all: enable x = <-ch or {...} (#6195)

vlib/sync/channel_array_mut_test.v

@@ -15,13 +15,12 @@ mut:
 
 // this function gets an array of channels for `St` references
 fn do_rec_calc_send(chs []chan mut St) {
-	mut s := &St(0)
 	for {
-		if !(&sync.Channel(chs[0])).pop(&s) {
+		mut s := <-chs[0] or {
 			break
 		}
 		s.n++
-		(&sync.Channel(chs[1])).push(&s)
+		chs[1] <- s
 	}
 }
 
@@ -32,8 +31,8 @@ fn test_channel_array_mut() {
 		n: 100
 	}
 	for _ in 0 .. num_iterations {
-		(&sync.Channel(chs[0])).push(&t)
-		(&sync.Channel(chs[1])).pop(&t)
+		chs[0] <- t
+		t = <-chs[1]
 	}
 	(&sync.Channel(chs[0])).close()
 	assert t.n == 100 + num_iterations

vlib/sync/channel_opt_propagate_test.v

@@ -0,0 +1,39 @@
+import sync
+
+const (
+	num_iterations = 10000
+)
+
+fn get_val_from_chan(ch chan i64) ?i64 {
+	r := <-ch?
+	return r
+}
+
+// this function gets an array of channels for `i64`
+fn do_rec_calc_send(chs []chan i64, sem sync.Semaphore) {
+	mut msg := ''
+	for {
+		mut s := get_val_from_chan(chs[0]) or {
+			msg = err.str()
+			break
+		}
+		s++
+		chs[1] <- s
+	}
+	assert msg == 'channel closed'
+	sem.post()
+}
+
+fn test_channel_array_mut() {
+	mut chs := [chan i64{}, chan i64{cap: 10}]
+	sem := sync.new_semaphore()
+	go do_rec_calc_send(chs, sem)
+	mut t := i64(100)
+	for _ in 0 .. num_iterations {
+		chs[0] <- t
+		t = <-chs[1]
+	}
+	(&sync.Channel(chs[0])).close()
+	sem.wait()
+	assert t == 100 + num_iterations
+}