tcfail133.hs:2:61: Warning:
    -XDatatypeContexts is deprecated: It was widely considered a misfeature, and has been removed from the Haskell language.

tcfail133.hs:68:7:
    No instance for (Show a0) arising from a use of `show'
    The type variable `a0' is ambiguous
    Possible fix: add a type signature that fixes these type variable(s)
    Note: there are several potential instances:
      instance Show Zero -- Defined at tcfail133.hs:8:29
      instance Show One -- Defined at tcfail133.hs:9:28
      instance (Show a, Show b, Number a, Digit b) => Show (a :@ b)
        -- Defined at tcfail133.hs:11:54
      ...plus 29 others
    In the expression: show
    In the expression: show $ add (One :@ Zero) (One :@ One)
    In an equation for `foo':
        foo = show $ add (One :@ Zero) (One :@ One)

tcfail133.hs:68:14:
    No instance for (AddDigit (Zero :@ (One :@ One)) One a0)
      arising from a use of `add'
    Possible fix:
      add an instance declaration for
      (AddDigit (Zero :@ (One :@ One)) One a0)
    In the second argument of `($)', namely
      `add (One :@ Zero) (One :@ One)'
    In the expression: show $ add (One :@ Zero) (One :@ One)
    In an equation for `foo':
        foo = show $ add (One :@ Zero) (One :@ One)