Get more data to track down issue 25884

pkg/analysis_server/lib/src/computer/computer_overrides.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library computer.overrides;
 
 import 'package:analysis_server/src/collections.dart';
 import 'package:analysis_server/src/protocol_server.dart' as proto;
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
@@ skipping 120 matching lines @@
   String _name;
   List<ElementKind> _kinds;
 
   List<Element> _superElements = <Element>[];
   List<Element> _interfaceElements = <Element>[];
   Set<InterfaceType> _visited = new Set<InterfaceType>();
 
   _OverriddenElementsFinder(Element seed) {
     _seed = seed;
     _class = seed.enclosingElement;
+    if (_class == null) {
+      // TODO(brianwilkerson) Remove this code when the issue has been fixed
+      // (https://github.com/dart-lang/sdk/issues/25884)
+      Type type = seed.runtimeType;
+      String name = seed.name;
+      throw new ArgumentError(
+          'The $type named $name does not have an enclosing element');
+    }
     _library = _class.library;
     _name = seed.displayName;
     if (seed is MethodElement) {
       _kinds = METHOD_KINDS;
     } else if (seed is PropertyAccessorElement) {
       _kinds = seed.isGetter ? GETTER_KINDS : SETTER_KINDS;
     } else {
       _kinds = FIELD_KINDS;
     }
   }
@@ skipping 71 matching lines @@
     if (_kinds.contains(ElementKind.SETTER)) {
       member = classElement.lookUpSetter(_name + '=', _library);
       if (member != null) {
         return member;
       }
     }
     // not found
     return null;
   }
 }