Update to typescript v4.x and research deno transpiler

[klesun]

Some articles claim that typescript got a compile speed boost in 3.9, should try it out. Though the boost could be only related to type check, not the bare transpilation which I think is bottlenecked at some internal logging or stuff, as it's not intended use case of typescript.

There is a discussion regarding means to just transpile ts code ASAP in deno: https://github.com/denoland/deno/issues/4323, maybe some useful info can be mined there.

That is certainly a possibility. That is something we would likely do in swc as well, and it would be blazing fast. Ry and I have talked about it in general terms, but this discussion here is a compelling use case. It certainly would be more preferable than a watch mode.

Upd.: SWCSWCSWC