
tcfail047.hs:6:10:
    Illegal instance declaration for `A (a, (b, c))'
      (All instance types must be of the form (T a1 ... an)
       where a1 ... an are *distinct type variables*,
       and each type variable appears at most once in the instance head.
       Use -XFlexibleInstances if you want to disable this.)
    In the instance declaration for `A (a, (b, c))'
