Use failedAt in more places

pkg/compiler/lib/src/js_backend/checked_mode_helpers.dart

Index: pkg/compiler/lib/src/js_backend/checked_mode_helpers.dart
diff --git a/pkg/compiler/lib/src/js_backend/checked_mode_helpers.dart b/pkg/compiler/lib/src/js_backend/checked_mode_helpers.dart
index d239c1aa9b7a0e027fe0d8ad08b697e3a762555a..ba2ddd64cbdd39a67048d634698fc47bf3c13a1c 100644
--- a/pkg/compiler/lib/src/js_backend/checked_mode_helpers.dart
+++ b/pkg/compiler/lib/src/js_backend/checked_mode_helpers.dart
@@ -212,8 +212,8 @@ class CheckedModeHelpers {
       return typeCast ? 'functionTypeCast' : 'functionTypeCheck';
     }
 
-    assert(invariant(NO_LOCATION_SPANNABLE, type.isInterfaceType,
-        message: "Unexpected type: $type"));
+    assert(type.isInterfaceType,
+        failedAt(NO_LOCATION_SPANNABLE, "Unexpected type: $type"));
     InterfaceType interfaceType = type;
     ClassEntity element = interfaceType.element;
     bool nativeCheck = true;