Add a getter to TypeProvider for Future<Null>.

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 54 matching lines @@
    * to have a bare "return;" in an async method.
    */
   final InterfaceType _futureNullType;
 
   /**
    * Create a new instance of the [BestPracticesVerifier].
    *
    * @param errorReporter the error reporter
    */
   BestPracticesVerifier(this._errorReporter, TypeProvider typeProvider)
-      : _futureNullType = typeProvider.futureType.substitute4(
-          <DartType>[typeProvider.nullType]);
+      : _futureNullType = typeProvider.futureNullType;
 
   @override
   Object visitArgumentList(ArgumentList node) {
     _checkForArgumentTypesNotAssignableInList(node);
     return super.visitArgumentList(node);
   }
 
   @override
   Object visitAsExpression(AsExpression node) {
     _checkForUnnecessaryCast(node);
@@ skipping 13313 matching lines @@
   DartType get dynamicType;
 
   /**
    * Return the type representing the built-in type 'Function'.
    *
    * @return the type representing the built-in type 'Function'
    */
   InterfaceType get functionType;
 
   /**
+   * Return the type representing 'Future<Null>'.
+   */
+  InterfaceType get futureNullType;
+
+  /**
    * Return the type representing the built-in type 'Future'.
    */
   InterfaceType get futureType;
 
   /**
    * Return the type representing the built-in type 'int'.
    *
    * @return the type representing the built-in type 'int'
    */
   InterfaceType get intType;
@@ skipping 96 matching lines @@
    * The type representing the built-in type 'dynamic'.
    */
   DartType _dynamicType;
 
   /**
    * The type representing the built-in type 'Function'.
    */
   InterfaceType _functionType;
 
   /**
+   * The type representing 'Future<Null>'.
+   */
+  InterfaceType _futureNullType;
+
+  /**
    * The type representing the built-in type 'Future'.
    */
   InterfaceType _futureType;
 
   /**
    * The type representing the built-in type 'int'.
    */
   InterfaceType _intType;
 
   /**
@@ skipping 67 matching lines @@
   @override
   InterfaceType get doubleType => _doubleType;
 
   @override
   DartType get dynamicType => _dynamicType;
 
   @override
   InterfaceType get functionType => _functionType;
 
   @override
+  InterfaceType get futureNullType => _futureNullType;
+
+  @override
   InterfaceType get futureType => _futureType;
 
   @override
   InterfaceType get intType => _intType;
 
   @override
   InterfaceType get listType => _listType;
 
   @override
   InterfaceType get mapType => _mapType;
@@ skipping 62 matching lines @@
     _listType = _getType(coreNamespace, "List");
     _mapType = _getType(coreNamespace, "Map");
     _nullType = _getType(coreNamespace, "Null");
     _numType = _getType(coreNamespace, "num");
     _objectType = _getType(coreNamespace, "Object");
     _stackTraceType = _getType(coreNamespace, "StackTrace");
     _stringType = _getType(coreNamespace, "String");
     _symbolType = _getType(coreNamespace, "Symbol");
     _typeType = _getType(coreNamespace, "Type");
     _undefinedType = UndefinedTypeImpl.instance;
+    _futureNullType = _futureType.substitute4(<DartType>[_nullType]);
   }
 }
 
 /**
  * Instances of the class `TypeResolverVisitor` are used to resolve the types associated with
  * the elements in the element model. This includes the types of superclasses, mixins, interfaces,
  * fields, methods, parameters, and local variables. As a side-effect, this also finishes building
  * the type hierarchy.
  */
 class TypeResolverVisitor extends ScopedVisitor {
@@ skipping 1879 matching lines @@
    * library.
    */
   final HashSet<String> members = new HashSet<String>();
 
   /**
    * Names of resolved or unresolved class members that are read in the
    * library.
    */
   final HashSet<String> readMembers = new HashSet<String>();
 }