void constrainComponent(Context ctx, Node node) {
   if (node instanceof CommandSetNode || node instanceof ConstantSetNode) {
     node.constrain(ctx);
   } else {
     error("Expected 'CommandSet' item, got: " + node);
   }
 }
 void constrainComponent(Context ctx, Node node) {
   if (node instanceof TypeNode) {
     node.constrain(ctx);
   } else {
     error("Expected type descriptor item, got: " + node);
   }
 }