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In GHC 7.8.4, the following code is legal:

{-# LANGUAGE NullaryTypeClasses, TypeFamilies #-}
module NullaryData where

class NullaryClass where
    data NullaryData

In GHC 7.10, NullaryTypeClasses was deprecated in favor of MultiParamTypeClasses. However, running this code on GHC 7.10-rc1:

{-# LANGUAGE MultiParamTypeClasses, TypeFamilies #-}
module NullaryData where

class NullaryClass where
    data NullaryData

results in this error:

NullaryData.hs:4:1:
    The associated type ‘NullaryData’
    mentions none of the type or kind variables of the class ‘NullaryClass’
    In the class declaration for ‘NullaryClass’

It's probably related to this earlier bugfix.

Trac metadata

Trac field	Value
Version	7.10.1-rc1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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