T3208b.hs:15:10:
    Could not deduce: OTerm o0 ~ STerm o0
    from the context: (OTerm a ~ STerm a, OBJECT a, SUBST a)
      bound by the type signature for:
               fce' :: (OTerm a ~ STerm a, OBJECT a, SUBST a) => a -> c
      at T3208b.hs:14:9-56
    The type variable ‘o0’ is ambiguous
    In the expression: fce (apply f)
    In an equation for ‘fce'’: fce' f = fce (apply f)

T3208b.hs:15:15:
    Could not deduce: OTerm o0 ~ STerm a
    from the context: (OTerm a ~ STerm a, OBJECT a, SUBST a)
      bound by the type signature for:
               fce' :: (OTerm a ~ STerm a, OBJECT a, SUBST a) => a -> c
      at T3208b.hs:14:9-56
    The type variable ‘o0’ is ambiguous
    In the first argument of ‘fce’, namely ‘(apply f)’
    In the expression: fce (apply f)
    In an equation for ‘fce'’: fce' f = fce (apply f)
    Relevant bindings include
      f :: a (bound at T3208b.hs:15:6)
      fce' :: a -> c (bound at T3208b.hs:15:1)