Rollback instrumentation during analysis and validate resolved ASTs instead.

pkg/front_end/testcases/inference/type_promotion_stopped_by_mutation_in_a_closure.dart

Index: pkg/front_end/testcases/inference/type_promotion_stopped_by_mutation_in_a_closure.dart
diff --git a/pkg/front_end/testcases/inference/type_promotion_stopped_by_mutation_in_a_closure.dart b/pkg/front_end/testcases/inference/type_promotion_stopped_by_mutation_in_a_closure.dart
index 1d23ed3f6c13f7d19085bde722b26e77598311db..b1707d8b045be31b77c03c40937e54987d321850 100644
--- a/pkg/front_end/testcases/inference/type_promotion_stopped_by_mutation_in_a_closure.dart
+++ b/pkg/front_end/testcases/inference/type_promotion_stopped_by_mutation_in_a_closure.dart
@@ -2,15 +2,15 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE.md file.
 
+/*@testedFeatures=inference*/
 library test;
 
-/*@testedFeatures=inference*/
 main() {
   num n = null;
   if (/*@promotedType=none*/ n is int) {
     var /*@type=num*/ i = /*@promotedType=none*/ n;
   }
-  /*@type=() → Null*/ () {
+  /*@returnType=Null*/ () {
     n = null;
   };
 }