Region isolation of array elements

Using Swift
3

The same problem also arises when not dealing with Array:

class File {
    func read() -> String { "" }
}

func someFunction(
    file: File
) async throws {
    await withTaskGroup(of: Void.self) { group in
        group.addTask { // same error as before
            let c = file.read()
            print(c)
        }
    }
}

Neither will the following trick work:

func someFunction(
    file: sending File
) async throws {
    func helper(_ file: sending File, _ group: inout TaskGroup<Void>) {
        group.addTask {
            let c = file.read()
            print(c)
        }
    }

    await withTaskGroup(of: Void.self) { group in
        helper(file, &group)  // error: Sending 'file' risks causing data races
    }
}

There's some related discussions about this in the forum (e.g. New task-creation APIs - #5 by philipp.gabriel) but no elegant solution can be found. I agree with jrose that withTaskGroup is nowadays best suited with Sendable inputs.

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