assert isAsynchronous and isGenerator false if parseAsync is false

pkg/analyzer/lib/src/generated/parser.dart

Index: pkg/analyzer/lib/src/generated/parser.dart
diff --git a/pkg/analyzer/lib/src/generated/parser.dart b/pkg/analyzer/lib/src/generated/parser.dart
index de0306f68f7c9a3cc8eca99b9598f94f1bbd2b18..9774a7331e8191f050417d6347cfe1252ec51510 100644
--- a/pkg/analyzer/lib/src/generated/parser.dart
+++ b/pkg/analyzer/lib/src/generated/parser.dart
@@ -6101,9 +6101,13 @@ class Parser {
         keyword = getAndAdvance();
         if (!_parseAsync) {
           _reportErrorForToken(ParserErrorCode.ASYNC_NOT_SUPPORTED, keyword);
+          keyword = null;

[Brian Wilkerson, 2016/01/13 21:38:01]

I don't think we want to make these changes to the parser (other than the error
code fix). As a general principle we capture the actual content of the file even
if it's invalid. More specifically, there are UX implications:
 - If we've already told the user that async isn't supported, then that should
be enough. Do we really want them to get an error every time they used an async
'for', 'await' or 'yield'?
 - If we have quick assists to help them convert their code it might be harder
to implement correctly if we've lost information.

Is there a problem that you're seeing that this fixes?

[danrubel, 2016/01/13 22:02:20]

Yes. There are a number of places in the resolver and elsewhere that first check
isAsynchronous and then access resolver.futureType, resolver.streamType, etc.
These will all be null if there is no dart:async library. This seemed the best
way to fix resolution when async is not supported.

An alternate approach is to revert this change and have the resolver define
placeholder/mock declarations and elements for Future and Stream when dart:async
is not available. Would that be a better approach?

         }
         if (_matches(TokenType.STAR)) {
           star = getAndAdvance();
+          if (!_parseAsync) {
+            star = null;
+          }
           _inGenerator = true;
         }
         _inAsync = true;
@@ -6111,9 +6115,13 @@ class Parser {
         keyword = getAndAdvance();
         if (!_parseAsync) {
           _reportErrorForToken(ParserErrorCode.ASYNC_NOT_SUPPORTED, keyword);
+          keyword = null;
         }
         if (_matches(TokenType.STAR)) {
           star = getAndAdvance();
+          if (!_parseAsync) {
+            star = null;
+          }
           _inGenerator = true;
         }
       }
@@ -9381,8 +9389,8 @@ class ParserErrorCode extends ErrorCode {
   /**
    * Some environments, such as Fletch, do not support async.
    */
-  static const CompileTimeErrorCode ASYNC_NOT_SUPPORTED =
-      const CompileTimeErrorCode('ASYNC_NOT_SUPPORTED',
+  static const ParserErrorCode ASYNC_NOT_SUPPORTED =
+      const ParserErrorCode('ASYNC_NOT_SUPPORTED',
           "Async and sync are not supported in this environment.");
 
   static const ParserErrorCode BREAK_OUTSIDE_OF_LOOP = const ParserErrorCode(