tc168b.hs:7:1: error: [GHC-39999]
    • Could not deduce ‘C a (u, v0, w0, x0, y0, z0)’
      from the context: C a (u, v, w, x, y, z)
        bound by the inferred type for ‘g’:
                   forall {a} {u} {v} {w} {x} {y} {z}.
                   C a (u, v, w, x, y, z) =>
                   a -> u
        at tc168b.hs:7:1-16
      The type variables ‘v0’, ‘w0’, ‘x0’, ‘y0’, ‘z0’ are ambiguous
    • In the ambiguity check for the inferred type for ‘g’
      To defer the ambiguity check to use sites, enable AllowAmbiguousTypes
      When checking the inferred type
        g :: forall {a} {u} {v} {w} {x} {y} {z}.
             C a (u, v, w, x, y, z) =>
             a -> u