Enable noFallthroughCasesInSwitch

[ghost]

Since we have // @ts-ignore comments now, we don't need to use the lint rule for this any more.

[weswigham]

I dislike this, since @ts-ignore squelches all errors on the following line. If we remove one of these syntax kinds for some reason (or just introduce a typo), that use site will not be marked as an error after the removal (or typo introduction). I dislike the collateral damage this causes in terms of potential safety losses - this feels way too clunky.

[DanielRosenwasser]

. If we remove one of these syntax kinds for some reason

Precisely - we actually can detect cases when an enum will never match in a switch/case given accurate types, which you don't want to ignore.

[Jessidhia]

This goes back to the problem of not being able to specify which specific error is ignored by // @ts-ignore; it's just a blanket ignore all things marker.

Is there no provision for, say, a // fallthrough or // fallsthrough comment in the lint rule? I believe at least the eslint rule that checks for this supports such comments.

[ghost]

OK, let's wait on #9448 to be fixed first.
@Kovensky the tslint rule supports // falls through comments, but the TypeScript implementation does not.