start using some Go 1.22 features

We no longer need to worry about the scope of range variables,
we can iterate over integers directly, and we can use cmp.Or too.

I haven't paid close attention to using these everywhere.
This is mainly testing out the new features where I saw some benefit.

bench_test.go

@@ -70,7 +70,7 @@ func BenchmarkBuild(b *testing.B) {
 
 	b.ResetTimer()
 	b.StopTimer()
-	for i := 0; i < b.N; i++ {
+	for i := range b.N {
 		// First we do a fresh build, using empty cache directories,
 		// and the second does an incremental rebuild reusing the same cache directories.
 		goCache := filepath.Join(tdir, "go-cache")

main.go

@@ -7,6 +7,7 @@ package main
 import (
 	"bufio"
 	"bytes"
+	"cmp"
 	cryptorand "crypto/rand"
 	"encoding/base64"
 	"encoding/binary"
@@ -287,10 +288,7 @@ func goVersionOK() bool {
 
 	// Ensure that the version of Go that built the garble binary is equal or
 	// newer than cache.GoVersionSemver.
-	builtVersionFull := os.Getenv("GARBLE_TEST_GOVERSION")
-	if builtVersionFull == "" {
-		builtVersionFull = runtime.Version()
-	}
+	builtVersionFull := cmp.Or(os.Getenv("GARBLE_TEST_GOVERSION"), runtime.Version())
 	builtVersion := rxVersion.FindString(builtVersionFull)
 	if builtVersion == "" {
 		// If garble built itself, we don't know what Go version was used.
@@ -1727,7 +1725,7 @@ func recordType(used, origin types.Type, done map[*types.Named]bool, fieldToStru
 		recordType(used.Underlying(), used.Origin().Underlying(), done, fieldToStruct)
 	case *types.Struct:
 		origin := origin.(*types.Struct)
-		for i := 0; i < used.NumFields(); i++ {
+		for i := range used.NumFields() {
 			field := used.Field(i)
 			fieldToStruct[field] = origin
 
@@ -2383,9 +2381,6 @@ To install Go, see: https://go.dev/doc/install
 	if err := json.Unmarshal(out, &sharedCache.GoEnv); err != nil {
 		return fmt.Errorf(`cannot unmarshal from "go env -json": %w`, err)
 	}
-	sharedCache.GOGARBLE = os.Getenv("GOGARBLE")
-	if sharedCache.GOGARBLE == "" {
-		sharedCache.GOGARBLE = "*" // we default to obfuscating everything
-	}
+	sharedCache.GOGARBLE = cmp.Or(os.Getenv("GOGARBLE"), "*") // we default to obfuscating everything
 	return nil
 }

main_test.go

@@ -295,7 +295,7 @@ func generateLiterals(ts *testscript.TestScript, neg bool, args []string) {
 	var statements []ast.Stmt
 
 	// Assignments which append 100 random small literals to x: `x += "the_small_random_literal"`
-	for i := 0; i < 100; i++ {
+	for range 100 {
 		statements = append(
 			statements,
 			&ast.AssignStmt{
@@ -310,7 +310,7 @@ func generateLiterals(ts *testscript.TestScript, neg bool, args []string) {
 	// We add huge literals to make sure we obfuscate them fast.
 	// 5 * 128KiB is large enough that it would take a very, very long time
 	// to obfuscate those literals if too complex obfuscators are used.
-	for i := 0; i < 5; i++ {
+	for range 5 {
 		statements = append(
 			statements,
 			&ast.AssignStmt{
@@ -421,7 +421,6 @@ func TestSplitFlagsFromArgs(t *testing.T) {
 		},
 	}
 	for _, test := range tests {
-		test := test
 		t.Run(test.name, func(t *testing.T) {
 			t.Parallel()
 			flags, args := splitFlagsFromArgs(test.args)
@@ -459,7 +458,6 @@ func TestFilterForwardBuildFlags(t *testing.T) {
 		},
 	}
 	for _, test := range tests {
-		test := test
 		t.Run(test.name, func(t *testing.T) {
 			t.Parallel()
 			got, _ := filterForwardBuildFlags(test.flags)
@@ -488,7 +486,6 @@ func TestFlagValue(t *testing.T) {
 		{"StrEmpty", []string{"-buildid="}, "-buildid", ""},
 	}
 	for _, test := range tests {
-		test := test
 		t.Run(test.name, func(t *testing.T) {
 			t.Parallel()
 			got := flagValue(test.flags, test.flagName)

reflect.go

@@ -69,7 +69,7 @@ func (ri *reflectInspector) ignoreReflectedTypes(ssaPkg *ssa.Package) {
 			// so some logic is required to find the methods a type has
 
 			method := func(mset *types.MethodSet) {
-				for i, n := 0, mset.Len(); i < n; i++ {
+				for i := range mset.Len() {
 					at := mset.At(i)
 
 					if m := ssaPkg.Prog.MethodValue(at); m != nil {
@@ -112,7 +112,7 @@ func (ri *reflectInspector) checkMethodSignature(reflectParams map[int]bool, sig
 	}
 
 	params := sig.Params()
-	for i := 0; i < params.Len(); i++ {
+	for i := range params.Len() {
 		if reflectParams[i] {
 			continue
 		}
@@ -404,7 +404,7 @@ func (ri *reflectInspector) recursivelyRecordUsedForReflect(t types.Type) {
 		ri.recursivelyRecordUsedForReflect(t.Underlying())
 
 	case *types.Struct:
-		for i := 0; i < t.NumFields(); i++ {
+		for i := range t.NumFields() {
 			field := t.Field(i)
 
 			// This check is similar to the one in *types.Named.