diff --git a/godoc/analysis/analysis.go b/godoc/analysis/analysis.go
index 54611e87d96..54d692a59ec 100644
--- a/godoc/analysis/analysis.go
+++ b/godoc/analysis/analysis.go
@@ -62,15 +62,15 @@ type Link interface {
 // FileInfo holds analysis information for the source file view.
 // Clients must not mutate it.
 type FileInfo struct {
-	Data  []interface{} // JSON serializable values
-	Links []Link        // HTML link markup
+	Data  []any  // JSON serializable values
+	Links []Link // HTML link markup
 }
 
 // A fileInfo is the server's store of hyperlinks and JSON data for a
 // particular file.
 type fileInfo struct {
 	mu        sync.Mutex
-	data      []interface{} // JSON objects
+	data      []any // JSON objects
 	links     []Link
 	sorted    bool
 	hasErrors bool // TODO(adonovan): surface this in the UI
diff --git a/godoc/godoc.go b/godoc/godoc.go
index a9d806f7e8b..ac6ab23a0a1 100644
--- a/godoc/godoc.go
+++ b/godoc/godoc.go
@@ -190,13 +190,13 @@ func (p *Presentation) infoSnippet_htmlFunc(info SpotInfo) string {
 	return `<span class="alert">no snippet text available</span>`
 }
 
-func (p *Presentation) nodeFunc(info *PageInfo, node interface{}) string {
+func (p *Presentation) nodeFunc(info *PageInfo, node any) string {
 	var buf bytes.Buffer
 	p.writeNode(&buf, info, info.FSet, node)
 	return buf.String()
 }
 
-func (p *Presentation) node_htmlFunc(info *PageInfo, node interface{}, linkify bool) string {
+func (p *Presentation) node_htmlFunc(info *PageInfo, node any, linkify bool) string {
 	var buf1 bytes.Buffer
 	p.writeNode(&buf1, info, info.FSet, node)
 
@@ -477,9 +477,9 @@ func srcBreadcrumbFunc(relpath string) string {
 	return buf.String()
 }
 
-func newPosLink_urlFunc(srcPosLinkFunc func(s string, line, low, high int) string) func(info *PageInfo, n interface{}) string {
+func newPosLink_urlFunc(srcPosLinkFunc func(s string, line, low, high int) string) func(info *PageInfo, n any) string {
 	// n must be an ast.Node or a *doc.Note
-	return func(info *PageInfo, n interface{}) string {
+	return func(info *PageInfo, n any) string {
 		var pos, end token.Pos
 
 		switch n := n.(type) {
@@ -839,7 +839,7 @@ func replaceLeadingIndentation(body, oldIndent, newIndent string) string {
 // The provided fset must be non-nil. The pageInfo is optional. If
 // present, the pageInfo is used to add comments to struct fields to
 // say which version of Go introduced them.
-func (p *Presentation) writeNode(w io.Writer, pageInfo *PageInfo, fset *token.FileSet, x interface{}) {
+func (p *Presentation) writeNode(w io.Writer, pageInfo *PageInfo, fset *token.FileSet, x any) {
 	// convert trailing tabs into spaces using a tconv filter
 	// to ensure a good outcome in most browsers (there may still
 	// be tabs in comments and strings, but converting those into
@@ -918,7 +918,7 @@ var slashSlash = []byte("//")
 
 // WriteNode writes x to w.
 // TODO(bgarcia) Is this method needed? It's just a wrapper for p.writeNode.
-func (p *Presentation) WriteNode(w io.Writer, fset *token.FileSet, x interface{}) {
+func (p *Presentation) WriteNode(w io.Writer, fset *token.FileSet, x any) {
 	p.writeNode(w, nil, fset, x)
 }
 
diff --git a/godoc/index.go b/godoc/index.go
index 377837a0b36..05a1a9441ee 100644
--- a/godoc/index.go
+++ b/godoc/index.go
@@ -71,10 +71,10 @@ import (
 // InterfaceSlice is a helper type for sorting interface
 // slices according to some slice-specific sort criteria.
 
-type comparer func(x, y interface{}) bool
+type comparer func(x, y any) bool
 
 type interfaceSlice struct {
-	slice []interface{}
+	slice []any
 	less  comparer
 }
 
@@ -87,7 +87,7 @@ type interfaceSlice struct {
 // runs. For instance, a RunList containing pairs (x, y) may be compressed
 // into a RunList containing pair runs (x, {y}) where each run consists of
 // a list of y's with the same x.
-type RunList []interface{}
+type RunList []any
 
 func (h RunList) sort(less comparer) {
 	sort.Sort(&interfaceSlice{h, less})
@@ -99,7 +99,7 @@ func (p *interfaceSlice) Swap(i, j int)      { p.slice[i], p.slice[j] = p.slice[
 
 // Compress entries which are the same according to a sort criteria
 // (specified by less) into "runs".
-func (h RunList) reduce(less comparer, newRun func(h RunList) interface{}) RunList {
+func (h RunList) reduce(less comparer, newRun func(h RunList) any) RunList {
 	if len(h) == 0 {
 		return nil
 	}
@@ -143,10 +143,10 @@ func (k KindRun) Less(i, j int) bool { return k[i].Lori() < k[j].Lori() }
 func (k KindRun) Swap(i, j int)      { k[i], k[j] = k[j], k[i] }
 
 // FileRun contents are sorted by Kind for the reduction into KindRuns.
-func lessKind(x, y interface{}) bool { return x.(SpotInfo).Kind() < y.(SpotInfo).Kind() }
+func lessKind(x, y any) bool { return x.(SpotInfo).Kind() < y.(SpotInfo).Kind() }
 
 // newKindRun allocates a new KindRun from the SpotInfo run h.
-func newKindRun(h RunList) interface{} {
+func newKindRun(h RunList) any {
 	run := make(KindRun, len(h))
 	for i, x := range h {
 		run[i] = x.(SpotInfo)
@@ -214,7 +214,7 @@ type FileRun struct {
 }
 
 // Spots are sorted by file path for the reduction into FileRuns.
-func lessSpot(x, y interface{}) bool {
+func lessSpot(x, y any) bool {
 	fx := x.(Spot).File
 	fy := y.(Spot).File
 	// same as "return fx.Path() < fy.Path()" but w/o computing the file path first
@@ -224,7 +224,7 @@ func lessSpot(x, y interface{}) bool {
 }
 
 // newFileRun allocates a new FileRun from the Spot run h.
-func newFileRun(h RunList) interface{} {
+func newFileRun(h RunList) any {
 	file := h[0].(Spot).File
 
 	// reduce the list of Spots into a list of KindRuns
@@ -257,12 +257,12 @@ func (p *PakRun) Less(i, j int) bool { return p.Files[i].File.Name < p.Files[j].
 func (p *PakRun) Swap(i, j int)      { p.Files[i], p.Files[j] = p.Files[j], p.Files[i] }
 
 // FileRuns are sorted by package for the reduction into PakRuns.
-func lessFileRun(x, y interface{}) bool {
+func lessFileRun(x, y any) bool {
 	return x.(*FileRun).File.Pak.less(y.(*FileRun).File.Pak)
 }
 
 // newPakRun allocates a new PakRun from the *FileRun run h.
-func newPakRun(h RunList) interface{} {
+func newPakRun(h RunList) any {
 	pak := h[0].(*FileRun).File.Pak
 	files := make([]*FileRun, len(h))
 	for i, x := range h {
@@ -280,7 +280,7 @@ func newPakRun(h RunList) interface{} {
 type HitList []*PakRun
 
 // PakRuns are sorted by package.
-func lessPakRun(x, y interface{}) bool { return x.(*PakRun).Pak.less(y.(*PakRun).Pak) }
+func lessPakRun(x, y any) bool { return x.(*PakRun).Pak.less(y.(*PakRun).Pak) }
 
 func reduce(h0 RunList) HitList {
 	// reduce a list of Spots into a list of FileRuns
@@ -325,10 +325,10 @@ type AltWords struct {
 }
 
 // wordPairs are sorted by their canonical spelling.
-func lessWordPair(x, y interface{}) bool { return x.(*wordPair).canon < y.(*wordPair).canon }
+func lessWordPair(x, y any) bool { return x.(*wordPair).canon < y.(*wordPair).canon }
 
 // newAltWords allocates a new AltWords from the *wordPair run h.
-func newAltWords(h RunList) interface{} {
+func newAltWords(h RunList) any {
 	canon := h[0].(*wordPair).canon
 	alts := make([]string, len(h))
 	for i, x := range h {
@@ -1159,7 +1159,7 @@ func (x *Index) WriteTo(w io.Writer) (n int64, err error) {
 		return 0, err
 	}
 	if fulltext {
-		encode := func(x interface{}) error {
+		encode := func(x any) error {
 			return gob.NewEncoder(w).Encode(x)
 		}
 		if err := x.fset.Write(encode); err != nil {
@@ -1199,7 +1199,7 @@ func (x *Index) ReadFrom(r io.Reader) (n int64, err error) {
 	x.opts = fx.Opts
 	if fx.Fulltext {
 		x.fset = token.NewFileSet()
-		decode := func(x interface{}) error {
+		decode := func(x any) error {
 			return gob.NewDecoder(r).Decode(x)
 		}
 		if err := x.fset.Read(decode); err != nil {
diff --git a/godoc/search.go b/godoc/search.go
index 33e4febfaaa..a0afb8bf97b 100644
--- a/godoc/search.go
+++ b/godoc/search.go
@@ -36,7 +36,7 @@ func (c *Corpus) Lookup(query string) SearchResult {
 		// identifier search
 		if r, err := index.Lookup(query); err == nil {
 			result = r
-		} else if err != nil && !c.IndexFullText {
+		} else if !c.IndexFullText {
 			// ignore the error if full text search is enabled
 			// since the query may be a valid regular expression
 			result.Alert = "Error in query string: " + err.Error()
@@ -127,7 +127,7 @@ func (p *Presentation) HandleSearch(w http.ResponseWriter, r *http.Request) {
 
 func (p *Presentation) serveSearchDesc(w http.ResponseWriter, r *http.Request) {
 	w.Header().Set("Content-Type", "application/opensearchdescription+xml")
-	data := map[string]interface{}{
+	data := map[string]any{
 		"BaseURL": fmt.Sprintf("http://%s", r.Host),
 	}
 	applyTemplateToResponseWriter(w, p.SearchDescXML, &data)
diff --git a/godoc/server.go b/godoc/server.go
index afb28e2e187..92d1ec48d61 100644
--- a/godoc/server.go
+++ b/godoc/server.go
@@ -502,7 +502,7 @@ func packageExports(fset *token.FileSet, pkg *ast.Package) {
 	}
 }
 
-func applyTemplate(t *template.Template, name string, data interface{}) []byte {
+func applyTemplate(t *template.Template, name string, data any) []byte {
 	var buf bytes.Buffer
 	if err := t.Execute(&buf, data); err != nil {
 		log.Printf("%s.Execute: %s", name, err)
@@ -529,7 +529,7 @@ func (w *writerCapturesErr) Write(p []byte) (int, error) {
 // they come from the template processing and not the Writer; this avoid
 // polluting log files with error messages due to networking issues, such as
 // client disconnects and http HEAD protocol violations.
-func applyTemplateToResponseWriter(rw http.ResponseWriter, t *template.Template, data interface{}) {
+func applyTemplateToResponseWriter(rw http.ResponseWriter, t *template.Template, data any) {
 	w := &writerCapturesErr{w: rw}
 	err := t.Execute(w, data)
 	// There are some cases where template.Execute does not return an error when
@@ -839,7 +839,7 @@ func (p *Presentation) ServeText(w http.ResponseWriter, text []byte) {
 	w.Write(text)
 }
 
-func marshalJSON(x interface{}) []byte {
+func marshalJSON(x any) []byte {
 	var data []byte
 	var err error
 	const indentJSON = false // for easier debugging
diff --git a/godoc/spec.go b/godoc/spec.go
index 9ec94278db5..c8142363e9b 100644
--- a/godoc/spec.go
+++ b/godoc/spec.go
@@ -38,7 +38,7 @@ func (p *ebnfParser) next() {
 	p.lit = p.scanner.TokenText()
 }
 
-func (p *ebnfParser) printf(format string, args ...interface{}) {
+func (p *ebnfParser) printf(format string, args ...any) {
 	p.flush()
 	fmt.Fprintf(p.out, format, args...)
 }
diff --git a/godoc/template.go b/godoc/template.go
index 1e4e42e30e5..4418bea09b5 100644
--- a/godoc/template.go
+++ b/godoc/template.go
@@ -55,7 +55,7 @@ func (c *Corpus) contents(name string) string {
 }
 
 // stringFor returns a textual representation of the arg, formatted according to its nature.
-func stringFor(arg interface{}) string {
+func stringFor(arg any) string {
 	switch arg := arg.(type) {
 	case int:
 		return fmt.Sprintf("%d", arg)
@@ -70,7 +70,7 @@ func stringFor(arg interface{}) string {
 	return ""
 }
 
-func (p *Presentation) code(file string, arg ...interface{}) (s string, err error) {
+func (p *Presentation) code(file string, arg ...any) (s string, err error) {
 	defer func() {
 		if r := recover(); r != nil {
 			err = fmt.Errorf("%v", r)
@@ -85,7 +85,7 @@ func (p *Presentation) code(file string, arg ...interface{}) (s string, err erro
 		command = fmt.Sprintf("code %q", file)
 	case 1:
 		command = fmt.Sprintf("code %q %s", file, stringFor(arg[0]))
-		text = p.Corpus.oneLine(file, text, arg[0])
+		text = p.Corpus.oneLine(file, arg[0])
 	case 2:
 		command = fmt.Sprintf("code %q %s %s", file, stringFor(arg[0]), stringFor(arg[1]))
 		text = p.Corpus.multipleLines(file, text, arg[0], arg[1])
@@ -105,7 +105,7 @@ func (p *Presentation) code(file string, arg ...interface{}) (s string, err erro
 }
 
 // parseArg returns the integer or string value of the argument and tells which it is.
-func parseArg(arg interface{}, file string, max int) (ival int, sval string, isInt bool) {
+func parseArg(arg any, file string, max int) (ival int, sval string, isInt bool) {
 	switch n := arg.(type) {
 	case int:
 		if n <= 0 || n > max {
@@ -120,7 +120,7 @@ func parseArg(arg interface{}, file string, max int) (ival int, sval string, isI
 }
 
 // oneLine returns the single line generated by a two-argument code invocation.
-func (c *Corpus) oneLine(file, text string, arg interface{}) string {
+func (c *Corpus) oneLine(file string, arg any) string {
 	lines := strings.SplitAfter(c.contents(file), "\n")
 	line, pattern, isInt := parseArg(arg, file, len(lines))
 	if isInt {
@@ -130,7 +130,7 @@ func (c *Corpus) oneLine(file, text string, arg interface{}) string {
 }
 
 // multipleLines returns the text generated by a three-argument code invocation.
-func (c *Corpus) multipleLines(file, text string, arg1, arg2 interface{}) string {
+func (c *Corpus) multipleLines(file, text string, arg1, arg2 any) string {
 	lines := strings.SplitAfter(c.contents(file), "\n")
 	line1, pattern1, isInt1 := parseArg(arg1, file, len(lines))
 	line2, pattern2, isInt2 := parseArg(arg2, file, len(lines))
diff --git a/godoc/util/util.go b/godoc/util/util.go
index c08ca785fed..21390556e7f 100644
--- a/godoc/util/util.go
+++ b/godoc/util/util.go
@@ -18,18 +18,18 @@ import (
 // access to it and records the time the value was last set.
 type RWValue struct {
 	mutex     sync.RWMutex
-	value     interface{}
+	value     any
 	timestamp time.Time // time of last set()
 }
 
-func (v *RWValue) Set(value interface{}) {
+func (v *RWValue) Set(value any) {
 	v.mutex.Lock()
 	v.value = value
 	v.timestamp = time.Now()
 	v.mutex.Unlock()
 }
 
-func (v *RWValue) Get() (interface{}, time.Time) {
+func (v *RWValue) Get() (any, time.Time) {
 	v.mutex.RLock()
 	defer v.mutex.RUnlock()
 	return v.value, v.timestamp
diff --git a/godoc/vfs/emptyvfs.go b/godoc/vfs/emptyvfs.go
index 521bf71a51b..4ab5c7c649e 100644
--- a/godoc/vfs/emptyvfs.go
+++ b/godoc/vfs/emptyvfs.go
@@ -84,6 +84,6 @@ func (e *emptyVFS) IsDir() bool {
 	return true
 }
 
-func (e *emptyVFS) Sys() interface{} {
+func (e *emptyVFS) Sys() any {
 	return nil
 }
diff --git a/godoc/vfs/mapfs/mapfs.go b/godoc/vfs/mapfs/mapfs.go
index 9d0f465eb5e..06fb4f09543 100644
--- a/godoc/vfs/mapfs/mapfs.go
+++ b/godoc/vfs/mapfs/mapfs.go
@@ -158,9 +158,9 @@ func (fi mapFI) Mode() os.FileMode {
 	}
 	return 0444
 }
-func (fi mapFI) Name() string     { return pathpkg.Base(fi.name) }
-func (fi mapFI) Size() int64      { return int64(fi.size) }
-func (fi mapFI) Sys() interface{} { return nil }
+func (fi mapFI) Name() string { return pathpkg.Base(fi.name) }
+func (fi mapFI) Size() int64  { return int64(fi.size) }
+func (fi mapFI) Sys() any     { return nil }
 
 type nopCloser struct {
 	io.ReadSeeker
diff --git a/godoc/vfs/namespace.go b/godoc/vfs/namespace.go
index 23dd9794312..2566051a293 100644
--- a/godoc/vfs/namespace.go
+++ b/godoc/vfs/namespace.go
@@ -275,7 +275,7 @@ func (d dirInfo) Size() int64        { return 0 }
 func (d dirInfo) Mode() os.FileMode  { return os.ModeDir | 0555 }
 func (d dirInfo) ModTime() time.Time { return startTime }
 func (d dirInfo) IsDir() bool        { return true }
-func (d dirInfo) Sys() interface{}   { return nil }
+func (d dirInfo) Sys() any           { return nil }
 
 var startTime = time.Now()
 
diff --git a/godoc/vfs/zipfs/zipfs.go b/godoc/vfs/zipfs/zipfs.go
index 14c9820a1c7..cdf231a1abd 100644
--- a/godoc/vfs/zipfs/zipfs.go
+++ b/godoc/vfs/zipfs/zipfs.go
@@ -68,7 +68,7 @@ func (fi zipFI) IsDir() bool {
 	return fi.file == nil
 }
 
-func (fi zipFI) Sys() interface{} {
+func (fi zipFI) Sys() any {
 	return nil
 }
 
diff --git a/present/args.go b/present/args.go
index b4f7503b6da..17b9d4e87e8 100644
--- a/present/args.go
+++ b/present/args.go
@@ -96,7 +96,7 @@ func addrToByteRange(addr string, start int, data []byte) (lo, hi int, err error
 				j = i
 			}
 			pattern := addr[1:i]
-			lo, hi, err = addrRegexp(data, lo, hi, dir, pattern)
+			lo, hi, err = addrRegexp(data, hi, dir, pattern)
 			prevc = c
 			addr = addr[j:]
 			continue
@@ -202,7 +202,7 @@ func addrNumber(data []byte, lo, hi int, dir byte, n int, charOffset bool) (int,
 // addrRegexp searches for pattern in the given direction starting at lo, hi.
 // The direction dir is '+' (search forward from hi) or '-' (search backward from lo).
 // Backward searches are unimplemented.
-func addrRegexp(data []byte, lo, hi int, dir byte, pattern string) (int, int, error) {
+func addrRegexp(data []byte, hi int, dir byte, pattern string) (int, int, error) {
 	// We want ^ and $ to work as in sam/acme, so use ?m.
 	re, err := regexp.Compile("(?m:" + pattern + ")")
 	if err != nil {
diff --git a/present/code.go b/present/code.go
index f00f1f49d0b..d98f8384414 100644
--- a/present/code.go
+++ b/present/code.go
@@ -238,8 +238,8 @@ func codeLines(src []byte, start, end int) (lines []codeLine) {
 	return
 }
 
-func parseArgs(name string, line int, args []string) (res []interface{}, err error) {
-	res = make([]interface{}, len(args))
+func parseArgs(name string, line int, args []string) (res []any, err error) {
+	res = make([]any, len(args))
 	for i, v := range args {
 		if len(v) == 0 {
 			return nil, fmt.Errorf("%s:%d bad code argument %q", name, line, v)
diff --git a/present/parse.go b/present/parse.go
index 162a382b060..8b41dd2df52 100644
--- a/present/parse.go
+++ b/present/parse.go
@@ -15,6 +15,7 @@ import (
 	"net/url"
 	"os"
 	"regexp"
+	"slices"
 	"strings"
 	"time"
 	"unicode"
@@ -166,7 +167,7 @@ type Elem interface {
 // renderElem implements the elem template function, used to render
 // sub-templates.
 func renderElem(t *template.Template, e Elem) (template.HTML, error) {
-	var data interface{} = e
+	var data any = e
 	if s, ok := e.(Section); ok {
 		data = struct {
 			Section
@@ -191,7 +192,7 @@ func init() {
 
 // execTemplate is a helper to execute a template and return the output as a
 // template.HTML value.
-func execTemplate(t *template.Template, name string, data interface{}) (template.HTML, error) {
+func execTemplate(t *template.Template, name string, data any) (template.HTML, error) {
 	b := new(bytes.Buffer)
 	err := t.ExecuteTemplate(b, name, data)
 	if err != nil {
@@ -394,7 +395,7 @@ func parseSections(ctx *Context, name, prefix string, lines *Lines, number []int
 			}
 		}
 		section := Section{
-			Number: append(append([]int{}, number...), i),
+			Number: append(slices.Clone(number), i),
 			Title:  title,
 			ID:     id,
 		}
diff --git a/refactor/importgraph/graph.go b/refactor/importgraph/graph.go
index d2d8f098b3f..c24ff882c7b 100644
--- a/refactor/importgraph/graph.go
+++ b/refactor/importgraph/graph.go
@@ -68,7 +68,7 @@ func Build(ctxt *build.Context) (forward, reverse Graph, errors map[string]error
 		err  error
 	}
 
-	ch := make(chan interface{})
+	ch := make(chan any)
 
 	go func() {
 		sema := make(chan int, 20) // I/O concurrency limiting semaphore
diff --git a/refactor/rename/check.go b/refactor/rename/check.go
index 8350ad7bc32..4a058321ca4 100644
--- a/refactor/rename/check.go
+++ b/refactor/rename/check.go
@@ -19,7 +19,7 @@ import (
 )
 
 // errorf reports an error (e.g. conflict) and prevents file modification.
-func (r *renamer) errorf(pos token.Pos, format string, args ...interface{}) {
+func (r *renamer) errorf(pos token.Pos, format string, args ...any) {
 	r.hadConflicts = true
 	reportError(r.iprog.Fset.Position(pos), fmt.Sprintf(format, args...))
 }