# File lib/kramdown/parser/kramdown/footnote.rb, line 50
      def parse_footnote_marker
        @src.pos += @src.matched_size
        fn_def = @footnotes[@src[1]]
        if fn_def
          valid = fn_def[:marker] && fn_def[:stack][0..-2].zip(fn_def[:stack][1..-1]).all? do |par, child|
            par.children.include?(child)
          end
          if !fn_def[:marker] || !valid
            fn_def[:marker] = Element.new(:footnote, fn_def[:content], nil, :name => @src[1])
            fn_def[:stack] = [@stack.map {|s| s.first}, @tree, fn_def[:marker]].flatten.compact
            @tree.children << fn_def[:marker]
          else
            warning("Footnote marker '#{@src[1]}' already appeared in document, ignoring newly found marker")
            add_text(@src.matched)
          end
        else
          warning("Footnote definition for '#{@src[1]}' not found")
          add_text(@src.matched)
        end
      end