Set 'enclosingElement' for FunctionElementImpl_forLUB.

pkg/analyzer/lib/src/dart/element/element.dart

Index: pkg/analyzer/lib/src/dart/element/element.dart
diff --git a/pkg/analyzer/lib/src/dart/element/element.dart b/pkg/analyzer/lib/src/dart/element/element.dart
index a22e9bb6f08c0413fe692e249ce20622cb2aa803..cbf2bfc4433fb89868694740f044f409feacb908 100644
--- a/pkg/analyzer/lib/src/dart/element/element.dart
+++ b/pkg/analyzer/lib/src/dart/element/element.dart
@@ -4543,17 +4543,10 @@ class FunctionElementImpl_forFunctionTypedParameter
  * that was synthesized by a LUB computation.
  */
 class FunctionElementImpl_forLUB extends FunctionElementImpl {
-  @override
-  final CompilationUnitElementImpl enclosingUnit;
-
-  @override
-  final TypeParameterizedElementMixin enclosingTypeParameterContext;
-
   final EntityRef _entityRef;
 
-  FunctionElementImpl_forLUB(
-      this.enclosingUnit, this.enclosingTypeParameterContext, this._entityRef)
-      : super('', -1);
+  FunctionElementImpl_forLUB(ElementImpl enclosingElement, this._entityRef)
+      : super.forSerialized(null, enclosingElement);
 
   @override
   bool get isSynthetic => true;