Imutability for macro nodes

ASTPlayground/Myc.Fmx.AstEditor.Text.pas

@@ -117,7 +117,7 @@ begin
     // To represent a macro expansion as a single line of text, the most
     // informative representation is the original call itself. We can simply
     // delegate to the VisitFunctionCall implementation to format it.
-    Result := VisitFunctionCall(Node);
+    Result := VisitFunctionCall(Node.CallNode);
 end;
 
 function TAstToTextVisitor.VisitRecurNode(const Node: IRecurNode): string;