I'm continuing with the migration towards Swift 6. Within one of our libraries, I want to check whether a parameter object: Any? confirms to Sendable.
I tried the most obvious one:
if let sendable = object as? Sendable {
}
But that results into the compiler error "Marker protocol 'Sendable' cannot be used in a conditional cast".
Is there an other way to do this?
That’s not surprising. Sendable is a marker protocol, which means it has no runtime presence, which means that a runtime type check isn’t feasible.
I’ve never seen folks bump into this before because a key goal of Swift concurrency is to have the compiler validate your concurrency at build time. Checking stuff at runtime kinda runs counter to that goal.
I don’t think there’s an obvious path forward here. I suspect you’ll have to take a step back and look at some bigger picture options, like converting this parameter to a generic or adding another routine that takes any Sendable.
If you can provide more details about the big picture, I’d be happy to offer further advice.
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I have this issue, in the case where I get a userInfo dictionary from an OS API which is [String: Any], and I need to store it as a [String: any Sendable] to be able to fit it into my own code which is Sendable. What to do in this case?