t := l.Type()
	if t == nil {
		n.SetType(nil)
		return n
	}
	if !t.IsChan() {
		base.Errorf("invalid operation: %v (non-chan type %v)", n, t)
		n.SetType(nil)
		return n
	}

	if !t.ChanDir().CanSend() {
		base.Errorf("invalid operation: %v (cannot close receive-only channel)", n)
		n.SetType(nil)
		return n
	}
	return n
}

// tcComplex typechecks an OCOMPLEX node.

			break
		}
		om := fmtsort.Sort(val)
		for _, m := range om {
			oneIteration(m.Key, m.Value)
		}
		return
	case reflect.Chan:
		if val.IsNil() {
			break
		}
		if val.Type().ChanDir() == reflect.SendDir {
			s.errorf("range over send-only channel %v", val)
			break
		}
		i := 0
		for ; ; i++ {
			elem, ok := val.Recv()
			if !ok {
				break
			}