@typescript-bot test this
@typescript-bot user test this
@typescript-bot run dt

Heya @ahejlsberg, I've started to run the extended test suite on this PR at fd1a4cb. You can monitor the build here.

Heya @ahejlsberg, I've started to run the parallelized Definitely Typed test suite on this PR at fd1a4cb. You can monitor the build here.

Heya @ahejlsberg, I've started to run the parallelized community code test suite on this PR at fd1a4cb. You can monitor the build here.

The user suite test run you requested has finished and failed. I've opened a PR with the baseline diff from master.

The only test changes related to this PR are some new errors in the RWC vscode project. All but one of them are flagging real issues. For example, code that declares something as a KeyCode[], but then compares element values to -1, which doesn't match any declared KeyCode member. So, the array declaration should really be (KeyCode | -1)[].

The one undesired new error is related to this enum declaration in vs/editor/common/modes.ts:

/**
 * Open ended enum at runtime
 * @internal
 */
export const enum LanguageId {
	Null = 0,
	PlainText = 1
}

The intent here is for LanguageId to be a numeric (i.e. non-union) enum. This can be accomplished by changing one of the enum values to a computed expression:

export const enum LanguageId {
	Null = +0,
	PlainText = 1
}

Subtle, but actually an intended and documented behavior.

This seems like almost pure goodness, but I would still err on the side of saying that this can wait for 4.3. That +0 workaround is pretty subtle.

What is the case for the non-union enum? It's unclear from that example.

Let me know if https://github.com/microsoft/TypeScript/wiki/Breaking-Changes#union-enums-cannot-be-compared-to-any-number accurately reflects the change here.

What is the case for the non-union enum? It's unclear from that example.

The code that broke compares a value of type LanguageId to the numeric value 73. I guess the intent is to create symbolic names for a few special language IDs, but otherwise allow any integer value.

Let me know if https://github.com/microsoft/TypeScript/wiki/Breaking-Changes#union-enums-cannot-be-compared-to-any-number accurately reflects the change here.

Yes, looks good.