tcfail125.hs:1:14:
    Warning: -XDatatypeContexts is deprecated: It was widely considered a misfeature, and has been removed from the Haskell language.

tcfail125.hs:11:4:
    No instance for (Show a)
      arising from a use of `LiftObs'
    In the pattern: LiftObs _ _
    In an equation for `f': f (LiftObs _ _) = "yes"