_nt_label (Treetop::Compiler::Metagrammar)

    # File lib/treetop/compiler/metagrammar.rb, line 1397
          def _nt_label
            start_index = index
            if node_cache[:label].has_key?(index)
              cached = node_cache[:label][index]
              @index = cached.interval.end if cached
              return cached
            end

            i0 = index
            i1, s1 = index, []
            i2, s2 = index, []
            r3 = _nt_alpha_char
            s2 << r3
            if r3
              s4, i4 = [], index
              loop do
                r5 = _nt_alphanumeric_char
                if r5
                  s4 << r5
                else
                  break
                end
              end
              r4 = instantiate_node(SyntaxNode,input, i4...index, s4)
              s2 << r4
            end
            if s2.last
              r2 = instantiate_node(SyntaxNode,input, i2...index, s2)
              r2.extend(Label0)
            else
              self.index = i2
              r2 = nil
            end
            s1 << r2
            if r2
              if input.index(':', index) == index
                r6 = instantiate_node(SyntaxNode,input, index...(index + 1))
                @index += 1
              else
                terminal_parse_failure(':')
                r6 = nil
              end
              s1 << r6
            end
            if s1.last
              r1 = instantiate_node(SyntaxNode,input, i1...index, s1)
              r1.extend(Label1)
              r1.extend(Label2)
            else
              self.index = i1
              r1 = nil
            end
            if r1
              r0 = r1
            else
              if input.index('', index) == index
                r7 = instantiate_node(SyntaxNode,input, index...(index + 0))
                r7.extend(Label3)
                @index += 0
              else
                terminal_parse_failure('')
                r7 = nil
              end
              if r7
                r0 = r7
              else
                self.index = i0
                r0 = nil
              end
            end

            node_cache[:label][start_index] = r0

            return r0
          end