simplify (AppTy t1 t2) = SimpleType s (ts ++ maybeToList (simplify_maybe t2))
  where (SimpleType s ts) = simplify t1
simplify (AppTy t1 t2) = SimpleType s (ts ++ maybeToList (simplify_maybe t2))
  where (SimpleType s ts) = simplify t1
simplify (AppTy t1 t2) = SimpleType s (ts ++ maybeToList (simplify_maybe t2))
  where (SimpleType s ts) = simplify t1