7 Jul
2014
7 Jul
'14
7:58 a.m.
Hi Yuras, Thank you for your reply.
I'm 90% sure you have MonadIO and RWST imported from different versions of transformers. Try to load the code into ghci and check ':i MonadIO' and ':i RWST'. If you'll see fully qualified (including package name and version) names somewhere, then that is the issue. See also http://stackoverflow.com/questions/11068272/acid-state-monadstate-instance-f...
Yes. Probably MonadIO belongs to transformers 0.3.0.0 while RWST does to transformers 0.4.1.0. My question is why this happens. I think that GHCi should use RWST provided by transformers 0.3.0.0. --Kazu