all: update references to symbols moved from io/ioutil to io

The old ioutil references are still valid, but update our code
to reflect best practices and get used to the new locations.

Code compiled with the bootstrap toolchain
(cmd/asm, cmd/dist, cmd/compile, debug/elf)
must remain Go 1.4-compatible and is excluded.
Also excluded vendored code.

For #41190.

Change-Id: I6d86f2bf7bc37a9d904b6cee3fe0c7af6d94d5b1
Reviewed-on: https://go-review.googlesource.com/c/go/+/263142
Trust: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>

3 files changed, 22 insertions, 23 deletions

diff --git a/src/image/gif/writer_test.go b/src/image/gif/writer_test.go
index 1e622b3674..af0105c6be 100644
--- a/src/image/gif/writer_test.go
+++ b/src/image/gif/writer_test.go
@@ -11,7 +11,7 @@ import (
 	"image/color/palette"
 	"image/draw"
 	_ "image/png"
-	"io/ioutil"
+	"io"
 	"math/rand"
 	"os"
 	"reflect"
@@ -285,7 +285,7 @@ func TestEncodeMismatchDelay(t *testing.T) {
 		Image: images,
 		Delay: make([]int, 1),
 	}
-	if err := EncodeAll(ioutil.Discard, g0); err == nil {
+	if err := EncodeAll(io.Discard, g0); err == nil {
 		t.Error("expected error from mismatched delay and image slice lengths")
 	}
 
@@ -297,13 +297,13 @@ func TestEncodeMismatchDelay(t *testing.T) {
 	for i := range g1.Disposal {
 		g1.Disposal[i] = DisposalNone
 	}
-	if err := EncodeAll(ioutil.Discard, g1); err == nil {
+	if err := EncodeAll(io.Discard, g1); err == nil {
 		t.Error("expected error from mismatched disposal and image slice lengths")
 	}
 }
 
 func TestEncodeZeroGIF(t *testing.T) {
-	if err := EncodeAll(ioutil.Discard, &GIF{}); err == nil {
+	if err := EncodeAll(io.Discard, &GIF{}); err == nil {
 		t.Error("expected error from providing empty gif")
 	}
 }
@@ -324,7 +324,7 @@ func TestEncodeAllFramesOutOfBounds(t *testing.T) {
 				Height: upperBound,
 			},
 		}
-		err := EncodeAll(ioutil.Discard, g)
+		err := EncodeAll(io.Discard, g)
 		if upperBound >= 8 {
 			if err != nil {
 				t.Errorf("upperBound=%d: %v", upperBound, err)
@@ -430,7 +430,7 @@ func TestEncodeImplicitConfigSize(t *testing.T) {
 			Image: images,
 			Delay: make([]int, len(images)),
 		}
-		err := EncodeAll(ioutil.Discard, g)
+		err := EncodeAll(io.Discard, g)
 		if lowerBound >= 0 {
 			if err != nil {
 				t.Errorf("lowerBound=%d: %v", lowerBound, err)
@@ -509,7 +509,7 @@ func TestEncodeBadPalettes(t *testing.T) {
 				}
 			}
 
-			err := EncodeAll(ioutil.Discard, &GIF{
+			err := EncodeAll(io.Discard, &GIF{
 				Image: []*image.Paletted{
 					image.NewPaletted(image.Rect(0, 0, w, h), pal),
 				},
@@ -668,7 +668,7 @@ func BenchmarkEncodeRandomPaletted(b *testing.B) {
 	b.ReportAllocs()
 	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
-		Encode(ioutil.Discard, paletted, nil)
+		Encode(io.Discard, paletted, nil)
 	}
 }
 
@@ -691,7 +691,7 @@ func BenchmarkEncodeRandomRGBA(b *testing.B) {
 	b.ReportAllocs()
 	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
-		Encode(ioutil.Discard, rgba, nil)
+		Encode(io.Discard, rgba, nil)
 	}
 }
 
@@ -708,7 +708,7 @@ func BenchmarkEncodeRealisticPaletted(b *testing.B) {
 	b.ReportAllocs()
 	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
-		Encode(ioutil.Discard, paletted, nil)
+		Encode(io.Discard, paletted, nil)
 	}
 }
 
@@ -729,6 +729,6 @@ func BenchmarkEncodeRealisticRGBA(b *testing.B) {
 	b.ReportAllocs()
 	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
-		Encode(ioutil.Discard, rgba, nil)
+		Encode(io.Discard, rgba, nil)
 	}
 }
diff --git a/src/image/jpeg/writer_test.go b/src/image/jpeg/writer_test.go
index 3aff742632..abd5e32333 100644
--- a/src/image/jpeg/writer_test.go
+++ b/src/image/jpeg/writer_test.go
@@ -10,7 +10,7 @@ import (
 	"image"
 	"image/color"
 	"image/png"
-	"io/ioutil"
+	"io"
 	"math/rand"
 	"os"
 	"testing"
@@ -261,7 +261,7 @@ func BenchmarkEncodeRGBA(b *testing.B) {
 	b.ResetTimer()
 	options := &Options{Quality: 90}
 	for i := 0; i < b.N; i++ {
-		Encode(ioutil.Discard, img, options)
+		Encode(io.Discard, img, options)
 	}
 }
 
@@ -283,6 +283,6 @@ func BenchmarkEncodeYCbCr(b *testing.B) {
 	b.ResetTimer()
 	options := &Options{Quality: 90}
 	for i := 0; i < b.N; i++ {
-		Encode(ioutil.Discard, img, options)
+		Encode(io.Discard, img, options)
 	}
 }
diff --git a/src/image/png/writer_test.go b/src/image/png/writer_test.go
index 5d131ff823..47aa861339 100644
--- a/src/image/png/writer_test.go
+++ b/src/image/png/writer_test.go
@@ -12,7 +12,6 @@ import (
 	"image"
 	"image/color"
 	"io"
-	"io/ioutil"
 	"testing"
 )
 
@@ -169,7 +168,7 @@ func TestWriterPaletted(t *testing.T) {
 						t.Error(err)
 						return
 					}
-					n, err := io.Copy(ioutil.Discard, r)
+					n, err := io.Copy(io.Discard, r)
 					if err != nil {
 						t.Errorf("got error while reading image data: %v", err)
 					}
@@ -234,7 +233,7 @@ func BenchmarkEncodeGray(b *testing.B) {
 	b.ReportAllocs()
 	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
-		Encode(ioutil.Discard, img)
+		Encode(io.Discard, img)
 	}
 }
 
@@ -259,7 +258,7 @@ func BenchmarkEncodeGrayWithBufferPool(b *testing.B) {
 	b.ReportAllocs()
 	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
-		e.Encode(ioutil.Discard, img)
+		e.Encode(io.Discard, img)
 	}
 }
 
@@ -279,7 +278,7 @@ func BenchmarkEncodeNRGBOpaque(b *testing.B) {
 	b.ReportAllocs()
 	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
-		Encode(ioutil.Discard, img)
+		Encode(io.Discard, img)
 	}
 }
 
@@ -292,7 +291,7 @@ func BenchmarkEncodeNRGBA(b *testing.B) {
 	b.ReportAllocs()
 	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
-		Encode(ioutil.Discard, img)
+		Encode(io.Discard, img)
 	}
 }
 
@@ -305,7 +304,7 @@ func BenchmarkEncodePaletted(b *testing.B) {
 	b.ReportAllocs()
 	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
-		Encode(ioutil.Discard, img)
+		Encode(io.Discard, img)
 	}
 }
 
@@ -325,7 +324,7 @@ func BenchmarkEncodeRGBOpaque(b *testing.B) {
 	b.ReportAllocs()
 	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
-		Encode(ioutil.Discard, img)
+		Encode(io.Discard, img)
 	}
 }
 
@@ -338,6 +337,6 @@ func BenchmarkEncodeRGBA(b *testing.B) {
 	b.ReportAllocs()
 	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
-		Encode(ioutil.Discard, img)
+		Encode(io.Discard, img)
 	}
 }