[rorymalcolm]

It is popular in newgen tooling but I feel its more a function of the slowness of `tsc` than anything else. I get why `tsc` is slow, and have a lot of respect for the team and the constraints they work under but I can't help but feeling if we were to get a faster type checker (potentially `stc` from the creator of `swc` which also does this? https://github.com/dudykr/stc), this choice would be less popular. However if I'm honest I don't know if TypeScript's type system means that there are some natural constraints on how fast it can be validated.

[WorldMaker]

I feel like part of the issue is not as much that typechecking is slow, but that at runtime type checking "doesn't matter". I think a lot of people would like to see the Stage 1 Type Annotations proposal [1] move forward where JS would allow and ignore type annotations at runtime and even "type stripping" disappears at runtime for TS files.

It doesn't matter how fast a type checker is at that point at runtime.

The only reason to bring back type checking at runtime would be if V8 et al ever also started using type hints as JIT hints and you want to triple check you are sending the right type hints and not accidentally stomping on your own runtime performance. (Which is intentionally not in that Stage 1 proposal mind you: no one is expecting runtime type hints in the near future.)

[1] https://github.com/tc39/proposal-type-annotations