os: make IsExist report true on ERROR_DIR_NOT_EMPTY on Windows

Fixes #17164

Change-Id: I3e626d92293c1379e2922276f033fdee6f48dda3
Reviewed-on: https://go-review.googlesource.com/29753Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/os/error_windows.go

@@ -9,6 +9,7 @@ import "syscall"
 func isExist(err error) bool {
 	err = underlyingError(err)
 	return err == syscall.ERROR_ALREADY_EXISTS ||
+		err == syscall.ERROR_DIR_NOT_EMPTY ||
 		err == syscall.ERROR_FILE_EXISTS || err == ErrExist
 }
 

src/os/error_windows_test.go

@@ -26,6 +26,10 @@ func init() {
 		isExistTest{err: &os.PathError{Err: syscall.ERROR_PATH_NOT_FOUND}, is: false, isnot: true},
 		isExistTest{err: &os.LinkError{Err: syscall.ERROR_PATH_NOT_FOUND}, is: false, isnot: true},
 		isExistTest{err: &os.SyscallError{Err: syscall.ERROR_PATH_NOT_FOUND}, is: false, isnot: true},
+
+		isExistTest{err: &os.PathError{Err: syscall.ERROR_DIR_NOT_EMPTY}, is: true, isnot: false},
+		isExistTest{err: &os.LinkError{Err: syscall.ERROR_DIR_NOT_EMPTY}, is: true, isnot: false},
+		isExistTest{err: &os.SyscallError{Err: syscall.ERROR_DIR_NOT_EMPTY}, is: true, isnot: false},
 	)
 	isPermissionTests = append(isPermissionTests,
 		isPermissionTest{err: &os.PathError{Err: syscall.ERROR_ACCESS_DENIED}, want: true},

src/syscall/ztypes_windows.go

@@ -18,6 +18,7 @@ const (
 	ERROR_INSUFFICIENT_BUFFER Errno = 122
 	ERROR_MOD_NOT_FOUND       Errno = 126
 	ERROR_PROC_NOT_FOUND      Errno = 127
+	ERROR_DIR_NOT_EMPTY       Errno = 145
 	ERROR_ALREADY_EXISTS      Errno = 183
 	ERROR_ENVVAR_NOT_FOUND    Errno = 203
 	ERROR_MORE_DATA           Errno = 234