Fix for instance fields inference when a setter has no parameter.

pkg/analyzer/test/src/summary/top_level_inference_test.dart

 // Copyright (c) 2017, 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.
 
 import 'dart:async';
 
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/src/dart/analysis/driver.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
@@ skipping 1432 matching lines @@
     var library = await _encodeDecodeLibrary(r'''
 var V = throw 42;
 ''');
     checkElementText(
         library,
         r'''
 Null V;
 ''');
   }
 
+  test_instanceField_error_noSetterParameter() async {
+    var library = await _encodeDecodeLibrary(r'''
+abstract class A {
+  int x;
+}
+class B implements A {
+  set x() {}
+}
+''');
+    checkElementText(
+        library,
+        r'''
+abstract class A {
+  int x;
+}
+class B implements A {
+  void set x() {}
+}
+''');
+  }
+
   test_instanceField_fieldFormal() async {
     var library = await _encodeDecodeLibrary(r'''
 class A {
   var f = 0;
   A([this.f = 'hello']);
 }
 ''');
     checkElementText(
         library,
         r'''
@@ skipping 1261 matching lines @@
 
   Future<LibraryElement> _encodeDecodeLibrary(String text) async {
     String path = _p('/test.dart');
     provider.newFile(path, text);
     UnitElementResult result = await driver.getUnitElement(path);
     return result.element.library;
   }
 
   String _p(String path) => provider.convertPath(path);
 }