[DanielHB]

not super familiar with Rust but isn't Option<T> just an union type of null and T? I get the language has special semantics for this compared to a union type but it is conceptionally just an union.

For example this is something you can do with typescript.

  function(args: Arguments) { ... }

  type Arguments = { a: number, b: number } | { a: number, b: string, c: number }

the Arguments { a: 1, b: 1, c: 1 } is not representable.

[0x457]

> not super familiar with Rust but isn't Option<T> just an union type of null and T?

Only if there is a niche optimization happens if T is never null, otherwise it's a tagged union.

That's not what you're replying to is about.

[qzzi]

I'm pretty sure they're talking about reference counting that depends on the arguments, not about optional arguments or invalid argument combinations.