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{-# LANGUAGE GADTs #-}
-- Provoked by
-- http://www.haskell.org/pipermail/haskell-cafe/2007-January/021086.html
module ShouldCompile where
import Data.Set as Set
data Teq a b where Teq :: Teq a a
---------------------
data SetM1 a where
SM1 :: Ord w => Teq w a -> Set.Set w -> SetM1 a
unionA1 :: SetM1 a -> SetM1 a -> SetM1 a
unionA1 (SM1 Teq m1) (SM1 Teq m2)
= SM1 Teq (m1 `Set.union` m2)
unionB1 :: SetM1 a -> SetM1 a -> SetM1 a
unionB1 (SM1 p1 m1) (SM1 p2 m2)
= case p1 of Teq -> case p2 of Teq -> SM1 Teq (m1 `Set.union` m2)
unionC1 :: SetM1 a -> SetM1 a -> SetM1 a
unionC1 (SM1 p1 m1) (SM1 p2 m2)
= case (p1,p2) of (Teq,Teq) -> SM1 Teq (m1 `Set.union` m2)
---------------------
data SetM2 a where
SM2 :: Ord w => Teq a w -> Set.Set w -> SetM2 a
-- Different order of args in Teq
unionA2 :: SetM2 a -> SetM2 a -> SetM2 a
unionA2 (SM2 Teq m1) (SM2 Teq m2)
= SM2 Teq (m1 `Set.union` m2)
unionB2 :: SetM2 a -> SetM2 a -> SetM2 a
unionB2 (SM2 p1 m1) (SM2 p2 m2)
= case p1 of Teq -> case p2 of Teq -> SM2 Teq (m1 `Set.union` m2)
unionC2 :: SetM2 a -> SetM2 a -> SetM2 a
unionC2 (SM2 p1 m1) (SM2 p2 m2)
= case (p1,p2) of (Teq,Teq) -> SM2 Teq (m1 `Set.union` m2)
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