[Haskell-cafe] Deriving Eq and Show instances for testing

Ruben Astudillo ruben.astud at gmail.com
Thu Mar 31 15:50:24 UTC 2016

On 31/03/16 12:43, Anakreontas wrote:
> I have datatypes for which I need an Eq and Show instance only for testing.
> I could derive those instances in the datatype declaration but I prefer not
> to add unnecessary functionality. With StandaloneDeriving extension I can
> derive the instances in the test module but this produces many warning
> about orphan instances. Is there a better approach or a way to stop reports
> about orphan instance warnings?
> Regards
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You can put
     {-# OPTIONS_GHC -fno-warn-orphans #-}
At the top of such files to stop warnings, see also [1]


-- Ruben Astudillo

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