cgen: implement channel push()/pop() using <- operator (#6154)

vlib/sync/channel_select_2_test.v

@@ -1,45 +1,42 @@
 import sync
+import time
 
 fn do_rec_i64(ch chan i64) {
 	mut sum := i64(0)
 	for _ in 0 .. 300 {
-		mut a := i64(0)
-		(&sync.Channel(ch)).pop(&a)
-		sum += a
+		sum += <-ch
 	}
 	assert sum == 300 * (300 - 1) / 2
 }
 
 fn do_send_int(ch chan int) {
 	for i in 0 .. 300 {
-		(&sync.Channel(ch)).push(&i)
+		ch <- i
 	}
 }
 
 fn do_send_byte(ch chan byte) {
 	for i in 0 .. 300 {
-		ii := byte(i)
-		(&sync.Channel(ch)).push(&ii)
+		ch <- byte(i)
 	}
 }
 
-fn do_send_i64(mut ch sync.Channel) {
+fn do_send_i64(ch chan i64) {
 	for i in 0 .. 300 {
-		ii := i64(i)
-		ch.push(&ii)
+		ch <- i
 	}
 }
 
 fn test_select() {
 	chi := chan int{}
-	mut chl := sync.new_channel<i64>(1)
+	chl := chan i64{cap: 1}
 	chb := chan byte{cap: 10}
 	recch := chan i64{cap: 0}
 	go do_rec_i64(recch)
 	go do_send_int(chi)
 	go do_send_byte(chb)
-	go do_send_i64(mut chl)
-	mut channels := [&sync.Channel(chi), &sync.Channel(recch), chl, &sync.Channel(chb)]
+	go do_send_i64(chl)
+	mut channels := [&sync.Channel(chi), &sync.Channel(recch), &sync.Channel(chl), &sync.Channel(chb)]
 	directions := [sync.Direction.pop, .push, .pop, .pop]
 	mut sum := i64(0)
 	mut rl := i64(0)
@@ -73,4 +70,5 @@ fn test_select() {
 		256 * (256 - 1) / 2 +
 		44 * (44 - 1) / 2
 	assert sum == expected_sum
+	time.sleep_ms(20) // to give assert in coroutine enough time
 }