address #25232 in strong mode (dart1 behavior unchanged)

pkg/analyzer/test/src/task/strong/checker_test.dart

 // Copyright (c) 2015, 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.
 
 library analyzer.test.src.task.strong.checker_test;
 
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import 'strong_test_helper.dart';
 
@@ skipping 482 matching lines @@
   (/*info:DYNAMIC_INVOKE*/toStringClosure2());
   int hashCode = /*info:DYNAMIC_CAST*/helper.hashCode;
 
   baz().toString();
   baz().hashCode;
 }
 ''');
   }
 
   void test_covariantOverride() {
-    addFile(r'''
-library meta;
-class _Checked { const _Checked(); }
-const Object checked = const _Checked();
-    ''', name: '/meta.dart');
-
+    _addMetaLibrary();
     checkFile(r'''
 import 'meta.dart';
 class C {
   num f(num x) => x;
 }
 class D extends C {
   int f(@checked int x) => x;
 }
 class E extends D {
   int f(Object x) => /*info:DOWN_CAST_IMPLICIT*/x;
@@ skipping 12 matching lines @@
 class F_error extends E {
   /*error:INVALID_METHOD_OVERRIDE*/int f(@checked double x) => 0;
 }
 class G_error extends E implements D {
   /*error:INVALID_METHOD_OVERRIDE*/int f(@checked double x) => 0;
 }
     ''');
   }
 
   void test_covariantOverride_leastUpperBound() {
-    addFile(r'''
-library meta;
-class _Checked { const _Checked(); }
-const Object checked = const _Checked();
-    ''', name: '/meta.dart');
-
+    _addMetaLibrary();
     checkFile(r'''
 import "meta.dart";
 abstract class Top {}
 abstract class Left implements Top {}
 abstract class Right implements Top {}
 abstract class Bottom implements Left, Right {}
 
 abstract class TakesLeft {
   m(Left x);
 }
 abstract class TakesRight {
   m(Right x);
 }
 abstract class TakesTop implements TakesLeft, TakesRight {
   m(Top x); // works today
 }
 abstract class TakesBottom implements TakesLeft, TakesRight {
   // LUB(Left, Right) == Top, so this is an implicit cast from Top to Bottom.
   m(@checked Bottom x);
 }
     ''');
   }
 
   void test_covariantOverride_markerIsInherited() {
-    addFile(r'''
-library meta;
-class _Checked { const _Checked(); }
-const Object checked = const _Checked();
-    ''', name: '/meta.dart');
-
+    _addMetaLibrary();
     checkFile(r'''
 import 'meta.dart';
 class C {
   num f(@checked num x) => x;
 }
 class D extends C {
   int f(int x) => x;
 }
 class E extends D {
   int f(Object x) => /*info:DOWN_CAST_IMPLICIT*/x;
@@ skipping 2521 matching lines @@
   n(B b);
 }
 abstract class D extends C {
   /*error:INVALID_METHOD_OVERRIDE*/m(B b);
   n(A a);
 }
     ''');
     check(implicitCasts: false);
   }
 
+  void test_overrideNarrowsType_noDuplicateError() {
+    // Regression test for https://github.com/dart-lang/sdk/issues/25232
+    _addMetaLibrary();
+    checkFile(r'''
+import 'meta.dart';
+abstract class A { void test(A arg) { } }
+abstract class B extends A {
+  /*error:INVALID_METHOD_OVERRIDE*/void test(B arg) { }
+}
+abstract class X implements A { }
+class C extends B with X { }
+
+// We treat "implements A" as asking for another check.
+// This feels inconsistent to me.
+class D /*error:INVALID_METHOD_OVERRIDE_FROM_BASE*/extends B implements A { }
+    ''');
+  }
+
+  void test_overrideNarrowsType_legalWithChecked() {
+    // Regression test for https://github.com/dart-lang/sdk/issues/25232
+    _addMetaLibrary();
+    checkFile(r'''
+import 'meta.dart';
+abstract class A { void test(A arg) { } }
+abstract class B extends A { void test(@checked B arg) { } }
+abstract class X implements A { }
+class C extends B with X { }
+class D extends B implements A { }
+    ''');
+  }
+
   void test_privateOverride() {
     addFile(
         '''
 import 'main.dart' as main;
 
 class Base {
   var f1;
   var _f2;
   var _f3;
   get _f4 => null;
@@ skipping 705 matching lines @@
     // Regression test for https://github.com/dart-lang/sdk/issues/25069
     checkFile('''
 typedef int Foo();
 void foo() {}
 void main () {
   Foo x = /*error:INVALID_ASSIGNMENT,info:USE_OF_VOID_RESULT*/foo();
 }
 ''');
   }
 }
+
+void _addMetaLibrary() {
+  addFile(r'''
+library meta;
+class _Checked { const _Checked(); }
+const Object checked = const _Checked();
+    ''', name: '/meta.dart');
+}