# File lib/treetop/compiler/metagrammar.rb, line 2578
      def _nt_character_class
        start_index = index
        if node_cache[:character_class].has_key?(index)
          cached = node_cache[:character_class][index]
          if cached
            cached = SyntaxNode.new(input, index...(index + 1)) if cached == true
            @index = cached.interval.end
          end
          return cached
        end

        i0, s0 = index, []
        if has_terminal?('[', false, index)
          r1 = instantiate_node(SyntaxNode,input, index...(index + 1))
          @index += 1
        else
          terminal_parse_failure('[')
          r1 = nil
        end
        s0 << r1
        if r1
          s2, i2 = [], index
          loop do
            i3, s3 = index, []
            i4 = index
            if has_terminal?(']', false, index)
              r5 = instantiate_node(SyntaxNode,input, index...(index + 1))
              @index += 1
            else
              terminal_parse_failure(']')
              r5 = nil
            end
            if r5
              r4 = nil
            else
              @index = i4
              r4 = instantiate_node(SyntaxNode,input, index...index)
            end
            s3 << r4
            if r4
              i6 = index
              i7, s7 = index, []
              if has_terminal?('\\', false, index)
                r8 = instantiate_node(SyntaxNode,input, index...(index + 1))
                @index += 1
              else
                terminal_parse_failure('\\')
                r8 = nil
              end
              s7 << r8
              if r8
                if index < input_length
                  r9 = instantiate_node(SyntaxNode,input, index...(index + 1))
                  @index += 1
                else
                  terminal_parse_failure("any character")
                  r9 = nil
                end
                s7 << r9
              end
              if s7.last
                r7 = instantiate_node(SyntaxNode,input, i7...index, s7)
                r7.extend(CharacterClass0)
              else
                @index = i7
                r7 = nil
              end
              if r7
                r6 = r7
              else
                i10, s10 = index, []
                i11 = index
                if has_terminal?('\\', false, index)
                  r12 = instantiate_node(SyntaxNode,input, index...(index + 1))
                  @index += 1
                else
                  terminal_parse_failure('\\')
                  r12 = nil
                end
                if r12
                  r11 = nil
                else
                  @index = i11
                  r11 = instantiate_node(SyntaxNode,input, index...index)
                end
                s10 << r11
                if r11
                  if index < input_length
                    r13 = instantiate_node(SyntaxNode,input, index...(index + 1))
                    @index += 1
                  else
                    terminal_parse_failure("any character")
                    r13 = nil
                  end
                  s10 << r13
                end
                if s10.last
                  r10 = instantiate_node(SyntaxNode,input, i10...index, s10)
                  r10.extend(CharacterClass1)
                else
                  @index = i10
                  r10 = nil
                end
                if r10
                  r6 = r10
                else
                  @index = i6
                  r6 = nil
                end
              end
              s3 << r6
            end
            if s3.last
              r3 = instantiate_node(SyntaxNode,input, i3...index, s3)
              r3.extend(CharacterClass2)
            else
              @index = i3
              r3 = nil
            end
            if r3
              s2 << r3
            else
              break
            end
          end
          if s2.empty?
            @index = i2
            r2 = nil
          else
            r2 = instantiate_node(SyntaxNode,input, i2...index, s2)
          end
          s0 << r2
          if r2
            if has_terminal?(']', false, index)
              r14 = instantiate_node(SyntaxNode,input, index...(index + 1))
              @index += 1
            else
              terminal_parse_failure(']')
              r14 = nil
            end
            s0 << r14
          end
        end
        if s0.last
          r0 = instantiate_node(CharacterClass,input, i0...index, s0)
          r0.extend(CharacterClass3)
          r0.extend(CharacterClass4)
        else
          @index = i0
          r0 = nil
        end

        node_cache[:character_class][start_index] = r0

        r0
      end