[Experiment] feat(51556): support satisfies operator on functions/classes

[a-tarasyuk]

Fixes #51556

[typescript-bot]

Looks like you're introducing a change to the public API surface area. If this includes breaking changes, please document them on our wiki's API Breaking Changes page.

Also, please make sure @DanielRosenwasser and @RyanCavanaugh are aware of the changes, just as a heads up.

[alvis]

@a-tarasyuk Really appreciate for your effort for making satisfies works on functions! Is this PR still in draft status or close to ship?

Plz consider adding it to typescript 5.6 🙏🏼 @DanielRosenwasser and @RyanCavanaugh

[a-tarasyuk]

@alvis It's still a draft because there's no final consensus on certain cases. In addition, I think that version 5.6 won't include this feature...

I'm uncertain about the future of this feature, however, @RyanCavanaugh or @DanielRosenwasser might have more information.

[louwers]

Looking forward to this functionality. I think the satisfies operator is already supported on functions, it's just not supported on function declarations.

Does this also bring support for @satisfies in JSDoc? Could you add tests for it? See my comment here for an example that is expected to work.

[a-tarasyuk]

@louwers You're right — satisfies currently works only for expressions. I think it’s better to handle JSDoc support in a separate PR. This PR should focus on supporting satisfies for func declarations (and possibly class declarations #60849?).