# File lib/treetop/compiler/metagrammar.rb, line 2916
      def _nt_alphanumeric_char
        start_index = index
        if node_cache[:alphanumeric_char].has_key?(index)
          cached = node_cache[:alphanumeric_char][index]
          @index = cached.interval.end if cached
          return cached
        end

        i0 = index
        r1 = _nt_alpha_char
        if r1
          r0 = r1
        else
          if input.index(Regexp.new('[0-9]'), index) == index
            r2 = instantiate_node(SyntaxNode,input, index...(index + 1))
            @index += 1
          else
            r2 = nil
          end
          if r2
            r0 = r2
          else
            self.index = i0
            r0 = nil
          end
        end

        node_cache[:alphanumeric_char][start_index] = r0

        return r0
      end