How do you get labeled associated values from Mirror children?

[Jens]

No, I wasn't actually sure what you meant, thanks for clarifying.

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@anon9791410

It doesn't matter if we can't use the type, if we can cast it to something we can use. It's the same as throwing out argument labels when you store a function as a closure.

I simply think that if single element tuples are banned (as they currently are), they shouldn't be in the language.

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@anon9791410

I hate that we don't have single-element labeled tuples across the board, but I'm happy that they're in there somewhere. It shows that they're useful and will inspire somebody to fix the situation someday.

OK, yes I agree that single element tuples (labeled and unlabeled) should be allowed. Banning them is just an exception that causes confusion (and creates unfortunate situations like the one in the OP).

Allowing them doesn't seem totally impossible:

@Joe_Groff

They were banned because the “classic” function-argument-tuple model and tuple conversion rules caused type system problems, particularly because every T was implicitly convertible to (label: T) and back. We’ve since shored up the argument label model, and various people have discussed limiting the tuple conversion rules to be less unpredictable and less straining on the type checker. If we solve that problem, then there’s no technical reason remaining for single-element tuples to be banned.

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Since tuples are not the only things in Swift which happen to be written using parentheses, I guess unlabeled single element tuples would have to be written as eg:

let foo = (_: 123)
print(type(of: foo)) // (_: Int)

or

let foo = (123,)
print(type(of: foo)) // (Int,)