Change the calling convention of the sync* body to fix bugs and avoid allocations.
- Body takes the controlling _SyncStarIterator as a parameter.
- `yield` assigns directly to the `_current` field and returns.
- `yield*` calls a method on the controlling iterator (rather than returning the iterable). This avoids an allocation to wrap the iterable, a type test to distinguish `yield` from `yield*`, and allows the `get:iterator` call to happen in the dynamic scope of try-catch surrounding the `yield*` to that it will catch any exceptions.
- Avoid using IIFE to bind constants just to call the body.
- Use a dummy body to avoid the need to testing termination of the body.
Tests now passing:
co19_2/Language/Statements/Yield_and_Yield_Each/Yield_Each/execution_sync_t05
language_2/sync_star/move_past_end_test
language_2/sync_star/sync_star_exception_current_test
language_2/sync_star/sync_star_exception_iterator_test
language_2/sync_star/sync_star_exception_nested_test
language_2/sync_star/sync_star_exception_test
Bug: #51992
Change-Id: I397b470e121b8d71242ac28b3130637b78a1d0dc
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/294685
Reviewed-by: Mayank Patke <fishythefish@google.com>
Commit-Queue: Stephen Adams <sra@google.com>
Stephen Adams
4c0de8ed89