Temp.hs

{-# LANGUAGE GADTs #-}                                                                                             
{-# LANGUAGE TypeFamilies #-}                                                                                      
{-# LANGUAGE DataKinds #-}                                                                                         
module Temp where                                                                                                  
                                                                                                                   
data A = A1 | A2                                                                                                   
data B = B1 | B2                                                                                                   
                                                                                                                   
data C (a :: A) (b :: B)where                                                                                      
  C1 :: Int ->  C a b                                                                                              
  C2 :: Char ->  C 'A1 b                                                                                           
  C3 :: Bool ->  C 'A1 'B1                                                                                         
                                                                                                                   
type family ResT (b :: B) where                                                                                    
  ResT B1 = C 'A1 'B1                                                                                              
  ResT B2 = C 'A2 'B2                                                                                              
                                                                                                                   
data D (b :: B) where                                                                                              
  D1 :: ResT 'B1 ->  C 'A1 'B1 ->  D 'B1                                                                           
  D2 :: ResT b ->  C 'A1 b ->  D b                                                                                 
                                                                                                                   
intermediate_func1 :: Int ->  D 'B1                                                                                
intermediate_func1 i = D2 (C1 i) (C1 i)                                                                            
                                                                                                                   
intermediate_func2 :: Int ->  D 'B2                                                                                
intermediate_func2 i = D2 (C1 i) (C1 i)                                                                            
                                                                                                                   
intermediate_func :: Int ->  D (b :: B)                                                                            
intermediate_func i = D2 (C1 i) (C1 i)