Implement new return type checking rules in analyzer.

pkg/analyzer/lib/src/generated/error.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.error;
 
 import 'dart:collection';
 
 import 'ast.dart' show AstNode;
 import 'element.dart';
@@ skipping 3266 matching lines @@
    * implements the built-in class <i>Map&lt;K, V></i> is allocated.
    *
    * @param numTypeArgument the number of provided type arguments
    */
   static const StaticTypeWarningCode EXPECTED_TWO_MAP_TYPE_ARGUMENTS =
       const StaticTypeWarningCode(
           'EXPECTED_TWO_MAP_TYPE_ARGUMENTS',
           "Map literal requires exactly two type arguments or none, but {0} found");
 
   /**
+   * 9 Functions: It is a static warning if the declared return type of a
+   * function marked async* may not be assigned to Stream.
+   */
+  static const StaticTypeWarningCode ILLEGAL_ASYNC_GENERATOR_RETURN_TYPE =
+      const StaticTypeWarningCode(
+          'ILLEGAL_ASYNC_GENERATOR_RETURN_TYPE',
+          "Functions marked 'async*' must have a return type assignable to 'Stream'");
+
+  /**
+   * 9 Functions: It is a static warning if the declared return type of a
+   * function marked async may not be assigned to Future.
+   */
+  static const StaticTypeWarningCode ILLEGAL_ASYNC_RETURN_TYPE =
+      const StaticTypeWarningCode(
+          'ILLEGAL_ASYNC_RETURN_TYPE',
+          "Functions marked 'async' must have a return type assignable to 'Future'");
+
+  /**
+   * 9 Functions: It is a static warning if the declared return type of a
+   * function marked sync* may not be assigned to Iterable.
+   */
+  static const StaticTypeWarningCode ILLEGAL_SYNC_GENERATOR_RETURN_TYPE =
+      const StaticTypeWarningCode(
+          'ILLEGAL_SYNC_GENERATOR_RETURN_TYPE',
+          "Functions marked 'sync*' must have a return type assignable to 'Iterable'");
+
+  /**
    * 12.18 Assignment: Let <i>T</i> be the static type of <i>e<sub>1</sub></i>.
    * It is a static type warning if <i>T</i> does not have an accessible
    * instance setter named <i>v=</i>.
    *
    * See [UNDEFINED_SETTER].
    */
   static const StaticTypeWarningCode INACCESSIBLE_SETTER =
       const StaticTypeWarningCode('INACCESSIBLE_SETTER', "");
 
   /**
@@ skipping 1697 matching lines @@
    * Initialize a newly created error code to have the given [name].
    */
   const TodoCode(String name) : super(name, "{0}");
 
   @override
   ErrorSeverity get errorSeverity => ErrorSeverity.INFO;
 
   @override
   ErrorType get type => ErrorType.TODO;
 }