Support async/await in the dart2js frontend.

sdk/lib/_internal/compiler/implementation/warnings.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.
 
 part of dart2js;
 
 const DONT_KNOW_HOW_TO_FIX = "";
 
 /**
  * The messages in this file should meet the following guide lines:
@@ skipping 64 matching lines @@
   /**
    *  Examples will be checked by
    *  tests/compiler/dart2js/message_kind_test.dart.
    *
    *  An example is either a String containing the example source code or a Map
    *  from filenames to source code. In the latter case, the filename for the
    *  main library code must be 'main.dart'.
    */
   final List examples;
 
-  const MessageKind(this.template, {this.howToFix, this.examples});
+  /// Additional options needed for the examples to work.
+  final List<String> options;
+
+  const MessageKind(this.template,
+                    {this.howToFix,
+                     this.examples,
+                     this.options: const <String>[]});
 
   /// Do not use this. It is here for legacy and debugging. It violates item 4
   /// above.
   static const MessageKind GENERIC = const MessageKind('#{text}');
 
   static const MessageKind NOT_ASSIGNABLE = const MessageKind(
       "'#{fromType}' is not assignable to '#{toType}'.");
 
   static const MessageKind VOID_EXPRESSION = const MessageKind(
       "Expression does not yield a value.");
@@ skipping 1873 matching lines @@
       "#{warnings} warning(s) suppressed in #{uri}.");
 
   static const MessageKind HIDDEN_HINTS = const MessageKind(
       "#{hints} hint(s) suppressed in #{uri}.");
 
   static const MessageKind PREAMBLE = const MessageKind(
     "When run on the command-line, the compiled output might"
     " require a preamble file located in:\n"
     "  <sdk>/lib/_internal/compiler/js_lib/preambles.");
 
+
+  static const MessageKind EXPERIMENTAL_ASYNC_AWAIT = const MessageKind(
+      "Experimental language feature 'async/await' is not supported.");
+
+  static const MessageKind INVALID_STARRED_KEYWORD = const MessageKind(
+      "Invalid '#{keyword}' keyword.",
+      options: const ['--enable-async'],
+      howToFix: "Try removing whitespace between '#{keyword}' and '*'.",
+      examples: const [
+        "main() async * {}",
+        "main() sync * {}",
+        "main() async* { yield * 0; }"
+      ]);
+
+  static const MessageKind INVALID_SYNC_MODIFIER = const MessageKind(
+      "Invalid modifier 'sync'.",
+      options: const ['--enable-async'],
+      howToFix: "Try replacing 'sync' with 'sync*'.",
+      examples: const [
+        "main() sync {}"
+      ]);
+
+  static const MessageKind INVALID_AWAIT_FOR = const MessageKind(
+      "'await' is only supported on for-in loops.",
+      options: const ['--enable-async'],
+      howToFix: "Try rewriting the loop as a for-in loop or removing the "
+                "'await' keyword.",
+      examples: const ["""
+main() async* {
+  await for (int i = 0; i < 10; i++) {}
+}
+"""]);
+
+  static const MessageKind ASYNC_MODIFIER_ON_ABSTRACT_METHOD =
+      const MessageKind(
+          "The modifier '#{modifier}' is not allowed on an abstract method.",
+          options: const ['--enable-async'],
+          howToFix: "Try removing the '#{modifier}' modifier or adding a "
+                    "body to the method.",
+          examples: const ["""
+abstract class A {
+  method() async;
+}
+class B extends A {
+  method() {}
+}
+main() {
+  A a = new B();
+  a.method();
+}
+"""]);
+
+  static const MessageKind ASYNC_MODIFIER_ON_CONSTRUCTOR =
+      const MessageKind(
+          "The modifier '#{modifier}' is not allowed on constructors.",
+          options: const ['--enable-async'],
+          howToFix: "Try removing the '#{modifier}' modifier.",
+          examples: const ["""
+class A {
+  A() async;
+}
+main() => new A();""",
+
+"""
+class A {
+  A();
+  factory A.a() async* => new A();
+}
+main() => new A.a();"""]);
+
+  static const MessageKind YIELDING_MODIFIER_ON_ARROW_BODY =
+      const MessageKind(
+          "The modifier '#{modifier}' is not allowed on methods implemented "
+          "using '=>'.",
+          options: const ['--enable-async'],
+          howToFix: "Try removing the '#{modifier}' modifier or implementing "
+                    "the method body using a block: '{ ... }'.",
+          examples: const ["main() sync* => null;", "main() async* => null;"]);
+
+  // TODO(johnniwinther): Check for 'async' as identifier.
+  static const MessageKind ASYNC_KEYWORD_AS_IDENTIFIER = const MessageKind(
+      "'#{keyword}' cannot be used as an identifier in a function body marked "
+      "with '#{modifier}'.",
+      options: const ['--enable-async'],
+      howToFix: "Try removing the '#{modifier}' modifier or renaming the "
+                "identifier.",
+      examples: const ["""
+main() async {
+ var await;
+}""",
+"""
+main() async* {
+ var yield;
+}""",
+"""
+main() sync* {
+ var yield;
+}"""]);
+
   //////////////////////////////////////////////////////////////////////////////
   // Patch errors start.
   //////////////////////////////////////////////////////////////////////////////
 
   static const MessageKind PATCH_RETURN_TYPE_MISMATCH = const MessageKind(
       "Patch return type '#{patchReturnType}' does not match "
       "'#{originReturnType}' on origin method '#{methodName}'.");
 
   static const MessageKind PATCH_REQUIRED_PARAMETER_COUNT_MISMATCH =
       const MessageKind(
@@ skipping 140 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';
   }
 }