unexpected ambiguity

Niklas Sorensson nik at cs.chalmers.se
Mon Apr 10 10:48:15 EDT 2006

wizztick-ghc at douma.eu.org wrote:
> Niklas Sorensson wrote:
>> Main.hs:8:15:
>>     Ambiguous occurrence `lift'
>>     It could refer to either `Control.Monad.Trans.lift', ...
>>                           or `Apa.lift', imported from Apa at ...
>> Is this correct? I would have expected that an unqualified lift could only 
>> refer to the one exported from Apa in this case.
> The error is correct. The module Control.Monad.State re-export the lift
> identifier from Control.Monad.Trans.
> Thus the line 'import Control.Monad.State' is the evildoer. Use for
> example:
> import Control.Monad.State hiding (lift)
> The error message surly makes you look in the wrong direction.

Ideed. Thanks for the explanation!


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