[jfindley]

Generics in go, as they're implemented today, sadly have a fair bit of performance overhead. I haven't tried but my assumption would be that go generics are not fast enough to make an effective arena allocator. I'd be thrilled if someone could prove me wrong though!

[throwaway894345]

The performance overhead is when you're calling a method on the generic type--Go has to lookup the specific implementation in a dictionary. Pretty sure that doesn't apply for straight-up container use cases like this one.