tcfail164.hs:11:5:
    Bad call to tagToEnum# at type a
      Specify the type by giving a type signature
      e.g. (tagToEnum# x) :: Bool
    In the expression: tagToEnum# 0#
    In an equation for `f': f = tagToEnum# 0#

tcfail164.hs:17:34:
    Bad call to tagToEnum# at type Int
      Result type must be an enumeration type
    In the expression: tagToEnum# value#
    In an equation for `readUnboxable':
        readUnboxable (I# value#) = tagToEnum# value#
    In the instance declaration for `Unboxable Int'