Report error on JS-interop operator [] and []= methods.

pkg/compiler/lib/src/diagnostics/messages.dart

 // Copyright (c) 2011, 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.
 
 
 /**
  * The messages in this file should meet the following guide lines:
  *
  * 1. The message should be a complete sentence starting with an uppercase
  * letter, and ending with a period.
@@ skipping 272 matching lines @@
   INVALID_SOURCE_FILE_LOCATION,
   INVALID_SYMBOL,
   INVALID_SYNC_MODIFIER,
   INVALID_TYPE_VARIABLE_BOUND,
   INVALID_UNNAMED_CONSTRUCTOR_NAME,
   INVALID_URI,
   INVALID_USE_OF_SUPER,
   INVALID_YIELD,
   JS_INTEROP_CLASS_CANNOT_EXTEND_DART_CLASS,
   JS_INTEROP_CLASS_NON_EXTERNAL_MEMBER,
+  JS_INTEROP_INDEX_NOT_SUPPORTED,
+  JS_INTEROP_METHOD_WITH_NAMED_ARGUMENTS,
   JS_OBJECT_LITERAL_CONSTRUCTOR_WITH_POSITIONAL_ARGUMENTS,
-  JS_INTEROP_METHOD_WITH_NAMED_ARGUMENTS,
   JS_PLACEHOLDER_CAPTURE,
   LIBRARY_NAME_MISMATCH,
   LIBRARY_NOT_FOUND,
   LIBRARY_NOT_SUPPORTED,
   LIBRARY_TAG_MUST_BE_FIRST,
   MAIN_HAS_PART_OF,
   MAIN_NOT_A_FUNCTION,
   MAIN_WITH_EXTRA_PARAMETER,
   MALFORMED_STRING_LITERAL,
   MEMBER_NOT_FOUND,
@@ skipping 2024 matching lines @@
 
               @JS()
               class Foo {
                 external bar(foo, {baz});
               }
 
               main() {
                 new Foo().bar(4, baz: 5);
               }
               """]),
+      MessageKind.JS_INTEROP_INDEX_NOT_SUPPORTED:
+        const MessageTemplate(
+           MessageKind.JS_INTEROP_INDEX_NOT_SUPPORTED,
+           "Js-interop does not support [] and []= operator methods.",
+           howToFix: "Try replacing [] and []= operator methods with normal "
+                     "methods.",
+           examples: const [
+               """
+        import 'package:js/js.dart';
+
+        @JS()
+        class Foo {
+          external operator [](arg);
+        }
+
+        main() {
+          new Foo()[0];
+        }
+        """, """
+        import 'package:js/js.dart';
+
+        @JS()
+        class Foo {
+          external operator []=(arg, value);
+        }
+
+        main() {
+          new Foo()[0] = 1;
+        }
+        """]),
 
       MessageKind.JS_OBJECT_LITERAL_CONSTRUCTOR_WITH_POSITIONAL_ARGUMENTS:
         const MessageTemplate(
           MessageKind.JS_OBJECT_LITERAL_CONSTRUCTOR_WITH_POSITIONAL_ARGUMENTS,
           "Parameter '#{parameter}' in anonymous js-interop class '#{cls}' "
           "object literal constructor is positional instead of named."
           ".",
           howToFix: "Make all arguments in external factory object literal "
                     "constructors named.",
           examples: const [
@@ skipping 1377 matching lines @@
   static String convertToString(value) {
     if (value is ErrorToken) {
       // Shouldn't happen.
       return value.assertionMessage;
     } else if (value is Token) {
       value = value.value;
     }
     return '$value';
   }
 }