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  def self.new
    if block_given?
      env = MethodContext.current.block
    else
      # Support for ancient pre-block-pass style:
      # def something; Proc.new; end
      # something { a_block } => Proc instance
      env = MethodContext.current.sender.block
    end

    if env
      return from_environment(env)
    else
      raise ArgumentError, "tried to create a Proc object without a block"
    end
  end