Update tests to make latent errors explicit.

tests/language/regress_22976_test.dart

Index: tests/language/regress_22976_test.dart
diff --git a/tests/language/regress_22976_test.dart b/tests/language/regress_22976_test.dart
index 67d69570b3f775d24e480c763b501f95d4f29786..ea29319e8c062d87228ba904170e75c8964822cd 100644
--- a/tests/language/regress_22976_test.dart
+++ b/tests/language/regress_22976_test.dart
@@ -9,6 +9,8 @@ class B<T> implements A<T> {}
 class C<S, T> implements B<S>, A<T> {}
 
 main() {
-  A<int> a0 = new C<int, String>(); /// 01: ok
-  A<int> a1 = new C<String, int>(); /// 02: ok
+  C<int, String> c1 = new C<int, String>();
+  C<String, int> c2 = new C<String, int>();
+  A<int> a0 = c1; /// 01: ok
+  A<int> a1 = c2; /// 02: ok
 }