Does that work for all class members? I think I've only ever seen that on private members, though I don't know whether that's because it's so much easier to check whether a private member is used or because an unused public member isn't an issue for eg a library.
This feels like an issue that reduces down to the Halting Problem, though. Halting is a function that could be made a member of a class, so if you could tell whether that method is used or not then you could tell whether the program will halt or not. I think it's one of those things that feels like it should be fairly easy, and it's really really not.
Comparing this to the halting problem isn't really meaningful here because even if you could make a full mapping (which yours isn't), you can prove that a rather large subset of programs halt, which is good enough for a tree shaker.
I don't need to be able to eliminate every single unused function in every situation, but if I can prove that certain functions are unused then I can delete just those functions. We're already doing this regularly with standalone functions, so my question is just why this isn't done with class members.
Ah, I see your question now. Prototypes maybe? I’m not nearly a good enough JS dev to have a reasonable guess at that specifically.
Being able to access class members using square bracket syntax with a variable also seems like it would make it really difficult to prove that something isn’t used. I’m thinking something unhinged like using parameters to build a string named after a class member and then accessing it that way.
Dunno, I would be curious if someone has a definitive answer as well.
This feels like an issue that reduces down to the Halting Problem, though. Halting is a function that could be made a member of a class, so if you could tell whether that method is used or not then you could tell whether the program will halt or not. I think it's one of those things that feels like it should be fairly easy, and it's really really not.