// len()/cap() on a channel must report the ring, not zero.
//
// stage4's len/cap lowering had no *TCChan arm, so it fell through to the
// "return zero" default while legacy called runtime.chanLen/chanCap. Every
// len(chan)/cap(chan) therefore read 0 under stage4 and disagreed with
// legacy. The channel needs both a sender and a listener or the compiler
// rejects it, so the body sends and receives.
package main

func main() {
	ch := chan int32{4}
	if cap(ch) != 4 {
		panic("cap(chan) is not the ring capacity")
	}
	if len(ch) != 0 {
		panic("len(chan) of a new channel is not 0")
	}
	ch <- 7
	if len(ch) != 1 {
		panic("len(chan) after one send is not 1")
	}
	if <-ch != 7 {
		panic("receive returned the wrong value")
	}
	if len(ch) != 0 {
		panic("len(chan) after receive is not 0")
	}
	println("ok")
}