channel direction tests

(will submit with compiler fixes).

R=r
DELTA=44  (44 added, 0 deleted, 0 changed)
OCL=29211
CL=29248

test/chan/perm.go

+// errchk $G -e $D/$F.go
+
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+var (
+	cr <-chan int;
+	cs chan<- int;
+	c chan int;
+)
+
+func main() {
+	cr = c;		// ok
+	cs = c;		// ok
+	c = cr;		// ERROR "illegal types"
+	c = cs;		// ERROR "illegal types"
+	cr = cs;	// ERROR "illegal types"
+	cs = cr;	// ERROR "illegal types"
+
+	c <- 0;		// ok
+	ok := c <- 0;	// ok
+	<-c;		// ok
+	x, ok := <-c;	// ok
+
+	cr <- 0;	// ERROR "send"
+	ok = cr <- 0;	// ERROR "send"
+	<-cr;		// ok
+	x, ok = <-cr;	// ok
+
+	cs <- 0;	// ok
+	ok = cs <- 0;	// ok
+	<-cs;		// ERROR "receive"
+	x, ok = <-cs;	// ERROR "receive"
+
+	select {
+	case c <- 0:	// ok
+	case x := <-c:	// ok
+
+	case cr <- 0:	// ERROR "send"
+	case x := <-cr:	// ok
+
+	case cs <- 0:	// ok;
+	case x := <-cs:	// ERROR "receive"
+	}
+}