Swift with sending parameter

README.md

What sending enforces

Using sending tells the compiler:

• This value will be consumed by a concurrent context (e.g., a task).
• It must not be accessed again from the current task.
• If it is accessed again (e.g., reused or mutated), the compiler will raise an error.

In the code below, it enforces running the operation once. Using it in the 2nd Task causes a compiler error.

/// Using `sending` with a function.
func run(operation: sending @escaping @isolated(any) () async throws -> Void) {
    Task {
        print("1st task")
        try await operation()
    }
    // 2nd call to operation is not allowed
    Task {
        print("2nd task")
        // try await operation() // compiler error when uncommented
    }
}