Special channel features example needs set capacity to success

[jorgeluismireles]

Describe the issue

The example at the doc don't push a channel successfully unless the channel cap is set.

Original code:

struct Abc {
    x int
}

a := 2.13
ch := chan f64{}
res := ch.try_push(a) // try to perform `ch <- a`
println(res)
l := ch.len // number of elements in queue
c := ch.cap // maximum queue length
is_closed := ch.closed // bool flag - has `ch` been closed
println(l)
println(c)
mut b := Abc{}
ch2 := chan Abc{}
res2 := ch2.try_pop(mut b) // try to perform `b = <-ch2`

Produces

not_ready
0
0

With the following change:

ch := chan f64{ cap:1 }

Produces what we expect:

success
1
1

Don't know if default capacity should not be zero (bug) or not. When you adapt this code for you don't get receptions. Then debug and found result not_ready and then when you set the capacity you get your messages.

Links

https://docs.vlang.io/concurrency.html#special-channel-features

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[huly-for-github]

Connected to Huly®: V_0.6-21911

[jorgeluismireles]

Another way to document try_push success is consuming first and leaving the channel unbuffered:

a := 2.13
ch := chan f64{}
spawn fn[ch]() {
	println('pop: ${<-ch}')
	exit(0)
}()
push := ch.try_push(a) // try to perform `ch <- a`
println('push:${push} len:${ch.len} cap:${ch.cap} closed:${ch.closed}')
for { }

push:success len:0 cap:0 closed:false
pop: 2.13