Deduplicate grouping rules

lib/racc/grammarfileparser.rb

@@ -239,12 +239,13 @@ def add_rule_block(list)
     end
 
     def _add_rule_block(target, enum)
+      rules = [] # [ [seqs, sprec], .. ]
       curr = []
       sprec = nil
       while (sym, idx = enum.next rescue nil)
         case sym
         when OrMark
-          add_rule target, curr, sprec
+          rules << [curr, sprec]
           curr = []
           sprec = nil
         when OptionMark
@@ -254,26 +255,41 @@ def _add_rule_block(target, enum)
         when Many1Mark
           curr << _add_many1_rule(curr.pop)
         when GroupStartMark
-          @many_seq ||= 0
-          @many_seq += 1
-          t = _gen_target_name("group", @grammar.intern(@many_seq.to_s))
-          syms, _ = _add_rule_block(t, enum)
-          src = SourceText.new("result = val", __FILE__, __LINE__)
-          @grammar.add Rule.new(t, syms, UserAction.source_text(src))
-          curr << t
+          group_target = @grammar.intern("-temp-group")
+          group_rules, _ = _add_rule_block(group_target, enum)
+          group_target_name = _gen_group_target_name_str(group_rules)
+          @group_rule_registry ||= {}
+          if group_target = @group_rule_registry[group_target_name]
+          else
+            group_target = @grammar.intern("-group@#{group_target_name}")
+            @group_rule_registry[group_target_name] = group_target
+            src = SourceText.new("result = val", __FILE__, __LINE__)
+            act = UserAction.source_text(src)
+            group_rules.each do |syms, sprec|
+              rule = Rule.new(group_target, syms, act)
+              rule.specified_prec = sprec
+              @grammar.add rule
+            end
+          end
+          curr << group_target
         when GroupEndMark
-          return curr, sym, idx
+          rules << [curr, sprec]
+          return rules, sym, idx
         when Prec
           raise CompileError, "'=<prec>' used twice in one rule" if sprec
           sprec = sym.symbol
         else
           curr.push sym
         end
       end
-      add_rule target, curr, sprec
+      rules << [curr, sprec]
+      rules.each do |syms, sprec|
+        add_rule target, syms, sprec
+      end
       nil
     end
 
+
     def _add_option_rule(prev)
       @option_rule_registry ||= {}
       target = @option_rule_registry[prev.to_s]
@@ -316,6 +332,10 @@ def _gen_target_name(type, sym)
       @grammar.intern("-#{type}@#{sym.value}")
     end
 
+    def _gen_group_target_name_str(rules)
+      rules.map{|syms, sprec| syms.join("-")}.join("|")
+    end
+
     def add_rule(target, list, sprec)
       if list.last.kind_of?(UserAction)
         act = list.pop