GenSynth.hs:26:11:
    Ambiguous type variable `t0' in the constraint:
      (Random t0) arising from the ambiguity check for g'
    Probable fix: add a type signature that fixes these type variable(s)
    When checking that g'
      has the inferred type `forall t. Random t => t1'
    Probable cause: the inferred type is ambiguous
    In an equation for `s':
        s g
          = u1
          where
              (u1, g') = random g