annfail12.hs:5:1: error:
    Exception when trying to run compile-time code:
      You were meant to see this error!
CallStack (from ImplicitParams):
  error, called at annfail12.hs:5:12 in main:Annfail12
    In the annotation:
      {-# ANN f (error "You were meant to see this error!" :: Int) #-}