# File lib/type_checker.rb, line 378
  def process_const(exp)
    c = exp.shift
    if c.to_s =~ /^[A-Z]/ then
      # TODO: validate that it really is a const?
      type = @genv.lookup(c) rescue @env.lookup(c)
      return t(:const, c, type)
    else
      raise "I don't know what to do with const #{c.inspect}. It doesn't look like a class."
    end
    raise "need to finish process_const in #{self.class}"
  end