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DeriveDataTypeable - deriving Data for several type constructor applications

    • Closed Issue created by lspitzner @trac-lspitzner 
    {-# LANGUAGE DeriveDataTypeable, StandaloneDeriving #-}
import qualified Data.Data

data Mu f = Mu (f (Mu f))
deriving instance Data.Data.Data (Mu [])
deriving instance Data.Data.Data (Mu IO)

    produces

        Multiple declarations of ‘$t3Ecq4GuAmh1HtkHHwEpyjp’
    [..]
    Multiple declarations of ‘$c3Ecq4GuAmh1HtkHHwEpyjp’
    [..]
    Duplicate type signatures for ‘$t3Ecq4GuAmh1HtkHHwEpyjp’
    [..]
    Duplicate type signatures for ‘$c3Ecq4GuAmh1HtkHHwEpyjp’
    [..]

    As a workaround one can define instances in separate modules.

    Trac metadata
    Trac field Value
    Version 8.0.1
    Type Bug
    TypeOfFailure OtherFailure
    Priority normal
    Resolution Unresolved
    Component Compiler
    Test case
    Differential revisions
    BlockedBy
    Related
    Blocking
    CC
    Operating system
    Architecture
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