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>

6 files changed, 18 insertions, 15 deletions

diff --git a/src/go/build/build.go b/src/go/build/build.go
index 7a96680e77..6141f4a90e 100644
--- a/src/go/build/build.go
+++ b/src/go/build/build.go
@@ -15,6 +15,7 @@ import (
 	"internal/goroot"
 	"internal/goversion"
 	"io"
+	"io/fs"
 	"io/ioutil"
 	"os"
 	"os/exec"
@@ -98,10 +99,10 @@ type Context struct {
 	// filepath.EvalSymlinks.
 	HasSubdir func(root, dir string) (rel string, ok bool)
 
-	// ReadDir returns a slice of os.FileInfo, sorted by Name,
+	// ReadDir returns a slice of fs.FileInfo, sorted by Name,
 	// describing the content of the named directory.
 	// If ReadDir is nil, Import uses ioutil.ReadDir.
-	ReadDir func(dir string) ([]os.FileInfo, error)
+	ReadDir func(dir string) ([]fs.FileInfo, error)
 
 	// OpenFile opens a file (not a directory) for reading.
 	// If OpenFile is nil, Import uses os.Open.
@@ -183,7 +184,7 @@ func hasSubdir(root, dir string) (rel string, ok bool) {
 }
 
 // readDir calls ctxt.ReadDir (if not nil) or else ioutil.ReadDir.
-func (ctxt *Context) readDir(path string) ([]os.FileInfo, error) {
+func (ctxt *Context) readDir(path string) ([]fs.FileInfo, error) {
 	if f := ctxt.ReadDir; f != nil {
 		return f(path)
 	}
@@ -794,7 +795,7 @@ Found:
 		if d.IsDir() {
 			continue
 		}
-		if (d.Mode() & os.ModeSymlink) != 0 {
+		if d.Mode()&fs.ModeSymlink != 0 {
 			if fi, err := os.Stat(filepath.Join(p.Dir, d.Name())); err == nil && fi.IsDir() {
 				// Symlinks to directories are not source files.
 				continue
diff --git a/src/go/build/deps_test.go b/src/go/build/deps_test.go
index 96e239ad77..9e72c8f234 100644
--- a/src/go/build/deps_test.go
+++ b/src/go/build/deps_test.go
@@ -11,6 +11,7 @@ import (
 	"bytes"
 	"fmt"
 	"internal/testenv"
+	"io/fs"
 	"io/ioutil"
 	"os"
 	"path/filepath"
@@ -500,7 +501,7 @@ func listStdPkgs(goroot string) ([]string, error) {
 	var pkgs []string
 
 	src := filepath.Join(goroot, "src") + string(filepath.Separator)
-	walkFn := func(path string, fi os.FileInfo, err error) error {
+	walkFn := func(path string, fi fs.FileInfo, err error) error {
 		if err != nil || !fi.IsDir() || path == src {
 			return nil
 		}
diff --git a/src/go/doc/doc_test.go b/src/go/doc/doc_test.go
index f1e612c18b..ab98bed62b 100644
--- a/src/go/doc/doc_test.go
+++ b/src/go/doc/doc_test.go
@@ -12,8 +12,8 @@ import (
 	"go/parser"
 	"go/printer"
 	"go/token"
+	"io/fs"
 	"io/ioutil"
-	"os"
 	"path/filepath"
 	"regexp"
 	"strings"
@@ -66,7 +66,7 @@ func indentFmt(indent, s string) string {
 	return indent + strings.ReplaceAll(s, "\n", "\n"+indent) + end
 }
 
-func isGoFile(fi os.FileInfo) bool {
+func isGoFile(fi fs.FileInfo) bool {
 	name := fi.Name()
 	return !fi.IsDir() &&
 		len(name) > 0 && name[0] != '.' && // ignore .files
@@ -86,7 +86,7 @@ func test(t *testing.T, mode Mode) {
 		if err != nil {
 			t.Fatal(err)
 		}
-		filter = func(fi os.FileInfo) bool {
+		filter = func(fi fs.FileInfo) bool {
 			return isGoFile(fi) && rx.MatchString(fi.Name())
 		}
 	}
diff --git a/src/go/doc/headscan.go b/src/go/doc/headscan.go
index 3f782cc1b4..8ea462366e 100644
--- a/src/go/doc/headscan.go
+++ b/src/go/doc/headscan.go
@@ -23,6 +23,7 @@ import (
 	"go/parser"
 	"go/token"
 	"internal/lazyregexp"
+	"io/fs"
 	"os"
 	"path/filepath"
 	"runtime"
@@ -39,7 +40,7 @@ var html_h = lazyregexp.New(`<h3 id="[^"]*">`)
 
 const html_endh = "</h3>\n"
 
-func isGoFile(fi os.FileInfo) bool {
+func isGoFile(fi fs.FileInfo) bool {
 	return strings.HasSuffix(fi.Name(), ".go") &&
 		!strings.HasSuffix(fi.Name(), "_test.go")
 }
@@ -68,7 +69,7 @@ func main() {
 	flag.Parse()
 	fset := token.NewFileSet()
 	nheadings := 0
-	err := filepath.Walk(*root, func(path string, fi os.FileInfo, err error) error {
+	err := filepath.Walk(*root, func(path string, fi fs.FileInfo, err error) error {
 		if !fi.IsDir() {
 			return nil
 		}
diff --git a/src/go/parser/interface.go b/src/go/parser/interface.go
index 54f9d7b80a..b2d834fdec 100644
--- a/src/go/parser/interface.go
+++ b/src/go/parser/interface.go
@@ -12,8 +12,8 @@ import (
 	"go/ast"
 	"go/token"
 	"io"
+	"io/fs"
 	"io/ioutil"
-	"os"
 	"path/filepath"
 	"strings"
 )
@@ -123,7 +123,7 @@ func ParseFile(fset *token.FileSet, filename string, src interface{}, mode Mode)
 // directory specified by path and returns a map of package name -> package
 // AST with all the packages found.
 //
-// If filter != nil, only the files with os.FileInfo entries passing through
+// If filter != nil, only the files with fs.FileInfo entries passing through
 // the filter (and ending in ".go") are considered. The mode bits are passed
 // to ParseFile unchanged. Position information is recorded in fset, which
 // must not be nil.
@@ -132,7 +132,7 @@ func ParseFile(fset *token.FileSet, filename string, src interface{}, mode Mode)
 // returned. If a parse error occurred, a non-nil but incomplete map and the
 // first error encountered are returned.
 //
-func ParseDir(fset *token.FileSet, path string, filter func(os.FileInfo) bool, mode Mode) (pkgs map[string]*ast.Package, first error) {
+func ParseDir(fset *token.FileSet, path string, filter func(fs.FileInfo) bool, mode Mode) (pkgs map[string]*ast.Package, first error) {
 	list, err := ioutil.ReadDir(path)
 	if err != nil {
 		return nil, err
diff --git a/src/go/parser/parser_test.go b/src/go/parser/parser_test.go
index 25a374eeef..7193a329fe 100644
--- a/src/go/parser/parser_test.go
+++ b/src/go/parser/parser_test.go
@@ -9,7 +9,7 @@ import (
 	"fmt"
 	"go/ast"
 	"go/token"
-	"os"
+	"io/fs"
 	"strings"
 	"testing"
 )
@@ -40,7 +40,7 @@ func nameFilter(filename string) bool {
 	return false
 }
 
-func dirFilter(f os.FileInfo) bool { return nameFilter(f.Name()) }
+func dirFilter(f fs.FileInfo) bool { return nameFilter(f.Name()) }
 
 func TestParseFile(t *testing.T) {
 	src := "package p\nvar _=s[::]+\ns[::]+\ns[::]+\ns[::]+\ns[::]+\ns[::]+\ns[::]+\ns[::]+\ns[::]+\ns[::]+\ns[::]+\ns[::]"