Add missing compile-time errors for async/await.

pkg/compiler/lib/src/diagnostics/dart2js_messages.dart

 // Copyright (c) 2015, 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.
 //
 // 2. Reserved words and embedded identifiers should be in single quotes, so
@@ skipping 3167 matching lines @@
   'PREAMBLE': {
     'id': 'GXGWIF',
     'template': "When run on the command-line, the compiled output might"
         " require a preamble file located in:\n"
         "  <sdk>/lib/_internal/js_runtime/lib/preambles.",
   },
 
   'INVALID_SYNC_MODIFIER': {
     'id': 'FNYUYU',
     'template': "Invalid modifier 'sync'.",
-    'options': ['--enable-async'],
     'howToFix': "Try replacing 'sync' with 'sync*'.",
     'examples': ["main() sync {}"],
   },
 
   'INVALID_AWAIT_FOR': {
     'id': 'IEYGCY',
     'template': "'await' is only supported on for-in loops.",
-    'options': ['--enable-async'],
     'howToFix': "Try rewriting the loop as a for-in loop or removing the "
         "'await' keyword.",
     'examples': [
       """
 main() async* {
 await for (int i = 0; i < 10; i++) {}
 }
 """
     ],
   },
 
+  'INVALID_AWAIT_FOR_IN': {
+    'id': 'FIEYGC',
+    'template': "'await' is only supported in methods with an 'async' or "
+                "'async*' body modifier.",
+    'howToFix': "Try adding 'async' or 'async*' to the method body or "
+                "removing the 'await' keyword.",
+    'examples': [
+      """
+main(o) sync* {
+  await for (var e in o) {}
+}
+"""
+    ],
+  },
+
+  'INVALID_AWAIT': {
+    'id': 'IEYHYD',
+    'template': "'await' is only supported in methods with an 'async' or "
+                "'async*' body modifier.",
+    'howToFix': "Try adding 'async' or 'async*' to the method body.",
+    'examples': [
+      """
+main() sync* {
+  await null;
+}
+"""
+    ],
+  },
+
+  'INVALID_YIELD': {
+    'id': 'IPGGCY',
+    'template': "'yield' is only supported in methods with a 'sync*' or "
+                "'async*' body modifier.",
+    'howToFix': "Try adding 'sync*' or 'async*' to the method body.",
+    'examples': [
+      """
+main() async {
+  yield 0;
+}
+"""
+    ],
+  },
+
   'ASYNC_MODIFIER_ON_ABSTRACT_METHOD': {
     'id': 'VRISLY',
     'template':
         "The modifier '#{modifier}' is not allowed on an abstract method.",
     'options': ['--enable-async'],
     'howToFix': "Try removing the '#{modifier}' modifier or adding a "
         "body to the method.",
     'examples': [
       """
 abstract class A {
@@ skipping 447 matching lines @@
         "more code and prevents the compiler from doing some optimizations.",
     'howToFix': "Consider removing this 'noSuchMethod' implementation."
   },
 
   'UNRECOGNIZED_VERSION_OF_LOOKUP_MAP': {
     'id': 'OVAFEW',
     'template': "Unsupported version of package:lookup_map.",
     'howToFix': DONT_KNOW_HOW_TO_FIX
   },
 };