anchor.diff:          compareConstAstLists(
               r.arguments?.arguments, o.arguments?.arguments, desc);
           Element expectedElement = o.element;
  -        if (oName is PrefixedIdentifier && o.constructorName != null) {
  +        if (oName is PrefixedIdentifier &&
  +            o.constructorName != null &&
  +            o.element != null) {
             // Due to dartbug.com/25706, [o.element] incorrectly points to the
             // class rather than the named constructor.  Hack around this.
             // TODO(paulberry): when dartbug.com/25706 is fixed, remove this.
  
positive.code:     checkLibrary('f() {} g() {}');
    }
  
    test_unresolved_export() {
      allowMissingFiles = true;
      checkLibrary("export 'foo.dart';", allowErrors: true);
  
negative.code: 
    void compareElementAnnotations(ElementAnnotationImpl resynthesized,
        ElementAnnotationImpl original, String desc) {
      if (original.element == null) {
        expect(resynthesized.element, isNull);
      } else {
        expect(resynthesized.element, isNotNull, reason: desc);
        expect(resynthesized.element.kind, original.element.kind, reason: desc);
        expect(resynthesized.element.location, original.element.location,
            reason: desc);
      }
      expect(resynthesized.compilationUnit, isNotNull, reason: desc);
      expect(resynthesized.compilationUnit.location,
          original.compilationUnit.location,
  