[tialaramex]

Zero Size optimisations are a thing in Rust too though, and I don't think an empty struct being zero size is any more surprising than Rust's empty tuple being zero size.

Like, if you tell Rust you want 4 million empty tuples in a vector, it will give you a vector with exactly 4 million empty tuples in it and no heap allocation because those empty tuples don't take space, so, 4 million of them also doesn't take up any space.

[woodruffw]

The key difference being knowledge: I don't have to know `HashSet` is really just a map with a ZST to use it efficiently. All I need to know is that I don't need a value, and the ecosystem obliges me. This in contrast to Go, where I need to know that `struct{}` is a ZST, that the "right" way to do a set is to use it as the map value, &c.

[typical182]

There is also a WIP Go proposal for adding a set to the standard library using the upcoming generics:

https://github.com/golang/go/discussions/47331