No instance for (resourcet-1.1.6:Control.Monad.Trans.Resource.Internal.MonadResource IO)

[joehillen]

main = do
  e <- newEnv Oregon Discover
  runAWS e $ send describeInstances
  return ()

gives this error:

    No instance for (resourcet-1.1.6:Control.Monad.Trans.Resource.Internal.MonadResource
                       IO)
      arising from a use of ‘runAWS’
    In the expression: runAWS e
    In a stmt of a 'do' block: runAWS e $ void $ send describeInstances
    In the expression:
      do { e <- newEnv Oregon Discover;
           runAWS e $ void $ send describeInstances;
           return () }

Not a very helpful error message. I can't figure out what is wrong.

[brendanhay]

The result of runAWS is MonadResource m => m a, which needs to be further unwrapped (m a -> IO a) using runResourceT. This is exported by Network.AWS and should be available in scope.

For example:

runResourceT . runAWS e $ do
    ...

[brendanhay]

I'll close this for now. If you have more questions feel free to re-open or create a new issue, you can also use the Gitter chat.

[joehillen]

My confusion came from the example at the top of that page uses runAWS in IO. https://hackage.haskell.org/package/amazonka-1.3.2.1/docs/Network-AWS.html#g:1

[brendanhay]

Thanks, I'll fix the docs