Ensure mustCallSuper check visits children (flutter#11646).

pkg/analyzer/test/generated/hint_code_test.dart

 // Copyright (c) 2016, 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.generated.hint_code_test;
 
 import 'package:analyzer/error/error.dart';
 import 'package:analyzer/src/error/codes.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/parser.dart';
@@ skipping 2130 matching lines @@
   void a() {
     super.a(); //OK
   }
 }
 ''');
     await computeAnalysisResult(source);
     assertErrors(source, []);
     verify([source]);
   }
 
+  test_mustCallSuper_overridden_w_future() async {
+    //https://github.com/flutter/flutter/issues/11646
+    Source source = addSource(r'''
+import 'dart:async';
+import 'package:meta/meta.dart';
+class A {
+  @mustCallSuper
+  Future<Null> bar() => new Future<Null>.value();
+}
+class C extends A {
+  @override
+  Future<Null> bar() {
+    final value = super.bar();
+    return value.then((Null _) {
+      return null;
+    });
+  }
+}
+''');
+    await computeAnalysisResult(source);
+    assertErrors(source, []);
+    verify([source]);
+  }
+
+  test_mustCallSuper_overridden_w_future2() async {
+    //https://github.com/flutter/flutter/issues/11646
+    Source source = addSource(r'''
+import 'dart:async';
+import 'package:meta/meta.dart';
+class A {
+  @mustCallSuper
+  Future<Null> bar() => new Future<Null>.value();
+}
+class C extends A {
+  @override
+  Future<Null> bar() {
+    return super.bar().then((Null _) {
+      return null;
+    });
+  }
+}
+''');
+    await computeAnalysisResult(source);
+    assertErrors(source, []);
+    verify([source]);
+  }
+
   test_nullAwareInCondition_assert() async {
     Source source = addSource(r'''
 m(x) {
   assert (x?.a);
 }
 ''');
     await computeAnalysisResult(source);
     assertErrors(source, [HintCode.NULL_AWARE_IN_CONDITION]);
     verify([source]);
   }
@@ skipping 2093 matching lines @@
   n() {
     var a = m(), b = m();
   }
 }''');
     await computeAnalysisResult(source);
     assertErrors(
         source, [HintCode.USE_OF_VOID_RESULT, HintCode.USE_OF_VOID_RESULT]);
     verify([source]);
   }
 }