all: update references to symbols moved from os to io/fs

The old os 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.

For #41190.

Change-Id: I8f9526977867c10a221e2f392f78d7dec073f1bd
Reviewed-on: https://go-review.googlesource.com/c/go/+/243907
Trust: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Rob Pike <r@golang.org>

2 files changed, 7 insertions, 5 deletions

diff --git a/src/cmd/gofmt/gofmt.go b/src/cmd/gofmt/gofmt.go
index 8c56af7559..48b6ad6f53 100644
--- a/src/cmd/gofmt/gofmt.go
+++ b/src/cmd/gofmt/gofmt.go
@@ -14,6 +14,7 @@ import (
 	"go/scanner"
 	"go/token"
 	"io"
+	"io/fs"
 	"io/ioutil"
 	"os"
 	"path/filepath"
@@ -73,7 +74,7 @@ func initParserMode() {
 	}
 }
 
-func isGoFile(f os.FileInfo) bool {
+func isGoFile(f fs.FileInfo) bool {
 	// ignore non-Go files
 	name := f.Name()
 	return !f.IsDir() && !strings.HasPrefix(name, ".") && strings.HasSuffix(name, ".go")
@@ -81,7 +82,7 @@ func isGoFile(f os.FileInfo) bool {
 
 // If in == nil, the source is the contents of the file with the given filename.
 func processFile(filename string, in io.Reader, out io.Writer, stdin bool) error {
-	var perm os.FileMode = 0644
+	var perm fs.FileMode = 0644
 	if in == nil {
 		f, err := os.Open(filename)
 		if err != nil {
@@ -163,7 +164,7 @@ func processFile(filename string, in io.Reader, out io.Writer, stdin bool) error
 	return err
 }
 
-func visitFile(path string, f os.FileInfo, err error) error {
+func visitFile(path string, f fs.FileInfo, err error) error {
 	if err == nil && isGoFile(f) {
 		err = processFile(path, nil, os.Stdout, false)
 	}
@@ -275,7 +276,7 @@ const chmodSupported = runtime.GOOS != "windows"
 // backupFile writes data to a new file named filename<number> with permissions perm,
 // with <number randomly chosen such that the file name is unique. backupFile returns
 // the chosen file name.
-func backupFile(filename string, data []byte, perm os.FileMode) (string, error) {
+func backupFile(filename string, data []byte, perm fs.FileMode) (string, error) {
 	// create backup file
 	f, err := ioutil.TempFile(filepath.Dir(filename), filepath.Base(filename))
 	if err != nil {
diff --git a/src/cmd/gofmt/long_test.go b/src/cmd/gofmt/long_test.go
index e2a6208f87..28306ce83e 100644
--- a/src/cmd/gofmt/long_test.go
+++ b/src/cmd/gofmt/long_test.go
@@ -16,6 +16,7 @@ import (
 	"go/printer"
 	"go/token"
 	"io"
+	"io/fs"
 	"os"
 	"path/filepath"
 	"runtime"
@@ -107,7 +108,7 @@ func testFiles(t *testing.T, filenames <-chan string, done chan<- int) {
 func genFilenames(t *testing.T, filenames chan<- string) {
 	defer close(filenames)
 
-	handleFile := func(filename string, fi os.FileInfo, err error) error {
+	handleFile := func(filename string, fi fs.FileInfo, err error) error {
 		if err != nil {
 			t.Error(err)
 			return nil