Refactoring for immutable nodes

Src/AST/Myc.Ast.Lowering.pas

@@ -85,16 +85,16 @@ end;
 
 function TAstLowerer.VisitFunctionCall(const Node: IFunctionCallNode): IAstNode;
 var
-    calleeIdentifier: TIdentifierNode;
+    calleeIdentifier: IIdentifierNode;
     binaryOp: TScalar.TBinaryOp;
     unaryOp: TScalar.TUnaryOp;
     left, right: IAstNode;
     nodeType: IStaticType;
 begin
     // --- Optimization: Operator Folding ---
-    if (Node.Callee is TIdentifierNode) then
+    if Node.Callee.Kind = akIdentifier then
     begin
-        calleeIdentifier := Node.Callee as TIdentifierNode;
+        calleeIdentifier := Node.Callee.AsIdentifier;
         // Get the type *before* replacing the node (it's an IAstTypedNode)
         nodeType := Node.AsTypedNode.StaticType;