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KindsDoNotUnify error is vague #3281

rndnoise opened this Issue Mar 15, 2018 · 0 comments


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rndnoise commented Mar 15, 2018

Below, the reason the code doesn't type check is that Query takes a type parameter but it was omitted. From the error message, it's not clear why the type checker is trying to unify Type with Type -> Type.

Perhaps a better error would be something like "Could not match kind Type with Type -> Type while checking the kind of Query in the expression MonadAff ( ... ) m => Eq i => Config i m -> ComponentHTML Query Input Output m".

  67  component
  68    :: forall i e m
  69     . MonadAff (ajax :: AJAX, avar :: AVAR, dom :: DOM | e) m
  70    => Eq i
  71    => TI.Config i m
  72    -> H.Component HH.HTML Query Input Output m

  Could not match kind


  with kind

    Type -> Type

  while checking the kind of MonadAff
                               ( ajax :: AJAX
                               , avar :: AVAR
                               , dom :: DOM
                               | e
                              => Eq i => Config i m -> Component HTML Query Input Output m
  in value declaration component
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