I'm glad people are working on this problem. Typescript's compiler performance is certainly a weakness.
Other commenters have rightly called out the complexity of the type system as the reason why this is difficult. The other reason is that Typescript does not have a formal specification. The tsc compiler is the only reference for the correct behaviour. It would be great if the official compiler and these reimplementations could share a common test suite to ensure compatibility.
Other commenters have rightly called out the complexity of the type system as the reason why this is difficult. The other reason is that Typescript does not have a formal specification. The tsc compiler is the only reference for the correct behaviour. It would be great if the official compiler and these reimplementations could share a common test suite to ensure compatibility.