language: Haskell (ghc-7.4.1)
date: 1215 days 8 hours ago
link:
visibility: public 
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{-# LANGUAGE MultiParamTypeClasses, TypeSynonymInstances #-}
 
class X a b where
    sth :: a b
 
data A b = A b
 
-- this works:
-- type A_1 = A
-- this doesn't:
type A_1 b = A b
 
instance X A_1 Int where
    sth = A 42
 
main :: IO ()
main = return ()
[1 of 1] Compiling Main             ( prog.hs, prog.o )

prog.hs:13:0:
    Type synonym `A_1' should have 1 argument, but has been given 0
    In the instance declaration for `X A_1 Int'