Fixed Issue #465: tests for overriding with NNBD re-named and corrected. New tests added.
diff --git a/LanguageFeatures/nnbd/override_checking_A02_ARGS_t01.dart b/LanguageFeatures/nnbd/override_checking_A02_ARGS_t01.dart
index de516e7..1cd28e6 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_ARGS_t01.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_ARGS_t01.dart
@@ -24,25 +24,11 @@
 void test() {}
 
 class A extends LEGACY_ARGS {
-  void test_int(int? i) {
-    Expect.equals(1, i);
-  }
-
-  void test_object(Object? i) {
-    Expect.equals(1, i);
-  }
-
-  void test_dynamic(dynamic i) {
-    Expect.equals(1, i);
-  }
-
-  void test_function(Function? i) {
-    Expect.equals(test, i);
-  }
-
-  void test_futureOr(FutureOr? i) {
-    Expect.equals(1, i);
-  }
+  void test_int(int? i)           { Expect.equals(1, i); }
+  void test_object(Object? i)     { Expect.equals(1, i); }
+  void test_dynamic(dynamic i)    { Expect.equals(1, i); }
+  void test_function(Function? i) { Expect.equals(test, i); }
+  void test_futureOr(FutureOr? i) { Expect.equals(1, i); }
 }
 
 main() {
diff --git a/LanguageFeatures/nnbd/override_checking_A02_ARGS_t02.dart b/LanguageFeatures/nnbd/override_checking_A02_ARGS_t02.dart
index 6d92b05..efdef7d 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_ARGS_t02.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_ARGS_t02.dart
@@ -22,29 +22,12 @@
 import "override_checking_legacy_lib.dart";
 
 class A extends LEGACY_ARGS {
-  void test_int(int? i) {
-    Expect.isNull(i);
-  }
-
-  void test_object(Object? i) {
-    Expect.isNull(i);
-  }
-
-  void test_dynamic(dynamic i) {
-    Expect.isNull(i);
-  }
-
-  void test_function(Function? i) {
-    Expect.isNull(i);
-  }
-
-  void test_futureOr(FutureOr? i) {
-    Expect.isNull(i);
-  }
-
-  void test_null(Null i) {
-    Expect.isNull(i);
-  }
+  void test_int(int? i)           { Expect.isNull(i); }
+  void test_object(Object? i)     { Expect.isNull(i); }
+  void test_dynamic(dynamic i)    { Expect.isNull(i); }
+  void test_function(Function? i) { Expect.isNull(i); }
+  void test_futureOr(FutureOr? i) { Expect.isNull(i); }
+  void test_null(Null i)          { Expect.isNull(i); }
 }
 
 main() {
diff --git a/LanguageFeatures/nnbd/override_checking_A02_ARGS_t03.dart b/LanguageFeatures/nnbd/override_checking_A02_ARGS_t03.dart
index 39542e7..c54cf65 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_ARGS_t03.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_ARGS_t03.dart
@@ -9,33 +9,28 @@
  * libraries in the super-interface chain, since a legacy library is permitted
  * to override otherwise incompatible signatures for a method.
  *
- * @description Check that compiler error is thrown if opted-in class extends
- * legacy class and child migrated method with non-nullable parameter overrides
- * legacy method which parameter is nullable.
+ * @description Check that if opted-in class extends legacy class child
+ * migrated method with non-nullable parameter can override legacy method.
  *
  * @author iarkh@unipro.ru
  */
 // SharedOptions=--enable-experiment=non-nullable
 
 import "override_checking_legacy_lib.dart";
+import "../../Utils/expect.dart";
 
 class A extends LEGACY_ARGS {
-  void test_int(int i) {}
-//     ^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-
-  void test_object(Object i) {}
-//     ^^^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-
-  void test_function(Function i) {}
-//     ^^^^^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
+  void test_int(int i)           { Expect.equals(1, i); }
+  void test_object(Object i)     { Expect.equals(1, i); }
+  void test_function(Function i) { Expect.equals(testme, i); }
 }
 
-main() {}
+void testme() {}
+
+main() {
+  A a = A();
+
+  a.test_int(1);
+  a.test_object(1);
+  a.test_function(testme);
+}
diff --git a/LanguageFeatures/nnbd/override_checking_A02_ARGS_t04.dart b/LanguageFeatures/nnbd/override_checking_A02_ARGS_t04.dart
index 7840a24..cb63015 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_ARGS_t04.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_ARGS_t04.dart
@@ -21,9 +21,7 @@
 import "override_checking_legacy_lib.dart";
 
 class A extends LEGACY_ARGS {
-  void test_futureOr(FutureOr i) {
-    Expect.equals(1, i);
-  }
+  void test_futureOr(FutureOr i) { Expect.equals(1, i); }
 }
 
 main() {
diff --git a/LanguageFeatures/nnbd/override_checking_A02_ARGS_t05.dart b/LanguageFeatures/nnbd/override_checking_A02_ARGS_t05.dart
index 6ba24bf..fc8c655 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_ARGS_t05.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_ARGS_t05.dart
@@ -21,9 +21,7 @@
 import "override_checking_legacy_lib.dart";
 
 class A extends LEGACY_ARGS {
-  void test_futureOr(FutureOr i) {
-    Expect.isNull(i);
-  }
+  void test_futureOr(FutureOr i) { Expect.isNull(i); }
 }
 
 main() {
diff --git a/LanguageFeatures/nnbd/override_checking_A02_ARGS_t06.dart b/LanguageFeatures/nnbd/override_checking_A02_ARGS_t06.dart
index 19a95b5..0defe30 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_ARGS_t06.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_ARGS_t06.dart
@@ -24,25 +24,11 @@
 void test() {}
 
 class A implements LEGACY_ARGS {
-  void test_int(int? i) {
-    Expect.equals(1, i);
-  }
-
-  void test_object(Object? i) {
-    Expect.equals(1, i);
-  }
-
-  void test_dynamic(dynamic i) {
-    Expect.equals(1, i);
-  }
-
-  void test_function(Function? i) {
-    Expect.equals(test, i);
-  }
-
-  void test_futureOr(FutureOr? i) {
-    Expect.equals(1, i);
-  }
+  void test_int(int? i)           { Expect.equals(1, i); }
+  void test_object(Object? i)     { Expect.equals(1, i); }
+  void test_dynamic(dynamic i)    { Expect.equals(1, i); }
+  void test_function(Function? i) { Expect.equals(test, i); }
+  void test_futureOr(FutureOr? i) { Expect.equals(1, i); }
 
   void test_null(Null i) {}
 }
diff --git a/LanguageFeatures/nnbd/override_checking_A02_ARGS_t07.dart b/LanguageFeatures/nnbd/override_checking_A02_ARGS_t07.dart
index f2eac7a..9511c71 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_ARGS_t07.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_ARGS_t07.dart
@@ -21,29 +21,12 @@
 import "override_checking_legacy_lib.dart";
 
 class A implements LEGACY_ARGS {
-  void test_int(int? i) {
-    Expect.isNull(i);
-  }
-
-  void test_object(Object? i) {
-    Expect.isNull(i);
-  }
-
-  void test_dynamic(dynamic i) {
-    Expect.isNull(i);
-  }
-
-  void test_function(Function? i) {
-    Expect.isNull(i);
-  }
-
-  void test_futureOr(FutureOr? i) {
-    Expect.isNull(i);
-  }
-
-  void test_null(Null i) {
-    Expect.isNull(i);
-  }
+  void test_int(int? i)           { Expect.isNull(i); }
+  void test_object(Object? i)     { Expect.isNull(i); }
+  void test_dynamic(dynamic i)    { Expect.isNull(i); }
+  void test_function(Function? i) { Expect.isNull(i); }
+  void test_futureOr(FutureOr? i) { Expect.isNull(i); }
+  void test_null(Null i)          { Expect.isNull(i); }
 }
 
 main() {
diff --git a/LanguageFeatures/nnbd/override_checking_A02_ARGS_t08.dart b/LanguageFeatures/nnbd/override_checking_A02_ARGS_t08.dart
index 97b8fd9..81c278c 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_ARGS_t08.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_ARGS_t08.dart
@@ -19,26 +19,24 @@
 
 import "dart:async";
 import "override_checking_legacy_lib.dart";
+import "../../Utils/expect.dart";
 
 class A implements LEGACY_ARGS {
-  void test_int(int i) {}
-//     ^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
+  void test_int(int i)           { Expect.equals(1, i); }
+  void test_object(Object i)     { Expect.equals(1, i); }
+  void test_function(Function i) { Expect.equals(testme, i); }
 
-  void test_object(Object i) {}
-//     ^^^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  void test_function(Function i) {}
-//     ^^^^^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  void test_dynamic(dynamic i) {}
+  void test_dynamic(dynamic i)   {}
   void test_futureOr(FutureOr i) {}
-  void test_null(Null i) {}
+  void test_null(Null i)         {}
 }
 
-main() {}
+void testme() {}
+
+main() {
+  A a = A();
+
+  a.test_int(1);
+  a.test_object(1);
+  a.test_function(testme);
+}
diff --git a/LanguageFeatures/nnbd/override_checking_A02_ARGS_t09.dart b/LanguageFeatures/nnbd/override_checking_A02_ARGS_t09.dart
index c306b89..cd30a9a 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_ARGS_t09.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_ARGS_t09.dart
@@ -21,15 +21,13 @@
 import "override_checking_legacy_lib.dart";
 
 class A implements LEGACY_ARGS {
-  void test_futureOr(FutureOr i) {
-    Expect.equals(1, i);
-  }
+  void test_futureOr(FutureOr i) { Expect.equals(1, i); }
 
-  void test_int(int? i) {}
-  void test_object(Object? i) {}
-  void test_dynamic(dynamic i) {}
+  void test_int(int? i)           {}
+  void test_object(Object? i)     {}
+  void test_dynamic(dynamic i)    {}
   void test_function(Function? i) {}
-  void test_null(Null i) {}
+  void test_null(Null i)          {}
 }
 
 main() {
diff --git a/LanguageFeatures/nnbd/override_checking_A02_ARGS_t10.dart b/LanguageFeatures/nnbd/override_checking_A02_ARGS_t10.dart
index 3949c82..dfe129d 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_ARGS_t10.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_ARGS_t10.dart
@@ -21,9 +21,7 @@
 import "override_checking_legacy_lib.dart";
 
 class A implements LEGACY_ARGS {
-  void test_futureOr(FutureOr i) {
-    Expect.isNull(i);
-  }
+  void test_futureOr(FutureOr i) { Expect.isNull(i); }
 
   void test_int(int? i) {}
   void test_object(Object? i) {}
diff --git a/LanguageFeatures/nnbd/override_checking_A02_ARGS_t11.dart b/LanguageFeatures/nnbd/override_checking_A02_ARGS_t11.dart
index 7a05872..a1769e5 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_ARGS_t11.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_ARGS_t11.dart
@@ -24,25 +24,11 @@
 void test() {}
 
 class A with LEGACY_ARGS {
-  void test_int(int? i) {
-    Expect.equals(1, i);
-  }
-
-  void test_object(Object? i) {
-    Expect.equals(1, i);
-  }
-
-  void test_dynamic(dynamic i) {
-    Expect.equals(1, i);
-  }
-
-  void test_function(Function? i) {
-    Expect.equals(test, i);
-  }
-
-  void test_futureOr(FutureOr? i) {
-    Expect.equals(1, i);
-  }
+  void test_int(int? i)           { Expect.equals(1, i);    }
+  void test_object(Object? i)     { Expect.equals(1, i);    }
+  void test_dynamic(dynamic i)    { Expect.equals(1, i);    }
+  void test_function(Function? i) { Expect.equals(test, i); }
+  void test_futureOr(FutureOr? i) { Expect.equals(1, i);    }
 }
 
 main() {
diff --git a/LanguageFeatures/nnbd/override_checking_A02_ARGS_t12.dart b/LanguageFeatures/nnbd/override_checking_A02_ARGS_t12.dart
index feeefec..722cd99 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_ARGS_t12.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_ARGS_t12.dart
@@ -22,29 +22,12 @@
 import "override_checking_legacy_lib.dart";
 
 class A with LEGACY_ARGS {
-  void test_int(int? i) {
-    Expect.isNull(i);
-  }
-
-  void test_object(Object? i) {
-    Expect.isNull(i);
-  }
-
-  void test_dynamic(dynamic i) {
-    Expect.isNull(i);
-  }
-
-  void test_function(Function? i) {
-    Expect.isNull(i);
-  }
-
-  void test_futureOr(FutureOr? i) {
-    Expect.isNull(i);
-  }
-
-  void test_null(Null i) {
-    Expect.isNull(i);
-  }
+  void test_int(int? i)           { Expect.isNull(i); }
+  void test_object(Object? i)     { Expect.isNull(i); }
+  void test_dynamic(dynamic i)    { Expect.isNull(i); }
+  void test_function(Function? i) { Expect.isNull(i); }
+  void test_futureOr(FutureOr? i) { Expect.isNull(i); }
+  void test_null(Null i)          { Expect.isNull(i); }
 }
 
 main() {
diff --git a/LanguageFeatures/nnbd/override_checking_A02_ARGS_t13.dart b/LanguageFeatures/nnbd/override_checking_A02_ARGS_t13.dart
index 14a232a..3ae1496 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_ARGS_t13.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_ARGS_t13.dart
@@ -9,33 +9,28 @@
  * libraries in the super-interface chain, since a legacy library is permitted
  * to override otherwise incompatible signatures for a method.
  *
- * @description Check that compiler error is thrown if opted-in class is a mixin
- * with legacy class and child migrated method with non-nullable parameter
- * overrides legacy method which parameter is nullable.
+ * @description Check that if opted-in class is a mixin with legacy class, child
+ * migrated method with non-nullable parameter can override legacy method.
  *
  * @author iarkh@unipro.ru
  */
 // SharedOptions=--enable-experiment=non-nullable
 
 import "override_checking_legacy_lib.dart";
+import "../../Utils/expect.dart";
 
 class A with LEGACY_ARGS {
-  void test_int(int i) {}
-//     ^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-
-  void test_object(Object i) {}
-//     ^^^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-
-  void test_function(Function i) {}
-//     ^^^^^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
+  void test_int(int i)           { Expect.equals(1, i); }
+  void test_object(Object i)     { Expect.equals(1, i); }
+  void test_function(Function i) { Expect.equals(testme, i); }
 }
 
-main() {}
+void testme() {}
+
+main() {
+  A a = A();
+
+  a.test_int(1);
+  a.test_object(1);
+  a.test_function(testme);
+}
diff --git a/LanguageFeatures/nnbd/override_checking_A02_ARGS_t14.dart b/LanguageFeatures/nnbd/override_checking_A02_ARGS_t14.dart
index b13c53e..fb5ab23 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_ARGS_t14.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_ARGS_t14.dart
@@ -21,9 +21,7 @@
 import "override_checking_legacy_lib.dart";
 
 class A with LEGACY_ARGS {
-  void test_futureOr(FutureOr i) {
-    Expect.equals(1, i);
-  }
+  void test_futureOr(FutureOr i) { Expect.equals(1, i); }
 }
 
 main() {
diff --git a/LanguageFeatures/nnbd/override_checking_A02_ARGS_t15.dart b/LanguageFeatures/nnbd/override_checking_A02_ARGS_t15.dart
index 46b9309..eaa3d61 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_ARGS_t15.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_ARGS_t15.dart
@@ -21,9 +21,7 @@
 import "override_checking_legacy_lib.dart";
 
 class A with LEGACY_ARGS {
-  void test_futureOr(FutureOr i) {
-    Expect.isNull(i);
-  }
+  void test_futureOr(FutureOr i) { Expect.isNull(i); }
 }
 
 main() {
diff --git a/LanguageFeatures/nnbd/override_checking_A02_ARGS_t16.dart b/LanguageFeatures/nnbd/override_checking_A02_ARGS_t16.dart
index bc5a6a2..de2c8cb 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_ARGS_t16.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_ARGS_t16.dart
@@ -33,26 +33,11 @@
 }
 
 class A implements B, LEGACY_ARGS {
-  void test_int(int? i) {
-    Expect.equals(1, i);
-  }
-
-  void test_object(Object? i) {
-    Expect.equals(1, i);
-  }
-
-  void test_dynamic(dynamic i) {
-    Expect.equals(1, i);
-  }
-
-  void test_function(Function? i) {
-    Expect.equals(test, i);
-  }
-
-  void test_futureOr(FutureOr? i) {
-    Expect.equals(1, i);
-  }
-
+  void test_int(int? i)           { Expect.equals(1, i); }
+  void test_object(Object? i)     { Expect.equals(1, i); }
+  void test_dynamic(dynamic i)    { Expect.equals(1, i); }
+  void test_function(Function? i) { Expect.equals(test, i); }
+  void test_futureOr(FutureOr? i) { Expect.equals(1, i); }
   void test_null(Null i) {}
 }
 
diff --git a/LanguageFeatures/nnbd/override_checking_A02_ARGS_t17.dart b/LanguageFeatures/nnbd/override_checking_A02_ARGS_t17.dart
index 48900c0..da56fb7 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_ARGS_t17.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_ARGS_t17.dart
@@ -32,29 +32,12 @@
 }
 
 class A implements B, LEGACY_ARGS {
-  void test_int(int? i) {
-    Expect.isNull(i);
-  }
-
-  void test_object(Object? i) {
-    Expect.isNull(i);
-  }
-
-  void test_dynamic(dynamic i) {
-    Expect.isNull(i);
-  }
-
-  void test_function(Function? i) {
-    Expect.isNull(i);
-  }
-
-  void test_futureOr(FutureOr? i) {
-    Expect.isNull(i);
-  }
-
-  void test_null(Null i) {
-    Expect.isNull(i);
-  }
+  void test_int(int? i) { Expect.isNull(i); }
+  void test_object(Object? i) { Expect.isNull(i); }
+  void test_dynamic(dynamic i) { Expect.isNull(i); }
+  void test_function(Function? i) { Expect.isNull(i); }
+  void test_futureOr(FutureOr? i) { Expect.isNull(i); }
+  void test_null(Null i) { Expect.isNull(i); }
 }
 
 main() {
@@ -65,4 +48,5 @@
   a.test_dynamic(null);
   a.test_function(null);
   a.test_futureOr(null);
+  a.test_null(null);
 }
diff --git a/LanguageFeatures/nnbd/override_checking_A02_ARGS_t18.dart b/LanguageFeatures/nnbd/override_checking_A02_ARGS_t18.dart
index b92e73e..a618aea 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_ARGS_t18.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_ARGS_t18.dart
@@ -9,15 +9,16 @@
  * libraries in the super-interface chain, since a legacy library is permitted
  * to override otherwise incompatible signatures for a method.
  *
- * @description Check that compiler error is thrown if opted-in class implements
- * two classes with some method, the first class is legacy and given method in
- * the second class  has argument of nullable type.
+ * @description Check that if opted-in class implements two classes with some
+ * method and the first class is legacy, child opted in method in the second
+ * class  can have argument of nullable type.
  *
  * @author iarkh@unipro.ru
  */
 // SharedOptions=--enable-experiment=non-nullable
 
 import "dart:async";
+import "../../Utils/expect.dart";
 import "override_checking_legacy_lib.dart";
 
 abstract class B {
@@ -27,26 +28,21 @@
 }
 
 class A implements B, LEGACY_ARGS {
-
-  void test_int(int i) {}
-//     ^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-void test_object(Object i) {}
-//   ^^^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  void test_function(Function i) {}
-//     ^^^^^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
+  void test_int(int i)           { Expect.equals(1, i); }
+  void test_object(Object i)     { Expect.equals(1, i); }
+  void test_function(Function i) { Expect.equals(testme, i); }
 
   void test_futureOr(FutureOr i) {}
-  void test_dynamic(dynamic i) {}
-  void test_null(Null i) {}
+  void test_dynamic(dynamic i)   {}
+  void test_null(Null i)         {}
 }
 
-main() {}
+void testme() {}
+
+main() {
+  A a = A();
+
+  a.test_int(1);
+  a.test_object(1);
+  a.test_function(testme);
+}
diff --git a/LanguageFeatures/nnbd/override_checking_A02_ARGS_t19.dart b/LanguageFeatures/nnbd/override_checking_A02_ARGS_t19.dart
index 5724e27..8512a06 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_ARGS_t19.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_ARGS_t19.dart
@@ -28,15 +28,13 @@
 
 class A implements B, LEGACY_ARGS {
 
-  void test_futureOr(FutureOr? i) {
-    Expect.equals(1, i);
-  }
+  void test_futureOr(FutureOr? i) { Expect.equals(1, i); }
 
-  void test_int(int? i) {}
-  void test_object(Object? i) {}
-  void test_dynamic(dynamic i) {}
+  void test_int(int? i)           {}
+  void test_object(Object? i)     {}
+  void test_dynamic(dynamic i)    {}
   void test_function(Function? i) {}
-  void test_null(Null i) {}
+  void test_null(Null i)          {}
 }
 
 main() {
diff --git a/LanguageFeatures/nnbd/override_checking_A02_ARGS_t20.dart b/LanguageFeatures/nnbd/override_checking_A02_ARGS_t20.dart
index 3ef88e7..2b234f4 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_ARGS_t20.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_ARGS_t20.dart
@@ -28,15 +28,13 @@
 
 class A implements B, LEGACY_ARGS {
 
-  void test_futureOr(FutureOr? i) {
-    Expect.isNull(i);
-  }
+  void test_futureOr(FutureOr? i) { Expect.isNull(i); }
 
-  void test_int(int? i) {}
-  void test_object(Object? i) {}
-  void test_dynamic(dynamic i) {}
+  void test_int(int? i)           {}
+  void test_object(Object? i)     {}
+  void test_dynamic(dynamic i)    {}
   void test_function(Function? i) {}
-  void test_null(Null i) {}
+  void test_null(Null i)          {}
 }
 
 main() {
diff --git a/LanguageFeatures/nnbd/override_checking_A02_FIELD_t02.dart b/LanguageFeatures/nnbd/override_checking_A02_FIELD_t02.dart
index 317e4df..c2eab4c 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_FIELD_t02.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_FIELD_t02.dart
@@ -10,8 +10,7 @@
  * to override otherwise incompatible signatures for a method.
  *
  * @description Check that if opted-in class extends legacy class, opted-in
- * field of non-nullable type cannot override legacy field, compile time error
- * is thrown in this case.
+ * field of non-nullable type can override legacy field.
  *
  * @author iarkh@unipro.ru
 */
@@ -19,92 +18,23 @@
 
 import "dart:async";
 import "override_checking_legacy_lib.dart";
-
-class A1 extends LEGACY_FIELD {
-  int i;
-//    ^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  Object o;
-//       ^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  Function func;
-//         ^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  FutureOr<int> fi;
-//              ^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  FutureOr<Function> ff;
-//                   ^^
-// [analyzer] unspecified
-// [cfe] unspecified
-}
-
-class A2 extends LEGACY_FIELD {
-  int i = null;
-//    ^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  Object o = null;
-//       ^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  Function func = null;
-//         ^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  FutureOr<int> fi = null;
-//              ^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  FutureOr<Function> ff = null;
-//                   ^^
-// [analyzer] unspecified
-// [cfe] unspecified
-}
+import "../../Utils/expect.dart";
 
 void testme() {}
 
-class A3 extends LEGACY_FIELD {
+class A extends LEGACY_FIELD {
   int i = 1;
-//    ^
-// [analyzer] unspecified
-// [cfe] unspecified
-
   Object o = "";
-//       ^
-// [analyzer] unspecified
-// [cfe] unspecified
-
   Function func = testme;
-//         ^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
   FutureOr<int> fi = 12345;
-//              ^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
   FutureOr<Function> ff = testme;
-//                   ^^
-// [analyzer] unspecified
-// [cfe] unspecified
 }
 
 main() {
-  A1();
-  A2();
-  A3();
+  A a = A();
+  Expect.equals(1, a.i);
+  Expect.equals("", a.o);
+  Expect.equals(testme, a.func);
+  Expect.equals(12345, a.fi);
+  Expect.equals(testme, a.ff);
 }
diff --git a/LanguageFeatures/nnbd/override_checking_A02_FIELD_t04.dart b/LanguageFeatures/nnbd/override_checking_A02_FIELD_t04.dart
index f5e9251..8eed77c 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_FIELD_t04.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_FIELD_t04.dart
@@ -10,8 +10,7 @@
  * to override otherwise incompatible signatures for a method.
  *
  * @description Check that if opted-in class implements legacy class, opted-in
- * field of non-nullable type cannot override legacy field, compile time error
- * is thrown in this case.
+ * field of non-nullable type can override legacy field.
  *
  * @author iarkh@unipro.ru
 */
@@ -19,98 +18,16 @@
 
 import "dart:async";
 import "override_checking_legacy_lib.dart";
-
-class A1 implements LEGACY_FIELD {
-  int i;
-//    ^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  Object o;
-//       ^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  Function func;
-//         ^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  FutureOr<int> fi;
-//              ^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  FutureOr<Function> ff;
-//                   ^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  dynamic d;
-  Null n;
-  FutureOr f;
-  void v;
-}
-
-class A2 implements LEGACY_FIELD {
-  int i = null;
-//    ^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  Object o = null;
-//       ^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  Function func = null;
-//         ^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  FutureOr<int> fi = null;
-//              ^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  FutureOr<Function> ff = null;
-//                   ^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  dynamic d = null;
-  Null n = null;
-  FutureOr f = null;
-  void v = null;
-}
+import "../../Utils/expect.dart";
 
 void testme() {}
 
-class A3 implements LEGACY_FIELD {
+class A implements LEGACY_FIELD {
   int i = 1;
-//    ^
-// [analyzer] unspecified
-// [cfe] unspecified
-
   Object o = "";
-//       ^
-// [analyzer] unspecified
-// [cfe] unspecified
-
   Function func = testme;
-//         ^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
   FutureOr<int> fi = 12345;
-//              ^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
   FutureOr<Function> ff = testme;
-//                   ^^
-// [analyzer] unspecified
-// [cfe] unspecified
 
   dynamic d = 1;
   Null n = null;
@@ -119,7 +36,10 @@
 }
 
 main() {
-  A1();
-  A2();
-  A3();
+  A a = A();
+  Expect.equals(1, a.i);
+  Expect.equals("", a.o);
+  Expect.equals(testme, a.func);
+  Expect.equals(12345, a.fi);
+  Expect.equals(testme, a.ff);
 }
diff --git a/LanguageFeatures/nnbd/override_checking_A02_FIELD_t06.dart b/LanguageFeatures/nnbd/override_checking_A02_FIELD_t06.dart
index c2d9ea0..fe0b619 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_FIELD_t06.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_FIELD_t06.dart
@@ -10,8 +10,7 @@
  * to override otherwise incompatible signatures for a method.
  *
  * @description Check that if opted-in class is a mixin with legacy class,
- * opted-in field of non-nullable type cannot override legacy field, compile
- * time error is thrown in this case.
+ * opted-in field of non-nullable type can override legacy field.
  *
  * @author iarkh@unipro.ru
 */
@@ -19,92 +18,23 @@
 
 import "dart:async";
 import "override_checking_legacy_lib.dart";
-
-class A1 with LEGACY_FIELD {
-  int i;
-//    ^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  Object o;
-//       ^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  Function func;
-//         ^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  FutureOr<int> fi;
-//              ^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  FutureOr<Function> ff;
-//                   ^^
-// [analyzer] unspecified
-// [cfe] unspecified
-}
-
-class A2 with LEGACY_FIELD {
-  int i = null;
-//    ^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  Object o = null;
-//       ^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  Function func = null;
-//         ^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  FutureOr<int> fi = null;
-//              ^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  FutureOr<Function> ff = null;
-//                   ^^
-// [analyzer] unspecified
-// [cfe] unspecified
-}
+import "../../Utils/expect.dart";
 
 void testme() {}
 
-class A3 with LEGACY_FIELD {
+class A with LEGACY_FIELD {
   int i = 1;
-//    ^
-// [analyzer] unspecified
-// [cfe] unspecified
-
   Object o = "";
-//       ^
-// [analyzer] unspecified
-// [cfe] unspecified
-
   Function func = testme;
-//         ^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
   FutureOr<int> fi = 12345;
-//              ^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
   FutureOr<Function> ff = testme;
-//                   ^^
-// [analyzer] unspecified
-// [cfe] unspecified
 }
 
 main() {
-  A1();
-  A2();
-  A3();
+  A a = A();
+  Expect.equals(1, a.i);
+  Expect.equals("", a.o);
+  Expect.equals(testme, a.func);
+  Expect.equals(12345, a.fi);
+  Expect.equals(testme, a.ff);
 }
diff --git a/LanguageFeatures/nnbd/override_checking_A02_FIELD_t08.dart b/LanguageFeatures/nnbd/override_checking_A02_FIELD_t08.dart
index bc90403..feb82b4 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_FIELD_t08.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_FIELD_t08.dart
@@ -10,8 +10,8 @@
  * to override otherwise incompatible signatures for a method.
  *
  * @description Check that if opted-in class implements two classes (one is
- * legacy) with some field, opted-in field of non-nullable type cannot override
- * legacy field, compile time error is thrown in this case.
+ * legacy) with some field, opted-in field of non-nullable type can override
+ * legacy field.
  *
  * @author iarkh@unipro.ru
 */
@@ -19,110 +19,25 @@
 
 import "dart:async";
 import "override_checking_legacy_lib.dart";
-
-abstract class AA {
-  int? i;
-  Object? o;
-  dynamic d;
-  Function? func;
-  Null n;
-  FutureOr? f;
-  FutureOr<int>? fi;
-  FutureOr<Function>? ff;
-  void v;
-}
-
-class A1 implements LEGACY_FIELD, AA {
-  int i;
-//    ^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  Object o;
-//       ^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  Function func;
-//         ^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  FutureOr<int> fi;
-//              ^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  FutureOr<Function> ff;
-//                   ^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  dynamic d;
-  Null n;
-  FutureOr f;
-  void v;
-}
-
-class A2 implements LEGACY_FIELD, AA {
-  int i = null;
-//    ^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  Object o = null;
-//       ^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  Function func = null;
-//         ^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  FutureOr<int> fi = null;
-//              ^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  FutureOr<Function> ff = null;
-//                   ^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  dynamic d = null;
-  Null n = null;
-  FutureOr f = null;
-  void v = null;
-}
+import "../../Utils/expect.dart";
 
 void testme() {}
+void testme1() {}
 
-class A3 implements LEGACY_FIELD, AA {
+abstract class AA {
+  int i = -1;
+  Object o = 5;
+  Function func = testme1;
+  FutureOr<int> fi = 2;
+  FutureOr<Function> ff = testme1;
+}
+
+class A implements LEGACY_FIELD, AA {
   int i = 1;
-//    ^
-// [analyzer] unspecified
-// [cfe] unspecified
-
   Object o = "";
-//       ^
-// [analyzer] unspecified
-// [cfe] unspecified
-
   Function func = testme;
-//         ^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
   FutureOr<int> fi = 12345;
-//              ^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
   FutureOr<Function> ff = testme;
-//                   ^^
-// [analyzer] unspecified
-// [cfe] unspecified
 
   dynamic d = 1;
   Null n = null;
@@ -131,7 +46,10 @@
 }
 
 main() {
-  A1();
-  A2();
-  A3();
+  A a = A();
+  Expect.equals(1, a.i);
+  Expect.equals("", a.o);
+  Expect.equals(testme, a.func);
+  Expect.equals(12345, a.fi);
+  Expect.equals(testme, a.ff);
 }
diff --git a/LanguageFeatures/nnbd/override_checking_A02_FIELD_t09.dart b/LanguageFeatures/nnbd/override_checking_A02_FIELD_t09.dart
new file mode 100644
index 0000000..bc057f2
--- /dev/null
+++ b/LanguageFeatures/nnbd/override_checking_A02_FIELD_t09.dart
@@ -0,0 +1,82 @@
+/*
+ * Copyright (c) 2019, 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.
+ */
+/**
+ * @assertion In a migrated library, override checking must check that an
+ * override is consistent with all overridden methods from other migrated
+ * libraries in the super-interface chain, since a legacy library is permitted
+ * to override otherwise incompatible signatures for a method.
+ *
+ * @description Check that if opted-in class extends legacy class, opted-in
+ * field of non-nullable type cannot be [Null] or unassigned, compile time error
+ * is thrown in this case.
+ *
+ * @Issue 39678
+ *
+ * @author iarkh@unipro.ru
+*/
+// SharedOptions=--enable-experiment=non-nullable
+
+import "dart:async";
+import "override_checking_legacy_lib.dart";
+
+class A1 extends LEGACY_FIELD {
+  int i;
+//    ^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  Object o;
+//       ^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  Function func;
+//         ^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  FutureOr<int> fi;
+//              ^^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  FutureOr<Function> ff;
+//                   ^^
+// [analyzer] unspecified
+// [cfe] unspecified
+}
+
+class A2 extends LEGACY_FIELD {
+  int i = null;
+//    ^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  Object o = null;
+//       ^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  Function func = null;
+//         ^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  FutureOr<int> fi = null;
+//              ^^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  FutureOr<Function> ff = null;
+//                   ^^
+// [analyzer] unspecified
+// [cfe] unspecified
+}
+
+main() {
+  A1();
+  A2();
+}
diff --git a/LanguageFeatures/nnbd/override_checking_A02_FIELD_t10.dart b/LanguageFeatures/nnbd/override_checking_A02_FIELD_t10.dart
new file mode 100644
index 0000000..30c52a4
--- /dev/null
+++ b/LanguageFeatures/nnbd/override_checking_A02_FIELD_t10.dart
@@ -0,0 +1,92 @@
+/*
+ * Copyright (c) 2019, 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.
+ */
+/**
+ * @assertion In a migrated library, override checking must check that an
+ * override is consistent with all overridden methods from other migrated
+ * libraries in the super-interface chain, since a legacy library is permitted
+ * to override otherwise incompatible signatures for a method.
+ *
+ * @description Check that if opted-in class implements legacy class, opted-in
+ * field of non-nullable type cannot be [Null] or unassigned, compile time error
+ * is thrown in this case.
+ *
+ * @Issue 39678
+ *
+ * @author iarkh@unipro.ru
+*/
+// SharedOptions=--enable-experiment=non-nullable
+
+import "dart:async";
+import "override_checking_legacy_lib.dart";
+
+class A1 implements LEGACY_FIELD {
+  int i;
+//    ^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  Object o;
+//       ^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  Function func;
+//         ^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  FutureOr<int> fi;
+//              ^^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  FutureOr<Function> ff;
+//                   ^^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  dynamic d;
+  Null n;
+  FutureOr f;
+  void v;
+}
+
+class A2 implements LEGACY_FIELD {
+  int i = null;
+//    ^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  Object o = null;
+//       ^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  Function func = null;
+//         ^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  FutureOr<int> fi = null;
+//              ^^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  FutureOr<Function> ff = null;
+//                   ^^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  dynamic d = null;
+  Null n = null;
+  FutureOr f = null;
+  void v = null;
+}
+
+main() {
+  A1();
+  A2();
+}
diff --git a/LanguageFeatures/nnbd/override_checking_A02_FIELD_t11.dart b/LanguageFeatures/nnbd/override_checking_A02_FIELD_t11.dart
new file mode 100644
index 0000000..4e4df05
--- /dev/null
+++ b/LanguageFeatures/nnbd/override_checking_A02_FIELD_t11.dart
@@ -0,0 +1,82 @@
+/*
+ * Copyright (c) 2019, 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.
+ */
+/**
+ * @assertion In a migrated library, override checking must check that an
+ * override is consistent with all overridden methods from other migrated
+ * libraries in the super-interface chain, since a legacy library is permitted
+ * to override otherwise incompatible signatures for a method.
+ *
+ * @description Check that if opted-in class is a mixin with legacy class,
+ * opted-in field of non-nullable type cannot be [Null] or unassigned, compile
+ * time error is thrown in this case.
+ *
+ * @Issue 39678
+ *
+ * @author iarkh@unipro.ru
+*/
+// SharedOptions=--enable-experiment=non-nullable
+
+import "dart:async";
+import "override_checking_legacy_lib.dart";
+
+class A1 with LEGACY_FIELD {
+  int i;
+//    ^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  Object o;
+//       ^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  Function func;
+//         ^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  FutureOr<int> fi;
+//              ^^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  FutureOr<Function> ff;
+//                   ^^
+// [analyzer] unspecified
+// [cfe] unspecified
+}
+
+class A2 with LEGACY_FIELD {
+  int i = null;
+//    ^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  Object o = null;
+//       ^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  Function func = null;
+//         ^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  FutureOr<int> fi = null;
+//              ^^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  FutureOr<Function> ff = null;
+//                   ^^
+// [analyzer] unspecified
+// [cfe] unspecified
+}
+
+main() {
+  A1();
+  A2();
+}
diff --git a/LanguageFeatures/nnbd/override_checking_A02_FIELD_t12.dart b/LanguageFeatures/nnbd/override_checking_A02_FIELD_t12.dart
new file mode 100644
index 0000000..6e87e80
--- /dev/null
+++ b/LanguageFeatures/nnbd/override_checking_A02_FIELD_t12.dart
@@ -0,0 +1,102 @@
+/*
+ * Copyright (c) 2019, 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.
+ */
+/**
+ * @assertion In a migrated library, override checking must check that an
+ * override is consistent with all overridden methods from other migrated
+ * libraries in the super-interface chain, since a legacy library is permitted
+ * to override otherwise incompatible signatures for a method.
+ *
+ * @description Check that if opted-in class implements two classes (one is
+ * legacy) with some field, opted-in field of non-nullable type cannot override
+ * legacy field, compile time error is thrown in this case.
+ *
+ *  @Issue 39678
+ *
+ * @author iarkh@unipro.ru
+*/
+// SharedOptions=--enable-experiment=non-nullable
+
+import "dart:async";
+import "override_checking_legacy_lib.dart";
+
+void testme() {}
+
+abstract class AA {
+  int i = -1;
+  Object o = 5;
+  Function func = testme;
+  FutureOr<int> fi = -1;
+  FutureOr<Function> ff = testme;
+}
+
+class A1 implements LEGACY_FIELD, AA {
+  int i;
+//    ^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  Object o;
+//       ^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  Function func;
+//         ^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  FutureOr<int> fi;
+//              ^^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  FutureOr<Function> ff;
+//                   ^^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  dynamic d;
+  Null n;
+  FutureOr f;
+  void v;
+}
+
+class A2 implements LEGACY_FIELD, AA {
+  int i = null;
+//    ^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  Object o = null;
+//       ^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  Function func = null;
+//         ^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  FutureOr<int> fi = null;
+//              ^^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  FutureOr<Function> ff = null;
+//                   ^^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  dynamic d = null;
+  Null n = null;
+  FutureOr f = null;
+  void v = null;
+}
+
+main() {
+  A1();
+  A2();
+}
diff --git a/LanguageFeatures/nnbd/override_checking_A02_REQ_ARGS_t01.dart b/LanguageFeatures/nnbd/override_checking_A02_REQ_ARGS_t01.dart
index 3f21d5e..093e86e 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_REQ_ARGS_t01.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_REQ_ARGS_t01.dart
@@ -21,13 +21,8 @@
 import "override_checking_legacy_lib.dart";
 
 class A extends LEGACY_REQUIRED_ARGS {
-  void test_default({required int? i}) {
-    Expect.equals(1, i);
-  }
-
-  void test_nondefault({required int? i}) {
-    Expect.equals(1, i);
-  }
+  void test_default({required int? i}) { Expect.equals(1, i); }
+  void test_nondefault({required int? i}) { Expect.equals(1, i); }
 }
 
 main() {
diff --git a/LanguageFeatures/nnbd/override_checking_A02_REQ_ARGS_t03.dart b/LanguageFeatures/nnbd/override_checking_A02_REQ_ARGS_t03.dart
index 0985941..01eb667 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_REQ_ARGS_t03.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_REQ_ARGS_t03.dart
@@ -21,13 +21,8 @@
 import "override_checking_legacy_lib.dart";
 
 class A implements LEGACY_REQUIRED_ARGS {
-  void test_default({required int? i}) {
-    Expect.equals(1, i);
-  }
-
-  void test_nondefault({required int? i}) {
-    Expect.equals(1, i);
-  }
+  void test_default({required int? i})    { Expect.equals(1, i); }
+  void test_nondefault({required int? i}) { Expect.equals(1, i); }
 }
 
 main() {
diff --git a/LanguageFeatures/nnbd/override_checking_A02_REQ_ARGS_t05.dart b/LanguageFeatures/nnbd/override_checking_A02_REQ_ARGS_t05.dart
index d15f75c..7fa470c 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_REQ_ARGS_t05.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_REQ_ARGS_t05.dart
@@ -21,13 +21,8 @@
 import "override_checking_legacy_lib.dart";
 
 class A with LEGACY_REQUIRED_ARGS {
-  void test_default({required int? i}) {
-    Expect.equals(1, i);
-  }
-
-  void test_nondefault({required int? i}) {
-    Expect.equals(1, i);
-  }
+  void test_default({required int? i})    { Expect.equals(1, i); }
+  void test_nondefault({required int? i}) { Expect.equals(1, i); }
 }
 
 main() {
diff --git a/LanguageFeatures/nnbd/override_checking_A02_REQ_ARGS_t07.dart b/LanguageFeatures/nnbd/override_checking_A02_REQ_ARGS_t07.dart
index fcea360..bf9e4b9 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_REQ_ARGS_t07.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_REQ_ARGS_t07.dart
@@ -26,13 +26,8 @@
 }
 
 class A implements B, LEGACY_REQUIRED_ARGS {
-  void test_default({required int? i}) {
-    Expect.equals(1, i);
-  }
-
-  void test_nondefault({required int? i}) {
-    Expect.equals(1, i);
-  }
+  void test_default({required int? i})    { Expect.equals(1, i); }
+  void test_nondefault({required int? i}) { Expect.equals(1, i); }
 }
 
 main() {
diff --git a/LanguageFeatures/nnbd/override_checking_A02_REQ_ARGS_t08.dart b/LanguageFeatures/nnbd/override_checking_A02_REQ_ARGS_t08.dart
index 0f3f351..1efe137 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_REQ_ARGS_t08.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_REQ_ARGS_t08.dart
@@ -20,7 +20,7 @@
 import "override_checking_legacy_lib.dart";
 
 abstract class B {
-  void test_default({required int? i}) {}
+  void test_default({required int? i})    {}
   void test_nondefault({required int? i}) {}
 }
 
diff --git a/LanguageFeatures/nnbd/override_checking_A02_REQ_ARGS_t15.dart b/LanguageFeatures/nnbd/override_checking_A02_REQ_ARGS_t15.dart
index 567ab6b..66c3c80 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_REQ_ARGS_t15.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_REQ_ARGS_t15.dart
@@ -19,11 +19,10 @@
  */
 // SharedOptions=--enable-experiment=non-nullable
 
-import "../../Utils/expect.dart";
 import "override_checking_legacy_lib.dart";
 
 abstract class B {
-  void test_default({required int i}) {}
+  void test_default({required int i})    {}
   void test_nondefault({required int i}) {}
 }
 
diff --git a/LanguageFeatures/nnbd/override_checking_A02_REQ_ARGS_t16.dart b/LanguageFeatures/nnbd/override_checking_A02_REQ_ARGS_t16.dart
index 6834de9..95e2eb9 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_REQ_ARGS_t16.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_REQ_ARGS_t16.dart
@@ -21,7 +21,7 @@
 import "override_checking_legacy_lib.dart";
 
 abstract class B {
-  void test_default({required int i}) {}
+  void test_default({required int i})    {}
   void test_nondefault({required int i}) {}
 }
 
diff --git a/LanguageFeatures/nnbd/override_checking_A02_RETURN_t13.dart b/LanguageFeatures/nnbd/override_checking_A02_RETURN_t13.dart
index 74bd4cd..27ba7bb 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_RETURN_t13.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_RETURN_t13.dart
@@ -9,14 +9,15 @@
  * libraries in the super-interface chain, since a legacy library is permitted
  * to override otherwise incompatible signatures for a method.
  *
- * @description Check that if opted-in class extends legacy class, migrated
- * method with [Never] return value can override legacy method.
+ * @description Check that if opted-in class extends legacy class, child
+ * migrated method can have [Never] return value.
  *
  * @author iarkh@unipro.ru
  */
 // SharedOptions=--enable-experiment=non-nullable
 
 import "override_checking_legacy_lib.dart";
+import "../../Utils/expect.dart";
 
 class A extends LEGACY_RETURN {
   Never getInt()              => throw "It's impossible!";
@@ -30,5 +31,14 @@
 }
 
 main() {
-  A();
+  A a = A();
+
+  Expect.throws(() { a.getInt(); });
+  Expect.throws(() { a.getObject(); });
+  Expect.throws(() { a.getDynamic(); });
+  Expect.throws(() { a.getFunction(); });
+  Expect.throws(() { a.getNull(); });
+  Expect.throws(() { a.getFutureOr(); });
+  Expect.throws(() { a.getFutureOrInt(); });
+  Expect.throws(() { a.getFutureOrFunction(); });
 }
diff --git a/LanguageFeatures/nnbd/override_checking_A02_RETURN_t14.dart b/LanguageFeatures/nnbd/override_checking_A02_RETURN_t14.dart
index b44661e..7ac57f4 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_RETURN_t14.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_RETURN_t14.dart
@@ -9,17 +9,17 @@
  * libraries in the super-interface chain, since a legacy library is permitted
  * to override otherwise incompatible signatures for a method.
  *
- * @description Check that if opted-in class extends legacy class, child
- * migrated method with [Never] return value cannot be called and compile error
- * is thrown in this case.
+ * @description Check that if opted-in class is a mixin with legacy class,
+ * migrated method with [Never] return value can override legacy method.
  *
  * @author iarkh@unipro.ru
  */
 // SharedOptions=--enable-experiment=non-nullable
 
 import "override_checking_legacy_lib.dart";
+import "../../Utils/expect.dart";
 
-class A extends LEGACY_RETURN {
+class A with LEGACY_RETURN {
   Never getInt()              => throw "It's impossible!";
   Never getObject()           => throw "It's impossible!";
   Never getDynamic()          => throw "It's impossible!";
@@ -33,43 +33,12 @@
 main() {
   A a = A();
 
-  a.getInt();
-//  ^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  a.getObject();
-//  ^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  a.getDynamic();
-//  ^^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  a.getFunction();
-//  ^^^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  a.getNull();
-//  ^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  a.getFutureOr();
-//  ^^^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  a.getFutureOrInt();
-//  ^^^^^^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  a.getFutureOrFunction();
-//  ^^^^^^^^^^^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
+  Expect.throws(() { a.getInt(); });
+  Expect.throws(() { a.getObject(); });
+  Expect.throws(() { a.getDynamic(); });
+  Expect.throws(() { a.getFunction(); });
+  Expect.throws(() { a.getNull(); });
+  Expect.throws(() { a.getFutureOr(); });
+  Expect.throws(() { a.getFutureOrInt(); });
+  Expect.throws(() { a.getFutureOrFunction(); });
 }
diff --git a/LanguageFeatures/nnbd/override_checking_A02_RETURN_t15.dart b/LanguageFeatures/nnbd/override_checking_A02_RETURN_t15.dart
index 5d876a6..e0b92fa 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_RETURN_t15.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_RETURN_t15.dart
@@ -9,16 +9,17 @@
  * libraries in the super-interface chain, since a legacy library is permitted
  * to override otherwise incompatible signatures for a method.
  *
- * @description Check that if opted-in class implements legacy class, migrated
- * method with [Never] return value can override legacy method.
+ * @description Check that if opted-in class is a mixin with legacy class, child
+ * migrated method can have [Never] return value.
  *
  * @author iarkh@unipro.ru
  */
 // SharedOptions=--enable-experiment=non-nullable
 
 import "override_checking_legacy_lib.dart";
+import "../../Utils/expect.dart";
 
-class A implements LEGACY_RETURN {
+class A with LEGACY_RETURN {
   Never getInt()              => throw "It's impossible!";
   Never getObject()           => throw "It's impossible!";
   Never getDynamic()          => throw "It's impossible!";
@@ -30,5 +31,14 @@
 }
 
 main() {
-  A();
+  A a = A();
+
+  Expect.throws(() { a.getInt(); });
+  Expect.throws(() { a.getObject(); });
+  Expect.throws(() { a.getDynamic(); });
+  Expect.throws(() { a.getFunction(); });
+  Expect.throws(() { a.getNull(); });
+  Expect.throws(() { a.getFutureOr(); });
+  Expect.throws(() { a.getFutureOrInt(); });
+  Expect.throws(() { a.getFutureOrFunction(); });
 }
diff --git a/LanguageFeatures/nnbd/override_checking_A02_RETURN_t16.dart b/LanguageFeatures/nnbd/override_checking_A02_RETURN_t16.dart
index 0343e52..35b7636 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_RETURN_t16.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_RETURN_t16.dart
@@ -9,17 +9,29 @@
  * libraries in the super-interface chain, since a legacy library is permitted
  * to override otherwise incompatible signatures for a method.
  *
- * @description Check that if opted-in class implements legacy class, child
- * migrated method with [Never] return value cannot be called and compile error
- * is thrown in this case.
+ * @description Check that if opted-in class implements two classes (one is
+ * legacy), child migrated method can have [Never] return value.
  *
  * @author iarkh@unipro.ru
  */
 // SharedOptions=--enable-experiment=non-nullable
 
+import "dart:async";
 import "override_checking_legacy_lib.dart";
+import "../../Utils/expect.dart";
 
-class A implements LEGACY_RETURN {
+abstract class AA {
+  int? getInt();
+  Object? getObject();
+  dynamic getDynamic();
+  Function? getFunction();
+  Null getNull();
+  FutureOr getFutureOr();
+  FutureOr<int>? getFutureOrInt();
+  FutureOr<Function>? getFutureOrFunction();
+}
+
+class A implements AA, LEGACY_RETURN {
   Never getInt()              => throw "It's impossible!";
   Never getObject()           => throw "It's impossible!";
   Never getDynamic()          => throw "It's impossible!";
@@ -33,43 +45,12 @@
 main() {
   A a = A();
 
-  a.getInt();
-//  ^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  a.getObject();
-//  ^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  a.getDynamic();
-//  ^^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  a.getFunction();
-//  ^^^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  a.getNull();
-//  ^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  a.getFutureOr();
-//  ^^^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  a.getFutureOrInt();
-//  ^^^^^^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  a.getFutureOrFunction();
-//  ^^^^^^^^^^^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
+  Expect.throws(() { a.getInt(); });
+  Expect.throws(() { a.getObject(); });
+  Expect.throws(() { a.getDynamic(); });
+  Expect.throws(() { a.getFunction(); });
+  Expect.throws(() { a.getNull(); });
+  Expect.throws(() { a.getFutureOr(); });
+  Expect.throws(() { a.getFutureOrInt(); });
+  Expect.throws(() { a.getFutureOrFunction(); });
 }
diff --git a/LanguageFeatures/nnbd/override_checking_A02_RETURN_t17.dart b/LanguageFeatures/nnbd/override_checking_A02_RETURN_t17.dart
deleted file mode 100644
index a3c1049..0000000
--- a/LanguageFeatures/nnbd/override_checking_A02_RETURN_t17.dart
+++ /dev/null
@@ -1,34 +0,0 @@
-/*
- * Copyright (c) 2019, 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.
- */
-/**
- * @assertion In a migrated library, override checking must check that an
- * override is consistent with all overridden methods from other migrated
- * libraries in the super-interface chain, since a legacy library is permitted
- * to override otherwise incompatible signatures for a method.
- *
- * @description Check that if opted-in class is a mixin with legacy class,
- * migrated method with [Never] return value can override legacy method.
- *
- * @author iarkh@unipro.ru
- */
-// SharedOptions=--enable-experiment=non-nullable
-
-import "override_checking_legacy_lib.dart";
-
-class A with LEGACY_RETURN {
-  Never getInt()              => throw "It's impossible!";
-  Never getObject()           => throw "It's impossible!";
-  Never getDynamic()          => throw "It's impossible!";
-  Never getFunction()         => throw "It's impossible!";
-  Never getNull()             => throw "It's impossible!";
-  Never getFutureOr()         => throw "It's impossible!";
-  Never getFutureOrInt()      => throw "It's impossible!";
-  Never getFutureOrFunction() => throw "It's impossible!";
-}
-
-main() {
-  A();
-}
diff --git a/LanguageFeatures/nnbd/override_checking_A02_RETURN_t18.dart b/LanguageFeatures/nnbd/override_checking_A02_RETURN_t18.dart
deleted file mode 100644
index bf86233..0000000
--- a/LanguageFeatures/nnbd/override_checking_A02_RETURN_t18.dart
+++ /dev/null
@@ -1,75 +0,0 @@
-/*
- * Copyright (c) 2019, 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.
- */
-/**
- * @assertion In a migrated library, override checking must check that an
- * override is consistent with all overridden methods from other migrated
- * libraries in the super-interface chain, since a legacy library is permitted
- * to override otherwise incompatible signatures for a method.
- *
- * @description Check that if opted-in class ia a mixin with legacy class, child
- * migrated method with [Never] return value cannot be called and compile error
- * is thrown in this case.
- *
- * @author iarkh@unipro.ru
- */
-// SharedOptions=--enable-experiment=non-nullable
-
-import "override_checking_legacy_lib.dart";
-
-class A with LEGACY_RETURN {
-  Never getInt()              => throw "It's impossible!";
-  Never getObject()           => throw "It's impossible!";
-  Never getDynamic()          => throw "It's impossible!";
-  Never getFunction()         => throw "It's impossible!";
-  Never getNull()             => throw "It's impossible!";
-  Never getFutureOr()         => throw "It's impossible!";
-  Never getFutureOrInt()      => throw "It's impossible!";
-  Never getFutureOrFunction() => throw "It's impossible!";
-}
-
-main() {
-  A a = A();
-
-  a.getInt();
-//  ^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  a.getObject();
-//  ^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  a.getDynamic();
-//  ^^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  a.getFunction();
-//  ^^^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  a.getNull();
-//  ^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  a.getFutureOr();
-//  ^^^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  a.getFutureOrInt();
-//  ^^^^^^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  a.getFutureOrFunction();
-//  ^^^^^^^^^^^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-}
diff --git a/LanguageFeatures/nnbd/override_checking_A02_RETURN_t19.dart b/LanguageFeatures/nnbd/override_checking_A02_RETURN_t19.dart
deleted file mode 100644
index affe857..0000000
--- a/LanguageFeatures/nnbd/override_checking_A02_RETURN_t19.dart
+++ /dev/null
@@ -1,46 +0,0 @@
-/*
- * Copyright (c) 2019, 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.
- */
-/**
- * @assertion In a migrated library, override checking must check that an
- * override is consistent with all overridden methods from other migrated
- * libraries in the super-interface chain, since a legacy library is permitted
- * to override otherwise incompatible signatures for a method.
- *
- * @description Check that if opted-in class implements two classes (one is
- * legacy), migrated method with [Never] return value can override legacy method.
- *
- * @author iarkh@unipro.ru
- */
-// SharedOptions=--enable-experiment=non-nullable
-
-import "dart:async";
-import "override_checking_legacy_lib.dart";
-
-abstract class AA {
-  int? getInt();
-  Object? getObject();
-  dynamic getDynamic();
-  Function? getFunction();
-  Null getNull();
-  FutureOr getFutureOr();
-  FutureOr<int>? getFutureOrInt();
-  FutureOr<Function>? getFutureOrFunction();
-}
-
-class A implements AA, LEGACY_RETURN {
-  Never getInt()              => throw "It's impossible!";
-  Never getObject()           => throw "It's impossible!";
-  Never getDynamic()          => throw "It's impossible!";
-  Never getFunction()         => throw "It's impossible!";
-  Never getNull()             => throw "It's impossible!";
-  Never getFutureOr()         => throw "It's impossible!";
-  Never getFutureOrInt()      => throw "It's impossible!";
-  Never getFutureOrFunction() => throw "It's impossible!";
-}
-
-main() {
-  A();
-}
diff --git a/LanguageFeatures/nnbd/override_checking_A02_RETURN_t20.dart b/LanguageFeatures/nnbd/override_checking_A02_RETURN_t20.dart
deleted file mode 100644
index c4cf300..0000000
--- a/LanguageFeatures/nnbd/override_checking_A02_RETURN_t20.dart
+++ /dev/null
@@ -1,87 +0,0 @@
-/*
- * Copyright (c) 2019, 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.
- */
-/**
- * @assertion In a migrated library, override checking must check that an
- * override is consistent with all overridden methods from other migrated
- * libraries in the super-interface chain, since a legacy library is permitted
- * to override otherwise incompatible signatures for a method.
- *
- * @description Check that if opted-in class implements two classes (one is
- * legacy), child migrated method with [Never] return value cannot be called and
- * compile error is thrown in this case.
- *
- * @author iarkh@unipro.ru
- */
-// SharedOptions=--enable-experiment=non-nullable
-
-import "dart:async";
-import "override_checking_legacy_lib.dart";
-
-abstract class AA {
-  int? getInt();
-  Object? getObject();
-  dynamic getDynamic();
-  Function? getFunction();
-  Null getNull();
-  FutureOr getFutureOr();
-  FutureOr<int>? getFutureOrInt();
-  FutureOr<Function>? getFutureOrFunction();
-}
-
-class A implements AA, LEGACY_RETURN {
-  Never getInt()              => throw "It's impossible!";
-  Never getObject()           => throw "It's impossible!";
-  Never getDynamic()          => throw "It's impossible!";
-  Never getFunction()         => throw "It's impossible!";
-  Never getNull()             => throw "It's impossible!";
-  Never getFutureOr()         => throw "It's impossible!";
-  Never getFutureOrInt()      => throw "It's impossible!";
-  Never getFutureOrFunction() => throw "It's impossible!";
-}
-
-main() {
-  A a = A();
-
-  a.getInt();
-//  ^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  a.getObject();
-//  ^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  a.getDynamic();
-//  ^^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  a.getFunction();
-//  ^^^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  a.getNull();
-//  ^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  a.getFutureOr();
-//  ^^^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  a.getFutureOrInt();
-//  ^^^^^^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  a.getFutureOrFunction();
-//  ^^^^^^^^^^^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-}
diff --git a/LanguageFeatures/nnbd/override_checking_A02_SETTER_t01.dart b/LanguageFeatures/nnbd/override_checking_A02_SETTER_t01.dart
index e0c985e..b68fabd 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_SETTER_t01.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_SETTER_t01.dart
@@ -23,36 +23,14 @@
 void testme() {}
 
 class A extends LEGACY_SETTER {
-  void set setInt(int? i) {
-    Expect.equals(1, i);
-  }
-
-  void set setObject(Object? o) {
-    Expect.equals(1, o);
-  }
-
-  void set setDynamic(dynamic? d) {
-    Expect.equals(1, d);
-  }
-
-  void set setNull(Null? n) {
-    Expect.isNull(n);
-  }
-
-  void set setFunction(Function? f) {
-    Expect.equals(testme, f);
-  }
-  void set setFutureOr(FutureOr? f) {
-    Expect.equals(1, f);
-  }
-
-  void set setFutureOrInt(FutureOr<int>? f) {
-    Expect.equals(1, f);
-  }
-
-  void set setFutureOrFunction(FutureOr<Function>? f) {
-    Expect.equals(testme, f);
-  }
+  void set setInt(int? i)                             { Expect.equals(1, i);      }
+  void set setObject(Object? o)                       { Expect.equals(1, o);      }
+  void set setDynamic(dynamic? d)                     { Expect.equals(1, d);      }
+  void set setNull(Null? n)                           { Expect.isNull(n);         }
+  void set setFunction(Function? f)                   { Expect.equals(testme, f); }
+  void set setFutureOr(FutureOr? f)                   { Expect.equals(1, f);      }
+  void set setFutureOrInt(FutureOr<int>? f)           { Expect.equals(1, f);      }
+  void set setFutureOrFunction(FutureOr<Function>? f) { Expect.equals(testme, f); }
 }
 
 main() {
diff --git a/LanguageFeatures/nnbd/override_checking_A02_SETTER_t02.dart b/LanguageFeatures/nnbd/override_checking_A02_SETTER_t02.dart
index 61a3684..27ae828 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_SETTER_t02.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_SETTER_t02.dart
@@ -21,37 +21,14 @@
 import "override_checking_legacy_lib.dart";
 
 class A extends LEGACY_SETTER {
-  void set setInt(int? i) {
-    Expect.isNull(i);
-  }
-
-  void set setObject(Object? o) {
-    Expect.isNull(o);
-  }
-
-  void set setDynamic(dynamic d) {
-    Expect.isNull(d);
-  }
-
-  void set setNull(Null n) {
-    Expect.isNull(n);
-  }
-
-  void set setFunction(Function? f) {
-    Expect.isNull(f);
-  }
-
-  void set setFutureOr(FutureOr f) {
-    Expect.isNull(f);
-  }
-
-  void set setFutureOrInt(FutureOr<int>? f) {
-    Expect.isNull(f);
-  }
-
-  void set setFutureOrFunction(FutureOr<Function>? f) {
-    Expect.isNull(f);
-  }
+  void set setInt(int? i)                             { Expect.isNull(i); }
+  void set setObject(Object? o)                       { Expect.isNull(o); }
+  void set setDynamic(dynamic d)                      { Expect.isNull(d); }
+  void set setNull(Null n)                            { Expect.isNull(n); }
+  void set setFunction(Function? f)                   { Expect.isNull(f); }
+  void set setFutureOr(FutureOr f)                    { Expect.isNull(f); }
+  void set setFutureOrInt(FutureOr<int>? f)           { Expect.isNull(f); }
+  void set setFutureOrFunction(FutureOr<Function>? f) { Expect.isNull(f); }
 }
 
 main() {
diff --git a/LanguageFeatures/nnbd/override_checking_A02_SETTER_t03.dart b/LanguageFeatures/nnbd/override_checking_A02_SETTER_t03.dart
index cac3350..b6eda98 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_SETTER_t03.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_SETTER_t03.dart
@@ -10,8 +10,7 @@
  * to override otherwise incompatible signatures for a method.
  *
  * @description Check that if opted-in class extends legacy class, opted-in
- * setter cannot have non-nullable argument and compile error is thrown in this
- * case.
+ * setter can have non-nullable argument.
  *
  * @author iarkh@unipro.ru
  */
@@ -19,39 +18,24 @@
 
 import "dart:async";
 import "override_checking_legacy_lib.dart";
+import "../../Utils/expect.dart";
+
+void testme() {}
 
 class A extends LEGACY_SETTER {
-  void set setInt(int i) {}
-//         ^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-
-  void set setObject(Object o) {}
-//         ^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  void set setFunction(Function f) {}
-//         ^^^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  void set setFutureOrInt(FutureOr<int> f) {}
-//         ^^^^^^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  void set setFutureOrFunction(FutureOr<Function> f) {}
-//         ^^^^^^^^^^^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  void set setDynamic(dynamic d) {}
-  void set setNull(Null n) {}
-  void set setFutureOr(FutureOr f) {}
+  void set setInt(int? i)                             { Expect.equals(1, i);      }
+  void set setObject(Object? o)                       { Expect.equals(1, o);      }
+  void set setFunction(Function? f)                   { Expect.equals(testme, f); }
+  void set setFutureOrInt(FutureOr<int>? f)           { Expect.equals(1, f);      }
+  void set setFutureOrFunction(FutureOr<Function>? f) { Expect.equals(testme, f); }
 }
 
 main() {
-  A();
+  A a = A();
+
+  a.setInt = 1;
+  a.setObject = 1;
+  a.setFunction = testme;
+  a.setFutureOrInt = 1;
+  a.setFutureOrFunction = testme;
 }
diff --git a/LanguageFeatures/nnbd/override_checking_A02_SETTER_t04.dart b/LanguageFeatures/nnbd/override_checking_A02_SETTER_t04.dart
index b86d7fc..a8d5563 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_SETTER_t04.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_SETTER_t04.dart
@@ -23,36 +23,14 @@
 void testme() {}
 
 class A implements LEGACY_SETTER {
-  void set setInt(int? i) {
-  Expect.equals(1, i);
-  }
-
-  void set setObject(Object? o) {
-  Expect.equals(1, o);
-  }
-
-  void set setDynamic(dynamic? d) {
-  Expect.equals(1, d);
-  }
-
-  void set setNull(Null? n) {
-  Expect.isNull(n);
-  }
-
-  void set setFunction(Function? f) {
-  Expect.equals(testme, f);
-  }
-  void set setFutureOr(FutureOr? f) {
-  Expect.equals(1, f);
-  }
-
-  void set setFutureOrInt(FutureOr<int>? f) {
-  Expect.equals(1, f);
-  }
-
-  void set setFutureOrFunction(FutureOr<Function>? f) {
-  Expect.equals(testme, f);
-  }
+  void set setInt(int? i)                             { Expect.equals(1, i);      }
+  void set setObject(Object? o)                       { Expect.equals(1, o);      }
+  void set setDynamic(dynamic? d)                     { Expect.equals(1, d);      }
+  void set setNull(Null? n)                           { Expect.isNull(n);         }
+  void set setFunction(Function? f)                   { Expect.equals(testme, f); }
+  void set setFutureOr(FutureOr? f)                   { Expect.equals(1, f);      }
+  void set setFutureOrInt(FutureOr<int>? f)           { Expect.equals(1, f);      }
+  void set setFutureOrFunction(FutureOr<Function>? f) { Expect.equals(testme, f); }
 }
 
 main() {
diff --git a/LanguageFeatures/nnbd/override_checking_A02_SETTER_t05.dart b/LanguageFeatures/nnbd/override_checking_A02_SETTER_t05.dart
index cfc0011..0308332 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_SETTER_t05.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_SETTER_t05.dart
@@ -21,36 +21,14 @@
 import "override_checking_legacy_lib.dart";
 
 class A implements LEGACY_SETTER {
-  void set setInt(int? i) {
-    Expect.isNull(i);
-  }
-
-  void set setObject(Object? o) {
-    Expect.isNull(o);
-  }
-
-  void set setDynamic(dynamic d) {
-    Expect.isNull(d);
-  }
-
-  void set setNull(Null n) {
-    Expect.isNull(n);
-  }
-
-  void set setFunction(Function? f) {
-    Expect.isNull(f);
-  }
-  void set setFutureOr(FutureOr f) {
-    Expect.isNull(f);
-  }
-
-  void set setFutureOrInt(FutureOr<int>? f) {
-    Expect.isNull(f);
-  }
-
-  void set setFutureOrFunction(FutureOr<Function>? f) {
-    Expect.isNull(f);
-  }
+  void set setInt(int? i)                             { Expect.isNull(i); }
+  void set setObject(Object? o)                       { Expect.isNull(o); }
+  void set setDynamic(dynamic d)                      { Expect.isNull(d); }
+  void set setNull(Null n)                            { Expect.isNull(n); }
+  void set setFunction(Function? f)                   { Expect.isNull(f); }
+  void set setFutureOr(FutureOr f)                    { Expect.isNull(f); }
+  void set setFutureOrInt(FutureOr<int>? f)           { Expect.isNull(f); }
+  void set setFutureOrFunction(FutureOr<Function>? f) { Expect.isNull(f); }
 }
 
 main() {
diff --git a/LanguageFeatures/nnbd/override_checking_A02_SETTER_t06.dart b/LanguageFeatures/nnbd/override_checking_A02_SETTER_t06.dart
index 3b508b6..0fbf503 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_SETTER_t06.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_SETTER_t06.dart
@@ -10,7 +10,7 @@
  * to override otherwise incompatible signatures for a method.
  *
  * @description Check that if opted-in class implements legacy class, child
- * opted-in setter cannot have non-nullable argument.
+ * opted-in setter can have non-nullable argument.
  *
  * @author iarkh@unipro.ru
  */
@@ -18,39 +18,28 @@
 
 import "dart:async";
 import "override_checking_legacy_lib.dart";
+import "../../Utils/expect.dart";
+
+void testme() {}
 
 class A implements LEGACY_SETTER {
-  void set setInt(int i) {}
-//         ^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
+  void set setInt(int? i)                             { Expect.equals(1, i);      }
+  void set setObject(Object? o)                       { Expect.equals(1, o);      }
+  void set setFunction(Function? f)                   { Expect.equals(testme, f); }
+  void set setFutureOrInt(FutureOr<int>? f)           { Expect.equals(1, f);      }
+  void set setFutureOrFunction(FutureOr<Function>? f) { Expect.equals(testme, f); }
 
-
-  void set setObject(Object o) {}
-//         ^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  void set setFunction(Function f) {}
-//         ^^^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  void set setFutureOrInt(FutureOr<int> f) {}
-//         ^^^^^^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  void set setFutureOrFunction(FutureOr<Function> f) {}
-//         ^^^^^^^^^^^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  void set setDynamic(dynamic d) {}
-  void set setNull(Null n) {}
+  void set setDynamic(dynamic d)   {}
+  void set setNull(Null n)         {}
   void set setFutureOr(FutureOr f) {}
 }
 
 main() {
-  A();
+  A a = A();
+
+  a.setInt = 1;
+  a.setObject = 1;
+  a.setFunction = testme;
+  a.setFutureOrInt = 1;
+  a.setFutureOrFunction = testme;
 }
diff --git a/LanguageFeatures/nnbd/override_checking_A02_SETTER_t07.dart b/LanguageFeatures/nnbd/override_checking_A02_SETTER_t07.dart
index 52e0acc..0e3a118 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_SETTER_t07.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_SETTER_t07.dart
@@ -23,36 +23,14 @@
 void testme() {}
 
 class A with LEGACY_SETTER {
-  void set setInt(int? i) {
-  Expect.equals(1, i);
-  }
-
-  void set setObject(Object? o) {
-  Expect.equals(1, o);
-  }
-
-  void set setDynamic(dynamic? d) {
-  Expect.equals(1, d);
-  }
-
-  void set setNull(Null? n) {
-  Expect.isNull(n);
-  }
-
-  void set setFunction(Function? f) {
-  Expect.equals(testme, f);
-  }
-  void set setFutureOr(FutureOr? f) {
-  Expect.equals(1, f);
-  }
-
-  void set setFutureOrInt(FutureOr<int>? f) {
-  Expect.equals(1, f);
-  }
-
-  void set setFutureOrFunction(FutureOr<Function>? f) {
-  Expect.equals(testme, f);
-  }
+  void set setInt(int? i)                             { Expect.equals(1, i);      }
+  void set setObject(Object? o)                       { Expect.equals(1, o);      }
+  void set setDynamic(dynamic? d)                     { Expect.equals(1, d);      }
+  void set setNull(Null? n)                           { Expect.isNull(n);         }
+  void set setFunction(Function? f)                   { Expect.equals(testme, f); }
+  void set setFutureOr(FutureOr? f)                   { Expect.equals(1, f);      }
+  void set setFutureOrInt(FutureOr<int>? f)           { Expect.equals(1, f);      }
+  void set setFutureOrFunction(FutureOr<Function>? f) { Expect.equals(testme, f); }
 }
 
 main() {
diff --git a/LanguageFeatures/nnbd/override_checking_A02_SETTER_t08.dart b/LanguageFeatures/nnbd/override_checking_A02_SETTER_t08.dart
index 9b1ee2c..a25cc1d 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_SETTER_t08.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_SETTER_t08.dart
@@ -21,37 +21,14 @@
 import "override_checking_legacy_lib.dart";
 
 class A with LEGACY_SETTER {
-  void set setInt(int? i) {
-    Expect.isNull(i);
-  }
-
-  void set setObject(Object? o) {
-    Expect.isNull(o);
-  }
-
-  void set setDynamic(dynamic d) {
-    Expect.isNull(d);
-  }
-
-  void set setNull(Null n) {
-    Expect.isNull(n);
-  }
-
-  void set setFunction(Function? f) {
-    Expect.isNull(f);
-  }
-
-  void set setFutureOr(FutureOr f) {
-    Expect.isNull(f);
-  }
-
-  void set setFutureOrInt(FutureOr<int>? f) {
-    Expect.isNull(f);
-  }
-
-  void set setFutureOrFunction(FutureOr<Function>? f) {
-    Expect.isNull(f);
-  }
+  void set setInt(int? i)                             { Expect.isNull(i); }
+  void set setObject(Object? o)                       { Expect.isNull(o); }
+  void set setDynamic(dynamic d)                      { Expect.isNull(d); }
+  void set setNull(Null n)                            { Expect.isNull(n); }
+  void set setFunction(Function? f)                   { Expect.isNull(f); }
+  void set setFutureOr(FutureOr f)                    { Expect.isNull(f); }
+  void set setFutureOrInt(FutureOr<int>? f)           { Expect.isNull(f); }
+  void set setFutureOrFunction(FutureOr<Function>? f) { Expect.isNull(f); }
 }
 
 main() {
diff --git a/LanguageFeatures/nnbd/override_checking_A02_SETTER_t09.dart b/LanguageFeatures/nnbd/override_checking_A02_SETTER_t09.dart
index d5d348b..5838373 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_SETTER_t09.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_SETTER_t09.dart
@@ -10,7 +10,7 @@
  * to override otherwise incompatible signatures for a method.
  *
  * @description Check that if opted-in class is a mixin with legacy class, child
- * opted-in setter cannot have non-nullable argument.
+ * opted-in setter can have non-nullable argument.
  *
  * @author iarkh@unipro.ru
  */
@@ -18,39 +18,24 @@
 
 import "dart:async";
 import "override_checking_legacy_lib.dart";
+import "../../Utils/expect.dart";
+
+void testme() {}
 
 class A with LEGACY_SETTER {
-  void set setInt(int i) {}
-//         ^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-
-  void set setObject(Object o) {}
-//         ^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  void set setFunction(Function f) {}
-//         ^^^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  void set setFutureOrInt(FutureOr<int> f) {}
-//         ^^^^^^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  void set setFutureOrFunction(FutureOr<Function> f) {}
-//         ^^^^^^^^^^^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  void set setDynamic(dynamic d) {}
-  void set setNull(Null n) {}
-  void set setFutureOr(FutureOr f) {}
+  void set setInt(int? i)                             { Expect.equals(1, i);      }
+  void set setObject(Object? o)                       { Expect.equals(1, o);      }
+  void set setFunction(Function? f)                   { Expect.equals(testme, f); }
+  void set setFutureOrInt(FutureOr<int>? f)           { Expect.equals(1, f);      }
+  void set setFutureOrFunction(FutureOr<Function>? f) { Expect.equals(testme, f); }
 }
 
 main() {
-  A();
+  A a = A();
+
+  a.setInt = 1;
+  a.setObject = 1;
+  a.setFunction = testme;
+  a.setFutureOrInt = 1;
+  a.setFutureOrFunction = testme;
 }
diff --git a/LanguageFeatures/nnbd/override_checking_A02_SETTER_t10.dart b/LanguageFeatures/nnbd/override_checking_A02_SETTER_t10.dart
index 214fa60..79101ac 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_SETTER_t10.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_SETTER_t10.dart
@@ -35,37 +35,14 @@
 }
 
 class A implements AA, LEGACY_SETTER {
-  void set setInt(int? i) {
-    Expect.equals(1, i);
-  }
-
-  void set setObject(Object? o) {
-    Expect.equals(1, o);
-  }
-
-  void set setDynamic(dynamic? d) {
-  Expect.equals(1, d);
-  }
-
-  void set setNull(Null? n) {
-    Expect.isNull(n);
-  }
-
-  void set setFunction(Function? f) {
-    Expect.equals(testme, f);
-  }
-
-  void set setFutureOr(FutureOr? f) {
-    Expect.equals(1, f);
-  }
-
-  void set setFutureOrInt(FutureOr<int>? f) {
-    Expect.equals(1, f);
-  }
-
-  void set setFutureOrFunction(FutureOr<Function>? f) {
-    Expect.equals(testme, f);
-  }
+  void set setInt(int? i)                             { Expect.equals(1, i);      }
+  void set setObject(Object? o)                       { Expect.equals(1, o);      }
+  void set setDynamic(dynamic? d)                     { Expect.equals(1, d);      }
+  void set setNull(Null? n)                           { Expect.isNull(n);         }
+  void set setFunction(Function? f)                   { Expect.equals(testme, f); }
+  void set setFutureOr(FutureOr? f)                   { Expect.equals(1, f);      }
+  void set setFutureOrInt(FutureOr<int>? f)           { Expect.equals(1, f);      }
+  void set setFutureOrFunction(FutureOr<Function>? f) { Expect.equals(testme, f); }
 }
 
 main() {
diff --git a/LanguageFeatures/nnbd/override_checking_A02_SETTER_t11.dart b/LanguageFeatures/nnbd/override_checking_A02_SETTER_t11.dart
index dc8d7fa..a464a2d 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_SETTER_t11.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_SETTER_t11.dart
@@ -35,37 +35,14 @@
 }
 
 class A implements AA, LEGACY_SETTER {
-  void set setInt(int? i) {
-    Expect.isNull(i);
-  }
-
-  void set setObject(Object? o) {
-    Expect.isNull(o);
-  }
-
-  void set setDynamic(dynamic d) {
-    Expect.isNull(d);
-  }
-
-  void set setNull(Null n) {
-  Expect.isNull(n);
-  }
-
-  void set setFunction(Function? f) {
-    Expect.isNull(f);
-  }
-
-  void set setFutureOr(FutureOr f) {
-    Expect.isNull(f);
-  }
-
-  void set setFutureOrInt(FutureOr<int>? f) {
-    Expect.isNull(f);
-  }
-
-  void set setFutureOrFunction(FutureOr<Function>? f) {
-    Expect.isNull(f);
-  }
+  void set setInt(int? i)                             { Expect.isNull(i); }
+  void set setObject(Object? o)                       { Expect.isNull(o); }
+  void set setDynamic(dynamic d)                      { Expect.isNull(d); }
+  void set setNull(Null n)                            { Expect.isNull(n); }
+  void set setFunction(Function? f)                   { Expect.isNull(f); }
+  void set setFutureOr(FutureOr f)                    { Expect.isNull(f); }
+  void set setFutureOrInt(FutureOr<int>? f)           { Expect.isNull(f); }
+  void set setFutureOrFunction(FutureOr<Function>? f) { Expect.isNull(f); }
 }
 
  main() {
diff --git a/LanguageFeatures/nnbd/override_checking_A02_SETTER_t12.dart b/LanguageFeatures/nnbd/override_checking_A02_SETTER_t12.dart
index 639402a..a7d140f 100644
--- a/LanguageFeatures/nnbd/override_checking_A02_SETTER_t12.dart
+++ b/LanguageFeatures/nnbd/override_checking_A02_SETTER_t12.dart
@@ -19,6 +19,9 @@
 
 import "dart:async";
 import "override_checking_legacy_lib.dart";
+import "../../Utils/expect.dart";
+
+void testme() {}
 
 abstract class AA {
   void set setInt(int? i);
@@ -32,37 +35,23 @@
 }
 
 class A implements AA, LEGACY_SETTER {
-  void set setInt(int i) {}
-//         ^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
+  void set setInt(int? i)                             { Expect.equals(1, i);      }
+  void set setObject(Object? o)                       { Expect.equals(1, o);      }
+  void set setFunction(Function? f)                   { Expect.equals(testme, f); }
+  void set setFutureOrInt(FutureOr<int>? f)           { Expect.equals(1, f);      }
+  void set setFutureOrFunction(FutureOr<Function>? f) { Expect.equals(testme, f); }
 
-
-  void set setObject(Object o) {}
-//         ^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  void set setFunction(Function f) {}
-//         ^^^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  void set setFutureOrInt(FutureOr<int> f) {}
-//         ^^^^^^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  void set setFutureOrFunction(FutureOr<Function> f) {}
-//         ^^^^^^^^^^^^^^^^^^^
-// [analyzer] unspecified
-// [cfe] unspecified
-
-  void set setDynamic(dynamic d) {}
-  void set setNull(Null n) {}
+  void set setDynamic(dynamic d)   {}
+  void set setNull(Null n)         {}
   void set setFutureOr(FutureOr f) {}
 }
 
 main() {
-  A();
+  A a = A();
+
+  a.setInt = 1;
+  a.setObject = 1;
+  a.setFunction = testme;
+  a.setFutureOrInt = 1;
+  a.setFutureOrFunction = testme;
 }