Regarding your update: I think there is some interest in passing TS type annotations on to the JS VM/JIT, but my impression is still that TC39 is rather shy on

Regarding your update: I think there is some interest in passing TS type annotations on to the JS VM/JIT, but my impression is still that TC39 is rather shy on the subject after the still not entirely healed scars of ES4. I know I would love to see TS type annotations made syntactically valid if semantically ignored (ala Python's type annotations PEPs), simply to make sure valid TS runs in the browser without a build step to better unify the "subset". It wouldn't be a far shot from there to seeing at least some small type annotation hints support in JS engines. Though I definitely understand the concerns and wariness that anything done there would be very engine-specific and in danger of lock in for the web. I heard there were some V8-specific prototype attempts from some of the Deno developers, but I don't recall how far those attempts got or if they had anything in the way of results.