Always check if instance method name collides with superclass static.

pkg/analyzer/test/generated/static_warning_code_test.dart

 // Copyright (c) 2014, 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 engine.static_warning_code_test;
 
 import 'package:analyzer/src/generated/source_io.dart';
 import 'package:analyzer/src/generated/error.dart';
 import 'package:analyzer/src/generated/parser.dart' show ParserErrorCode;
 import 'package:unittest/unittest.dart';
@@ skipping 1355 matching lines @@
 class B extends A {
 }
 class C extends B {
   void n() {}
 }''');
     resolve(source);
     assertErrors(source, [StaticWarningCode.INSTANCE_METHOD_NAME_COLLIDES_WITH_SUPERCLASS_STATIC]);
     verify([source]);
   }
 
+  void test_instanceMethodNameCollidesWithSuperclassStatic_interface() {
+    Source source = addSource(r'''
+class Base {
+  static foo() {}
+}
+abstract class Ifc {
+  foo();
+}
+class C extends Base implements Ifc {
+  foo() {}
+}
+''');
+    resolve(source);
+    assertErrors(source, [
+        StaticWarningCode.INSTANCE_METHOD_NAME_COLLIDES_WITH_SUPERCLASS_STATIC]);
+    verify([source]);
+  }
+
   void test_instanceMethodNameCollidesWithSuperclassStatic_method() {
     Source source = addSource(r'''
 class A {
   static n () {}
 }
 class B extends A {
   void n() {}
 }''');
     resolve(source);
     assertErrors(source, [StaticWarningCode.INSTANCE_METHOD_NAME_COLLIDES_WITH_SUPERCLASS_STATIC]);
@@ skipping 1751 matching lines @@
 }''');
     resolve(source);
     assertErrors(source, [StaticWarningCode.VOID_RETURN_FOR_GETTER]);
   }
 }
 
 main() {
   groupSep = ' | ';
   runReflectiveTests(StaticWarningCodeTest);
 }