Generate the proper error when a constant refers to itself.

pkg/analyzer/test/generated/compile_time_error_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.compile_time_error_code_test;
 
 import 'package:analyzer/src/generated/error.dart';
 import 'package:analyzer/src/generated/parser.dart' show ParserErrorCode;
 import 'package:analyzer/src/generated/source_io.dart';
 import 'package:unittest/unittest.dart' as _ut;
@@ skipping 4667 matching lines @@
   const C() : x = y;
   final x;
 }
 ''');
     resolve(source);
     assertErrors(
         source, [CompileTimeErrorCode.RECURSIVE_COMPILE_TIME_CONSTANT]);
     verify([source]);
   }
 
+  void test_recursiveCompileTimeConstant_singleVariable() {
+    Source source = addSource(r'''
+const x = x;
+''');
+    resolve(source);
+    assertErrors(
+        source, [CompileTimeErrorCode.RECURSIVE_COMPILE_TIME_CONSTANT]);
+    verify([source]);
+  }
+
   void test_recursiveConstructorRedirect() {
     Source source = addSource(r'''
 class A {
   A.a() : this.b();
   A.b() : this.a();
 }''');
     resolve(source);
     assertErrors(source, [
       CompileTimeErrorCode.RECURSIVE_CONSTRUCTOR_REDIRECT,
       CompileTimeErrorCode.RECURSIVE_CONSTRUCTOR_REDIRECT
@@ skipping 1032 matching lines @@
         source, [CompileTimeErrorCode.WRONG_NUMBER_OF_PARAMETERS_FOR_OPERATOR]);
     verify([source]);
     reset();
   }
 
   void _check_wrongNumberOfParametersForOperator1(String name) {
     _check_wrongNumberOfParametersForOperator(name, "");
     _check_wrongNumberOfParametersForOperator(name, "a, b");
   }
 }