Check for missing elements (issue 26987)

pkg/analyzer/lib/src/generated/error_verifier.dart

Index: pkg/analyzer/lib/src/generated/error_verifier.dart
diff --git a/pkg/analyzer/lib/src/generated/error_verifier.dart b/pkg/analyzer/lib/src/generated/error_verifier.dart
index 0a54caa945d7caa6d04eff3b93240b1e30095c02..423a58a5ba58d1c3f84ee30af33470959f676b18 100644
--- a/pkg/analyzer/lib/src/generated/error_verifier.dart
+++ b/pkg/analyzer/lib/src/generated/error_verifier.dart
@@ -4394,7 +4394,7 @@ class ErrorVerifier extends RecursiveAstVisitor<Object> {
   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]);
       }