cmd/stringer: replace ioutil with os

Change-Id: I16c8556a90a775e5e3addb2f5907cba04d9c4bb1
GitHub-Last-Rev: 12dc5e7872
GitHub-Pull-Request: golang/tools#408
Reviewed-on: https://go-review.googlesource.com/c/tools/+/439516
gopls-CI: kokoro <noreply+kokoro@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
Reviewed-by: Michael Knyszek <mknyszek@google.com>

cmd/stringer/endtoend_test.go

@@ -14,7 +14,6 @@ import (
 	"fmt"
 	"go/build"
 	"io"
-	"io/ioutil"
 	"os"
 	"os/exec"
 	"path"
@@ -113,7 +112,7 @@ func TestTags(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	result, err := ioutil.ReadFile(output)
+	result, err := os.ReadFile(output)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -128,7 +127,7 @@ func TestTags(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	result, err = ioutil.ReadFile(output)
+	result, err = os.ReadFile(output)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -184,7 +183,7 @@ func buildStringer(t *testing.T) (dir string, stringer string) {
 	t.Helper()
 	testenv.NeedsTool(t, "go")
 
-	dir, err := ioutil.TempDir("", "stringer")
+	dir, err := os.MkdirTemp("", "stringer")
 	if err != nil {
 		t.Fatal(err)
 	}

cmd/stringer/golden_test.go

@@ -10,7 +10,6 @@
 package main
 
 import (
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"strings"
@@ -452,7 +451,7 @@ func (i Token) String() string {
 func TestGolden(t *testing.T) {
 	testenv.NeedsTool(t, "go")
 
-	dir, err := ioutil.TempDir("", "stringer")
+	dir, err := os.MkdirTemp("", "stringer")
 	if err != nil {
 		t.Error(err)
 	}
@@ -466,7 +465,7 @@ func TestGolden(t *testing.T) {
 		input := "package test\n" + test.input
 		file := test.name + ".go"
 		absFile := filepath.Join(dir, file)
-		err := ioutil.WriteFile(absFile, []byte(input), 0644)
+		err := os.WriteFile(absFile, []byte(input), 0644)
 		if err != nil {
 			t.Error(err)
 		}

cmd/stringer/stringer.go

@@ -76,7 +76,6 @@ import (
 	"go/format"
 	"go/token"
 	"go/types"
-	"io/ioutil"
 	"log"
 	"os"
 	"path/filepath"
@@ -166,7 +165,7 @@ func main() {
 		baseName := fmt.Sprintf("%s_string.go", types[0])
 		outputName = filepath.Join(dir, strings.ToLower(baseName))
 	}
-	err := ioutil.WriteFile(outputName, src, 0644)
+	err := os.WriteFile(outputName, src, 0644)
 	if err != nil {
 		log.Fatalf("writing output: %s", err)
 	}