[everforward]

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.

[lolinder]

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.

[everforward]

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.