Discussion on: Easy Interfaces with Zig 0.10.0

Spoke with Spex and Andrew and they confirmed that doing switch (self.*) does not create a copy, so you can do this:

const Cat = struct {
    hp: usize,

    pub fn eat(self: *Cat) void {
        self.hp += 1;
    }
};

const Animal = union(enum) {
    cat: Cat,
    dog: Dog,

    pub fn eat(self: *Animal) void {
        switch (self.*) {
            inline else => |*case| case.eat(),
        }
    }
};

Diff:

1. eat now accepts a *Cat, not a *Animal
2. the switch case is now capturing |*case| and calling the function normally

This would not work if self.* created a copy, but since it never does, it's fine.