I think you are putting way too much emphasis on syntax here. The important contribution of Hack is the type system and this is something that a syntactic-sugar

I think you are putting way too much emphasis on syntax here. The important contribution of Hack is the type system and this is something that a syntactic-sugar translator like Coffeescript can't hope to achieve. I also wouldn't count Clojurescript here. Its a whole different language that just happensto compile down to JS.