Fix scope/context behavior in await transformer.

Fix scope/context behavior in await transformer.

We are not allowed to reuse LocalScope in different SequenceNode_s. The problem is that if a context needs to be created for that scope the FlowGraphbuilder will insert context creation code at all SequenNoce_s that use this scope. This results in scopes and contexts being out of sync and writing garbage. The fix is to just chain a new scope that is on the same function- and loop-level.

Also fix recognizing of "await" in async functions. A follow up CL will enable await in loops, if, return, ...

BUG=
R=hausner@google.com

Committed: https://code.google.com/p/dart/source/detail?r=39571

[Michael Lippautz (Google), 2014-08-26 20:08:17]

mlippautz@google.com changed reviewers:
+ hausner@google.com

[Michael Lippautz (Google), 2014-08-26 20:08:17]

The test covers both cases as 
a) it forces creation of a scope/context at the for loop and
b) ``await task`` did previously trigger a parse of a var decl which lead to
failure.

[hausner, 2014-08-26 20:45:48]

I hope you can make the IsIdentifier function cheaper. See comment below.

https://codereview.chromium.org/508643004/diff/1/runtime/vm/parser.cc
File runtime/vm/parser.cc (right):

https://codereview.chromium.org/508643004/diff/1/runtime/vm/parser.cc#newcode...
runtime/vm/parser.cc:6267: is_async = func.IsAsyncFunction() ||
func.is_async_closure();
I think this is too expensive. I think it would make sense to cache a boolean
value in the parser object that determines whether "async" is a regular
identifier or a keyword.

The value is known when the parser object is created, I believe.

[Michael Lippautz (Google), 2014-08-26 21:53:58]

Patchset #2 (id:20001) has been deleted

[Michael Lippautz (Google), 2014-08-26 21:55:39]

Patchset #2 (id:40001) has been deleted

[Michael Lippautz (Google), 2014-08-26 22:05:19]

Patchset #2 (id:60001) has been deleted

[Michael Lippautz (Google), 2014-08-26 22:06:11]

Patchset #2 (id:80001) has been deleted

[Michael Lippautz (Google), 2014-08-26 22:07:44]

PTAL

https://codereview.chromium.org/508643004/diff/1/runtime/vm/parser.cc
File runtime/vm/parser.cc (right):

https://codereview.chromium.org/508643004/diff/1/runtime/vm/parser.cc#newcode...
runtime/vm/parser.cc:6267: is_async = func.IsAsyncFunction() ||
func.is_async_closure();
On 2014/08/26 20:45:47, hausner wrote:
> I think this is too expensive. I think it would make sense to cache a boolean
> value in the parser object that determines whether "async" is a regular
> identifier or a keyword.
> 
> The value is known when the parser object is created, I believe.

Agree. I added the proposed indicator to the parser. It is only set/reset when
actually parsing the function body, i.e., in ParseFunc().

[hausner, 2014-08-26 22:48:07]

lgtm

https://codereview.chromium.org/508643004/diff/100001/runtime/vm/parser.cc
File runtime/vm/parser.cc (right):

https://codereview.chromium.org/508643004/diff/100001/runtime/vm/parser.cc#ne...
runtime/vm/parser.cc:3035: await_is_keyword_ = false;
Interesting. Why are you setting this flag to false here?

https://codereview.chromium.org/508643004/diff/100001/runtime/vm/parser.h
File runtime/vm/parser.h (right):

https://codereview.chromium.org/508643004/diff/100001/runtime/vm/parser.h#new...
runtime/vm/parser.h:774: // context async is not treated as identifier but as
primary.
as a keyword.

[Michael Lippautz (Google), 2014-08-26 22:59:54]

Patchset #3 (id:120001) has been deleted

[Michael Lippautz (Google), 2014-08-26 23:00:37]

Patchset #3 (id:140001) has been deleted

[Michael Lippautz (Google), 2014-08-26 23:01:44]

https://codereview.chromium.org/508643004/diff/100001/runtime/vm/parser.cc
File runtime/vm/parser.cc (right):

https://codereview.chromium.org/508643004/diff/100001/runtime/vm/parser.cc#ne...
runtime/vm/parser.cc:3035: await_is_keyword_ = false;
On 2014/08/26 22:48:06, hausner wrote:
> Interesting. Why are you setting this flag to false here?

As discussed offline: Need for parsing nested functions. Example:

foo() {
  bar() async {};
  // We need to have await_is_keyword_ set to false here.
}

https://codereview.chromium.org/508643004/diff/100001/runtime/vm/parser.h
File runtime/vm/parser.h (right):

https://codereview.chromium.org/508643004/diff/100001/runtime/vm/parser.h#new...
runtime/vm/parser.h:774: // context async is not treated as identifier but as
primary.
On 2014/08/26 22:48:06, hausner wrote:
> as a keyword.

Done.

[Michael Lippautz (Google), 2014-08-26 23:02:05]

Committed patchset #3 manually as 39571 (presubmit successful).