Use failedAt in more places

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

 // Copyright (c) 2013, 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.
 
 import '../common.dart';
 import '../common_elements.dart';
 import '../elements/elements.dart' show ErroneousElement;
 import '../elements/entities.dart';
 import '../elements/resolution_types.dart' show MalformedType;
 import '../elements/types.dart';
@@ skipping 194 matching lines @@
     if (type.isTypeVariable) {
       return typeCast
           ? 'subtypeOfRuntimeTypeCast'
           : 'assertSubtypeOfRuntimeType';
     }
 
     if (type.isFunctionType) {
       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;
     // TODO(13955), TODO(9731).  The test for non-primitive types should use an
     // interceptor.  The interceptor should be an argument to HTypeConversion so
     // that it can be optimized by standard interceptor optimizations.
     //  nativeCheckOnly || emitter.nativeEmitter.requiresNativeIsCheck(element);
 
     var suffix = typeCast ? 'TypeCast' : 'TypeCheck';
     if (element == _commonElements.jsStringClass ||
@@ skipping 56 matching lines @@
 
     if (nativeCheck) {
       // TODO(karlklose): can we get rid of this branch when we use
       // interceptors?
       return 'intercepted$suffix';
     } else {
       return 'property$suffix';
     }
   }
 }