[dart2js] sync* fixes

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>
11 files changed
tree: fe8bd20691c7e792ec10dd3558719bcc5696e79d
  1. .dart_tool/
  2. .github/
  3. benchmarks/
  4. build/
  5. docs/
  6. pkg/
  7. runtime/
  8. samples/
  9. sdk/
  10. tests/
  11. third_party/
  12. tools/
  13. utils/
  14. .clang-format
  15. .gitattributes
  16. .gitconfig
  17. .gitignore
  18. .gn
  19. .mailmap
  20. .style.yapf
  21. .vpython
  22. AUTHORS
  23. BUILD.gn
  24. CHANGELOG.md
  25. codereview.settings
  26. CONTRIBUTING.md
  27. DEPS
  28. LICENSE
  29. OWNERS
  30. PATENT_GRANT
  31. PRESUBMIT.py
  32. README.dart-sdk
  33. README.md
  34. sdk_args.gni
  35. SECURITY.md
  36. WATCHLISTS
README.md

Dart

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