Task.detachedはTask.initとは別のスレッドプールを持つが、無限に伸びるわけではない

main.swift

var greeting = "Hello, playground"
print(greeting, ProcessInfo.processInfo.processorCount)
defer {
    print(greeting)
}

for i in 0..<30 {
    Task.detached {
        print("detached", i)
        sleep(1)
    }
    Task {
        print(i)
        sleep(1)
    }
}

RunLoop.main.run(until: Date().addingTimeInterval(15))

output

Hello, playground 4
detached 0
detached 1
detached 2
0
1
detached 3
2
3
detached 4
detached 5
4
5
detached 6
detached 7
6
7
detached 9
detached 8
8
9
detached 10
detached 11
10
11
detached 12
detached 13
12
13
detached 15
detached 14
14
15
16
detached 16
detached 17
17
detached 18
detached 19
18
19
20
detached 20
detached 21
detached 22
22
23
detached 23
21
24
detached 24
detached 25
detached 26
25
26
detached 27
27
28
detached 28
29
detached 29
Hello, playground