tcfail072.hs:23:13:
    Ambiguous type variable `p0' in the constraint:
      (Ord p0) arising from a use of `g'
    Probable fix: add a type signature that fixes these type variable(s)
    In the expression: g A
    In an equation for `g': g (B _ _) = g A

tcfail072.hs:23:13:
    Ambiguous type variable `q0' in the constraint:
      (Ord q0) arising from a use of `g'
    Probable fix: add a type signature that fixes these type variable(s)
    In the expression: g A
    In an equation for `g': g (B _ _) = g A