Record dependencies and invalidate results.

pkg/analyzer/lib/src/task/dart.dart

 // Copyright (c) 2015, 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 analyzer.src.task.dart;
 
 import 'dart:collection';
 import 'dart:math' as math;
 
 import 'package:analyzer/src/generated/ast.dart';
@@ skipping 316 matching lines @@
 
   @override
   void internalPerform() {
     List<AnalysisError> errors = <AnalysisError>[];
     //
     // Prepare inputs.
     //
     ClassElementImpl classElement = this.target;
     List<ConstructorElement> superConstructors = inputs[SUPER_CONSTRUCTORS];
     DartType superType = classElement.supertype;
+    if (superType == null) {
+      return;
+    }
     ClassElement superElement = superType.element;
     //
     // Shortcut for ClassElement(s) without implicit constructors.
     //
     if (superConstructors == null) {
       outputs[CONSTRUCTORS] = classElement.constructors;
       outputs[CONSTRUCTORS_ERRORS] = AnalysisError.NO_ERRORS;
       return;
     }
     //
@@ skipping 2255 matching lines @@
   @override
   bool moveNext() {
     if (_newSources.isEmpty) {
       return false;
     }
     currentTarget = _newSources.first;
     _newSources.remove(currentTarget);
     return true;
   }
 }