Emit a hint when using generic method comment syntax (issue 30356)

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 144 matching lines @@
    * directory.
    */
   static const HintCode FILE_IMPORT_OUTSIDE_LIB_REFERENCES_FILE_INSIDE =
       const HintCode(
           'FILE_IMPORT_OUTSIDE_LIB_REFERENCES_FILE_INSIDE',
           "A file outside the 'lib' directory shouldn't reference a file "
           "inside the 'lib' directory using a relative path.",
           "Try using a package: URI instead.");
 
   /**
+   * Generic type comments (`/*<T>*/` and `/*=T*/`) are no longer necessary and
+   * will soon be ignored.
+   */
+  static const HintCode GENERIC_METHOD_COMMENT = const HintCode(
+      'GENERIC_METHOD_COMMENT',
+      "The generic type comment is being deprecated in favor of the real syntax.",
+      "Try replacing the comment with the actual type annotation.");
+
+  /**
    * Deferred libraries shouldn't define a top level function 'loadLibrary'.
    */
   static const HintCode IMPORT_DEFERRED_LIBRARY_WITH_LOAD_FUNCTION =
       const HintCode(
           'IMPORT_DEFERRED_LIBRARY_WITH_LOAD_FUNCTION',
           "The library '{0}' defines a top-level function named 'loadLibrary' "
           "which is hidden by deferring this library.",
           "Try changing the import to not be deferred, or "
           "rename the function in the imported library.");
 
@@ skipping 489 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;
 }