[Kostarrr]

I don’t think the Option presented here is sufficient (it is indeed a “crime”) as you cannot express Some(nil).

But you could probably achieve that using go's not-well-known sum types, e.g. like this

https://github.com/FSMaxB/type-safe-builder-experiment/blob/...

[tsimionescu]

Well, that doesn't really work, as "StaticOptional[T]" can't be used as the type of a variable. It can only be used to create another generic function.

For example, this doesn't work [0]:

  //compilation error: interface contains type constraints
  func TryParse123(s string) StaticOptional[int] {
     if s == "123" {
       return StaticSome[int]{123}
     }
     return StaticNone{}
  }

[0] https://go.dev/play/p/1CnieCLqESC

[Kostarrr]

My bad. I was not aware on incredibly limited go generics are. I tried to make it work despite all restrictions but gave up here https://go.dev/play/p/XVTuJ--ZLgS

[worg]

I'm not well versed in golang generics (at $WORK we use go, but not generics yet) but if you want type switches you'll need interface{} to do that https://go.dev/play/p/1Tn2O_7vCTQ

Which of course defeats the point of using generics

_edit: clarify that my attempt is a bad practice_

[jchw]

I’m pretty sure that’s an interface union, not a sum type. That said, you could definitely do an option type using interfaces, but it would be less efficient than pointers directly because of the itab overhead.

[tsimionescu]

> I’m pretty sure that’s an interface union, not a sum type.

It's a kind of sum type, but it can only be used to constrain types for a generic parameter.

That is, you can define `func foo[T StaticOptional[int]](x T)` and then call it as `foo(StaticNone{})` or `foo(StaticSome[int]{123})`, but you can't do `func foo() StaticOptional[int]` or even `func foo[T StaticOptional[int]]() T {return StaticNone{} }`.

[jchw]

I think that still eats the itab penalty so as long as the structures wind up with the same gcshape? But now I wonder.

[Koiwai]

That Option type is using pointer, not foremetioned Zero, &nil and nil are different things.

https://go.dev/play/p/88We4TDhGQc

[dolmen]

You can store nil in an Option[any] or in any pointer type such as Option[*int].