[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.