I don't think it's exactly right to call it a superset either.. It adds types and constraints that have no effect on the resulting transpiled code besides an i

I don't think it's exactly right to call it a superset either.. It adds types and constraints that have no effect on the resulting transpiled code besides an insurance that said type constraints are being met. To better illustrate what I mean, in the start of a Unix script you sometimes have them augmented with #!interpreter. But this extra contextual information is not a superset of the scripting language itself. Likewise Typescript is also an augmentation that lives within the code that provides contextual information to the Typescript transpiler itself, but does not necessarily effect the actuall produced JavaScript.