[DanielHB]

Typescript is too powerful, there are a lot of typescript constructs that can't be represented in OpenAPI specs. Or that could generate massively complex OpenAPI specs that would bring your tooling performance to a crawl.

A subset of typescript could work, but I imagine it would be fairly confusing to support some features here and other features there.

I think they are going for a minimum common denominator approach and eventually add other targets besides OpenAPI.