Use failedAt in more places

pkg/compiler/lib/src/common/resolution.dart

Index: pkg/compiler/lib/src/common/resolution.dart
diff --git a/pkg/compiler/lib/src/common/resolution.dart b/pkg/compiler/lib/src/common/resolution.dart
index 936b7df28a347cc0248209030e794ff874cdd746..586cddc6847520aa3d572874dc207dce4f310025 100644
--- a/pkg/compiler/lib/src/common/resolution.dart
+++ b/pkg/compiler/lib/src/common/resolution.dart
@@ -55,8 +55,8 @@ class _ResolutionWorkItem extends WorkItem implements ResolutionWorkItem {
   _ResolutionWorkItem(this.resolution, this.element);
 
   WorldImpact run() {
-    assert(invariant(element, !_isAnalyzed,
-        message: 'Element ${element} has already been analyzed'));
+    assert(!_isAnalyzed,
+        failedAt(element, 'Element ${element} has already been analyzed'));
     WorldImpact impact = resolution.computeWorldImpact(element);
     _isAnalyzed = true;
     return impact;