[surrealize]

Thanks, it's nice to hear it from the horse's mouth.

Does it make sense to think about TCP as being a matter of degree? Would it be correct to say that the number of constructs that would break TCP is fewer with let, const, and => than with earlier versions of ES?

I think a "partial TCP" would matter for manual refactoring, if not for (e.g.) a future macro system. On the other hand, perhaps it's more confusing to mention it if it's not total.

[BrendanEich]

Saw dherman's comment just now, he and you are right that there is a spectrum of TCP, and if you use a subset of JS to write expression-bodied => functions, you get the refactoring property that people associate with TCP.