Can anyone do a "explain lime I'm five" summary of the problem and how the solution would work when typescript is converted down to JavaScript again so the interpreter takes it? Looking from the top it seems like it would add more complexity (and potentially new bugs or exceptions) than it could make things faster and safer.

IF typescript was 100% its own thing and not built on top of JS, it would make complete sense to do it, but with a js engine below it...