Can't derive Foldable when using ClassyPrelude only

snoyberg / mono-traversable

Type classes for mapping, folding, and traversing monomorphic containers

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Closed YoEight closed 8 years ago

YoEight commented 8 years ago

Greetings,

When I try to do this:

import ClassyPrelude 

data Foo a = …

instance Foldable Foo where 
    foldMap = …

I got from GHC (8, haven't tried on older version yet)

‘foldMap’ is not a (visible) method of class ‘Foldable’

It's weird because ClassyPrelude re-export Data.Foldable.

I'm using classy-prelude-1.0.0.

I have to import Data.Foldable but have a warning saying logically that Data.Foldable is redundant.

Regards.

YoEight commented 8 years ago

Just saw classy-prelude re-export module Data.Foldable but only after importing Data.Foldable (Foldable)