#389. Fix NNBD static errors tests for X&S types where S is non-nullable
diff --git a/LanguageFeatures/nnbd/static_errors_A22_t10.dart b/LanguageFeatures/nnbd/static_errors_A22_t10.dart
index ed13955..350dcf3 100644
--- a/LanguageFeatures/nnbd/static_errors_A22_t10.dart
+++ b/LanguageFeatures/nnbd/static_errors_A22_t10.dart
@@ -20,15 +20,16 @@
  */
 // SharedOptions=--enable-experiment=non-nullable
 
-class X {}
-
 class S {}
 
-class C = X? with S;
+dynamic getDynamic(dynamic v) => v;
 
 main() {
-  C c = null;
+  var v = getDynamic(new S());
+  if (v is S) {
+    v = null;
 //      ^^^^
 // [analyzer] unspecified
 // [cfe] unspecified
+  }
 }
diff --git a/LanguageFeatures/nnbd/static_errors_A22_t11.dart b/LanguageFeatures/nnbd/static_errors_A22_t11.dart
index bcda655..561cb3b 100644
--- a/LanguageFeatures/nnbd/static_errors_A22_t11.dart
+++ b/LanguageFeatures/nnbd/static_errors_A22_t11.dart
@@ -15,22 +15,23 @@
  *  X & S where S is non-nullable
  *
  * @description Check that null cannot be assigned to non-nullable type. Test
- * X & S where S is non-nullable
+ * X & S where S is non-nullable. Test type aliases
  * @author sgrekhov@unipro.ru
  */
 // SharedOptions=--enable-experiment=non-nullable,nonfunction-type-aliases
 
-class X {}
-
 class S {}
 
-typedef XAlias = X?;
+typedef SAlias = S;
 
-class C = XAlias with S;
+dynamic getDynamic(dynamic v) => v;
 
 main() {
-  C c = null;
+  var v = getDynamic(new S());
+  if (v is SAlias) {
+    v = null;
 //      ^^^^
 // [analyzer] unspecified
 // [cfe] unspecified
+  }
 }
diff --git a/LanguageFeatures/nnbd/static_errors_A22_t12.dart b/LanguageFeatures/nnbd/static_errors_A22_t12.dart
index 93ffa9c..04211ce 100644
--- a/LanguageFeatures/nnbd/static_errors_A22_t12.dart
+++ b/LanguageFeatures/nnbd/static_errors_A22_t12.dart
@@ -21,13 +21,14 @@
 // SharedOptions=--enable-experiment=non-nullable
 import "legacy_library_lib.dart";
 
-class S {}
-
-class C = A with S;
+class S extends A {}
 
 main() {
-  C c = null;
+  A a = new S();
+  if (a is S) {
+    a = null;
 //      ^^^^
 // [analyzer] unspecified
 // [cfe] unspecified
+  }
 }
diff --git a/LanguageFeatures/nnbd/static_errors_A22_t13.dart b/LanguageFeatures/nnbd/static_errors_A22_t13.dart
index 651ded6..735aace 100644
--- a/LanguageFeatures/nnbd/static_errors_A22_t13.dart
+++ b/LanguageFeatures/nnbd/static_errors_A22_t13.dart
@@ -19,17 +19,18 @@
  * @author sgrekhov@unipro.ru
  */
 // SharedOptions=--enable-experiment=non-nullable,nonfunction-type-aliases
-import "legacy_library_lib.dart";
+import "legacy_library_aliases_lib.dart";
 
-typedef AAlias = A;
+class S extends AAlias {}
 
-class S {}
-
-class C = AAlias with S;
+typedef SAlias = S;
 
 main() {
-  C c = null;
+  AAlias a = new S();
+  if (a is SAlias) {
+    a = null;
 //      ^^^^
 // [analyzer] unspecified
 // [cfe] unspecified
+  }
 }