goprotobuf: Use encoding.TextMarshaler and encoding.TextUnmarshaler in place of

the identical custom interfaces.

encoding.Text{Marshaler,Unmarshaler} were added in Go 1.2 (April 2013);
it's safe to rely on them now.

LGTM=r
R=r
CC=golang-codereviews
https://codereview.appspot.com/181770043

proto/text.go

@@ -36,6 +36,7 @@ package proto
 import (
 	"bufio"
 	"bytes"
+	"encoding"
 	"fmt"
 	"io"
 	"log"
@@ -74,13 +75,6 @@ type textWriter struct {
 	w        writer
 }
 
-// textMarshaler is implemented by Messages that can marshal themsleves.
-// It is identical to encoding.TextMarshaler, introduced in go 1.2,
-// which will eventually replace it.
-type textMarshaler interface {
-	MarshalText() (text []byte, err error)
-}
-
 func (w *textWriter) WriteString(s string) (n int, err error) {
 	if !strings.Contains(s, "\n") {
 		if !w.compact && w.complete {
@@ -358,7 +352,7 @@ func writeAny(w *textWriter, v reflect.Value, props *Properties) error {
 			}
 		}
 		w.indent()
-		if tm, ok := v.Interface().(textMarshaler); ok {
+		if tm, ok := v.Interface().(encoding.TextMarshaler); ok {
 			text, err := tm.MarshalText()
 			if err != nil {
 				return err
@@ -653,7 +647,7 @@ func marshalText(w io.Writer, pb Message, compact bool) error {
 		compact:  compact,
 	}
 
-	if tm, ok := pb.(textMarshaler); ok {
+	if tm, ok := pb.(encoding.TextMarshaler); ok {
 		text, err := tm.MarshalText()
 		if err != nil {
 			return err

proto/text_parser.go

@@ -35,6 +35,7 @@ package proto
 // TODO: message sets.
 
 import (
+	"encoding"
 	"errors"
 	"fmt"
 	"reflect"
@@ -43,13 +44,6 @@ import (
 	"unicode/utf8"
 )
 
-// textUnmarshaler is implemented by Messages that can unmarshal themsleves.
-// It is identical to encoding.TextUnmarshaler, introduced in go 1.2,
-// which will eventually replace it.
-type textUnmarshaler interface {
-	UnmarshalText(text []byte) error
-}
-
 type ParseError struct {
 	Message string
 	Line    int // 1-based line number
@@ -659,7 +653,7 @@ func (p *textParser) readAny(v reflect.Value, props *Properties) error {
 		default:
 			return p.errorf("expected '{' or '<', found %q", tok.value)
 		}
-		// TODO: Handle nested messages which implement textUnmarshaler.
+		// TODO: Handle nested messages which implement encoding.TextUnmarshaler.
 		return p.readStruct(fv, terminator)
 	case reflect.Uint32:
 		if x, err := strconv.ParseUint(tok.value, 0, 32); err == nil {
@@ -680,7 +674,7 @@ func (p *textParser) readAny(v reflect.Value, props *Properties) error {
 // If a required field is not set and no other error occurs,
 // UnmarshalText returns *RequiredNotSetError.
 func UnmarshalText(s string, pb Message) error {
-	if um, ok := pb.(textUnmarshaler); ok {
+	if um, ok := pb.(encoding.TextUnmarshaler); ok {
 		err := um.UnmarshalText([]byte(s))
 		return err
 	}