Revert "Deprecate the use of `Function` as a class."

pkg/analyzer/lib/src/dart/error/hint_codes.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 analyzer.src.dart.error.hint_codes;
 
 import 'package:analyzer/error/error.dart';
 import 'package:analyzer/src/dart/element/element.dart';
 
 /**
@@ skipping 77 matching lines @@
    *
    * Parameters:
    * 0: the name of the member
    */
   static const HintCode DEPRECATED_MEMBER_USE = const HintCode(
       'DEPRECATED_MEMBER_USE',
       "'{0}' is deprecated and shouldn't be used.",
       "Try replacing the use of the deprecated member with the replacement.");
 
   /**
-   * Users should not create a class named `Function` anymore.
-   */
-  static const HintCode DEPRECATED_FUNCTION_CLASS_DECLARATION = const HintCode(
-      'DEPRECATED_FUNCTION_CLASS_DECLARATION',
-      "Declaring a class named 'Function' is deprecated.",
-      "Try renaming the class.");
-
-  /**
-   * `Function` should not be extended anymore.
-   */
-  static const HintCode DEPRECATED_EXTENDS_FUNCTION = const HintCode(
-      'DEPRECATED_EXTENDS_FUNCTION',
-      "Extending 'Function' is deprecated.",
-      "Try removing 'Function' from the 'extends' clause.");
-
-  /**
-   * `Function` should not be mixed in anymore.
-   */
-  static const HintCode DEPRECATED_MIXIN_FUNCTION = const HintCode(
-      'DEPRECATED_MIXIN_FUNCTION',
-      "Mixing in 'Function' is deprecated.",
-      "Try removing 'Function' from the 'with' clause.");
-
-  /**
    * Hint to use the ~/ operator.
    */
   static const HintCode DIVISION_OPTIMIZATION = const HintCode(
       'DIVISION_OPTIMIZATION',
       "The operator x ~/ y is more efficient than (x / y).toInt().",
       "Try re-writing the expression to use the '~/' operator.");
 
   /**
    * Duplicate imports.
    */
@@ skipping 504 matching lines @@
    */
   const HintCode(String name, String message, [String correction])
       : super(name, message, correction);
 
   @override
   ErrorSeverity get errorSeverity => ErrorType.HINT.severity;
 
   @override
   ErrorType get type => ErrorType.HINT;
 }