all: modernize (#5498)

* modernize string cut usage

* modernize string cut prefix usage

* modernize slices helper usage

* modernize min and max usage

* modernize loop variable copies

* modernize integer range loops

* modernize map copy loops

* modernize go types iterator usage

* modernize empty interface usage

* modernize atomic type usage

* modernize string builders

* modernize string split iteration

* modernize remaining loop variable copies

* modernize usb cdc min usage

* modernize src integer range loops

* modernize example empty interface usage

* modernize src min and max usage

* modernize src integer range loops

* modernize src empty interface usage

* modernize src atomic type usage

* modernize reflect type lookups

* modernize review nits

builder/build.go

@@ -14,6 +14,7 @@ import (
 	"fmt"
 	"go/types"
 	"hash/crc32"
+	"maps"
 	"math/bits"
 	"os"
 	"os/exec"
@@ -137,9 +138,7 @@ func Build(pkgName, outpath, tmpdir string, config *compileopts.Config) (BuildRe
 		if _, ok := globalValues[pkgPath]; !ok {
 			globalValues[pkgPath] = map[string]string{}
 		}
-		for k, v := range vals {
+		maps.Copy(globalValues[pkgPath], vals)
-			globalValues[pkgPath][k] = v
-		}
 	}
 
 	// Check for a libc dependency.
@@ -278,7 +277,6 @@ func Build(pkgName, outpath, tmpdir string, config *compileopts.Config) (BuildRe
 
 	var embedFileObjects []*compileJob
 	for _, pkg := range lprogram.Sorted() {
-		pkg := pkg // necessary to avoid a race condition
 
 		var undefinedGlobals []string
 		for name := range globalValues[pkg.Pkg.Path()] {
@@ -775,7 +773,6 @@ func Build(pkgName, outpath, tmpdir string, config *compileopts.Config) (BuildRe
 	// TODO: do this as part of building the package to be able to link the
 	// bitcode files together.
 	for _, pkg := range lprogram.Sorted() {
-		pkg := pkg
 		for _, filename := range pkg.CFiles {
 			abspath := filepath.Join(pkg.OriginalDir(), filename)
 			job := &compileJob{
@@ -914,7 +911,7 @@ func Build(pkgName, outpath, tmpdir string, config *compileopts.Config) (BuildRe
 			}
 
 			// Run wasm-opt for wasm binaries
-			if arch := strings.Split(config.Triple(), "-")[0]; arch == "wasm32" {
+			if arch, _, _ := strings.Cut(config.Triple(), "-"); arch == "wasm32" {
 				optLevel, _, _ := config.OptLevel()
 				opt := "-" + optLevel
 

builder/builder_test.go

@@ -47,7 +47,6 @@ func TestClangAttributes(t *testing.T) {
 		targetNames = append(targetNames, "esp32", "esp8266")
 	}
 	for _, targetName := range targetNames {
-		targetName := targetName
 		t.Run(targetName, func(t *testing.T) {
 			testClangAttributes(t, &compileopts.Options{Target: targetName})
 		})

builder/cc.go

@@ -281,7 +281,7 @@ func parseDepFile(s string) ([]string, error) {
 	s = strings.ReplaceAll(s, "\\\n", " ")
 
 	// Only use the first line, which is expected to begin with "deps:".
-	line := strings.SplitN(s, "\n", 2)[0]
+	line, _, _ := strings.Cut(s, "\n")
 	if !strings.HasPrefix(line, "deps:") {
 		return nil, errors.New("readDepFile: expected 'deps:' prefix")
 	}

builder/commands.go

@@ -17,7 +17,7 @@ import (
 var commands = map[string][]string{}
 
 func init() {
-	llvmMajor := strings.Split(llvm.Version, ".")[0]
+	llvmMajor, _, _ := strings.Cut(llvm.Version, ".")
 	commands["clang"] = []string{"clang-" + llvmMajor}
 	commands["ld.lld"] = []string{"ld.lld-" + llvmMajor, "ld.lld"}
 	commands["wasm-ld"] = []string{"wasm-ld-" + llvmMajor, "wasm-ld"}

builder/darwin-libsystem.go

@@ -15,7 +15,7 @@ func makeDarwinLibSystemJob(config *compileopts.Config, tmpdir string) *compileJ
 	return &compileJob{
 		description: "compile Darwin libSystem.dylib",
 		run: func(job *compileJob) (err error) {
-			arch := strings.Split(config.Triple(), "-")[0]
+			arch, _, _ := strings.Cut(config.Triple(), "-")
 			job.result = filepath.Join(tmpdir, "libSystem.dylib")
 			objpath := filepath.Join(tmpdir, "libSystem.o")
 			inpath := filepath.Join(goenv.Get("TINYGOROOT"), "lib/macos-minimal-sdk/src", arch, "libSystem.s")

builder/jobs.go

@@ -195,11 +195,11 @@ type intHeap struct {
 	sort.IntSlice
 }
 
-func (h *intHeap) Push(x interface{}) {
+func (h *intHeap) Push(x any) {
 	h.IntSlice = append(h.IntSlice, x.(int))
 }
 
-func (h *intHeap) Pop() interface{} {
+func (h *intHeap) Pop() any {
 	x := h.IntSlice[len(h.IntSlice)-1]
 	h.IntSlice = h.IntSlice[:len(h.IntSlice)-1]
 	return x

builder/library.go

@@ -232,7 +232,6 @@ func (l *Library) load(config *compileopts.Config, tmpdir string) (job *compileJ
 	}
 	for _, path := range paths {
 		// Strip leading "../" parts off the path.
-		path := path
 		cleanpath := path
 		for strings.HasPrefix(cleanpath, "../") {
 			cleanpath = cleanpath[3:]

builder/musl.go

@@ -28,8 +28,8 @@ func buildMuslAllTypes(arch, muslDir, outputBitsDir string) error {
 		if err != nil {
 			return err
 		}
-		lines := strings.Split(string(data), "\n")
+		lines := strings.SplitSeq(string(data), "\n")
-		for _, line := range lines {
+		for line := range lines {
 			if strings.HasPrefix(line, "TYPEDEF ") {
 				matches := regexp.MustCompile(`TYPEDEF (.*) ([^ ]*);`).FindStringSubmatch(line)
 				value := matches[1]

builder/sizes_test.go

@@ -51,7 +51,6 @@ func TestBinarySize(t *testing.T) {
 		// output varies by binaryen version.
 	}
 	for _, tc := range tests {
-		tc := tc
 		t.Run(tc.target+"/"+tc.path, func(t *testing.T) {
 			t.Parallel()
 
@@ -85,7 +84,6 @@ func TestSizeFull(t *testing.T) {
 	pkgMatch := regexp.MustCompile(`^[a-z/]+$`)    // example: "internal/task"
 
 	for _, target := range tests {
-		target := target
 		t.Run(target, func(t *testing.T) {
 			t.Parallel()
 

builder/tools.go

@@ -116,7 +116,7 @@ func parseLLDErrors(text string) error {
 		// This can happen in some cases like with CGo and //go:linkname tricker.
 		if matches := regexp.MustCompile(`^ld.lld(-[0-9]+)?: error: undefined symbol: (.*)\n`).FindStringSubmatch(message); matches != nil {
 			symbolName := matches[2]
-			for _, line := range strings.Split(message, "\n") {
+			for line := range strings.SplitSeq(message, "\n") {
 				matches := regexp.MustCompile(`referenced by .* \(((.*):([0-9]+))\)`).FindStringSubmatch(line)
 				if matches != nil {
 					parsedError = true

builder/uf2.go

@@ -40,7 +40,7 @@ func convertBinToUF2(input []byte, targetAddr uint32, uf2FamilyID string) ([]byt
 	}
 	bl.SetNumBlocks(len(blocks))
 
-	for i := 0; i < len(blocks); i++ {
+	for i := range blocks {
 		bl.SetBlockNo(i)
 		bl.SetData(blocks[i])
 

cgo/cgo.go

@@ -40,7 +40,7 @@ type cgoPackage struct {
 	tokenFiles      map[string]*token.File
 	definedGlobally map[string]ast.Node
 	noescapingFuncs map[string]*noescapingFunc // #cgo noescape lines
-	anonDecls       map[interface{}]string
+	anonDecls       map[any]string
 	cflags          []string // CFlags from #cgo lines
 	ldflags         []string // LDFlags from #cgo lines
 	visitedFiles    map[string][]byte
@@ -259,7 +259,7 @@ func Process(files []*ast.File, dir, importPath string, fset *token.FileSet, cfl
 		tokenFiles:      map[string]*token.File{},
 		definedGlobally: map[string]ast.Node{},
 		noescapingFuncs: map[string]*noescapingFunc{},
-		anonDecls:       map[interface{}]string{},
+		anonDecls:       map[any]string{},
 		visitedFiles:    map[string][]byte{},
 	}
 
@@ -302,7 +302,7 @@ func Process(files []*ast.File, dir, importPath string, fset *token.FileSet, cfl
 	// Find `import "C"` C fragments in the file.
 	p.cgoHeaders = make([]string, len(files)) // combined CGo header fragment for each file
 	for i, f := range files {
-		var cgoHeader string
+		var cgoHeader strings.Builder
 		for i := 0; i < len(f.Decls); i++ {
 			decl := f.Decls[i]
 			genDecl, ok := decl.(*ast.GenDecl)
@@ -337,7 +337,8 @@ func Process(files []*ast.File, dir, importPath string, fset *token.FileSet, cfl
 			// Iterate through all parts of the CGo header. Note that every //
 			// line is a new comment.
 			position := fset.Position(genDecl.Doc.Pos())
-			fragment := fmt.Sprintf("# %d %#v\n", position.Line, position.Filename)
+			var fragment strings.Builder
+			fragment.WriteString(fmt.Sprintf("# %d %#v\n", position.Line, position.Filename))
 			for _, comment := range genDecl.Doc.List {
 				// Find all #cgo lines, extract and use their contents, and
 				// replace the lines with spaces (to preserve locations).
@@ -354,12 +355,13 @@ func Process(files []*ast.File, dir, importPath string, fset *token.FileSet, cfl
 				} else { // comment
 					c = "  " + c[2:len(c)-2]
 				}
-				fragment += c + "\n"
+				fragment.WriteString(c)
+				fragment.WriteByte('\n')
 			}
-			cgoHeader += fragment
+			cgoHeader.WriteString(fragment.String())
 		}
 
-		p.cgoHeaders[i] = cgoHeader
+		p.cgoHeaders[i] = cgoHeader.String()
 	}
 
 	// Define CFlags that will be used while parsing the package.
@@ -1217,7 +1219,7 @@ func getPos(node ast.Node) token.Pos {
 // getUnnamedDeclName creates a name (with the given prefix) for the given C
 // declaration. This is used for structs, unions, and enums that are often
 // defined without a name and used in a typedef.
-func (p *cgoPackage) getUnnamedDeclName(prefix string, itf interface{}) string {
+func (p *cgoPackage) getUnnamedDeclName(prefix string, itf any) string {
 	if name, ok := p.anonDecls[itf]; ok {
 		return name
 	}

cgo/cgo_test.go

@@ -45,7 +45,6 @@ func TestCGo(t *testing.T) {
 		"flags",
 		"const",
 	} {
-		name := name // avoid a race condition
 		t.Run(name, func(t *testing.T) {
 			// Read the AST in memory.
 			path := filepath.Join("testdata", name+".go")

cgo/libclang.go

@@ -160,7 +160,7 @@ func (f *cgoFile) readNames(fragment string, cflags []string, filename string, c
 			pos := f.getClangLocationPosition(location, unit)
 			f.addError(pos, severity+": "+spelling)
 		}
-		for i := 0; i < numDiagnostics; i++ {
+		for i := range numDiagnostics {
 			diagnostic := C.clang_getDiagnostic(unit, C.uint(i))
 			addDiagnostic(diagnostic)
 
@@ -278,7 +278,7 @@ func (f *cgoFile) createASTNode(name string, c clangCursor) (ast.Node, any) {
 				Text:  strings.Join(doc, "\n"),
 			})
 		}
-		for i := 0; i < numArgs; i++ {
+		for i := range numArgs {
 			arg := C.tinygo_clang_Cursor_getArgument(c, C.uint(i))
 			argName := getString(C.tinygo_clang_getCursorSpelling(arg))
 			argType := C.clang_getArgType(cursorType, C.uint(i))
@@ -534,7 +534,7 @@ func tinygo_clang_globals_visitor(c, parent C.GoCXCursor, client_data C.CXClient
 
 // Get the precise location in the source code. Used for uniquely identifying
 // source locations.
-func (f *cgoFile) getUniqueLocationID(pos token.Pos, cursor C.GoCXCursor) interface{} {
+func (f *cgoFile) getUniqueLocationID(pos token.Pos, cursor C.GoCXCursor) any {
 	clangLocation := C.tinygo_clang_getCursorLocation(cursor)
 	var file C.CXFile
 	var line C.unsigned

cgo/sync.go

@@ -12,17 +12,17 @@ import "C"
 // C. It is useful if an API uses function pointers and you cannot pass a Go
 // pointer but only a C pointer.
 type refMap struct {
-	refs map[unsafe.Pointer]interface{}
+	refs map[unsafe.Pointer]any
 	lock sync.Mutex
 }
 
 // Put stores a value in the map. It can later be retrieved using Get. It must
 // be removed using Remove to avoid memory leaks.
-func (m *refMap) Put(v interface{}) unsafe.Pointer {
+func (m *refMap) Put(v any) unsafe.Pointer {
 	m.lock.Lock()
 	defer m.lock.Unlock()
 	if m.refs == nil {
-		m.refs = make(map[unsafe.Pointer]interface{}, 1)
+		m.refs = make(map[unsafe.Pointer]any, 1)
 	}
 	ref := C.malloc(1)
 	m.refs[ref] = v
@@ -31,7 +31,7 @@ func (m *refMap) Put(v interface{}) unsafe.Pointer {
 
 // Get returns a stored value previously inserted with Put. Use the same
 // reference as you got from Put.
-func (m *refMap) Get(ref unsafe.Pointer) interface{} {
+func (m *refMap) Get(ref unsafe.Pointer) any {
 	m.lock.Lock()
 	defer m.lock.Unlock()
 	return m.refs[ref]

compileopts/config.go

@@ -8,6 +8,7 @@ import (
 	"os"
 	"path/filepath"
 	"regexp"
+	"slices"
 	"strconv"
 	"strings"
 
@@ -140,13 +141,7 @@ func (c *Config) GC() string {
 func (c *Config) NeedsStackObjects() bool {
 	switch c.GC() {
 	case "conservative", "custom", "precise", "boehm":
-		for _, tag := range c.BuildTags() {
+		return slices.Contains(c.BuildTags(), "tinygo.wasm")
-			if tag == "tinygo.wasm" {
-				return true
-			}
-		}
-
-		return false
 	default:
 		return false
 	}
@@ -245,7 +240,7 @@ func (c *Config) RP2040BootPatch() bool {
 // Return a canonicalized architecture name, so we don't have to deal with arm*
 // vs thumb* vs arm64.
 func CanonicalArchName(triple string) string {
-	arch := strings.Split(triple, "-")[0]
+	arch, _, _ := strings.Cut(triple, "-")
 	if arch == "arm64" {
 		return "aarch64"
 	}

compileopts/options.go

@@ -3,6 +3,7 @@ package compileopts
 import (
 	"fmt"
 	"regexp"
+	"slices"
 	"strings"
 	"time"
 )
@@ -67,7 +68,7 @@ type Options struct {
 // Verify performs a validation on the given options, raising an error if options are not valid.
 func (o *Options) Verify() error {
 	if o.BuildMode != "" {
-		valid := isInArray(validBuildModeOptions, o.BuildMode)
+		valid := slices.Contains(validBuildModeOptions, o.BuildMode)
 		if !valid {
 			return fmt.Errorf(`invalid buildmode option '%s': valid values are %s`,
 				o.BuildMode,
@@ -75,7 +76,7 @@ func (o *Options) Verify() error {
 		}
 	}
 	if o.GC != "" {
-		valid := isInArray(validGCOptions, o.GC)
+		valid := slices.Contains(validGCOptions, o.GC)
 		if !valid {
 			return fmt.Errorf(`invalid gc option '%s': valid values are %s`,
 				o.GC,
@@ -84,7 +85,7 @@ func (o *Options) Verify() error {
 	}
 
 	if o.Scheduler != "" {
-		valid := isInArray(validSchedulerOptions, o.Scheduler)
+		valid := slices.Contains(validSchedulerOptions, o.Scheduler)
 		if !valid {
 			return fmt.Errorf(`invalid scheduler option '%s': valid values are %s`,
 				o.Scheduler,
@@ -93,7 +94,7 @@ func (o *Options) Verify() error {
 	}
 
 	if o.Serial != "" {
-		valid := isInArray(validSerialOptions, o.Serial)
+		valid := slices.Contains(validSerialOptions, o.Serial)
 		if !valid {
 			return fmt.Errorf(`invalid serial option '%s': valid values are %s`,
 				o.Serial,
@@ -102,7 +103,7 @@ func (o *Options) Verify() error {
 	}
 
 	if o.PrintSizes != "" {
-		valid := isInArray(validPrintSizeOptions, o.PrintSizes)
+		valid := slices.Contains(validPrintSizeOptions, o.PrintSizes)
 		if !valid {
 			return fmt.Errorf(`invalid size option '%s': valid values are %s`,
 				o.PrintSizes,
@@ -111,7 +112,7 @@ func (o *Options) Verify() error {
 	}
 
 	if o.PanicStrategy != "" {
-		valid := isInArray(validPanicStrategyOptions, o.PanicStrategy)
+		valid := slices.Contains(validPanicStrategyOptions, o.PanicStrategy)
 		if !valid {
 			return fmt.Errorf(`invalid panic option '%s': valid values are %s`,
 				o.PanicStrategy,
@@ -120,19 +121,10 @@ func (o *Options) Verify() error {
 	}
 
 	if o.Opt != "" {
-		if !isInArray(validOptOptions, o.Opt) {
+		if !slices.Contains(validOptOptions, o.Opt) {
 			return fmt.Errorf("invalid -opt=%s: valid values are %s", o.Opt, strings.Join(validOptOptions, ", "))
 		}
 	}
 
 	return nil
 }
-
-func isInArray(arr []string, item string) bool {
-	for _, i := range arr {
-		if i == item {
-			return true
-		}
-	}
-	return false
-}

compiler/compiler.go

@@ -168,7 +168,7 @@ type builder struct {
 	dilocals          map[*types.Var]llvm.Metadata
 	initInlinedAt     llvm.Metadata            // fake inlinedAt position
 	initPseudoFuncs   map[string]llvm.Metadata // fake "inlined" functions for proper init debug locations
-	allDeferFuncs     []interface{}
+	allDeferFuncs     []any
 	deferFuncs        map[*ssa.Function]int
 	deferInvokeFuncs  map[string]int
 	deferClosureFuncs map[*ssa.Function]int
@@ -2154,13 +2154,10 @@ func (c *compilerContext) maxSliceSize(elementType llvm.Type) uint64 {
 	if elementSize == 0 {
 		elementSize = 1
 	}
-	maxSize := maxPointerValue / elementSize
+	maxSize := min(
-
+		// len(slice) is an int. Make sure the length remains small enough to fit in
-	// len(slice) is an int. Make sure the length remains small enough to fit in
+		// an int.
-	// an int.
+		maxPointerValue/elementSize, maxIntegerValue)
-	if maxSize > maxIntegerValue {
-		maxSize = maxIntegerValue
-	}
 
 	return maxSize
 }

compiler/compiler_test.go

@@ -188,9 +188,9 @@ func TestCompilerErrors(t *testing.T) {
 		t.Error(err)
 	}
 	errorsFileString := strings.ReplaceAll(string(errorsFile), "\r\n", "\n")
-	for _, line := range strings.Split(errorsFileString, "\n") {
+	for line := range strings.SplitSeq(errorsFileString, "\n") {
-		if strings.HasPrefix(line, "// ERROR: ") {
+		if after, ok := strings.CutPrefix(line, "// ERROR: "); ok {
-			expectedErrors = append(expectedErrors, strings.TrimPrefix(line, "// ERROR: "))
+			expectedErrors = append(expectedErrors, after)
 		}
 	}
 

compiler/defer.go

@@ -669,8 +669,8 @@ func (b *builder) createRunDefers() {
 			fn := callback.Fn.(*ssa.Function)
 			valueTypes := []llvm.Type{b.uintptrType, b.dataPtrType}
 			params := fn.Signature.Params()
-			for i := 0; i < params.Len(); i++ {
+			for v := range params.Variables() {
-				valueTypes = append(valueTypes, b.getLLVMType(params.At(i).Type()))
+				valueTypes = append(valueTypes, b.getLLVMType(v.Type()))
 			}
 			valueTypes = append(valueTypes, b.dataPtrType) // closure
 			deferredCallType := b.ctx.StructType(valueTypes, false)
@@ -695,8 +695,8 @@ func (b *builder) createRunDefers() {
 
 			//Get signature from call results
 			params := callback.Type().Underlying().(*types.Signature).Params()
-			for i := 0; i < params.Len(); i++ {
+			for v := range params.Variables() {
-				valueTypes = append(valueTypes, b.getLLVMType(params.At(i).Type()))
+				valueTypes = append(valueTypes, b.getLLVMType(v.Type()))
 			}
 
 			deferredCallType := b.ctx.StructType(valueTypes, false)

compiler/func.go

@@ -81,8 +81,8 @@ func (c *compilerContext) getLLVMFunctionType(typ *types.Signature) llvm.Type {
 			paramTypes = append(paramTypes, info.llvmType)
 		}
 	}
-	for i := 0; i < typ.Params().Len(); i++ {
+	for v := range typ.Params().Variables() {
-		subType := c.getLLVMType(typ.Params().At(i).Type())
+		subType := c.getLLVMType(v.Type())
 		for _, info := range c.expandFormalParamType(subType, "", nil) {
 			paramTypes = append(paramTypes, info.llvmType)
 		}

compiler/gc.go

@@ -5,6 +5,7 @@ package compiler
 
 import (
 	"go/token"
+	"slices"
 
 	"golang.org/x/tools/go/ssa"
 	"tinygo.org/x/go-llvm"
@@ -88,7 +89,7 @@ func (b *builder) trackValue(value llvm.Value) {
 			return
 		}
 		numElements := typ.StructElementTypesCount()
-		for i := 0; i < numElements; i++ {
+		for i := range numElements {
 			subValue := b.CreateExtractValue(value, i, "")
 			b.trackValue(subValue)
 		}
@@ -97,7 +98,7 @@ func (b *builder) trackValue(value llvm.Value) {
 			return
 		}
 		numElements := typ.ArrayLength()
-		for i := 0; i < numElements; i++ {
+		for i := range numElements {
 			subValue := b.CreateExtractValue(value, i, "")
 			b.trackValue(subValue)
 		}
@@ -118,12 +119,7 @@ func typeHasPointers(t llvm.Type) bool {
 	case llvm.PointerTypeKind:
 		return true
 	case llvm.StructTypeKind:
-		for _, subType := range t.StructElementTypes() {
+		return slices.ContainsFunc(t.StructElementTypes(), typeHasPointers)
-			if typeHasPointers(subType) {
-				return true
-			}
-		}
-		return false
 	case llvm.ArrayTypeKind:
 		if t.ArrayLength() == 0 {
 			return false

compiler/goroutine.go

@@ -414,7 +414,7 @@ func (c *compilerContext) createGoroutineStartWrapper(fnType llvm.Type, fn llvm.
 			// Extract parameters from the state object, and call the function
 			// that's being wrapped.
 			var callParams []llvm.Value
-			for i := 0; i < numParams; i++ {
+			for i := range numParams {
 				gep := b.CreateInBoundsGEP(stateStruct, statePtr, []llvm.Value{
 					llvm.ConstInt(b.ctx.Int32Type(), 0, false),
 					llvm.ConstInt(b.ctx.Int32Type(), uint64(i), false),

compiler/inlineasm.go

@@ -146,13 +146,14 @@ func (b *builder) emitSVCall(args []ssa.Value, pos token.Pos) (llvm.Value, error
 	llvmArgs := []llvm.Value{}
 	argTypes := []llvm.Type{}
 	asm := "svc #" + strconv.FormatUint(num, 10)
-	constraints := "={r0}"
+	var constraints strings.Builder
+	constraints.WriteString("={r0}")
 	for i, arg := range args[1:] {
 		arg = arg.(*ssa.MakeInterface).X
 		if i == 0 {
-			constraints += ",0"
+			constraints.WriteString(",0")
 		} else {
-			constraints += ",{r" + strconv.Itoa(i) + "}"
+			constraints.WriteString(",{r" + strconv.Itoa(i) + "}")
 		}
 		llvmValue := b.getValue(arg, pos)
 		llvmArgs = append(llvmArgs, llvmValue)
@@ -161,9 +162,9 @@ func (b *builder) emitSVCall(args []ssa.Value, pos token.Pos) (llvm.Value, error
 	// Implement the ARM calling convention by marking r1-r3 as
 	// clobbered. r0 is used as an output register so doesn't have to be
 	// marked as clobbered.
-	constraints += ",~{r1},~{r2},~{r3}"
+	constraints.WriteString(",~{r1},~{r2},~{r3}")
 	fnType := llvm.FunctionType(b.uintptrType, argTypes, false)
-	target := llvm.InlineAsm(fnType, asm, constraints, true, false, 0, false)
+	target := llvm.InlineAsm(fnType, asm, constraints.String(), true, false, 0, false)
 	return b.CreateCall(fnType, target, llvmArgs, ""), nil
 }
 
@@ -184,13 +185,14 @@ func (b *builder) emitSV64Call(args []ssa.Value, pos token.Pos) (llvm.Value, err
 	llvmArgs := []llvm.Value{}
 	argTypes := []llvm.Type{}
 	asm := "svc #" + strconv.FormatUint(num, 10)
-	constraints := "={x0}"
+	var constraints strings.Builder
+	constraints.WriteString("={x0}")
 	for i, arg := range args[1:] {
 		arg = arg.(*ssa.MakeInterface).X
 		if i == 0 {
-			constraints += ",0"
+			constraints.WriteString(",0")
 		} else {
-			constraints += ",{x" + strconv.Itoa(i) + "}"
+			constraints.WriteString(",{x" + strconv.Itoa(i) + "}")
 		}
 		llvmValue := b.getValue(arg, pos)
 		llvmArgs = append(llvmArgs, llvmValue)
@@ -199,9 +201,9 @@ func (b *builder) emitSV64Call(args []ssa.Value, pos token.Pos) (llvm.Value, err
 	// Implement the ARM64 calling convention by marking x1-x7 as
 	// clobbered. x0 is used as an output register so doesn't have to be
 	// marked as clobbered.
-	constraints += ",~{x1},~{x2},~{x3},~{x4},~{x5},~{x6},~{x7}"
+	constraints.WriteString(",~{x1},~{x2},~{x3},~{x4},~{x5},~{x6},~{x7}")
 	fnType := llvm.FunctionType(b.uintptrType, argTypes, false)
-	target := llvm.InlineAsm(fnType, asm, constraints, true, false, 0, false)
+	target := llvm.InlineAsm(fnType, asm, constraints.String(), true, false, 0, false)
 	return b.CreateCall(fnType, target, llvmArgs, ""), nil
 }
 

compiler/interface.go

@@ -145,8 +145,8 @@ func (c *compilerContext) getTypeCode(typ types.Type) llvm.Value {
 	// For a non-interface type, it returns the number of exported methods.
 	// For an interface type, it returns the number of exported and unexported methods.
 	var numMethods int
-	for i := 0; i < ms.Len(); i++ {
+	for method := range ms.Methods() {
-		if isInterface || ms.At(i).Obj().Exported() {
+		if isInterface || method.Obj().Exported() {
 			numMethods++
 		}
 	}
@@ -193,8 +193,8 @@ func (c *compilerContext) getTypeCode(typ types.Type) llvm.Value {
 		}
 		// Compute the method set value for types that support methods.
 		var methods []*types.Func
-		for i := 0; i < ms.Len(); i++ {
+		for method := range ms.Methods() {
-			methods = append(methods, ms.At(i).Obj().(*types.Func))
+			methods = append(methods, method.Obj().(*types.Func))
 		}
 		methodSetType := types.NewStruct([]*types.Var{
 			types.NewVar(token.NoPos, nil, "length", types.Typ[types.Uintptr]),
@@ -490,10 +490,7 @@ func (c *compilerContext) getTypeCode(typ types.Type) llvm.Value {
 				c.getTypeMethodSet(typ),
 			}, typeFields...)
 		}
-		alignment := c.targetData.TypeAllocSize(c.dataPtrType)
+		alignment := max(c.targetData.TypeAllocSize(c.dataPtrType), 4)
-		if alignment < 4 {
-			alignment = 4
-		}
 		globalValue := c.ctx.ConstStruct(typeFields, false)
 		global.SetInitializer(globalValue)
 		if isLocal {
@@ -783,12 +780,12 @@ func (c *compilerContext) scanLocalTypes(ssaPkg *ssa.Package) {
 			walk(m, false)
 		case *ssa.Type:
 			mset := c.program.MethodSets.MethodSet(m.Type())
-			for i := 0; i < mset.Len(); i++ {
+			for method := range mset.Methods() {
-				walk(c.program.MethodValue(mset.At(i)), false)
+				walk(c.program.MethodValue(method), false)
 			}
 			pmset := c.program.MethodSets.MethodSet(types.NewPointer(m.Type()))
-			for i := 0; i < pmset.Len(); i++ {
+			for method := range pmset.Methods() {
-				walk(c.program.MethodValue(pmset.At(i)), false)
+				walk(c.program.MethodValue(method), false)
 			}
 		}
 	}
@@ -846,8 +843,8 @@ func (c *compilerContext) registerSyntheticLocalTypes(fn *ssa.Function) {
 				}
 			}
 			targs := t.TypeArgs()
-			for i := 0; i < targs.Len(); i++ {
+			for t := range targs.Types() {
-				visit(targs.At(i))
+				visit(t)
 			}
 			visit(t.Underlying())
 		case *types.Pointer:
@@ -862,23 +859,23 @@ func (c *compilerContext) registerSyntheticLocalTypes(fn *ssa.Function) {
 			visit(t.Key())
 			visit(t.Elem())
 		case *types.Struct:
-			for i := 0; i < t.NumFields(); i++ {
+			for field := range t.Fields() {
-				visit(t.Field(i).Type())
+				visit(field.Type())
 			}
 		case *types.Signature:
 			if p := t.Params(); p != nil {
-				for i := 0; i < p.Len(); i++ {
+				for v := range p.Variables() {
-					visit(p.At(i).Type())
+					visit(v.Type())
 				}
 			}
 			if r := t.Results(); r != nil {
-				for i := 0; i < r.Len(); i++ {
+				for v := range r.Variables() {
-					visit(r.At(i).Type())
+					visit(v.Type())
 				}
 			}
 		case *types.Tuple:
-			for i := 0; i < t.Len(); i++ {
+			for v := range t.Variables() {
-				visit(t.At(i).Type())
+				visit(v.Type())
 			}
 		case *types.Interface:
 			// A synthetic local type can be reachable only through a
@@ -887,8 +884,8 @@ func (c *compilerContext) registerSyntheticLocalTypes(fn *ssa.Function) {
 			// the interface's identifier, and the seen map breaks
 			// cycles formed by methods that mention the interface
 			// itself.
-			for i := 0; i < t.NumMethods(); i++ {
+			for method := range t.Methods() {
-				visit(t.Method(i).Type())
+				visit(method.Type())
 			}
 		}
 	}
@@ -939,8 +936,7 @@ func (c *compilerContext) getTypeMethodSet(typ types.Type) llvm.Value {
 
 		// Create method set.
 		var signatures, wrappers []llvm.Value
-		for i := 0; i < ms.Len(); i++ {
+		for method := range ms.Methods() {
-			method := ms.At(i)
 			signatureGlobal := c.getMethodSignature(method.Obj().(*types.Func))
 			signatures = append(signatures, signatureGlobal)
 			fn := c.program.MethodValue(method)
@@ -1189,8 +1185,8 @@ func (c *compilerContext) getInvokeFunction(instr *ssa.CallCommon) llvm.Value {
 	if llvmFn.IsNil() {
 		sig := instr.Method.Type().(*types.Signature)
 		var paramTuple []*types.Var
-		for i := 0; i < sig.Params().Len(); i++ {
+		for v := range sig.Params().Variables() {
-			paramTuple = append(paramTuple, sig.Params().At(i))
+			paramTuple = append(paramTuple, v)
 		}
 		paramTuple = append(paramTuple, types.NewVar(token.NoPos, nil, "$typecode", types.Typ[types.UnsafePointer]))
 		llvmFnType := c.getLLVMFunctionType(types.NewSignature(sig.Recv(), types.NewTuple(paramTuple...), sig.Results(), false))
@@ -1307,34 +1303,38 @@ func methodSignature(method *types.Func) string {
 //	() string
 //	(string, int) (int, error)
 func signature(sig *types.Signature) string {
-	s := ""
+	var s strings.Builder
 	if sig.Params().Len() == 0 {
-		s += "()"
+		s.WriteString("()")
 	} else {
-		s += "("
+		s.WriteString("(")
-		for i := 0; i < sig.Params().Len(); i++ {
+		i := 0
+		for v := range sig.Params().Variables() {
 			if i > 0 {
-				s += ", "
+				s.WriteString(", ")
 			}
-			s += typestring(sig.Params().At(i).Type())
+			s.WriteString(typestring(v.Type()))
+			i++
 		}
-		s += ")"
+		s.WriteString(")")
 	}
 	if sig.Results().Len() == 0 {
 		// keep as-is
 	} else if sig.Results().Len() == 1 {
-		s += " " + typestring(sig.Results().At(0).Type())
+		s.WriteString(" " + typestring(sig.Results().At(0).Type()))
 	} else {
-		s += " ("
+		s.WriteString(" (")
-		for i := 0; i < sig.Results().Len(); i++ {
+		i := 0
+		for v := range sig.Results().Variables() {
 			if i > 0 {
-				s += ", "
+				s.WriteString(", ")
 			}
-			s += typestring(sig.Results().At(i).Type())
+			s.WriteString(typestring(v.Type()))
+			i++
 		}
-		s += ")"
+		s.WriteString(")")
 	}
-	return s
+	return s.String()
 }
 
 // typestring returns a stable (human-readable) type string for the given type

compiler/llvm.go

@@ -206,7 +206,7 @@ func (c *compilerContext) makeGlobalArray(buf []byte, name string, elementType l
 	globalType := llvm.ArrayType(elementType, len(buf))
 	global := llvm.AddGlobal(c.mod, globalType, name)
 	value := llvm.Undef(globalType)
-	for i := 0; i < len(buf); i++ {
+	for i := range buf {
 		ch := uint64(buf[i])
 		value = c.builder.CreateInsertValue(value, llvm.ConstInt(elementType, ch, false), i, "")
 	}
@@ -390,7 +390,7 @@ func (c *compilerContext) buildPointerBitmap(
 			return
 		}
 		elementSize /= ptrAlign
-		for i := 0; i < len; i++ {
+		for i := range len {
 			c.buildPointerBitmap(
 				dst,
 				ptrAlign,
@@ -417,7 +417,7 @@ func (c *compilerContext) archFamily() string {
 // features string is not one for an ARM architecture.
 func (c *compilerContext) isThumb() bool {
 	var isThumb, isNotThumb bool
-	for _, feature := range strings.Split(c.Features, ",") {
+	for feature := range strings.SplitSeq(c.Features, ",") {
 		if feature == "+thumb-mode" {
 			isThumb = true
 		}

compiler/map.go

@@ -7,6 +7,7 @@ import (
 	"go/token"
 	"go/types"
 	"golang.org/x/tools/go/ssa"
+	"strings"
 	"tinygo.org/x/go-llvm"
 )
 
@@ -293,14 +294,15 @@ func hashmapCanonicalTypeName(t types.Type) string {
 		}
 		return t.String()
 	case *types.Struct:
-		s := "struct{"
+		var s strings.Builder
+		s.WriteString("struct{")
 		for i := 0; i < t.NumFields(); i++ {
 			if i > 0 {
-				s += "; "
+				s.WriteString("; ")
 			}
-			s += hashmapCanonicalTypeName(t.Field(i).Type())
+			s.WriteString(hashmapCanonicalTypeName(t.Field(i).Type()))
 		}
-		return s + "}"
+		return s.String() + "}"
 	case *types.Array:
 		return fmt.Sprintf("[%d]%s", t.Len(), hashmapCanonicalTypeName(t.Elem()))
 	}

compiler/sizes.go

@@ -29,8 +29,7 @@ func (s *stdSizes) Alignof(T types.Type) int64 {
 		// is the largest of the values unsafe.Alignof(x.f) for each
 		// field f of x, but at least 1."
 		max := int64(1)
-		for i := 0; i < t.NumFields(); i++ {
+		for f := range t.Fields() {
-			f := t.Field(i)
 			if a := s.Alignof(f.Type()); a > max {
 				max = a
 			}

compiler/symbol.go

@@ -8,6 +8,7 @@ import (
 	"go/ast"
 	"go/token"
 	"go/types"
+	"slices"
 	"strconv"
 	"strings"
 
@@ -85,8 +86,8 @@ func (c *compilerContext) getFunction(fn *ssa.Function) (llvm.Type, llvm.Value)
 		retType = c.getLLVMType(fn.Signature.Results().At(0).Type())
 	} else {
 		results := make([]llvm.Type, 0, fn.Signature.Results().Len())
-		for i := 0; i < fn.Signature.Results().Len(); i++ {
+		for v := range fn.Signature.Results().Variables() {
-			results = append(results, c.getLLVMType(fn.Signature.Results().At(i).Type()))
+			results = append(results, c.getLLVMType(v.Type()))
 		}
 		retType = c.ctx.StructType(results, false)
 	}
@@ -389,7 +390,7 @@ func (c *compilerContext) parsePragmas(info *functionInfo, f *ssa.Function) {
 			info.wasmName = info.linkName
 			info.exported = true
 		case "//go:interrupt":
-			if hasUnsafeImport(f.Pkg.Pkg) {
+			if slices.Contains(f.Pkg.Pkg.Imports(), types.Unsafe) {
 				info.interrupt = true
 			}
 		case "//go:wasm-module":
@@ -451,14 +452,14 @@ func (c *compilerContext) parsePragmas(info *functionInfo, f *ssa.Function) {
 			// This is a slightly looser requirement than what gc uses: gc
 			// requires the file to import "unsafe", not the package as a
 			// whole.
-			if hasUnsafeImport(f.Pkg.Pkg) {
+			if slices.Contains(f.Pkg.Pkg.Imports(), types.Unsafe) {
 				info.linkName = parts[2]
 			}
 		case "//go:section":
 			// Only enable go:section when the package imports "unsafe".
 			// go:section also implies go:noinline since inlining could
 			// move the code to a different section than that requested.
-			if len(parts) == 2 && hasUnsafeImport(f.Pkg.Pkg) {
+			if len(parts) == 2 && slices.Contains(f.Pkg.Pkg.Imports(), types.Unsafe) {
 				info.section = parts[1]
 				info.inline = inlineNone
 			}
@@ -467,7 +468,7 @@ func (c *compilerContext) parsePragmas(info *functionInfo, f *ssa.Function) {
 			// runtime functions.
 			// This is somewhat dangerous and thus only imported in packages
 			// that import unsafe.
-			if hasUnsafeImport(f.Pkg.Pkg) {
+			if slices.Contains(f.Pkg.Pkg.Imports(), types.Unsafe) {
 				info.nobounds = true
 			}
 		case "//go:noescape":
@@ -567,8 +568,8 @@ func (c *compilerContext) isValidWasmType(typ types.Type, site wasmSite) bool {
 				hasHostLayout = false // package structs added in go1.23
 			}
 		}
-		for i := 0; i < typ.NumFields(); i++ {
+		for field := range typ.Fields() {
-			ftyp := typ.Field(i).Type()
+			ftyp := field.Type()
 			if types.Unalias(ftyp).String() == "structs.HostLayout" {
 				hasHostLayout = true
 				continue
@@ -600,8 +601,8 @@ func getParams(sig *types.Signature) []*types.Var {
 	if sig.Recv() != nil {
 		params = append(params, sig.Recv())
 	}
-	for i := 0; i < sig.Params().Len(); i++ {
+	for v := range sig.Params().Variables() {
-		params = append(params, sig.Params().At(i))
+		params = append(params, v)
 	}
 	return params
 }
@@ -704,10 +705,7 @@ func (c *compilerContext) getGlobal(g *ssa.Global) llvm.Value {
 		llvmGlobal = llvm.AddGlobal(c.mod, llvmType, info.linkName)
 
 		// Set alignment from the //go:align comment.
-		alignment := c.targetData.ABITypeAlignment(llvmType)
+		alignment := max(info.align, c.targetData.ABITypeAlignment(llvmType))
-		if info.align > alignment {
-			alignment = info.align
-		}
 		if alignment <= 0 || alignment&(alignment-1) != 0 {
 			// Check for power-of-two (or 0).
 			// See: https://stackoverflow.com/a/108360
@@ -781,7 +779,7 @@ func (info *globalInfo) parsePragmas(doc *ast.CommentGroup, c *compilerContext,
 			// This is a slightly looser requirement than what gc uses: gc
 			// requires the file to import "unsafe", not the package as a
 			// whole.
-			if hasUnsafeImport(g.Pkg.Pkg) {
+			if slices.Contains(g.Pkg.Pkg.Imports(), types.Unsafe) {
 				info.linkName = parts[2]
 			}
 		}
@@ -797,13 +795,3 @@ func getAllMethods(prog *ssa.Program, typ types.Type) []*types.Selection {
 	}
 	return methods
 }
-
-// Return true if this package imports "unsafe", false otherwise.
-func hasUnsafeImport(pkg *types.Package) bool {
-	for _, imp := range pkg.Imports() {
-		if imp == types.Unsafe {
-			return true
-		}
-	}
-	return false
-}

compiler/syscall.go

@@ -26,24 +26,25 @@ func (b *builder) createRawSyscall(call *ssa.CallCommon) (llvm.Value, error) {
 		argTypes := []llvm.Type{b.uintptrType}
 		// Constraints will look something like:
 		//   "={rax},0,{rdi},{rsi},{rdx},{r10},{r8},{r9},~{rcx},~{r11}"
-		constraints := "={rax},0"
+		var constraints strings.Builder
+		constraints.WriteString("={rax},0")
 		for i, arg := range call.Args[1:] {
-			constraints += "," + [...]string{
+			constraints.WriteString("," + [...]string{
 				"{rdi}",
 				"{rsi}",
 				"{rdx}",
 				"{r10}",
 				"{r8}",
 				"{r9}",
-			}[i]
+			}[i])
 			llvmValue := b.getValue(arg, getPos(call))
 			args = append(args, llvmValue)
 			argTypes = append(argTypes, llvmValue.Type())
 		}
 		// rcx and r11 are clobbered by the syscall, so make sure they are not used
-		constraints += ",~{rcx},~{r11}"
+		constraints.WriteString(",~{rcx},~{r11}")
 		fnType := llvm.FunctionType(b.uintptrType, argTypes, false)
-		target := llvm.InlineAsm(fnType, "syscall", constraints, true, false, llvm.InlineAsmDialectIntel, false)
+		target := llvm.InlineAsm(fnType, "syscall", constraints.String(), true, false, llvm.InlineAsmDialectIntel, false)
 		return b.CreateCall(fnType, target, args, ""), nil
 
 	case b.GOARCH == "386" && b.GOOS == "linux":
@@ -55,22 +56,23 @@ func (b *builder) createRawSyscall(call *ssa.CallCommon) (llvm.Value, error) {
 		argTypes := []llvm.Type{b.uintptrType}
 		// Constraints will look something like:
 		//   "={eax},0,{ebx},{ecx},{edx},{esi},{edi},{ebp}"
-		constraints := "={eax},0"
+		var constraints strings.Builder
+		constraints.WriteString("={eax},0")
 		for i, arg := range call.Args[1:] {
-			constraints += "," + [...]string{
+			constraints.WriteString("," + [...]string{
 				"{ebx}",
 				"{ecx}",
 				"{edx}",
 				"{esi}",
 				"{edi}",
 				"{ebp}",
-			}[i]
+			}[i])
 			llvmValue := b.getValue(arg, getPos(call))
 			args = append(args, llvmValue)
 			argTypes = append(argTypes, llvmValue.Type())
 		}
 		fnType := llvm.FunctionType(b.uintptrType, argTypes, false)
-		target := llvm.InlineAsm(fnType, "int 0x80", constraints, true, false, llvm.InlineAsmDialectIntel, false)
+		target := llvm.InlineAsm(fnType, "int 0x80", constraints.String(), true, false, llvm.InlineAsmDialectIntel, false)
 		return b.CreateCall(fnType, target, args, ""), nil
 
 	case b.GOARCH == "arm" && b.GOOS == "linux":
@@ -88,9 +90,10 @@ func (b *builder) createRawSyscall(call *ssa.CallCommon) (llvm.Value, error) {
 		argTypes := []llvm.Type{}
 		// Constraints will look something like:
 		//   ={r0},0,{r1},{r2},{r7},~{r3}
-		constraints := "={r0}"
+		var constraints strings.Builder
+		constraints.WriteString("={r0}")
 		for i, arg := range call.Args[1:] {
-			constraints += "," + [...]string{
+			constraints.WriteString("," + [...]string{
 				"0", // tie to output
 				"{r1}",
 				"{r2}",
@@ -98,20 +101,20 @@ func (b *builder) createRawSyscall(call *ssa.CallCommon) (llvm.Value, error) {
 				"{r4}",
 				"{r5}",
 				"{r6}",
-			}[i]
+			}[i])
 			llvmValue := b.getValue(arg, getPos(call))
 			args = append(args, llvmValue)
 			argTypes = append(argTypes, llvmValue.Type())
 		}
 		args = append(args, num)
 		argTypes = append(argTypes, b.uintptrType)
-		constraints += ",{r7}" // syscall number
+		constraints.WriteString(",{r7}") // syscall number
 		for i := len(call.Args) - 1; i < 4; i++ {
 			// r0-r3 get clobbered after the syscall returns
-			constraints += ",~{r" + strconv.Itoa(i) + "}"
+			constraints.WriteString(",~{r" + strconv.Itoa(i) + "}")
 		}
 		fnType := llvm.FunctionType(b.uintptrType, argTypes, false)
-		target := llvm.InlineAsm(fnType, "svc #0", constraints, true, false, 0, false)
+		target := llvm.InlineAsm(fnType, "svc #0", constraints.String(), true, false, 0, false)
 		return b.CreateCall(fnType, target, args, ""), nil
 
 	case b.GOARCH == "arm64" && b.GOOS == "linux":
@@ -120,31 +123,32 @@ func (b *builder) createRawSyscall(call *ssa.CallCommon) (llvm.Value, error) {
 		argTypes := []llvm.Type{}
 		// Constraints will look something like:
 		//   ={x0},0,{x1},{x2},{x8},~{x3},~{x4},~{x5},~{x6},~{x7},~{x16},~{x17}
-		constraints := "={x0}"
+		var constraints strings.Builder
+		constraints.WriteString("={x0}")
 		for i, arg := range call.Args[1:] {
-			constraints += "," + [...]string{
+			constraints.WriteString("," + [...]string{
 				"0", // tie to output
 				"{x1}",
 				"{x2}",
 				"{x3}",
 				"{x4}",
 				"{x5}",
-			}[i]
+			}[i])
 			llvmValue := b.getValue(arg, getPos(call))
 			args = append(args, llvmValue)
 			argTypes = append(argTypes, llvmValue.Type())
 		}
 		args = append(args, num)
 		argTypes = append(argTypes, b.uintptrType)
-		constraints += ",{x8}" // syscall number
+		constraints.WriteString(",{x8}") // syscall number
 		for i := len(call.Args) - 1; i < 8; i++ {
 			// x0-x7 may get clobbered during the syscall following the aarch64
 			// calling convention.
-			constraints += ",~{x" + strconv.Itoa(i) + "}"
+			constraints.WriteString(",~{x" + strconv.Itoa(i) + "}")
 		}
-		constraints += ",~{x16},~{x17}" // scratch registers
+		constraints.WriteString(",~{x16},~{x17}") // scratch registers
 		fnType := llvm.FunctionType(b.uintptrType, argTypes, false)
-		target := llvm.InlineAsm(fnType, "svc #0", constraints, true, false, 0, false)
+		target := llvm.InlineAsm(fnType, "svc #0", constraints.String(), true, false, 0, false)
 		return b.CreateCall(fnType, target, args, ""), nil
 
 	case (b.GOARCH == "mips" || b.GOARCH == "mipsle") && b.GOOS == "linux":
@@ -163,7 +167,8 @@ func (b *builder) createRawSyscall(call *ssa.CallCommon) (llvm.Value, error) {
 		// faster and smaller code.
 		args := []llvm.Value{num}
 		argTypes := []llvm.Type{b.uintptrType}
-		constraints := "={$2},={$7},0"
+		var constraints strings.Builder
+		constraints.WriteString("={$2},={$7},0")
 		syscallParams := call.Args[1:]
 		if len(syscallParams) > 7 {
 			// There is one syscall that uses 7 parameters: sync_file_range.
@@ -172,7 +177,7 @@ func (b *builder) createRawSyscall(call *ssa.CallCommon) (llvm.Value, error) {
 			syscallParams = syscallParams[:7]
 		}
 		for i, arg := range syscallParams {
-			constraints += "," + [...]string{
+			constraints.WriteString("," + [...]string{
 				"{$4}", // arg1
 				"{$5}", // arg2
 				"{$6}", // arg3
@@ -180,7 +185,7 @@ func (b *builder) createRawSyscall(call *ssa.CallCommon) (llvm.Value, error) {
 				"r",    // arg5 on the stack
 				"r",    // arg6 on the stack
 				"r",    // arg7 on the stack
-			}[i]
+			}[i])
 			llvmValue := b.getValue(arg, getPos(call))
 			args = append(args, llvmValue)
 			argTypes = append(argTypes, llvmValue.Type())
@@ -221,10 +226,10 @@ func (b *builder) createRawSyscall(call *ssa.CallCommon) (llvm.Value, error) {
 				"addu $$sp, $$sp, 32\n" +
 				".set at\n"
 		}
-		constraints += ",~{$3},~{$4},~{$5},~{$6},~{$8},~{$9},~{$10},~{$11},~{$12},~{$13},~{$14},~{$15},~{$24},~{$25},~{hi},~{lo},~{memory}"
+		constraints.WriteString(",~{$3},~{$4},~{$5},~{$6},~{$8},~{$9},~{$10},~{$11},~{$12},~{$13},~{$14},~{$15},~{$24},~{$25},~{hi},~{lo},~{memory}")
 		returnType := b.ctx.StructType([]llvm.Type{b.uintptrType, b.uintptrType}, false)
 		fnType := llvm.FunctionType(returnType, argTypes, false)
-		target := llvm.InlineAsm(fnType, asm, constraints, true, true, 0, false)
+		target := llvm.InlineAsm(fnType, asm, constraints.String(), true, true, 0, false)
 		call := b.CreateCall(fnType, target, args, "")
 		resultCode := b.CreateExtractValue(call, 0, "") // r2
 		errorFlag := b.CreateExtractValue(call, 1, "")  // r7

corpus_test.go

@@ -59,7 +59,6 @@ func TestCorpus(t *testing.T) {
 	}
 
 	for _, repo := range repos {
-		repo := repo
 		name := repo.Repo
 		if repo.Tags != "" {
 			name += "(" + strings.ReplaceAll(repo.Tags, " ", "-") + ")"
@@ -132,7 +131,6 @@ func TestCorpus(t *testing.T) {
 			}
 
 			for _, dir := range repo.Subdirs {
-				dir := dir
 				t.Run(dir.Pkg, func(t *testing.T) {
 					t.Parallel()
 

diff.go

@@ -116,10 +116,7 @@ func Diff(oldName string, old []byte, newName string, new []byte) []byte {
 
 		// End chunk with common lines for context.
 		if len(ctext) > 0 {
-			n := end.x - start.x
+			n := min(end.x-start.x, C)
-			if n > C {
-				n = C
-			}
 			for _, s := range x[start.x : start.x+n] {
 				ctext = append(ctext, " "+s)
 				count.x++
@@ -234,7 +231,7 @@ func tgs(x, y []string) []pair {
 	for i := range T {
 		T[i] = n + 1
 	}
-	for i := 0; i < n; i++ {
+	for i := range n {
 		k := sort.Search(n, func(k int) bool {
 			return T[k] >= J[i]
 		})

errors_test.go

@@ -136,7 +136,7 @@ func readErrorMessages(t *testing.T, file string) string {
 	}
 
 	var errors []string
-	for _, line := range strings.Split(string(data), "\n") {
+	for line := range strings.SplitSeq(string(data), "\n") {
 		if strings.HasPrefix(line, "// ERROR: ") {
 			errors = append(errors, strings.TrimRight(line[len("// ERROR: "):], "\r\n"))
 		}

interp/compiler.go

@@ -151,7 +151,7 @@ func (r *runner) compileFunction(llvmFn llvm.Value) *function {
 			case llvm.PHI:
 				inst.name = llvmInst.Name()
 				incomingCount := inst.llvmInst.IncomingCount()
-				for i := 0; i < incomingCount; i++ {
+				for i := range incomingCount {
 					incomingBB := inst.llvmInst.IncomingBlock(i)
 					incomingValue := inst.llvmInst.IncomingValue(i)
 					inst.operands = append(inst.operands,

interp/interp_test.go

@@ -22,7 +22,6 @@ func TestInterp(t *testing.T) {
 		"alloc",
 		"slicedata",
 	} {
-		name := name // make local to this closure
 		t.Run(name, func(t *testing.T) {
 			t.Parallel()
 			runTest(t, "testdata/"+name)

interp/interpreter.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"math"
 	"os"
+	"slices"
 	"strconv"
 	"strings"
 	"time"
@@ -470,7 +471,7 @@ func (r *runner) run(fn *function, params []value, parentMem *memoryView, indent
 				// should be returned.
 				numMethods := int(r.builder.CreateExtractValue(methodSet, 0, "").ZExtValue())
 				var method llvm.Value
-				for i := 0; i < numMethods; i++ {
+				for i := range numMethods {
 					methodSignatureAgg := r.builder.CreateExtractValue(methodSet, 1, "")
 					methodSignature := r.builder.CreateExtractValue(methodSignatureAgg, i, "")
 					if methodSignature == signature {
@@ -907,7 +908,7 @@ func (r *runner) interpretICmp(lhs, rhs value, predicate llvm.IntPredicate) bool
 func (r *runner) runAtRuntime(fn *function, inst instruction, locals []value, mem *memoryView, indent string) *Error {
 	numOperands := inst.llvmInst.OperandsCount()
 	operands := make([]llvm.Value, numOperands)
-	for i := 0; i < numOperands; i++ {
+	for i := range numOperands {
 		operand := inst.llvmInst.Operand(i)
 		if !operand.IsAInstruction().IsNil() || !operand.IsAArgument().IsNil() {
 			var err error
@@ -985,9 +986,9 @@ func (r *runner) runAtRuntime(fn *function, inst instruction, locals []value, me
 			mem.instructions = append(mem.instructions, agg)
 		}
 		result = operands[1]
-		for i := len(indices) - 1; i >= 0; i-- {
+		for i, indice := range slices.Backward(indices) {
 			agg := aggregates[i]
-			result = r.builder.CreateInsertValue(agg, result, int(indices[i]), inst.name+".insertvalue"+strconv.Itoa(i))
+			result = r.builder.CreateInsertValue(agg, result, int(indice), inst.name+".insertvalue"+strconv.Itoa(i))
 			if i != 0 { // don't add last result to mem.instructions as it will be done at the end already
 				mem.instructions = append(mem.instructions, result)
 			}

interp/memory.go

@@ -18,8 +18,10 @@ import (
 	"encoding/binary"
 	"errors"
 	"fmt"
+	"maps"
 	"math"
 	"math/big"
+	"slices"
 	"strconv"
 	"strings"
 
@@ -80,9 +82,7 @@ func (mv *memoryView) extend(sub memoryView) {
 	if mv.objects == nil && len(sub.objects) != 0 {
 		mv.objects = make(map[uint32]object)
 	}
-	for key, value := range sub.objects {
+	maps.Copy(mv.objects, sub.objects)
-		mv.objects[key] = value
-	}
 	mv.instructions = append(mv.instructions, sub.instructions...)
 }
 
@@ -90,8 +90,8 @@ func (mv *memoryView) extend(sub memoryView) {
 // created in this memoryView. Do not reuse this memoryView.
 func (mv *memoryView) revert() {
 	// Erase instructions in reverse order.
-	for i := len(mv.instructions) - 1; i >= 0; i-- {
+	for _, llvmInst := range slices.Backward(mv.instructions) {
-		llvmInst := mv.instructions[i]
+
 		if llvmInst.IsAInstruction().IsNil() {
 			// The IR builder will try to create constant versions of
 			// instructions whenever possible. If it does this, it's not an
@@ -172,7 +172,7 @@ func (mv *memoryView) markExternal(llvmValue llvm.Value, mark uint8) error {
 							continue
 						}
 						numOperands := inst.OperandsCount()
-						for i := 0; i < numOperands; i++ {
+						for i := range numOperands {
 							// Using mark '2' (which means read/write access)
 							// because this might be a store instruction.
 							err := mv.markExternal(inst.Operand(i), 2)
@@ -215,7 +215,7 @@ func (mv *memoryView) markExternal(llvmValue llvm.Value, mark uint8) error {
 			// need any marking.
 		case llvm.StructTypeKind:
 			numElements := llvmType.StructElementTypesCount()
-			for i := 0; i < numElements; i++ {
+			for i := range numElements {
 				element := mv.r.builder.CreateExtractValue(llvmValue, i, "")
 				err := mv.markExternal(element, mark)
 				if err != nil {
@@ -224,7 +224,7 @@ func (mv *memoryView) markExternal(llvmValue llvm.Value, mark uint8) error {
 			}
 		case llvm.ArrayTypeKind:
 			numElements := llvmType.ArrayLength()
-			for i := 0; i < numElements; i++ {
+			for i := range numElements {
 				element := mv.r.builder.CreateExtractValue(llvmValue, i, "")
 				err := mv.markExternal(element, mark)
 				if err != nil {
@@ -366,7 +366,7 @@ func (mv *memoryView) store(v value, p pointerValue) bool {
 		buffer := obj.buffer.asRawValue(mv.r)
 		obj.buffer = buffer
 		v := v.asRawValue(mv.r)
-		for i := uint32(0); i < valueLen; i++ {
+		for i := range valueLen {
 			buffer.buf[p.offset()+i] = v.buf[i]
 		}
 	}
@@ -392,7 +392,7 @@ type value interface {
 // literalValue contains simple integer values that don't need to be stored in a
 // buffer.
 type literalValue struct {
-	value interface{}
+	value any
 }
 
 // Make a literalValue given the number of bits.
@@ -1015,7 +1015,7 @@ func (v *rawValue) set(llvmValue llvm.Value, r *runner) {
 		if err != nil {
 			panic(err)
 		}
-		for i := uint32(0); i < ptrSize; i++ {
+		for i := range ptrSize {
 			v.buf[i] = ptr.pointer
 		}
 	} else if !llvmValue.IsAConstantExpr().IsNil() {
@@ -1056,7 +1056,7 @@ func (v *rawValue) set(llvmValue llvm.Value, r *runner) {
 				panic(err)
 			}
 			ptrValue.pointer += totalOffset
-			for i := uint32(0); i < ptrSize; i++ {
+			for i := range ptrSize {
 				v.buf[i] = ptrValue.pointer
 			}
 		case llvm.ICmp:
@@ -1113,7 +1113,7 @@ func (v *rawValue) set(llvmValue llvm.Value, r *runner) {
 			}
 		case llvm.StructTypeKind:
 			numElements := llvmType.StructElementTypesCount()
-			for i := 0; i < numElements; i++ {
+			for i := range numElements {
 				offset := r.targetData.ElementOffset(llvmType, i)
 				field := rawValue{
 					buf: v.buf[offset:],
@@ -1124,7 +1124,7 @@ func (v *rawValue) set(llvmValue llvm.Value, r *runner) {
 			numElements := llvmType.ArrayLength()
 			childType := llvmType.ElementType()
 			childTypeSize := r.targetData.TypeAllocSize(childType)
-			for i := 0; i < numElements; i++ {
+			for i := range numElements {
 				offset := i * int(childTypeSize)
 				field := rawValue{
 					buf: v.buf[offset:],

main.go

@@ -786,15 +786,15 @@ func Debug(debugger, pkgName string, ocdOutput bool, options *compileopts.Option
 		}
 		defer func() {
 			daemon.Process.Signal(os.Interrupt)
-			var stopped uint32
+			var stopped atomic.Uint32
 			go func() {
 				time.Sleep(time.Millisecond * 100)
-				if atomic.LoadUint32(&stopped) == 0 {
+				if stopped.Load() == 0 {
 					daemon.Process.Kill()
 				}
 			}()
 			daemon.Wait()
-			atomic.StoreUint32(&stopped, 1)
+			stopped.Store(1)
 		}()
 	}
 
@@ -1046,7 +1046,7 @@ func buildAndRun(pkgName string, config *compileopts.Config, stdout io.Writer, c
 
 func touchSerialPortAt1200bps(port string) (err error) {
 	retryCount := 3
-	for i := 0; i < retryCount; i++ {
+	for range retryCount {
 		// Open port
 		p, e := serial.Open(port, &serial.Mode{BaudRate: 1200})
 		if e != nil {
@@ -1244,7 +1244,7 @@ func findFATMounts(options *compileopts.Options) ([]mountPoint, error) {
 		if err != nil {
 			return nil, fmt.Errorf("could not list mount points: %w", err)
 		}
-		for _, line := range strings.Split(string(tab), "\n") {
+		for line := range strings.SplitSeq(string(tab), "\n") {
 			fields := strings.Fields(line)
 			if len(fields) <= 2 {
 				continue
@@ -1273,7 +1273,7 @@ func findFATMounts(options *compileopts.Options) ([]mountPoint, error) {
 		}
 
 		// Extract data to convert to a []mountPoint slice.
-		for _, line := range strings.Split(out.String(), "\n") {
+		for line := range strings.SplitSeq(out.String(), "\n") {
 			words := strings.Fields(line)
 			if len(words) < 3 {
 				continue
@@ -1685,18 +1685,18 @@ func (m globalValuesFlag) String() string {
 }
 
 func (m globalValuesFlag) Set(value string) error {
-	equalsIndex := strings.IndexByte(value, '=')
+	before, after, ok := strings.Cut(value, "=")
-	if equalsIndex < 0 {
+	if !ok {
 		return errors.New("expected format pkgpath.Var=value")
 	}
-	pathAndName := value[:equalsIndex]
+	pathAndName := before
 	pointIndex := strings.LastIndexByte(pathAndName, '.')
 	if pointIndex < 0 {
 		return errors.New("expected format pkgpath.Var=value")
 	}
 	path := pathAndName[:pointIndex]
 	name := pathAndName[pointIndex+1:]
-	stringValue := value[equalsIndex+1:]
+	stringValue := after
 	if m[path] == nil {
 		m[path] = make(map[string]string)
 	}
@@ -2054,7 +2054,6 @@ func main() {
 		// This uses an additional semaphore to reduce the memory usage.
 		testSema := make(chan struct{}, cap(options.Semaphore))
 		for i, pkgName := range explicitPkgNames {
-			pkgName := pkgName
 			buf := &bufs[i]
 			testSema <- struct{}{}
 			wg.Add(1)

main_test.go

@@ -398,7 +398,7 @@ func emuCheck(t *testing.T, options compileopts.Options) {
 		t.Fatal("failed to load target spec:", err)
 	}
 	if spec.Emulator != "" {
-		emulatorCommand := strings.SplitN(spec.Emulator, " ", 2)[0]
+		emulatorCommand, _, _ := strings.Cut(spec.Emulator, " ")
 		_, err := exec.LookPath(emulatorCommand)
 		if err != nil {
 			if errors.Is(err, exec.ErrNotFound) {
@@ -493,7 +493,7 @@ func runTestWithConfig(name string, t *testing.T, options compileopts.Options, c
 	if err != nil {
 		w := &bytes.Buffer{}
 		diagnostics.CreateDiagnostics(err).WriteTo(w, "")
-		for _, line := range strings.Split(strings.TrimRight(w.String(), "\n"), "\n") {
+		for line := range strings.SplitSeq(strings.TrimRight(w.String(), "\n"), "\n") {
 			t.Log(line)
 		}
 		if stdout.Len() != 0 {
@@ -569,7 +569,6 @@ func TestWebAssembly(t *testing.T) {
 		{name: "panic-default", target: "wasip1", imports: []string{"wasi_snapshot_preview1.fd_write", "wasi_snapshot_preview1.random_get"}},
 		{name: "panic-trap", target: "wasm-unknown", panicStrategy: "trap", imports: []string{}},
 	} {
-		tc := tc
 		t.Run(tc.name, func(t *testing.T) {
 			t.Parallel()
 			tmpdir := t.TempDir()
@@ -691,7 +690,6 @@ func TestWasmExport(t *testing.T) {
 	}
 
 	for _, tc := range tests {
-		tc := tc
 		t.Run(tc.name, func(t *testing.T) {
 			t.Parallel()
 
@@ -861,7 +859,6 @@ func TestWasmExportJS(t *testing.T) {
 		{name: "c-shared", buildMode: "c-shared"},
 	}
 	for _, tc := range tests {
-		tc := tc
 		t.Run(tc.name, func(t *testing.T) {
 			t.Parallel()
 			// Build the wasm binary.
@@ -909,7 +906,6 @@ func TestWasmExit(t *testing.T) {
 		{name: "exit-1-sleep", output: "slept\nexit code: 1\n"},
 	}
 	for _, tc := range tests {
-		tc := tc
 		t.Run(tc.name, func(t *testing.T) {
 			t.Parallel()
 			options := optionsFromTarget("wasm", sema)
@@ -984,7 +980,6 @@ func TestTest(t *testing.T) {
 		)
 	}
 	for _, targ := range targs {
-		targ := targ
 		t.Run(targ.name, func(t *testing.T) {
 			t.Parallel()
 

src/examples/memstats/memstats.go

@@ -25,7 +25,7 @@ func main() {
 func escapesToHeap() {
 	n := rand.Intn(100)
 	println("Doing ", n, " iterations")
-	for i := 0; i < n; i++ {
+	for i := range n {
 		s := make([]byte, i)
 		_ = append(s, 42)
 	}

src/examples/test/test.go

@@ -70,7 +70,7 @@ func main() {
 	printItf(Number(3))
 	s := Stringer(thing)
 	println("Stringer.String():", s.String())
-	var itf interface{} = s
+	var itf any = s
 	println("Stringer.(*Thing).String():", itf.(Stringer).String())
 
 	// unusual calls
@@ -124,7 +124,7 @@ func strlen(s string) int {
 	return len(s)
 }
 
-func printItf(val interface{}) {
+func printItf(val any) {
 	switch val := val.(type) {
 	case Doubler:
 		println("is Doubler:", val.Double())

src/internal/bytealg/bytealg.go

@@ -45,11 +45,8 @@ func Compare(a, b []byte) int {
 // This function was copied from the Go 1.23 source tree (with runtime_cmpstring
 // manually inlined).
 func CompareString(a, b string) int {
-	l := len(a)
+	l := min(len(b), len(a))
-	if len(b) < l {
+	for i := range l {
-		l = len(b)
-	}
-	for i := 0; i < l; i++ {
 		c1, c2 := a[i], b[i]
 		if c1 < c2 {
 			return -1
@@ -170,7 +167,7 @@ const PrimeRK = 16777619
 // This function was removed in Go 1.22.
 func HashStrBytes(sep []byte) (uint32, uint32) {
 	hash := uint32(0)
-	for i := 0; i < len(sep); i++ {
+	for i := range sep {
 		hash = hash*PrimeRK + uint32(sep[i])
 	}
 	var pow, sq uint32 = 1, PrimeRK
@@ -249,7 +246,7 @@ func IndexRabinKarpBytes(s, sep []byte) int {
 	hashsep, pow := HashStrBytes(sep)
 	n := len(sep)
 	var h uint32
-	for i := 0; i < n; i++ {
+	for i := range n {
 		h = h*PrimeRK + uint32(s[i])
 	}
 	if h == hashsep && Equal(s[:n], sep) {
@@ -276,7 +273,7 @@ func IndexRabinKarp[T string | []byte](s, sep T) int {
 	hashss, pow := HashStr(sep)
 	n := len(sep)
 	var h uint32
-	for i := 0; i < n; i++ {
+	for i := range n {
 		h = h*PrimeRK + uint32(s[i])
 	}
 	if h == hashss && string(s[:n]) == string(sep) {

src/internal/cm/case.go

@@ -12,8 +12,8 @@ func CaseUnmarshaler[T ~uint8 | ~uint16 | ~uint32](cases []string) func(v *T, te
 				return &emptyTextError{}
 			}
 			s := string(text)
-			for i := 0; i < len(cases); i++ {
+			for i, c := range cases {
-				if cases[i] == s {
+				if c == s {
 					*v = T(i)
 					return nil
 				}

src/machine/usb/cdc/ring_test.go

@@ -268,7 +268,7 @@ func TestRing512_PutOversize(t *testing.T) {
 
 func TestRing512_MultiplePutPeekDiscard(t *testing.T) {
 	var r ring512
-	for i := 0; i < 2000; i++ {
+	for i := range 2000 {
 		msg := []byte(fmt.Sprintf("msg%04d", i))
 		if !r.Put(msg) {
 			t.Fatalf("Put failed at iteration %d, Free=%d, Used=%d", i, r.Free(), r.Used())
@@ -290,7 +290,7 @@ func TestRing512_HeadTailOverflow(t *testing.T) {
 		t.Fatalf("Used=%d Free=%d, want 0/512", r.Used(), r.Free())
 	}
 
-	for i := 0; i < 300; i++ {
+	for i := range 300 {
 		data := []byte{byte(i), byte(i + 1), byte(i + 2)}
 		if !r.Put(data) {
 			t.Fatalf("Put failed at iter %d (head=%d tail=%d)", i, r.head.Load(), r.tail.Load())
@@ -370,7 +370,7 @@ func TestRing512_PeekTotalEqualsUsed(t *testing.T) {
 // --- Concurrent SPSC Test ---
 
 func TestRing512_SPSC(t *testing.T) {
-	for trial := 0; trial < 20; trial++ {
+	for trial := range 20 {
 		var r ring512
 		const totalBytes = 1 << 18
 		produced := make([]byte, totalBytes)
@@ -431,7 +431,7 @@ func TestRing512_SPSCSmallChunks(t *testing.T) {
 
 	go func() {
 		defer wg.Done()
-		for i := 0; i < totalBytes; i++ {
+		for i := range totalBytes {
 			for !r.Put([]byte{byte(i)}) {
 			}
 		}
@@ -494,10 +494,7 @@ func FuzzRing512(f *testing.F) {
 
 			switch op {
 			case 0: // Put
-				size := int(arg)
+				size := min(int(arg), 512)
-				if size > 512 {
-					size = 512
-				}
 				data := make([]byte, size)
 				for j := range data {
 					data[j] = byte(j)

src/sync/cond_test.go

@@ -15,21 +15,21 @@ func TestCondSignal(t *testing.T) {
 	cond.L.Lock()
 
 	// Start a goroutine to signal us once we wait.
-	var signaled uint32
+	var signaled atomic.Uint32
 	go func() {
 		// Wait for the test goroutine to wait.
 		cond.L.Lock()
 		defer cond.L.Unlock()
 
 		// Send a signal to the test goroutine.
-		atomic.StoreUint32(&signaled, 1)
+		signaled.Store(1)
 		cond.Signal()
 	}()
 
 	// Wait for a signal.
 	// This will unlock the mutex, and allow the spawned goroutine to run.
 	cond.Wait()
-	if atomic.LoadUint32(&signaled) == 0 {
+	if signaled.Load() == 0 {
 		t.Error("wait returned before a signal was sent")
 	}
 }
@@ -44,7 +44,7 @@ func TestCondBroadcast(t *testing.T) {
 	// Start goroutines to wait for the broadcast.
 	var wg sync.WaitGroup
 	const n = 5
-	for i := 0; i < n; i++ {
+	for range n {
 		wg.Add(1)
 		mu.RLock()
 		go func() {

src/sync/mutex_test.go

@@ -14,7 +14,7 @@ type mutex interface {
 }
 
 func HammerMutex(m mutex, loops int, cdone chan bool) {
-	for i := 0; i < loops; i++ {
+	for i := range loops {
 		if i%3 == 0 {
 			if m.TryLock() {
 				m.Unlock()
@@ -41,10 +41,10 @@ func TestMutex(t *testing.T) {
 	m.Unlock()
 
 	c := make(chan bool)
-	for i := 0; i < 10; i++ {
+	for range 10 {
 		go HammerMutex(m, 1000, c)
 	}
-	for i := 0; i < 10; i++ {
+	for range 10 {
 		<-c
 	}
 }
@@ -54,7 +54,7 @@ func TestMutexUncontended(t *testing.T) {
 	var mu sync.Mutex
 
 	// Lock and unlock the mutex a few times.
-	for i := 0; i < 3; i++ {
+	for range 3 {
 		mu.Lock()
 		mu.Unlock()
 	}
@@ -69,7 +69,7 @@ func TestMutexConcurrent(t *testing.T) {
 	var fail atomic.Uint32
 
 	const n = 10
-	for i := 0; i < n; i++ {
+	for i := range n {
 		j := i
 		go func() {
 			// Delay a bit.
@@ -129,12 +129,12 @@ func TestRWMutexUncontended(t *testing.T) {
 
 	// Acquire several read locks.
 	const n = 5
-	for i := 0; i < n; i++ {
+	for range n {
 		mu.RLock()
 	}
 
 	// Release all of the read locks.
-	for i := 0; i < n; i++ {
+	for range n {
 		mu.RUnlock()
 	}
 
@@ -150,31 +150,31 @@ func TestRWMutexWriteToRead(t *testing.T) {
 	mu.Lock()
 
 	const n = 3
-	var readAcquires uint32
+	var readAcquires atomic.Uint32
-	var completed uint32
+	var completed atomic.Uint32
-	var unlocked uint32
+	var unlocked atomic.Uint32
 	var bad uint32
-	for i := 0; i < n; i++ {
+	for range n {
 		go func() {
 			// Acquire a read lock.
 			mu.RLock()
 
 			// Verify that the write lock is supposed to be released by now.
-			if atomic.LoadUint32(&unlocked) == 0 {
+			if unlocked.Load() == 0 {
 				// The write lock is still being held.
 				atomic.AddUint32(&bad, 1)
 			}
 
 			// Add ourselves to the read lock counter.
-			atomic.AddUint32(&readAcquires, 1)
+			readAcquires.Add(1)
 
 			// Wait for everything to hold the read lock simultaneously.
-			for atomic.LoadUint32(&readAcquires) < n {
+			for readAcquires.Load() < n {
 				runtime.Gosched()
 			}
 
 			// Notify of completion.
-			atomic.AddUint32(&completed, 1)
+			completed.Add(1)
 
 			// Release the read lock.
 			mu.RUnlock()
@@ -182,16 +182,16 @@ func TestRWMutexWriteToRead(t *testing.T) {
 	}
 
 	// Wait a bit for the goroutines to block.
-	for i := 0; i < 3*n; i++ {
+	for range 3 * n {
 		runtime.Gosched()
 	}
 
 	// Release the write lock so that the goroutines acquire read locks.
-	atomic.StoreUint32(&unlocked, 1)
+	unlocked.Store(1)
 	mu.Unlock()
 
 	// Wait for everything to complete.
-	for atomic.LoadUint32(&completed) < n {
+	for completed.Load() < n {
 		runtime.Gosched()
 	}
 
@@ -209,7 +209,7 @@ func TestRWMutexReadToWrite(t *testing.T) {
 	const n = 3
 	var mu sync.RWMutex
 	var readers uint32
-	for i := 0; i < n; i++ {
+	for range n {
 		mu.RLock()
 		readers++
 	}
@@ -230,7 +230,7 @@ func TestRWMutexReadToWrite(t *testing.T) {
 	}()
 
 	// Release the read locks.
-	for i := 0; i < n; i++ {
+	for range n {
 		runtime.Gosched()
 		atomic.AddUint32(&readers, ^uint32(0))
 		mu.RUnlock()
@@ -261,10 +261,10 @@ func TestRWMutex(t *testing.T) {
 	m.Unlock()
 
 	c := make(chan bool)
-	for i := 0; i < 10; i++ {
+	for range 10 {
 		go HammerMutex(m, 1000, c)
 	}
-	for i := 0; i < 10; i++ {
+	for range 10 {
 		<-c
 	}
 }

src/sync/pool_test.go

@@ -11,7 +11,7 @@ type testItem struct {
 
 func TestPool(t *testing.T) {
 	p := sync.Pool{
-		New: func() interface{} {
+		New: func() any {
 			return &testItem{}
 		},
 	}

src/sync/waitgroup_test.go

@@ -27,7 +27,7 @@ func TestWaitGroup(t *testing.T) {
 	const n = 5
 	var wg sync.WaitGroup
 	wg.Add(n)
-	for i := 0; i < n; i++ {
+	for range n {
 		go wg.Done()
 	}
 

src/testing/benchmark.go

@@ -170,20 +170,6 @@ func (b *B) runN(n int) {
 	b.StopTimer()
 }
 
-func min(x, y int64) int64 {
-	if x > y {
-		return y
-	}
-	return x
-}
-
-func max(x, y int64) int64 {
-	if x < y {
-		return y
-	}
-	return x
-}
-
 // run1 runs the first iteration of benchFunc. It reports whether more
 // iterations of this benchmarks should be run.
 func (b *B) run1() bool {

src/testing/fuzz.go

@@ -53,7 +53,7 @@ type corpusEntry = struct {
 	Parent     string
 	Path       string
 	Data       []byte
-	Values     []interface{}
+	Values     []any
 	Generation int
 	IsSeed     bool
 }
@@ -61,8 +61,8 @@ type corpusEntry = struct {
 // Add will add the arguments to the seed corpus for the fuzz test. This will be
 // a no-op if called after or within the fuzz target, and args must match the
 // arguments for the fuzz target.
-func (f *F) Add(args ...interface{}) {
+func (f *F) Add(args ...any) {
-	var values []interface{}
+	var values []any
 	for i := range args {
 		if t := reflect.TypeOf(args[i]); !supportedTypes[t] {
 			panic(fmt.Sprintf("testing: unsupported type to Add %v", t))
@@ -74,23 +74,23 @@ func (f *F) Add(args ...interface{}) {
 
 // supportedTypes represents all of the supported types which can be fuzzed.
 var supportedTypes = map[reflect.Type]bool{
-	reflect.TypeOf(([]byte)("")):  true,
+	reflect.TypeFor[[]byte]():     true,
-	reflect.TypeOf((string)("")):  true,
+	reflect.TypeFor[string]():     true,
 	reflect.TypeOf((bool)(false)): true,
-	reflect.TypeOf((byte)(0)):     true,
+	reflect.TypeFor[byte]():       true,
-	reflect.TypeOf((rune)(0)):     true,
+	reflect.TypeFor[rune]():       true,
-	reflect.TypeOf((float32)(0)):  true,
+	reflect.TypeFor[float32]():    true,
-	reflect.TypeOf((float64)(0)):  true,
+	reflect.TypeFor[float64]():    true,
-	reflect.TypeOf((int)(0)):      true,
+	reflect.TypeFor[int]():        true,
-	reflect.TypeOf((int8)(0)):     true,
+	reflect.TypeFor[int8]():       true,
-	reflect.TypeOf((int16)(0)):    true,
+	reflect.TypeFor[int16]():      true,
-	reflect.TypeOf((int32)(0)):    true,
+	reflect.TypeFor[int32]():      true,
-	reflect.TypeOf((int64)(0)):    true,
+	reflect.TypeFor[int64]():      true,
-	reflect.TypeOf((uint)(0)):     true,
+	reflect.TypeFor[uint]():       true,
-	reflect.TypeOf((uint8)(0)):    true,
+	reflect.TypeFor[uint8]():      true,
-	reflect.TypeOf((uint16)(0)):   true,
+	reflect.TypeFor[uint16]():     true,
-	reflect.TypeOf((uint32)(0)):   true,
+	reflect.TypeFor[uint32]():     true,
-	reflect.TypeOf((uint64)(0)):   true,
+	reflect.TypeFor[uint64]():     true,
 }
 
 // Fuzz runs the fuzz function, ff, for fuzz testing. If ff fails for a set of
@@ -119,7 +119,7 @@ var supportedTypes = map[reflect.Type]bool{
 // When fuzzing, F.Fuzz does not return until a problem is found, time runs out
 // (set with -fuzztime), or the test process is interrupted by a signal. F.Fuzz
 // should be called exactly once, unless F.Skip or F.Fail is called beforehand.
-func (f *F) Fuzz(ff interface{}) {
+func (f *F) Fuzz(ff any) {
 	f.failed = true
 	f.result.N = 0
 	f.result.T = 0

src/testing/testing.go

@@ -137,7 +137,7 @@ func Testing() bool {
 
 // flushToParent writes c.output to the parent after first writing the header
 // with the given format and arguments.
-func (c *common) flushToParent(testName, format string, args ...interface{}) {
+func (c *common) flushToParent(testName, format string, args ...any) {
 	if c.parent == nil {
 		// The fake top-level test doesn't want a FAIL or PASS banner.
 		// Not quite sure how this works upstream.
@@ -157,21 +157,21 @@ func fmtDuration(d time.Duration) string {
 type TB interface {
 	Cleanup(func())
 	Context() context.Context
-	Error(args ...interface{})
+	Error(args ...any)
-	Errorf(format string, args ...interface{})
+	Errorf(format string, args ...any)
 	Fail()
 	FailNow()
 	Failed() bool
-	Fatal(args ...interface{})
+	Fatal(args ...any)
-	Fatalf(format string, args ...interface{})
+	Fatalf(format string, args ...any)
 	Helper()
-	Log(args ...interface{})
+	Log(args ...any)
-	Logf(format string, args ...interface{})
+	Logf(format string, args ...any)
 	Name() string
 	Setenv(key, value string)
-	Skip(args ...interface{})
+	Skip(args ...any)
 	SkipNow()
-	Skipf(format string, args ...interface{})
+	Skipf(format string, args ...any)
 	Skipped() bool
 	TempDir() string
 }
@@ -238,47 +238,47 @@ func (c *common) log(s string) {
 // and records the text in the error log. For tests, the text will be printed only if
 // the test fails or the -test.v flag is set. For benchmarks, the text is always
 // printed to avoid having performance depend on the value of the -test.v flag.
-func (c *common) Log(args ...interface{}) { c.log(fmt.Sprintln(args...)) }
+func (c *common) Log(args ...any) { c.log(fmt.Sprintln(args...)) }
 
 // Logf formats its arguments according to the format, analogous to Printf, and
 // records the text in the error log. A final newline is added if not provided. For
 // tests, the text will be printed only if the test fails or the -test.v flag is
 // set. For benchmarks, the text is always printed to avoid having performance
 // depend on the value of the -test.v flag.
-func (c *common) Logf(format string, args ...interface{}) { c.log(fmt.Sprintf(format, args...)) }
+func (c *common) Logf(format string, args ...any) { c.log(fmt.Sprintf(format, args...)) }
 
 // Error is equivalent to Log followed by Fail.
-func (c *common) Error(args ...interface{}) {
+func (c *common) Error(args ...any) {
 	c.log(fmt.Sprintln(args...))
 	c.Fail()
 }
 
 // Errorf is equivalent to Logf followed by Fail.
-func (c *common) Errorf(format string, args ...interface{}) {
+func (c *common) Errorf(format string, args ...any) {
 	c.log(fmt.Sprintf(format, args...))
 	c.Fail()
 }
 
 // Fatal is equivalent to Log followed by FailNow.
-func (c *common) Fatal(args ...interface{}) {
+func (c *common) Fatal(args ...any) {
 	c.log(fmt.Sprintln(args...))
 	c.FailNow()
 }
 
 // Fatalf is equivalent to Logf followed by FailNow.
-func (c *common) Fatalf(format string, args ...interface{}) {
+func (c *common) Fatalf(format string, args ...any) {
 	c.log(fmt.Sprintf(format, args...))
 	c.FailNow()
 }
 
 // Skip is equivalent to Log followed by SkipNow.
-func (c *common) Skip(args ...interface{}) {
+func (c *common) Skip(args ...any) {
 	c.log(fmt.Sprintln(args...))
 	c.SkipNow()
 }
 
 // Skipf is equivalent to Logf followed by SkipNow.
-func (c *common) Skipf(format string, args ...interface{}) {
+func (c *common) Skipf(format string, args ...any) {
 	c.log(fmt.Sprintf(format, args...))
 	c.SkipNow()
 }
@@ -672,7 +672,7 @@ func (t *T) report() {
 // Not implemented.
 func AllocsPerRun(runs int, f func()) (avg float64) {
 	f()
-	for i := 0; i < runs; i++ {
+	for range runs {
 		f()
 	}
 	return 0
@@ -688,7 +688,7 @@ type InternalExample struct {
 // MainStart is meant for use by tests generated by 'go test'.
 // It is not meant to be called directly and is not subject to the Go 1 compatibility document.
 // It may change signature from release to release.
-func MainStart(deps interface{}, tests []InternalTest, benchmarks []InternalBenchmark, fuzzTargets []InternalFuzzTarget, examples []InternalExample) *M {
+func MainStart(deps any, tests []InternalTest, benchmarks []InternalBenchmark, fuzzTargets []InternalFuzzTarget, examples []InternalExample) *M {
 	Init()
 	return &M{
 		Tests:      tests,

src/unique/handle.go

@@ -71,4 +71,4 @@ func Make[T comparable](value T) Handle[T] {
 }
 
 //go:linkname decomposeInterface runtime.decomposeInterface
-func decomposeInterface(i interface{}) (unsafe.Pointer, unsafe.Pointer)
+func decomposeInterface(i any) (unsafe.Pointer, unsafe.Pointer)

transform/interface-lowering.go

@@ -150,11 +150,11 @@ func (p *lowerInterfacesPass) run() error {
 
 	// Collect all type codes.
 	for global := p.mod.FirstGlobal(); !global.IsNil(); global = llvm.NextGlobal(global) {
-		if strings.HasPrefix(global.Name(), "reflect/types.type:") {
+		if after, ok := strings.CutPrefix(global.Name(), "reflect/types.type:"); ok {
 			// Retrieve Go type information based on an opaque global variable.
 			// Only the name of the global is relevant, the object itself is
 			// discarded afterwards.
-			name := strings.TrimPrefix(global.Name(), "reflect/types.type:")
+			name := after
 			if _, ok := p.types[name]; !ok {
 				t := &typeInfo{
 					name:     name,
@@ -463,7 +463,7 @@ func (p *lowerInterfacesPass) addTypeMethods(t *typeInfo, methodSet llvm.Value)
 	signatures := p.builder.CreateExtractValue(set, 1, "")
 	wrappers := p.builder.CreateExtractValue(set, 2, "")
 	numMethods := signatures.Type().ArrayLength()
-	for i := 0; i < numMethods; i++ {
+	for i := range numMethods {
 		signatureGlobal := p.builder.CreateExtractValue(signatures, i, "")
 		function := p.builder.CreateExtractValue(wrappers, i, "")
 		function = stripPointerCasts(function) // strip bitcasts
@@ -489,7 +489,7 @@ func (p *lowerInterfacesPass) addInterface(methodsString string) {
 		signatures: make(map[string]*signatureInfo),
 	}
 	p.interfaces[methodsString] = t
-	for _, method := range strings.Split(methodsString, "; ") {
+	for method := range strings.SplitSeq(methodsString, "; ") {
 		signature := p.getSignature(method)
 		signature.interfaces = append(signature.interfaces, t)
 		t.signatures[method] = signature
@@ -683,7 +683,7 @@ func (p *lowerInterfacesPass) extractMethodSigs(field llvm.Value) []string {
 	methodArray := p.builder.CreateExtractValue(field, 1, "")
 	n := methodArray.Type().ArrayLength()
 	sigs := make([]string, 0, n)
-	for j := 0; j < n; j++ {
+	for j := range n {
 		sig := p.builder.CreateExtractValue(methodArray, j, "")
 		sig = stripPointerCasts(sig)
 		sigs = append(sigs, sig.Name())
@@ -727,7 +727,7 @@ func (p *lowerInterfacesPass) filterMethodSet(field llvm.Value, keepSigs map[str
 	}
 	entries := make([]methodEntry, numMethods)
 	nameSet := make(map[string]struct{}, numMethods)
-	for j := 0; j < numMethods; j++ {
+	for j := range numMethods {
 		sig := p.builder.CreateExtractValue(methodArray, j, "")
 		stripped := stripPointerCasts(sig)
 		name := stripped.Name()

transform/llvm.go

@@ -34,7 +34,7 @@ func hasUses(value llvm.Value) bool {
 // contents, and returns the global and initializer type.
 // Note that it is left with the default linkage etc., you should set
 // linkage/constant/etc properties yourself.
-func makeGlobalArray(mod llvm.Module, bufItf interface{}, name string, elementType llvm.Type) (llvm.Type, llvm.Value) {
+func makeGlobalArray(mod llvm.Module, bufItf any, name string, elementType llvm.Type) (llvm.Type, llvm.Value) {
 	buf := reflect.ValueOf(bufItf)
 	var values []llvm.Value
 	for i := 0; i < buf.Len(); i++ {
@@ -64,7 +64,7 @@ func getGlobalBytes(global llvm.Value, builder llvm.Builder) []byte {
 // replaceGlobalByteWithArray replaces a global integer type in the module with
 // an integer array, using a GEP to make the types match. It is a convenience
 // function used for creating reflection sidetables, for example.
-func replaceGlobalIntWithArray(mod llvm.Module, name string, buf interface{}) llvm.Value {
+func replaceGlobalIntWithArray(mod llvm.Module, name string, buf any) llvm.Value {
 	oldGlobal := mod.NamedGlobal(name)
 	globalType, global := makeGlobalArray(mod, buf, name+".tmp", oldGlobal.GlobalValueType())
 	gep := llvm.ConstGEP(globalType, global, []llvm.Value{