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

pkg/analyzer/lib/error/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 analyzer.error.error;
 
 import 'dart:collection';
 
 import 'package:analyzer/error/listener.dart';
 import 'package:analyzer/src/dart/scanner/scanner.dart' show ScannerErrorCode;
@@ skipping 215 matching lines @@
   CompileTimeErrorCode.WRONG_NUMBER_OF_PARAMETERS_FOR_SETTER,
   CompileTimeErrorCode.YIELD_EACH_IN_NON_GENERATOR,
   CompileTimeErrorCode.YIELD_IN_NON_GENERATOR,
   HintCode.ABSTRACT_SUPER_MEMBER_REFERENCE,
   HintCode.ARGUMENT_TYPE_NOT_ASSIGNABLE,
   HintCode.CAN_BE_NULL_AFTER_NULL_AWARE,
   HintCode.DEAD_CODE,
   HintCode.DEAD_CODE_CATCH_FOLLOWING_CATCH,
   HintCode.DEAD_CODE_ON_CATCH_SUBTYPE,
   HintCode.DEPRECATED_MEMBER_USE,
-  HintCode.DEPRECATED_FUNCTION_CLASS_DECLARATION,
-  HintCode.DEPRECATED_EXTENDS_FUNCTION,
-  HintCode.DEPRECATED_MIXIN_FUNCTION,
   HintCode.DIVISION_OPTIMIZATION,
   HintCode.DUPLICATE_IMPORT,
   HintCode.FILE_IMPORT_INSIDE_LIB_REFERENCES_FILE_OUTSIDE,
   HintCode.FILE_IMPORT_OUTSIDE_LIB_REFERENCES_FILE_INSIDE,
   HintCode.IMPORT_DEFERRED_LIBRARY_WITH_LOAD_FUNCTION,
   HintCode.INVALID_ASSIGNMENT,
   HintCode.INVALID_FACTORY_ANNOTATION,
   HintCode.INVALID_FACTORY_METHOD_DECL,
   HintCode.INVALID_FACTORY_METHOD_IMPL,
   HintCode.INVALID_METHOD_OVERRIDE_TYPE_PARAMETERS,
@@ skipping 652 matching lines @@
 
   @override
   int get hashCode => ordinal;
 
   @override
   int compareTo(ErrorProperty other) => ordinal - other.ordinal;
 
   @override
   String toString() => name;
 }