[msoad]

Unfortunately TypeScript is doing all of type-checking synchronously mostly due how it needs to build a global symbols list first. There are some hints that they might move towards more parallel processing but it requires a lot of major changes

https://github.com/microsoft/TypeScript/issues/30235

[constexpr]

Yeah I was afraid of that. Ideally it would be possible to do type checking in parallel at the function level or something, but TypeScript allows you to omit the return type and then infers the return type from the function body which adds additional dependencies and makes that more complicated to parallelize. I wonder if it would still be possible though. Maybe just for functions where the return type and all argument types are present? Then the approach would be sort of outside-in where you type check the unparallelizable global stuff serially first and then type check the remaining isolated function body stuff in parallel afterward.