourceStrictness, VarT var_a)]
    var_a = mkName "a"