Verify a corner case of const constructor cycle detection with summaires.

pkg/analyzer/test/src/summary/linker_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.
 
 import 'package:analyzer/src/summary/format.dart';
 import 'package:analyzer/src/summary/link.dart';
 import 'package:unittest/unittest.dart';
 
 import '../../reflective_tests.dart';
 import 'summarize_ast_test.dart';
@@ skipping 91 matching lines @@
 }
 class C extends B {
   var c;
 }
 ''');
     LibraryElementForLink library = linker.getLibrary(linkerInputs.testDartUri);
     library.libraryCycleForLink.ensureLinked();
     // No assertions--just make sure it doesn't crash.
   }
 
+  void test_constCycle_viaLength() {
+    createLinker('''
+class C {
+  final y;
+  const C() : y = x.length;
+}
+const x = [const C()];
+''');
+    testLibrary.libraryCycleForLink.ensureLinked();
+    ClassElementForLink classC = testLibrary.getContainedName('C');
+    expect(classC.unnamedConstructor.isCycleFree, false);
+  }
+
   void test_inferredType_instanceField_dynamic() {
     createLinker('''
 var x;
 class C {
   var f = x; // Inferred type: dynamic
 }
 ''');
     LibraryElementForLink library = linker.getLibrary(linkerInputs.testDartUri);
     library.libraryCycleForLink.ensureLinked();
     ClassElementForLink_Class cls = library.getContainedName('C');
@@ skipping 358 matching lines @@
 class C extends B with I {}
 class D extends C {
   void f() {}
 }
 ''');
     LibraryElementForLink library = linker.getLibrary(linkerInputs.testDartUri);
     library.libraryCycleForLink.ensureLinked();
     // No assertions--just make sure it doesn't crash.
   }
 }