go code: replace closed(c) with x, ok := <-c

R=golang-dev, rog, bradfitzwork, r
CC=golang-dev
https://golang.org/cl/4243072

src/pkg/netchan/common.go

@@ -306,7 +306,7 @@ func (nch *netChan) sender() {
 }
 
 // Receive value from local side for sending to remote side.
-func (nch *netChan) recv() (val reflect.Value, closed bool) {
+func (nch *netChan) recv() (val reflect.Value, ok bool) {
 	if nch.dir != Send {
 		panic("recv on wrong direction of channel")
 	}
@@ -317,7 +317,7 @@ func (nch *netChan) recv() (val reflect.Value, closed bool) {
 		nch.space++
 	}
 	nch.space--
-	return nch.ch.Recv(), nch.ch.Closed()
+	return nch.ch.Recv()
 }
 
 // acked is called when the remote side indicates that

src/pkg/netchan/export.go

@@ -181,8 +181,8 @@ func (client *expClient) run() {
 // The header is passed by value to avoid issues of overwriting.
 func (client *expClient) serveRecv(nch *netChan, hdr header, count int64) {
 	for {
-		val, closed := nch.recv()
+		val, ok := nch.recv()
-		if closed {
+		if !ok {
 			if err := client.encode(&hdr, payClosed, nil); err != nil {
 				expLog("error encoding server closed message:", err)
 			}

src/pkg/netchan/import.go

@@ -213,8 +213,8 @@ func (imp *Importer) ImportNValues(name string, chT interface{}, dir Dir, size,
 	if dir == Send {
 		go func() {
 			for i := 0; n == -1 || i < n; i++ {
-				val, closed := nch.recv()
+				val, ok := nch.recv()
-				if closed {
+				if !ok {
 					if err = imp.encode(hdr, payClosed, nil); err != nil {
 						impLog("error encoding client closed message:", err)
 					}

src/pkg/netchan/netchan_test.go

@@ -41,8 +41,8 @@ func exportReceive(exp *Exporter, t *testing.T, expDone chan bool) {
 		t.Fatal("exportReceive:", err)
 	}
 	for i := 0; i < count; i++ {
-		v := <-ch
+		v, ok := <-ch
-		if closed(ch) {
+		if !ok {
 			if i != closeCount {
 				t.Errorf("exportReceive expected close at %d; got one at %d", closeCount, i)
 			}
@@ -78,8 +78,8 @@ func importReceive(imp *Importer, t *testing.T, done chan bool) {
 		t.Fatal("importReceive:", err)
 	}
 	for i := 0; i < count; i++ {
-		v := <-ch
+		v, ok := <-ch
-		if closed(ch) {
+		if !ok {
 			if i != closeCount {
 				t.Errorf("importReceive expected close at %d; got one at %d", closeCount, i)
 			}
@@ -212,8 +212,8 @@ func TestExportHangup(t *testing.T) {
 	}
 	// Now hang up the channel.  Importer should see it close.
 	exp.Hangup("exportedSend")
-	v = <-ich
+	v, ok := <-ich
-	if !closed(ich) {
+	if ok {
 		t.Fatal("expected channel to be closed; got value", v)
 	}
 }
@@ -242,8 +242,8 @@ func TestImportHangup(t *testing.T) {
 	}
 	// Now hang up the channel.  Exporter should see it close.
 	imp.Hangup("exportedRecv")
-	v = <-ech
+	v, ok := <-ech
-	if !closed(ech) {
+	if ok {
 		t.Fatal("expected channel to be closed; got value", v)
 	}
 }

src/pkg/os/inotify/inotify_linux_test.go

@@ -35,6 +35,7 @@ func TestInotifyEvents(t *testing.T) {
 	// Receive events on the event channel on a separate goroutine
 	eventstream := watcher.Event
 	var eventsReceived = 0
+	done := make(chan bool)
 	go func() {
 		for event := range eventstream {
 			// Only count relevant events
@@ -45,6 +46,7 @@ func TestInotifyEvents(t *testing.T) {
 				t.Logf("unexpected event received: %s", event)
 			}
 		}
+		done <- true
 	}()
 
 	// Create a file
@@ -64,16 +66,12 @@ func TestInotifyEvents(t *testing.T) {
 	t.Log("calling Close()")
 	watcher.Close()
 	t.Log("waiting for the event channel to become closed...")
-	var i = 0
+	select {
-	for !closed(eventstream) {
+	case <-done:
-		if i >= 20 {
+		t.Log("event channel closed")
-			t.Fatal("event stream was not closed after 1 second, as expected")
+	case <-time.After(1e9):
-		}
+		t.Fatal("event stream was not closed after 1 second")
-		t.Log("waiting for 50 ms...")
-		time.Sleep(50e6) // 50 ms
-		i++
 	}
-	t.Log("event channel closed")
 }
 
 

src/pkg/reflect/all_test.go

@@ -968,28 +968,28 @@ func TestChan(t *testing.T) {
 
 		// Recv
 		c <- 3
-		if i := cv.Recv().(*IntValue).Get(); i != 3 {
+		if i, ok := cv.Recv(); i.(*IntValue).Get() != 3 || !ok {
-			t.Errorf("native send 3, reflect Recv %d", i)
+			t.Errorf("native send 3, reflect Recv %d, %t", i.(*IntValue).Get(), ok)
 		}
 
 		// TryRecv fail
-		val := cv.TryRecv()
+		val, ok := cv.TryRecv()
-		if val != nil {
+		if val != nil || ok {
-			t.Errorf("TryRecv on empty chan: %s", valueToString(val))
+			t.Errorf("TryRecv on empty chan: %s, %t", valueToString(val), ok)
 		}
 
 		// TryRecv success
 		c <- 4
-		val = cv.TryRecv()
+		val, ok = cv.TryRecv()
 		if val == nil {
 			t.Errorf("TryRecv on ready chan got nil")
-		} else if i := val.(*IntValue).Get(); i != 4 {
+		} else if i := val.(*IntValue).Get(); i != 4 || !ok {
-			t.Errorf("native send 4, TryRecv %d", i)
+			t.Errorf("native send 4, TryRecv %d, %t", i, ok)
 		}
 
 		// TrySend fail
 		c <- 100
-		ok := cv.TrySend(NewValue(5))
+		ok = cv.TrySend(NewValue(5))
 		i := <-c
 		if ok {
 			t.Errorf("TrySend on full chan succeeded: value %d", i)
@@ -1008,20 +1008,11 @@ func TestChan(t *testing.T) {
 		// Close
 		c <- 123
 		cv.Close()
-		if cv.Closed() {
+		if i, ok := cv.Recv(); i.(*IntValue).Get() != 123 || !ok {
-			t.Errorf("closed too soon - 1")
+			t.Errorf("send 123 then close; Recv %d, %t", i.(*IntValue).Get(), ok)
 		}
-		if i := cv.Recv().(*IntValue).Get(); i != 123 {
+		if i, ok := cv.Recv(); i.(*IntValue).Get() != 0 || ok {
-			t.Errorf("send 123 then close; Recv %d", i)
+			t.Errorf("after close Recv %d, %t", i.(*IntValue).Get(), ok)
-		}
-		if cv.Closed() {
-			t.Errorf("closed too soon - 2")
-		}
-		if i := cv.Recv().(*IntValue).Get(); i != 0 {
-			t.Errorf("after close Recv %d", i)
-		}
-		if !cv.Closed() {
-			t.Errorf("not closed")
 		}
 	}
 
@@ -1032,7 +1023,7 @@ func TestChan(t *testing.T) {
 	if cv.TrySend(NewValue(7)) {
 		t.Errorf("TrySend on sync chan succeeded")
 	}
-	if cv.TryRecv() != nil {
+	if v, ok := cv.TryRecv(); v != nil || ok {
 		t.Errorf("TryRecv on sync chan succeeded")
 	}
 

src/pkg/reflect/value.go

@@ -671,19 +671,12 @@ func (v *ChanValue) Get() uintptr { return *(*uintptr)(v.addr) }
 
 // implemented in ../pkg/runtime/reflect.cgo
 func makechan(typ *runtime.ChanType, size uint32) (ch *byte)
-func chansend(ch, val *byte, pres *bool)
+func chansend(ch, val *byte, selected *bool)
-func chanrecv(ch, val *byte, pres *bool)
+func chanrecv(ch, val *byte, selected *bool, ok *bool)
-func chanclosed(ch *byte) bool
 func chanclose(ch *byte)
 func chanlen(ch *byte) int32
 func chancap(ch *byte) int32
 
-// Closed returns the result of closed(c) on the underlying channel.
-func (v *ChanValue) Closed() bool {
-	ch := *(**byte)(v.addr)
-	return chanclosed(ch)
-}
-
 // Close closes the channel.
 func (v *ChanValue) Close() {
 	ch := *(**byte)(v.addr)
@@ -700,52 +693,61 @@ func (v *ChanValue) Cap() int {
 	return int(chancap(ch))
 }
 
-// internal send; non-blocking if b != nil
+// internal send; non-blocking if selected != nil
-func (v *ChanValue) send(x Value, b *bool) {
+func (v *ChanValue) send(x Value, selected *bool) {
 	t := v.Type().(*ChanType)
 	if t.Dir()&SendDir == 0 {
 		panic("send on recv-only channel")
 	}
 	typesMustMatch(t.Elem(), x.Type())
 	ch := *(**byte)(v.addr)
-	chansend(ch, (*byte)(x.getAddr()), b)
+	chansend(ch, (*byte)(x.getAddr()), selected)
 }
 
-// internal recv; non-blocking if b != nil
+// internal recv; non-blocking if selected != nil
-func (v *ChanValue) recv(b *bool) Value {
+func (v *ChanValue) recv(selected *bool) (Value, bool) {
 	t := v.Type().(*ChanType)
 	if t.Dir()&RecvDir == 0 {
 		panic("recv on send-only channel")
 	}
 	ch := *(**byte)(v.addr)
 	x := MakeZero(t.Elem())
-	chanrecv(ch, (*byte)(x.getAddr()), b)
+	var ok bool
-	return x
+	chanrecv(ch, (*byte)(x.getAddr()), selected, &ok)
+	return x, ok
 }
 
 // Send sends x on the channel v.
 func (v *ChanValue) Send(x Value) { v.send(x, nil) }
 
 // Recv receives and returns a value from the channel v.
-func (v *ChanValue) Recv() Value { return v.recv(nil) }
+// The receive blocks until a value is ready.
+// The boolean value ok is true if the value x corresponds to a send
+// on the channel, false if it is a zero value received because the channel is closed.
+func (v *ChanValue) Recv() (x Value, ok bool) {
+	return v.recv(nil)
+}
 
 // TrySend attempts to sends x on the channel v but will not block.
 // It returns true if the value was sent, false otherwise.
 func (v *ChanValue) TrySend(x Value) bool {
-	var ok bool
+	var selected bool
-	v.send(x, &ok)
+	v.send(x, &selected)
-	return ok
+	return selected
 }
 
 // TryRecv attempts to receive a value from the channel v but will not block.
-// It returns the value if one is received, nil otherwise.
+// If the receive cannot finish without blocking, TryRecv instead returns x == nil.
-func (v *ChanValue) TryRecv() Value {
+// If the receive can finish without blocking, TryRecv returns x != nil.
-	var ok bool
+// The boolean value ok is true if the value x corresponds to a send
-	x := v.recv(&ok)
+// on the channel, false if it is a zero value received because the channel is closed.
-	if !ok {
+func (v *ChanValue) TryRecv() (x Value, ok bool) {
-		return nil
+	var selected bool
+	x, ok = v.recv(&selected)
+	if !selected {
+		return nil, false
 	}
-	return x
+	return x, ok
 }
 
 // MakeChan creates a new channel with the specified type and buffer size.

src/pkg/template/template.go

@@ -896,8 +896,8 @@ func (t *Template) executeRepeated(r *repeatedElement, st *state) {
 		}
 	} else if ch := iter(field); ch != nil {
 		for {
-			e := ch.Recv()
+			e, ok := ch.Recv()
-			if ch.Closed() {
+			if !ok {
 				break
 			}
 			loopBody(st.clone(e))

src/pkg/testing/script/script.go

@@ -306,8 +306,8 @@ func recvValues(multiplex chan<- interface{}, channel interface{}) {
 	c := reflect.NewValue(channel).(*reflect.ChanValue)
 
 	for {
-		v := c.Recv()
+		v, ok := c.Recv()
-		if c.Closed() {
+		if !ok {
 			multiplex <- channelClosed{channel}
 			return
 		}

test/chan/perm.go

@@ -22,21 +22,18 @@ func main() {
 
 	c <- 0 // ok
 	<-c    // ok
-	//TODO(rsc): uncomment when this syntax is valid for receive+check closed
+	x, ok := <-c	// ok
-	//	x, ok := <-c	// ok
+	_, _ = x, ok
-	//	_, _ = x, ok
 
 	cr <- 0 // ERROR "send"
 	<-cr    // ok
-	//TODO(rsc): uncomment when this syntax is valid for receive+check closed
+	x, ok = <-cr	// ok
-	//	x, ok = <-cr	// ok
+	_, _ = x, ok
-	//	_, _ = x, ok
 
 	cs <- 0 // ok
 	<-cs    // ERROR "receive"
-	////TODO(rsc): uncomment when this syntax is valid for receive+check closed
+	x, ok = <-cs	// ERROR "receive"
-	////	x, ok = <-cs	// ERROR "receive"
+	_, _ = x, ok
-	////	_, _ = x, ok
 
 	select {
 	case c <- 0: // ok

test/chan/select3.go

@@ -88,12 +88,16 @@ func main() {
 		ch <- 7
 	})
 
-	// receiving (a small number of times) from a closed channel never blocks
+	// receiving from a closed channel never blocks
 	testBlock(never, func() {
 		for i := 0; i < 10; i++ {
 			if <-closedch != 0 {
 				panic("expected zero value when reading from closed channel")
 			}
+			if x, ok := <-closedch; x != 0 || ok {
+				println("closedch:", x, ok)
+				panic("expected 0, false from closed channel")
+			}
 		}
 	})
 
@@ -191,12 +195,24 @@ func main() {
 		case <-closedch:
 		}
 	})
+	testBlock(never, func() {
+		select {
+		case x := <-closedch:
+			_ = x
+		}
+	})
+	testBlock(never, func() {
+		select {
+		case x, ok := <-closedch:
+			_, _ = x, ok
+		}
+	})
 	testPanic(always, func() {
 		select {
 		case closedch <- 7:
 		}
 	})
-	
+
 	// select should not get confused if it sees itself
 	testBlock(always, func() {
 		c := make(chan int)

test/closedchan.go

@@ -4,7 +4,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// Test close(c), closed(c).
+// Test close(c), receive of closed channel.
 //
 // TODO(rsc): Doesn't check behavior of close(c) when there
 // are blocked senders/receivers.
@@ -14,10 +14,11 @@ package main
 type Chan interface {
 	Send(int)
 	Nbsend(int) bool
-	Recv() int
+	Recv() (int)
 	Nbrecv() (int, bool)
+	Recv2() (int, bool)
+	Nbrecv2() (int, bool, bool)
 	Close()
-	Closed() bool
 	Impl() string
 }
 
@@ -52,12 +53,23 @@ func (c XChan) Nbrecv() (int, bool) {
 	panic("nbrecv")
 }
 
-func (c XChan) Close() {
+func (c XChan) Recv2() (int, bool) {
-	close(c)
+	x, ok := <-c
+	return x, ok
 }
 
-func (c XChan) Closed() bool {
+func (c XChan) Nbrecv2() (int, bool, bool) {
-	return closed(c)
+	select {
+	case x, ok := <-c:
+		return x, ok, true
+	default:
+		return 0, false, false
+	}
+	panic("nbrecv2")
+}
+
+func (c XChan) Close() {
+	close(c)
 }
 
 func (c XChan) Impl() string {
@@ -101,12 +113,26 @@ func (c SChan) Nbrecv() (int, bool) {
 	panic("nbrecv")
 }
 
-func (c SChan) Close() {
+func (c SChan) Recv2() (int, bool) {
-	close(c)
+	select {
+	case x, ok := <-c:
+		return x, ok
+	}
+	panic("recv")
 }
 
-func (c SChan) Closed() bool {
+func (c SChan) Nbrecv2() (int, bool, bool) {
-	return closed(c)
+	select {
+	default:
+		return 0, false, false
+	case x, ok := <-c:
+		return x, ok, true
+	}
+	panic("nbrecv")
+}
+
+func (c SChan) Close() {
+	close(c)
 }
 
 func (c SChan) Impl() string {
@@ -156,12 +182,28 @@ func (c SSChan) Nbrecv() (int, bool) {
 	panic("nbrecv")
 }
 
-func (c SSChan) Close() {
+func (c SSChan) Recv2() (int, bool) {
-	close(c)
+	select {
+	case <-dummy:
+	case x, ok := <-c:
+		return x, ok
+	}
+	panic("recv")
 }
 
-func (c SSChan) Closed() bool {
+func (c SSChan) Nbrecv2() (int, bool, bool) {
-	return closed(c)
+	select {
+	case <-dummy:
+	default:
+		return 0, false, false
+	case x, ok := <-c:
+		return x, ok, true
+	}
+	panic("nbrecv")
+}
+
+func (c SSChan) Close() {
+	close(c)
 }
 
 func (c SSChan) Impl() string {
@@ -179,29 +221,23 @@ func shouldPanic(f func()) {
 }
 
 func test1(c Chan) {
-	// not closed until the close signal (a zero value) has been received.
-	if c.Closed() {
-		println("test1: Closed before Recv zero:", c.Impl())
-	}
-
 	for i := 0; i < 3; i++ {
 		// recv a close signal (a zero value)
 		if x := c.Recv(); x != 0 {
-			println("test1: recv on closed got non-zero:", x, c.Impl())
+			println("test1: recv on closed:", x, c.Impl())
+		}
+		if x, ok := c.Recv2(); x != 0 || ok {
+			println("test1: recv2 on closed:", x, ok, c.Impl())
 		}
 
-		// should now be closed.
+		// should work with select: received a value without blocking, so selected == true.
-		if !c.Closed() {
+		x, selected := c.Nbrecv()
-			println("test1: not closed after recv zero", c.Impl())
+		if x != 0 || !selected {
+			println("test1: recv on closed nb:", x, selected, c.Impl())
 		}
-
+		x, ok, selected := c.Nbrecv2()
-		// should work with ,ok: received a value without blocking, so ok == true.
+		if x != 0 || ok || !selected {
-		x, ok := c.Nbrecv()
+			println("test1: recv2 on closed nb:", x, ok, selected, c.Impl())
-		if !ok {
-			println("test1: recv on closed got not ok", c.Impl())
-		}
-		if x != 0 {
-			println("test1: recv ,ok on closed got non-zero:", x, c.Impl())
 		}
 	}
 
@@ -221,11 +257,6 @@ func test1(c Chan) {
 }
 
 func testasync1(c Chan) {
-	// not closed until the close signal (a zero value) has been received.
-	if c.Closed() {
-		println("testasync1: Closed before Recv zero:", c.Impl())
-	}
-
 	// should be able to get the last value via Recv
 	if x := c.Recv(); x != 1 {
 		println("testasync1: Recv did not get 1:", x, c.Impl())
@@ -235,19 +266,31 @@ func testasync1(c Chan) {
 }
 
 func testasync2(c Chan) {
-	// not closed until the close signal (a zero value) has been received.
+	// should be able to get the last value via Recv2
-	if c.Closed() {
+	if x, ok := c.Recv2(); x != 1 || !ok {
-		println("testasync2: Closed before Recv zero:", c.Impl())
+		println("testasync1: Recv did not get 1, true:", x, ok, c.Impl())
 	}
 
+	test1(c)
+}
+
+func testasync3(c Chan) {
 	// should be able to get the last value via Nbrecv
-	if x, ok := c.Nbrecv(); !ok || x != 1 {
+	if x, selected := c.Nbrecv(); x != 1 || !selected {
-		println("testasync2: Nbrecv did not get 1, true:", x, ok, c.Impl())
+		println("testasync2: Nbrecv did not get 1, true:", x, selected, c.Impl())
 	}
 
 	test1(c)
 }
 
+func testasync4(c Chan) {
+	// should be able to get the last value via Nbrecv2
+	if x, ok, selected := c.Nbrecv2(); x != 1 || !ok || !selected {
+		println("testasync2: Nbrecv did not get 1, true, true:", x, ok, selected, c.Impl())
+	}
+	test1(c)
+}
+
 func closedsync() chan int {
 	c := make(chan int)
 	close(c)
@@ -261,15 +304,27 @@ func closedasync() chan int {
 	return c
 }
 
-func main() {
+var mks = []func(chan int) Chan {
-	test1(XChan(closedsync()))
+	func(c chan int) Chan { return XChan(c) },
-	test1(SChan(closedsync()))
+	func(c chan int) Chan { return SChan(c) },
-	test1(SSChan(closedsync()))
+	func(c chan int) Chan { return SSChan(c) },
-
+}
-	testasync1(XChan(closedasync()))
+
-	testasync1(SChan(closedasync()))
+var testcloseds = []func(Chan) {
-	testasync1(SSChan(closedasync()))
+	testasync1,
-	testasync2(XChan(closedasync()))
+	testasync2,
-	testasync2(SChan(closedasync()))
+	testasync3,
-	testasync2(SSChan(closedasync()))
+	testasync4,
+}
+
+func main() {
+	for _, mk := range mks {
+		test1(mk(closedsync()))
+	}
+	
+	for _, testclosed := range testcloseds {
+		for _, mk := range mks {
+			testclosed(mk(closedasync()))
+		}
+	}
 }

test/ddd1.go

@@ -35,7 +35,6 @@ func bad(args ...int) {
 	ch := make(chan int)
 	close(ch...)	// ERROR "[.][.][.]"
 	_ = len(args...)	// ERROR "[.][.][.]"
-	_ = closed(ch...)	// ERROR "[.][.][.]"
 	_ = new(int...)	// ERROR "[.][.][.]"
 	n := 10
 	_ = make([]byte, n...)	// ERROR "[.][.][.]"

test/named1.go

@@ -43,10 +43,6 @@ func main() {
 	_, b = m[2] // ERROR "cannot .* bool.*type Bool"
 	m[2] = 1, b // ERROR "cannot use.*type Bool.*as type bool"
 
-	////TODO(rsc): uncomment when this syntax is valid for receive+check closed
-	////	_, b = <-c // ERROR "cannot .* bool.*type Bool"
-	////	_ = b
-
 	var inter interface{}
 	_, b = inter.(Map) // ERROR "cannot .* bool.*type Bool"
 	_ = b
@@ -57,8 +53,9 @@ func main() {
 	_, b = minter.(Map) // ERROR "cannot .* bool.*type Bool"
 	_ = b
 
-	asBool(closed(c)) // ERROR "cannot use.*type bool.*as type Bool"
+	_, bb := <-c
-	b = closed(c)     // ERROR "cannot use.*type bool.*type Bool"
+	asBool(bb) // ERROR "cannot use.*type bool.*as type Bool"
+	_, b = <-c     // ERROR "cannot .* bool.*type Bool"
 	_ = b
 
 	asString(String(slice)) // ERROR "cannot .*type Slice.*type String"