avoid generating redundent node class for the same rule

sometimes the CST node class for the same rule is generated more than twice.
avoid doing this by keep tracking on which node is already generated.

Author: Palatis

Parakeet/CstCodeBuilder.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.Runtime.CompilerServices;
 using Ara3D.Utils;
@@ -100,13 +100,19 @@ public static HashSet<string> GatherFields(Rule r, HashSet<string> fields = null
             throw new NotImplementedException($"Unhandled type {r}");
         }
 
-        public static CodeBuilder OutputNodeClass(CodeBuilder cb, Grammar g, Rule r)
+        public static CodeBuilder OutputNodeClass(CodeBuilder cb, Grammar g, Rule r, HashSet<Rule> generated = default)
         {
+            if (generated is null)
+                generated = new HashSet<Rule>();
+            if (generated.Contains(r))
+                return cb;
+            generated.Add(r);
+
             if (r is SequenceRule seq)
             {
                 foreach (var child in seq.Rules)
                     if (child is NodeRule nr2)
-                        OutputNodeClass(cb, g, nr2);
+                        OutputNodeClass(cb, g, nr2, generated);
             }
 
             if (!(r is NodeRule nr))
@@ -171,9 +177,10 @@ public static CodeBuilder OutputNodeClass(CodeBuilder cb, Grammar g, Rule r)
         public static void OutputCstClasses(CodeBuilder cb, Grammar g)
         {
             var rules = g.GetRules();
+            var generated = new HashSet<Rule>();
             foreach (var r in rules)
             {
-                OutputNodeClass(cb, g,r);
+                OutputNodeClass(cb, g, r, generated);
             }
         }