class Regexp::Expression::Base

exp.one_of?({meta: [:dot], set: :*})
# meta dots and any set tokens

exp.one_of?(:meta => [:dot, :alternation])
# meta dots and alternations

exp.one_of?(:meta => :*)
# any expression of type meta

exp.one_of?(:group)
# like exp.type?(:group)

exp.one_of?(:*) # always true
# any expression

expression.
from a hash, it will be checked against the token of the
type of the expression. If it's being called for a value
a symbol then it will always be checked against the
the level of the call. If one_of? is called directly with
. A symbol: matches the expression's token or type, depending on

evaluate the key's value.
case, when the scope is a hash, one_of? calls itself to
and the value is either a symbol or an array. In this
. A hash: Where the key is interpreted as the expression type

of the expression's token.
. An array: Interpreted as a set of tokens, tested for inclusion

A scope spec can be one of:

Test if this expression matches an entry in the given scope spec.

def one_of?(scope, top = true)
  case scope
  when Array
    scope.include?(:*) || scope.include?(token)
  when Hash
    if scope.has_key?(:*)
      test_type = scope.has_key?(type) ? type : :*
      one_of?(scope[test_type], false)
    else
      scope.has_key?(type) && one_of?(scope[type], false)
    end
  when Symbol
    scope.equal?(:*) || (top ? type?(scope) : is?(scope))
  else
    raise ArgumentError,
          "Array, Hash, or Symbol expected, #{scope.class.name} given"
  end
end