Use failedAt in more places

pkg/compiler/lib/src/enqueue.dart

Index: pkg/compiler/lib/src/enqueue.dart
diff --git a/pkg/compiler/lib/src/enqueue.dart b/pkg/compiler/lib/src/enqueue.dart
index a0ea7811a70f1e79864067b36e43b9ebdb293370..dceab7c1c7283115f93b9bc5b48ef4986847703e 100644
--- a/pkg/compiler/lib/src/enqueue.dart
+++ b/pkg/compiler/lib/src/enqueue.dart
@@ -46,8 +46,10 @@ class EnqueueTask extends CompilerTask {
 
   // TODO(johnniwinther): Remove the need for this.
   ResolutionEnqueuer get resolution {
-    assert(invariant(NO_LOCATION_SPANNABLE, _resolution != null,
-        message: "ResolutionEnqueuer has not been created yet."));
+    assert(
+        _resolution != null,
+        failedAt(NO_LOCATION_SPANNABLE,
+            "ResolutionEnqueuer has not been created yet."));
     return _resolution;
   }