libgo: update to Go1.16beta1 release

This does not yet include support for the //go:embed directive added
in this release.

	* Makefile.am (check-runtime): Don't create check-runtime-dir.
	(mostlyclean-local): Don't remove check-runtime-dir.
	(check-go-tool, check-vet): Copy in go.mod and modules.txt.
	(check-cgo-test, check-carchive-test): Add go.mod file.
	* Makefile.in: Regenerate.

Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/280172

4 files changed, 26 insertions, 12 deletions

diff --git a/libgo/go/strings/reader.go b/libgo/go/strings/reader.go
index eb2fa11..6f069a6 100644
--- a/libgo/go/strings/reader.go
+++ b/libgo/go/strings/reader.go
@@ -10,8 +10,8 @@ import (
 	"unicode/utf8"
 )
 
-// A Reader implements the io.Reader, io.ReaderAt, io.Seeker, io.WriterTo,
-// io.ByteScanner, and io.RuneScanner interfaces by reading
+// A Reader implements the io.Reader, io.ReaderAt, io.ByteReader, io.ByteScanner,
+// io.RuneReader, io.RuneScanner, io.Seeker, and io.WriterTo interfaces by reading
 // from a string.
 // The zero value for Reader operates like a Reader of an empty string.
 type Reader struct {
@@ -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")
diff --git a/libgo/go/strings/reader_test.go b/libgo/go/strings/reader_test.go
index a4c211d..5adea6f 100644
--- a/libgo/go/strings/reader_test.go
+++ b/libgo/go/strings/reader_test.go
@@ -8,7 +8,6 @@ import (
 	"bytes"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"strings"
 	"sync"
 	"testing"
@@ -162,7 +161,7 @@ func TestWriteTo(t *testing.T) {
 // tests that Len is affected by reads, but Size is not.
 func TestReaderLenSize(t *testing.T) {
 	r := strings.NewReader("abc")
-	io.CopyN(ioutil.Discard, r, 1)
+	io.CopyN(io.Discard, r, 1)
 	if r.Len() != 2 {
 		t.Errorf("Len = %d; want 2", r.Len())
 	}
@@ -182,7 +181,7 @@ func TestReaderReset(t *testing.T) {
 	if err := r.UnreadRune(); err == nil {
 		t.Errorf("UnreadRune: expected error, got nil")
 	}
-	buf, err := ioutil.ReadAll(r)
+	buf, err := io.ReadAll(r)
 	if err != nil {
 		t.Errorf("ReadAll: unexpected error: %v", err)
 	}
@@ -228,7 +227,7 @@ func TestReaderZero(t *testing.T) {
 		t.Errorf("UnreadRune: got nil, want error")
 	}
 
-	if n, err := (&strings.Reader{}).WriteTo(ioutil.Discard); n != 0 || err != nil {
+	if n, err := (&strings.Reader{}).WriteTo(io.Discard); n != 0 || err != nil {
 		t.Errorf("WriteTo: got %d, %v; want 0, nil", n, err)
 	}
 }
diff --git a/libgo/go/strings/strings.go b/libgo/go/strings/strings.go
index d6f5cea..b429735 100644
--- a/libgo/go/strings/strings.go
+++ b/libgo/go/strings/strings.go
@@ -934,8 +934,8 @@ func Replace(s, old, new string, n int) string {
 	}
 
 	// Apply replacements to buffer.
-	t := make([]byte, len(s)+n*(len(new)-len(old)))
-	w := 0
+	var b Builder
+	b.Grow(len(s) + n*(len(new)-len(old)))
 	start := 0
 	for i := 0; i < n; i++ {
 		j := start
@@ -947,12 +947,12 @@ func Replace(s, old, new string, n int) string {
 		} else {
 			j += Index(s[start:], old)
 		}
-		w += copy(t[w:], s[start:j])
-		w += copy(t[w:], new)
+		b.WriteString(s[start:j])
+		b.WriteString(new)
 		start = j + len(old)
 	}
-	w += copy(t[w:], s[start:])
-	return string(t[0:w])
+	b.WriteString(s[start:])
+	return b.String()
 }
 
 // ReplaceAll returns a copy of the string s with all
diff --git a/libgo/go/strings/strings_test.go b/libgo/go/strings/strings_test.go
index 095e482..c15aca3 100644
--- a/libgo/go/strings/strings_test.go
+++ b/libgo/go/strings/strings_test.go
@@ -1904,3 +1904,12 @@ func BenchmarkTrimSpace(b *testing.B) {
 		})
 	}
 }
+
+var stringSink string
+
+func BenchmarkReplaceAll(b *testing.B) {
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		stringSink = ReplaceAll("banana", "a", "<>")
+	}
+}