libgo: update to Go 1.13beta1 release

    
    Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/193497

From-SVN: r275473

1 files changed, 3 insertions, 4 deletions

diff --git a/libgo/go/bytes/buffer.go b/libgo/go/bytes/buffer.go
index aff2db5..f19a4cf 100644
--- a/libgo/go/bytes/buffer.go
+++ b/libgo/go/bytes/buffer.go
@@ -21,9 +21,6 @@ type Buffer struct {
 	buf      []byte // contents are the bytes buf[off : len(buf)]
 	off      int    // read at &buf[off], write at &buf[len(buf)]
 	lastRead readOp // last read operation, so that Unread* can work correctly.
-
-	// FIXME: it would be advisable to align Buffer to cachelines to avoid false
-	// sharing.
 }
 
 // The readOp constants describe the last action performed on
@@ -385,13 +382,15 @@ func (b *Buffer) UnreadRune() error {
 	return nil
 }
 
+var errUnreadByte = errors.New("bytes.Buffer: UnreadByte: previous operation was not a successful read")
+
 // UnreadByte unreads the last byte returned by the most recent successful
 // read operation that read at least one byte. If a write has happened since
 // the last read, if the last read returned an error, or if the read read zero
 // bytes, UnreadByte returns an error.
 func (b *Buffer) UnreadByte() error {
 	if b.lastRead == opInvalid {
-		return errors.New("bytes.Buffer: UnreadByte: previous operation was not a successful read")
+		return errUnreadByte
 	}
 	b.lastRead = opInvalid
 	if b.off > 0 {