Set 'enclosingElement' for FunctionElementImpl_forLUB.

pkg/analyzer/test/src/task/strong/front_end_inference_test.dart

Index: pkg/analyzer/test/src/task/strong/front_end_inference_test.dart
diff --git a/pkg/analyzer/test/src/task/strong/front_end_inference_test.dart b/pkg/analyzer/test/src/task/strong/front_end_inference_test.dart
index e976a5607260e22f83ae2864de40d864f074f26e..2b30ed75748961fffb2935d3f315695fcea18b95 100644
--- a/pkg/analyzer/test/src/task/strong/front_end_inference_test.dart
+++ b/pkg/analyzer/test/src/task/strong/front_end_inference_test.dart
@@ -119,7 +119,7 @@ class _InstrumentationValueForType extends fasta.InstrumentationValue {
   }
 
   void _appendElementName(StringBuffer buffer, Element element) {
-    String name = element.name;
+    String name = element.name ?? '';
     if (element.library == null) {
       // TODO(scheglov) This is wrong - every element must be in a library.
       buffer.write('<unknown>::$name');