Test case for issue 475 and related bug.

R=iant
CC=golang-dev
https://golang.org/cl/183087

test/bugs/bug239.go

+// $G $D/$F.go || echo BUG: bug239
+
+// 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.
+
+// Test case for issue 475. This file should compile.
+
+package main
+
+import . "unsafe"
+
+func main() {
+	var x int
+	println(Sizeof(x))
+}
+
+/*
+bug239.go:11: imported and not used: unsafe
+bug239.go:15: undefined: Sizeof
+*/

test/bugs/bug240.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
+
+import . "unsafe"
+
+func main() {
+	var x int
+	println(unsafe.Sizeof(x)) // ERROR "undefined"
+}
+
+/*
+After a '.' import, "unsafe" shouldn't be defined as
+an identifier. 6g complains correctly for imports other
+than "unsafe".
+*/

test/golden.out

@@ -151,3 +151,11 @@ BUG: bug219
 
 =========== bugs/bug238.go
 BUG: errchk: command succeeded unexpectedly
+
+=========== bugs/bug239.go
+bugs/bug239.go:11: imported and not used: unsafe
+bugs/bug239.go:15: undefined: Sizeof
+BUG: bug239
+
+=========== bugs/bug240.go
+BUG: errchk: command succeeded unexpectedly