regex interpreter now can build partial correct AST (i forget groups), but in bad shape. building an optimizer.

StgSharp.RegularAnalysis/Abstraction/AbstractSyntaxTree.cs

@@ -29,6 +29,7 @@ using StgSharp.Collections;
 
 using System;
 using System.Collections.Generic;
+using System.Runtime.CompilerServices;
 using System.Text;
 using System.Xml.Schema;
 
@@ -38,6 +39,8 @@ namespace StgSharp.RegularAnalysis.Abstraction
         where TType : unmanaged
     {
 
+        private HashSet<TNode> _allToken = new();
+
         private TNode _root;
 
         public int Count
@@ -45,17 +48,31 @@ namespace StgSharp.RegularAnalysis.Abstraction
             get { return _allToken.Count; }
         }
 
-        public TNode Root => _root;
+        public TNode Root
+        {
+            get;
+            internal set
+            {
+                if (_allToken.Contains(value)) {
+                    field = value;
+                }
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public bool AddNode(
+                    TNode node
+        )
+        {
+            return _allToken.Add(node);
+        }
 
         public bool Contains(
                     TNode node
         )
         {
-            return _allToken<TLabel>.Contains(node);
+            return _allToken.Contains(node);
         }
 
-        private List<TNode> _allToken<TLabel> = 
-new();
-
     }
 }