[Doc] Expands detach documentation in thread::JoinHande.

[gamazeps]

Part of #29378 .

• Adds an example of a thread detaching.
• Expands what detaching means.

r? @steveklabnik

[nagisa]

The example could be simplified with a plain scope or function instead of spawning two threads.

There’s no parent-child relationship between the threads in a process.

[gamazeps]

The example could indeed be simplified to

fn main() {
    {
        thread::spawn(||{
            thread::sleep(Duration::from_millis(10));
            println!("hey");
        });
    }
    thread::sleep(Duration::from_millis(1000));
}

But this is not a form that I have ever encountered in real rust code, thus this example would not be very helpful.
On the other hand a thread spawning a new thread and being joined before the new thread is a behaviour that is encountered in real rust code. It is thus a bit more complex than needed, but I believe that it is also more helpful.

There are indeed no parent-child relationship between thread, this just seemed a good illustration, if you have a better name in mind I'll change for it.

[GuillaumeGomez]

Well, the current example seems fine to me. But if improvements are possible, I'm open to it as long as it's easy to understand for readers.

[steveklabnik]

I am happy with either.

[gamazeps]

Changed the child notation for spawned or associated.

On the other hand I still believe the current example to more helpful.

[gamazeps]

r? @rust-lang/docs

[steveklabnik]

could you put an extra newline above here

[gamazeps]

Done

[steveklabnik]

and below here, please? that is, an empty ///. This feels a bit cramped.

[gamazeps]

Done

[steveklabnik]

I am happy with either.

[gamazeps]

Done :)

[Mark-Simulacrum]

@steveklabnik I think this is ready for another review and should be ready to go.

[frewsxcv]

This should be marked no_run so we compile the code but don't run it during tests (we don't want this test to take a full second)

see also: https://doc.rust-lang.org/nightly/book/first-edition/documentation.html#running-documentation-tests

[steveklabnik]

r=me after the change @frewsxcv mentioned, thank you!

[alexcrichton]

ping @gamazeps, just wanted to make sure this was still on your radar!

[gamazeps]

@alexcrichton and you were right to do so :)

[gamazeps]

Done :)

[frewsxcv]

@bors r+ rollup

[bors]

📌 Commit b76b9e1 has been approved by frewsxcv