Move "null2" getter from ConstantVisitor to TypeProvider.

pkg/analyzer/lib/src/generated/resolver.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.resolver;
 
 import "dart:math" as math;
 import 'dart:collection';
 
 import 'package:analyzer/src/generated/utilities_collection.dart';
@@ skipping 13154 matching lines @@
   InterfaceType get listType;
 
   /**
    * Return the type representing the built-in type 'Map'.
    *
    * @return the type representing the built-in type 'Map'
    */
   InterfaceType get mapType;
 
   /**
+   * Return a [DartObjectImpl] representing the `null` object.
+   */
+  DartObjectImpl get nullObject;
+
+  /**
    * Return the type representing the built-in type 'Null'.
    *
    * @return the type representing the built-in type 'null'
    */
   InterfaceType get nullType;
 
   /**
    * Return the type representing the built-in type 'num'.
    *
    * @return the type representing the built-in type 'num'
@@ skipping 120 matching lines @@
    * The type representing the built-in type 'List'.
    */
   InterfaceType _listType;
 
   /**
    * The type representing the built-in type 'Map'.
    */
   InterfaceType _mapType;
 
   /**
+   * An shared object representing the value 'null'.
+   */
+  DartObjectImpl _nullObject;
+
+  /**
    * The type representing the type 'Null'.
    */
   InterfaceType _nullType;
 
   /**
    * The type representing the built-in type 'num'.
    */
   InterfaceType _numType;
 
   /**
@@ skipping 93 matching lines @@
   @override
   InterfaceType get iterableType => _iterableType;
 
   @override
   InterfaceType get listType => _listType;
 
   @override
   InterfaceType get mapType => _mapType;
 
   @override
+  DartObjectImpl get nullObject {
+    if (_nullObject == null) {
+      _nullObject = new DartObjectImpl(nullType, NullState.NULL_STATE);
+    }
+    return _nullObject;
+  }
+
+  @override
   InterfaceType get nullType => _nullType;
 
   @override
   InterfaceType get numType => _numType;
 
   @override
   InterfaceType get objectType => _objectType;
 
   @override
   InterfaceType get stackTraceType => _stackTraceType;
@@ skipping 1950 matching lines @@
   }
 
   bool isCatchException(LocalVariableElement element) {
     return catchExceptionElements.contains(element);
   }
 
   bool isCatchStackTrace(LocalVariableElement element) {
     return catchStackTraceElements.contains(element);
   }
 }