[async-iteration] implement spec-change to `yield` in async generators

Per https://github.com/tc39/proposal-async-iteration/pull/102/files:

AsyncGeneratorResolve no longer unwraps a value component. Instead, the
value is unwrapped before the builtin call via Await, allowing Promise
rejections to affect the generator control flow.

Thus, all `yield <expr>` implicitly become `yield await <expr>`.

Additionally, `return <expr>` becomes `return await <expr>`. Finally, when
the generator is resumed with `.return()`, the parameter passed to .return()
is awaited before generator execution properly continues).

BUG=v8:5855
R=littledan@chromium.org, neis@chromium.org, adamk@chromium.org

Cq-Include-Trybots: master.tryserver.v8:v8_linux_noi18n_rel_ng
Change-Id: Ife084076c3ed434b5467e6aeba14082f8b410ad5
Reviewed-on: https://chromium-review.googlesource.com/523844
Commit-Queue: Caitlin Potter <caitp@igalia.com>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47011}
19 files changed
tree: 805ac6caa76472b9d779243ddff4c7a8e76a15d4
  1. benchmarks/
  2. build_overrides/
  3. docs/
  4. gni/
  5. gypfiles/
  6. include/
  7. infra/
  8. samples/
  9. src/
  10. test/
  11. testing/
  12. third_party/
  13. tools/
  14. .clang-format
  15. .editorconfig
  16. .gitignore
  17. .gn
  18. .ycm_extra_conf.py
  19. AUTHORS
  20. BUILD.gn
  21. ChangeLog
  22. CODE_OF_CONDUCT.md
  23. codereview.settings
  24. DEPS
  25. LICENSE
  26. LICENSE.fdlibm
  27. LICENSE.strongtalk
  28. LICENSE.v8
  29. LICENSE.valgrind
  30. Makefile
  31. Makefile.android
  32. OWNERS
  33. PRESUBMIT.py
  34. README.md
  35. snapshot_toolchain.gni
  36. WATCHLISTS
README.md

V8 JavaScript Engine

V8 is Google's open source JavaScript engine.

V8 implements ECMAScript as specified in ECMA-262.

V8 is written in C++ and is used in Google Chrome, the open source browser from Google.

V8 can run standalone, or can be embedded into any C++ application.

V8 Project page: https://github.com/v8/v8/wiki

Getting the Code

Checkout depot tools, and run

    fetch v8

This will checkout V8 into the directory v8 and fetch all of its dependencies. To stay up to date, run

    git pull origin
    gclient sync

For fetching all branches, add the following into your remote configuration in .git/config:

    fetch = +refs/branch-heads/*:refs/remotes/branch-heads/*
    fetch = +refs/tags/*:refs/tags/*

Contributing

Please follow the instructions mentioned on the V8 wiki.