ref: ed1920f106e8cf23b02910ec2ecae3af3b6f22a7
dir: /tests/StandDer.hs/
module StandDer where data X = X deriving instance Show X data T a = A | B | C a | D (T a) deriving instance (Show a) => Show (T a) main :: IO () main = do print X print [A, B, C True, D A]