Partially implement the _fetch part. We still need to bind the builde…

…r argument.

packages/rfw/lib/src/flutter/runtime.dart

@@ -445,6 +445,25 @@ class Runtime extends ChangeNotifier {
       final DynamicMap subArguments = _bindArguments(context, node.arguments, arguments, stateDepth, usedWidgets) as DynamicMap;
       return _applyConstructorAndBindArguments(FullyQualifiedWidgetName(context.library, node.name), subArguments, stateDepth, usedWidgets, node);
     }
+    if (node is FunctionDeclaration) {
+      return (DynamicMap builderArg) {
+        // TODO(tugorez): bind the builder argument.
+        final DynamicMap subArguments = _bindArguments(
+          context,
+          node.constructorCall.arguments,
+          arguments,
+          stateDepth,
+          usedWidgets,
+        ) as DynamicMap;
+        return _applyConstructorAndBindArguments(
+          FullyQualifiedWidgetName(context.library, node.constructorCall.name),
+          subArguments,
+          stateDepth,
+          usedWidgets,
+          node,
+        );
+      };
+    }
     if (node is DynamicMap) {
       return node.map<String, Object?>(
         (String name, Object? value) => MapEntry<String, Object?>(name, _bindArguments(context, value!, arguments, stateDepth, usedWidgets)),
@@ -990,7 +1009,6 @@ class _WidgetState extends State<_Widget> implements DataSource {
   Widget? optionalBuilder(List<Object> argsKey, DynamicMap builderArg) {
     final Object value = _fetch(argsKey, expandLists: false);
     if (value is _RemoteWidgetBuilder) {
-      // TODO(tugorez): make sure the [builderArg] is binded.
       final _CurriedWidget curriedWidget = value(builderArg) as _CurriedWidget;
       return curriedWidget.build(
         context,