[kernel] set dartAsyncMarker to Sync for continuations

[kernel] set dartAsyncMarker to Sync for continuations

After 89b68e905b6a096148cedc580016a595e106dcdd debugging of async
functions via kernel haven't worked.
Prior to this the dartAsyncMarker for e.g. a rewritte async function
would have been Sync, after it was Yielding.
This changes it back in the continuations rewriting cases.
An alternative fix would be to change
  function.set_is_debuggable(
      kernel_procedure->function()->dart_async_marker() == FunctionNode::kSync);

to something like
  function.set_is_debuggable(
      kernel_procedure->function()->dart_async_marker() == FunctionNode::kSync ||
      kernel_procedure->function()->dart_async_marker() == FunctionNode::kYielding);

in the C++ code.

BUG=
R=kmillikin@google.com

Committed: https://github.com/dart-lang/sdk/commit/4c38b85cb59fd12f07a07bc96b50d86bba38108d

[jensj, 2017-03-13 10:29:09]

jensj@google.com changed reviewers:
+ kmillikin@google.com

[Kevin Millikin (Google), 2017-03-13 11:20:35]

LGTM with a comment at both sites.

https://codereview.chromium.org/2743283002/diff/1/pkg/kernel/lib/transformati...
File pkg/kernel/lib/transformations/continuation.dart (right):

https://codereview.chromium.org/2743283002/diff/1/pkg/kernel/lib/transformati...
pkg/kernel/lib/transformations/continuation.dart:132: dartAsyncMarker:
AsyncMarker.Sync)
This is a fresh function that doesn't correspond directly to any Dart function,
so thinking about its async marker is weird.

We need a comment here explaining why we chose sync and what the consequences
are.  You could say: "SyncYielding functions have no Dart equivalent.  Since
they are synchronous, we use Sync.  (The Dart VM backend uses the Dart async
marker to decide if functions are debuggable.)

Really, this suggests to me that we should consider bringing back is_debuggable
as a separate bit on functions, if we want to hide some but not all of them from
the debugger.

[jensj, 2017-03-13 13:37:10]

Description was changed from

==========
[kernel] set dartAsyncMarker to Sync for continuations

After 89b68e905b6a096148cedc580016a595e106dcdd debugging of async
functions via kernel haven't worked.
Prior to this the dartAsyncMarker for e.g. a rewritte async function
would have been Sync, after it was Yielding.
This changes it back in the continuations rewriting cases.
An alternative fix would be to change
  function.set_is_debuggable(
      kernel_procedure->function()->dart_async_marker() == FunctionNode::kSync);

to something like
  function.set_is_debuggable(
      kernel_procedure->function()->dart_async_marker() == FunctionNode::kSync
||
      kernel_procedure->function()->dart_async_marker() ==
FunctionNode::kYielding);

in the C++ code.

BUG=
==========

to

==========
[kernel] set dartAsyncMarker to Sync for continuations

After 89b68e905b6a096148cedc580016a595e106dcdd debugging of async
functions via kernel haven't worked.
Prior to this the dartAsyncMarker for e.g. a rewritte async function
would have been Sync, after it was Yielding.
This changes it back in the continuations rewriting cases.
An alternative fix would be to change
  function.set_is_debuggable(
      kernel_procedure->function()->dart_async_marker() == FunctionNode::kSync);

to something like
  function.set_is_debuggable(
      kernel_procedure->function()->dart_async_marker() == FunctionNode::kSync
||
      kernel_procedure->function()->dart_async_marker() ==
FunctionNode::kYielding);

in the C++ code.

BUG=
R=kmillikin@google.com

Committed:
https://github.com/dart-lang/sdk/commit/4c38b85cb59fd12f07a07bc96b50d86bba38108d
==========

[jensj, 2017-03-13 13:37:12]

Committed patchset #2 (id:20001) manually as
4c38b85cb59fd12f07a07bc96b50d86bba38108d (presubmit successful).