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

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 230 matching lines @@
   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.GENERIC_METHOD_COMMENT,
   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_IMMUTABLE_ANNOTATION,
   HintCode.INVALID_METHOD_OVERRIDE_TYPE_PARAMETERS,
   HintCode.INVALID_METHOD_OVERRIDE_TYPE_PARAMETER_BOUND,
   HintCode.INVALID_REQUIRED_PARAM,
   HintCode.INVALID_USE_OF_PROTECTED_MEMBER,
@@ skipping 585 matching lines @@
    * a single list of errors.
    */
   static List<AnalysisError> mergeLists(List<List<AnalysisError>> errorLists) {
     Set<AnalysisError> errors = new HashSet<AnalysisError>();
     for (List<AnalysisError> errorList in errorLists) {
       errors.addAll(errorList);
     }
     return errors.toList();
   }
 }