source_location_demo_1.rb

[1,2,3,4,5].method(:length).source_location
#=> nil

"Ruby".method(:concat).source_location
#=> nil

class Array
  def subset?(sub_array)
    sub_array.each do |element|
      return false unless self.include?(element)
    end
    true
  end
end 

[1,2,3,4].method(:subset?).source_location
#=> ['source_location_demo_1.rb', 8]