strings: complete documentation of strings.Reader

There is no documentation on a number of methods of the strings.Reader
struct, so this change adds documentation referring to the relevant
io.* interfaces implemented. This is consistent with pre-existing
documentation in this struct.

Fixes #40381

Change-Id: I3dec65ecafca5b79d85d30a676d297e5ee9ab47e
GitHub-Last-Rev: f42429946a2b90b9fbfbd1ea5943f0c50e0439b5
GitHub-Pull-Request: golang/go#40654
Reviewed-on: https://go-review.googlesource.com/c/go/+/247523
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
Trust: Ian Lance Taylor <iant@golang.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/src/strings/reader.go b/src/strings/reader.go
index eb2fa1164c..e03f3c5cf8 100644
--- a/src/strings/reader.go
+++ b/src/strings/reader.go
@@ -35,6 +35,7 @@ func (r *Reader) Len() int {
 // to any other method.
 func (r *Reader) Size() int64 { return int64(len(r.s)) }
 
+// Read implements the io.Reader interface.
 func (r *Reader) Read(b []byte) (n int, err error) {
 	if r.i >= int64(len(r.s)) {
 		return 0, io.EOF
@@ -45,6 +46,7 @@ func (r *Reader) Read(b []byte) (n int, err error) {
 	return
 }
 
+// ReadAt implements the io.ReaderAt interface.
 func (r *Reader) ReadAt(b []byte, off int64) (n int, err error) {
 	// cannot modify state - see io.ReaderAt
 	if off < 0 {
@@ -60,6 +62,7 @@ func (r *Reader) ReadAt(b []byte, off int64) (n int, err error) {
 	return
 }
 
+// ReadByte implements the io.ByteReader interface.
 func (r *Reader) ReadByte() (byte, error) {
 	r.prevRune = -1
 	if r.i >= int64(len(r.s)) {
@@ -70,6 +73,7 @@ func (r *Reader) ReadByte() (byte, error) {
 	return b, nil
 }
 
+// UnreadByte implements the io.ByteScanner interface.
 func (r *Reader) UnreadByte() error {
 	if r.i <= 0 {
 		return errors.New("strings.Reader.UnreadByte: at beginning of string")
@@ -79,6 +83,7 @@ func (r *Reader) UnreadByte() error {
 	return nil
 }
 
+// ReadRune implements the io.RuneReader interface.
 func (r *Reader) ReadRune() (ch rune, size int, err error) {
 	if r.i >= int64(len(r.s)) {
 		r.prevRune = -1
@@ -94,6 +99,7 @@ func (r *Reader) ReadRune() (ch rune, size int, err error) {
 	return
 }
 
+// UnreadRune implements the io.RuneScanner interface.
 func (r *Reader) UnreadRune() error {
 	if r.i <= 0 {
 		return errors.New("strings.Reader.UnreadRune: at beginning of string")