@type t() ::
  (((((((((((((((((((:addition | :subtraction) | :resolve_variant) | :multiply)
                  | :divide)
                 | :equals)
                | :not_equal)
               | :less_than)
              | :less_than_or_equal)
             | :greater_than)
            | :greater_than_or_equal)
           | :and)
          | :or)
         | :not)
        | :stringify)
       | :ternary)
      | :var_mode_lookup)
     | :negate)
    | :is_truthy)
   | :keyframe)
  | integer()