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  1. {-# LANGUAGE RankNTypes, KindSignatures, MultiParamTypeClasses, FunctionalDependencies #-}
  2.  
  3. module Test where 
  4.  
  5. import Prelude hiding (div)
  6.  
  7. class MonadWidget t (m :: * -> *) | m -> t 
  8.  
  9. div :: forall t m a . MonadWidget t m => m a -> m a
  10. div = (undefined :: forall t m a . MonadWidget t m => m a -> m a)
  11.  
  12. -- app :: forall t m . MonadWidget t m => m ()
  13. app = (div (undefined :: forall t m . MonadWidget t m => m ())
  14.         :: forall t m . MonadWidget t m => m () )
Compilation error #stdin compilation error #stdout 0s 0KB
comments (?)
stdin 
Standard input is empty
compilation info 
[1 of 1] Compiling Test             ( prog.hs, prog.o )

prog.hs:13:8:
    No instance for (MonadWidget t0 m0)
      arising from an expression type signature
    In the expression:
      (div (undefined :: forall t m. MonadWidget t m => m ()) ::
         forall t m. MonadWidget t m => m ())
    In an equation for `app':
        app
          = (div (undefined :: forall t m. MonadWidget t m => m ()) ::
               forall t m. MonadWidget t m => m ())
stdout 
Standard output is empty
https://ideone.com/jlciqw
language:
Haskell (ghc 8.4.4)
created:
8 years ago
visibility:
public

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