Wrong implementation of yield/yield* in dartdevk

[sgrekhov]

dartdevk doesn't implement yield/yield* behavior described in https://github.com/dart-lang/language/blob/master/accepted/future-releases/async-star-behavior/feature-specification.md

There are several issues.

1. If execution is paused on yield/yield* and stream is cancelled, then yield* should act like a return; statement. But it isn't so and it causes failure of the following co19 tests

co19/Language/Statements/Yield_and_Yield_Each/Yield/execution_async_A03_t01
co19/Language/Statements/Yield_and_Yield_Each/Yield/execution_async_A03_t01
co19/Language/Statements/Yield_and_Yield_Each/Yield_Each/execution_async_A03_t07
co19/Language/Statements/Yield_and_Yield_Each/Yield_Each/execution_async_A03_t08
co19/Language/Statements/Yield_and_Yield_Each/Yield_Each/execution_async_A03_t09

2. In an asynchronous function, an await for (var event in stream) ... loop first listens on the iterated stream, then for each data event, it executes the body. If the body performs any asynchronous operation (that is, it does not complete synchronously because it executes any await, wait for or yield* operation, or it blocks at a yield), then the stream subscription must be paused. It is resumed again when the body completes normally. But it isn't so and it causes failure of

co19/Language/Statements/Yield_and_Yield_Each/Yield/execution_async_A05_t02

3. If execution is paused then execution should be blocked at yield. See failures of

co19/Language/Statements/Yield_and_Yield_Each/Yield/execution_async_A01_t01
co19/Language/Statements/Yield_and_Yield_Each/Yield/execution_async_A01_t02
co19/Language/Statements/Yield_and_Yield_Each/Yield/execution_async_A01_t03
co19/Language/Statements/Yield_and_Yield_Each/Yield/execution_async_A01_t04
co19/Language/Statements/Yield_and_Yield_Each/Yield/execution_async_A01_t05
co19/Language/Statements/Yield_and_Yield_Each/Yield/execution_async_A01_t06
co19/Language/Statements/Yield_and_Yield_Each/Yield/execution_async_A01_t07
co19/Language/Statements/Yield_and_Yield_Each/Yield/execution_async_A01_t08

See full log at https://dart-ci.firebaseapp.com/cl/253664/1

[Markzipan]

We're receiving bugs about this inconsistency internally as well. Another repro by a Googler:

Stream<int> f() async* {
  var count = 0;
  yield* Stream.fromIterable([1, 2, 3]).map((x) {
    count++;
    return x;
  });
  expect(count, 3);
}

final s = f().listen(null);
s.onData((x) => s.cancel());

which fails on DDC with:

Expected: <3>
  Actual: <1>

since DDC resumes execution of the body despite canceling the stream.

[natebosch]

Potential duplicates or related issues:

#53062
#47764
#47342
#42764
#35624
#54411