TypeScript 4.0: Allow spread in the middle of tuples

[nicolo-ribaudo]

Q	A
Patch: Bug Fix?
Major: Breaking Change?
Minor: New Feature?	Yes
Tests Added + Pass?	Yes
Documentation PR Link
Any Dependency Changes?
License	MIT

https://devblogs.microsoft.com/typescript/announcing-typescript-4-0-beta/#variadic-tuple-types

Example:

type Strings = [string, string];
type Numbers = [number, number];

// [string, string, number, number]
type StrStrNumNum = [...Strings, ...Numbers];

Note: currently the node is called TSRestType and not TSSpreadType. I think we should rename it in the future.

Merged to #11760, not landed in main yet.

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[DanielRosenwasser]

@weswigham @ahejlsberg anything special here? Looks reasonable to me

[weswigham]

Only question I'd have is if this plays well with the labeled tuple member support.

[nicolo-ribaudo]

Only question I'd have is if this plays well with the labeled tuple member support.

There is a disable test in the other PR to test the integration between these 👍

[nicolo-ribaudo]

I'm merging this to a feat-7.11.0/ts-4.0 branch so that we can test the PRs together before merging them to main.