Working on tree optimizer

StgSharp.RegularAnalysis/Abstraction/AbstractSyntaxTree.cs

@@ -181,9 +181,20 @@ namespace StgSharp.RegularAnalysis.Abstraction
             _state = 0;
         }
 
-        public void SkipNode()
+        /// <summary>
+        ///   Skips the node and its subtree if the current node is the given node. Otherwise, do
+        ///   nothing.
+        /// </summary>
+        /// <param name="node">
+        ///   The node to skip.
+        /// </param>
+        public void SkipNode(
+                    TNode node
+        )
         {
-            if (_stack.TryPop(out Record? r)) {
+            if (_stack.TryPeek(out Record? r) && ReferenceEquals(r.Node, node))
+            {
+                _ = _stack.Pop();
                 _recycle.Push(r);
             }
         }

StgSharp.RegularAnalysis/Abstraction/CompileStack.cs

@@ -176,6 +176,7 @@ namespace StgSharp.RegularAnalysis.Abstraction
 
         #region depth
 
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void DecreaseDepth(
         )
         {
@@ -185,6 +186,7 @@ namespace StgSharp.RegularAnalysis.Abstraction
             }
         }
 
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void IncreaseDepth(
                     int mark
         )

StgSharp.RegularAnalysis/Abstraction/ISyntaxNode.cs

@@ -66,14 +66,6 @@ namespace StgSharp.RegularAnalysis.Abstraction
              TNode nextToken
         );
 
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public static virtual bool IsNullOrEmpty(
-                                   TNode node
-        )
-        {
-            return node is null || node.Equals(TNode.Empty);
-        }
-
         void PrependNode(
              TNode previousNode
         );