Type error when deriving Generic for an associated data type
Bas van Dijk
v.dijk.bas at gmail.com
Thu Jul 12 12:27:53 CEST 2012
Hi,
I'm hitting on an issue when deriving Generic for an associated data type:
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE DeriveGeneric #-}
import GHC.Generics
class Foo a where
data T a :: *
instance Foo Int where
data T Int = Bla deriving Generic
Couldn't match type `Rep (T Int)' with `M1 t0 t1 (M1 t2 t3 U1)'
Expected type: Rep (T Int) x
Actual type: M1 t0 t1 (M1 t2 t3 U1) x
In the pattern: M1 (M1 U1)
In an equation for `to': to (M1 (M1 U1)) = Bla
In the instance declaration for `Generic (T Int)'
The GHC trac seems to be down. Is this a known issue?
Cheers,
Bas
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