Check for missing elements (issue 26987)

pkg/analyzer/lib/src/generated/error_verifier.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 analyzer.src.generated.error_verifier;
 
 import 'dart:collection';
 import "dart:math" as math;
 
 import 'package:analyzer/dart/ast/ast.dart';
@@ skipping 4376 matching lines @@
             offset,
             end - offset,
             [constantNames[i]]);
       }
     }
   }
 
   void _checkForMissingJSLibAnnotation(Annotation node) {
     if (node.elementAnnotation?.isJS ?? false) {
       Element element = ElementLocator.locate(node.parent);
-      if (element?.library?.isJS != true) {
+      if (element != null && element.library?.isJS != true) {

[pquitslund, 2016/07/29 18:05:25]

Should this be triggered if the library is null?

If not, maybe this would this be a better test?

if (element?.library?.isJS == false) { ... }

[Brian Wilkerson, 2016/07/29 18:56:22]

I have no idea. The library should never be null; if it is it means there's a
bug in analyzer.

That said, in the process of fixing the other failing test I realized that this
is more complex than it needs to be, so the question is now moot.

         _errorReporter.reportErrorForNode(
             HintCode.MISSING_JS_LIB_ANNOTATION, node, [element.name]);
       }
     }
   }
 
   /**
    * Verify that the given function [body] does not contain return statements
    * that both have and do not have return values.
    *
@@ skipping 2047 matching lines @@
 class _InvocationCollector extends RecursiveAstVisitor {
   final List<String> superCalls = <String>[];
 
   @override
   visitMethodInvocation(MethodInvocation node) {
     if (node.target is SuperExpression) {
       superCalls.add(node.methodName.name);
     }
   }
 }