Initial inline value support

[Kingwl]

Fixes #43449

[typescript-bot]

Thanks for the PR! It looks like you've changed the TSServer protocol in some way. Please ensure that any changes here don't break consumers of the current TSServer API. For some extra review, we'll ping @sheetalkamat, @amcasey, @mjbvz, @minestarks for you. Feel free to loop in other consumers/maintainers if necessary

[typescript-bot]

The TypeScript team hasn't accepted the linked issue #43449. If you can get it accepted, this PR will have a better chance of being reviewed.

[Kingwl]

/cc: @mjbvz @DanielRosenwasser @connor4312 @sheetalkamat

[Kingwl]

Not pretty sure what should we do in class-like.

[Kingwl]

Basically ready for review except class like element.

[andrewbranch]

Thanks @Kingwl! FYI, we do want the implementation to go in a TS Server plugin rather than in TS Server directly. I believe we have the ability to do that thanks to your PR at #44291. I also need to understand more about what VS Code wants with the expression spans we return in order to give any implementation a good review. Maybe @connor4312 and @hediet can help here: mainly I was surprised by this part of the description from #43449:

Property assignments should be evaluated, foo() in { x: foo() }

I just want to confirm that it’s ok that the expressions in the spans we return may have side effects. Obviously a call expression can have side effects, but property expressions can too (through getters). I want to ensure that our syntactic analysis is not supposed to filter out constructs that are possibly-effectful.

[connor4312]

I just want to confirm that it’s ok that the expressions in the spans we return may have side effects.

Yea, that's fine. V8 provides debugger-level functionality that lets us prevent evaluations from causing side effects.