Remove ES2018 transforms for ES2018 target

[saschanaz]

Fixes #20463

[DanielRosenwasser]

Seems like there should be a test to ensure that ES2018 actually preserves these features.

[DanielRosenwasser]

@rbuckton can you take a look at this PR?

[saschanaz]

@DanielRosenwasser Yeah... but where should the test go? Can you point an existing test which can be a guide?

[rbuckton]

@saschanaz: You would likely need to move around some of the tests in tests/cases/conformance to align them with the correct ECMAScript edition.

[saschanaz]

I fixed the tests for async generator / for-await to correctly target es2018 instead of esnext.

[saschanaz]

Couldn't replace @lib: esnext yet as it depends on #26220.

[saschanaz]

So it seems this is blocked again? #28354

[weswigham]

That's TypeFlags not TransformFlags. Different enum.

[saschanaz]

Oops!

[weswigham]

Ping @rbuckton for review again - this looks pretty done. esnext just being optional catch clause right now is pretty great (sad it didn't make it on the 2018 train, would have made this even easier).

[saschanaz]

Rebased with git file rename, now it should be easier to review commit-by-commit.

[fearthecowboy]

Is this going to make it in 3.3?