They probably just don't know the name. STT is what TypeScript uses, and that's pretty well-known, though a lot of the STT power is considered "advanced typing.

They probably just don't know the name. STT is what TypeScript uses, and that's pretty well-known, though a lot of the STT power is considered "advanced typing." I write a lot in other language that uses ADTs, and I really miss STTs for the ease by which I can construct a "Partial" data type with significantly less boilerplate. Of course, it also enables laziness, as instead of considerig whether it's proper to have a specific Partial product type, I just create it and move on. Easier to break loosey-goosey on modeling the domain.