Allowing `e` of any type in `void f(...) => e` in the analyzer.

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 3518 matching lines @@
 }
  ''');
   }
 
   test_setterReturnTypes() async {
     await checkFile('''
 void voidFn() => null;
 class A {
   set a(y) => 4;
   set b(y) => voidFn();
-  void set c(y) => /*error:RETURN_OF_INVALID_TYPE*/4;
+  void set c(y) => 4;
   void set d(y) => voidFn();
   /*warning:NON_VOID_RETURN_FOR_SETTER*/int set e(y) => 4;
   /*warning:NON_VOID_RETURN_FOR_SETTER*/int set f(y) =>
       /*error:RETURN_OF_INVALID_TYPE*/voidFn();
   set g(y) {return /*error:RETURN_OF_INVALID_TYPE*/4;}
   void set h(y) {return /*error:RETURN_OF_INVALID_TYPE*/4;}
   /*warning:NON_VOID_RETURN_FOR_SETTER*/int set i(y) {return 4;}
 }
 ''');
   }
@@ skipping 653 matching lines @@
 class CheckerTest_Driver extends CheckerTest {
   @override
   bool get enableNewAnalysisDriver => true;
 
   @failingTest
   @override
   test_covariantOverride_fields() async {
     await super.test_covariantOverride_fields();
   }
 }