*: apply modernize suggestions

decode.go

@@ -532,10 +532,7 @@ func (d *decodeState) array(v reflect.Value) {
 		if v.Kind() == reflect.Slice {
 			// Grow slice if necessary
 			if i >= v.Cap() {
-				newcap := v.Cap() + v.Cap()/2
-				if newcap < 4 {
-					newcap = 4
-				}
+				newcap := max(v.Cap()+v.Cap()/2, 4)
 				newv := reflect.MakeSlice(v.Type(), v.Len(), newcap)
 				reflect.Copy(newv, v)
 				v.Set(newv)
@@ -581,7 +578,7 @@ func (d *decodeState) array(v reflect.Value) {
 }
 
 var nullLiteral = []byte("null")
-var textUnmarshalerType = reflect.TypeOf(new(encoding.TextUnmarshaler)).Elem()
+var textUnmarshalerType = reflect.TypeFor[encoding.TextUnmarshaler]()
 
 // object consumes an object from d.data[d.off-1:], decoding into the value v.
 // the first byte ('{') of the object has been read already.
@@ -808,12 +805,12 @@ func (d *decodeState) convertNumber(s string) (any, error) {
 	}
 	f, err := strconv.ParseFloat(s, 64)
 	if err != nil {
-		return nil, &UnmarshalTypeError{Value: "number " + s, Type: reflect.TypeOf(0.0), Offset: int64(d.off)}
+		return nil, &UnmarshalTypeError{Value: "number " + s, Type: reflect.TypeFor[float64](), Offset: int64(d.off)}
 	}
 	return f, nil
 }
 
-var numberType = reflect.TypeOf(Number(""))
+var numberType = reflect.TypeFor[Number]()
 
 // literalStore decodes a literal stored in item into v.
 //

decode_test.go

@@ -88,11 +88,11 @@ func (u unmarshalerText) MarshalText() ([]byte, error) {
 }
 
 func (u *unmarshalerText) UnmarshalText(b []byte) error {
-	pos := bytes.Index(b, []byte(":"))
-	if pos == -1 {
+	before, after, ok := bytes.Cut(b, []byte(":"))
+	if !ok {
 		return errors.New("missing separator")
 	}
-	u.A, u.B = string(b[:pos]), string(b[pos+1:])
+	u.A, u.B = string(before), string(after)
 	return nil
 }
 
@@ -106,7 +106,7 @@ type ustructText struct {
 type u8marshal uint8
 
 func (u8 u8marshal) MarshalText() ([]byte, error) {
-	return []byte(fmt.Sprintf("u%d", u8)), nil
+	return fmt.Appendf(nil, "u%d", u8), nil
 }
 
 var errMissingU8Prefix = errors.New("missing 'u' prefix")
@@ -262,7 +262,7 @@ func mapAddr(x map[string]int) *map[string]int { return &x }
 type byteWithMarshalJSON byte
 
 func (b byteWithMarshalJSON) MarshalJSON() ([]byte, error) {
-	return []byte(fmt.Sprintf(`"Z%.2x"`, byte(b))), nil
+	return fmt.Appendf(nil, `"Z%.2x"`, byte(b)), nil
 }
 
 func (b *byteWithMarshalJSON) UnmarshalJSON(data []byte) error {
@@ -290,7 +290,7 @@ func (b *byteWithPtrMarshalJSON) UnmarshalJSON(data []byte) error {
 type byteWithMarshalText byte
 
 func (b byteWithMarshalText) MarshalText() ([]byte, error) {
-	return []byte(fmt.Sprintf(`Z%.2x`, byte(b))), nil
+	return fmt.Appendf(nil, `Z%.2x`, byte(b)), nil
 }
 
 func (b *byteWithMarshalText) UnmarshalText(data []byte) error {
@@ -318,7 +318,7 @@ func (b *byteWithPtrMarshalText) UnmarshalText(data []byte) error {
 type intWithMarshalJSON int
 
 func (b intWithMarshalJSON) MarshalJSON() ([]byte, error) {
-	return []byte(fmt.Sprintf(`"Z%.2x"`, int(b))), nil
+	return fmt.Appendf(nil, `"Z%.2x"`, int(b)), nil
 }
 
 func (b *intWithMarshalJSON) UnmarshalJSON(data []byte) error {
@@ -346,7 +346,7 @@ func (b *intWithPtrMarshalJSON) UnmarshalJSON(data []byte) error {
 type intWithMarshalText int
 
 func (b intWithMarshalText) MarshalText() ([]byte, error) {
-	return []byte(fmt.Sprintf(`Z%.2x`, int(b))), nil
+	return fmt.Appendf(nil, `Z%.2x`, int(b)), nil
 }
 
 func (b *intWithMarshalText) UnmarshalText(data []byte) error {
@@ -400,7 +400,7 @@ var unmarshalTests = []unmarshalTest{
 	{in: `"g-clef: \uD834\uDD1E"`, ptr: new(string), out: "g-clef: \U0001D11E"},
 	{in: `"invalid: \uD834x\uDD1E"`, ptr: new(string), out: "invalid: \uFFFDx\uFFFD"},
 	{in: "null", ptr: new(any), out: nil},
-	{in: `{"X": [1,2,3], "Y": 4}`, ptr: new(T), out: T{Y: 4}, err: &UnmarshalTypeError{"array", reflect.TypeOf(""), 7, "T", "X"}},
+	{in: `{"X": [1,2,3], "Y": 4}`, ptr: new(T), out: T{Y: 4}, err: &UnmarshalTypeError{"array", reflect.TypeFor[string](), 7, "T", "X"}},
 	{in: `{"x": 1}`, ptr: new(tx), out: tx{}},
 	{in: `{"F1":1,"F2":2,"F3":3}`, ptr: new(V), out: V{F1: float64(1), F2: int32(2), F3: Number("3")}},
 	{in: `{"F1":1,"F2":2,"F3":3}`, ptr: new(V), out: V{F1: Number("1"), F2: int32(2), F3: Number("3")}, useNumber: true},
@@ -515,22 +515,22 @@ var unmarshalTests = []unmarshalTest{
 	{
 		in:  `{"abc":"abc"}`,
 		ptr: new(map[int]string),
-		err: &UnmarshalTypeError{Value: "number abc", Type: reflect.TypeOf(0), Offset: 2},
+		err: &UnmarshalTypeError{Value: "number abc", Type: reflect.TypeFor[int](), Offset: 2},
 	},
 	{
 		in:  `{"256":"abc"}`,
 		ptr: new(map[uint8]string),
-		err: &UnmarshalTypeError{Value: "number 256", Type: reflect.TypeOf(uint8(0)), Offset: 2},
+		err: &UnmarshalTypeError{Value: "number 256", Type: reflect.TypeFor[uint8](), Offset: 2},
 	},
 	{
 		in:  `{"128":"abc"}`,
 		ptr: new(map[int8]string),
-		err: &UnmarshalTypeError{Value: "number 128", Type: reflect.TypeOf(int8(0)), Offset: 2},
+		err: &UnmarshalTypeError{Value: "number 128", Type: reflect.TypeFor[int8](), Offset: 2},
 	},
 	{
 		in:  `{"-1":"abc"}`,
 		ptr: new(map[uint8]string),
-		err: &UnmarshalTypeError{Value: "number -1", Type: reflect.TypeOf(uint8(0)), Offset: 2},
+		err: &UnmarshalTypeError{Value: "number -1", Type: reflect.TypeFor[uint8](), Offset: 2},
 	},
 
 	// Map keys can be encoding.TextUnmarshalers.
@@ -664,12 +664,12 @@ var unmarshalTests = []unmarshalTest{
 	{
 		in:  `{"2009-11-10T23:00:00Z": "hello world"}`,
 		ptr: &map[Point]string{},
-		err: &UnmarshalTypeError{Value: "object", Type: reflect.TypeOf(map[Point]string{}), Offset: 1},
+		err: &UnmarshalTypeError{Value: "object", Type: reflect.TypeFor[map[Point]string](), Offset: 1},
 	},
 	{
 		in:  `{"asdf": "hello world"}`,
 		ptr: &map[unmarshaler]string{},
-		err: &UnmarshalTypeError{Value: "object", Type: reflect.TypeOf(map[unmarshaler]string{}), Offset: 1},
+		err: &UnmarshalTypeError{Value: "object", Type: reflect.TypeFor[map[unmarshaler]string](), Offset: 1},
 	},
 
 	// related to issue 13783.
@@ -769,7 +769,7 @@ var unmarshalTests = []unmarshalTest{
 			Value:  "string",
 			Struct: "V",
 			Field:  "F2",
-			Type:   reflect.TypeOf(int32(0)),
+			Type:   reflect.TypeFor[int32](),
 			Offset: 20,
 		},
 	},
@@ -780,7 +780,7 @@ var unmarshalTests = []unmarshalTest{
 			Value:  "string",
 			Struct: "V",
 			Field:  "F2",
-			Type:   reflect.TypeOf(int32(0)),
+			Type:   reflect.TypeFor[int32](),
 			Offset: 30,
 		},
 	},

encode.go

@@ -15,6 +15,7 @@ import (
 	"encoding"
 	"encoding/base64"
 	"fmt"
+	"maps"
 	"math"
 	"reflect"
 	"runtime"
@@ -376,9 +377,9 @@ func typeEncoder(t reflect.Type) encoderFunc {
 }
 
 var (
-	marshalerType     = reflect.TypeOf(new(Marshaler)).Elem()
-	textMarshalerType = reflect.TypeOf(new(encoding.TextMarshaler)).Elem()
-	orderedObjectType = reflect.TypeOf(new(OrderedObject)).Elem()
+	marshalerType     = reflect.TypeFor[Marshaler]()
+	textMarshalerType = reflect.TypeFor[encoding.TextMarshaler]()
+	orderedObjectType = reflect.TypeFor[OrderedObject]()
 )
 
 // newTypeEncoder constructs an encoderFunc for a type.
@@ -1334,9 +1335,7 @@ func cachedTypeFields(t reflect.Type) []field {
 	fieldCache.mu.Lock()
 	m, _ = fieldCache.value.Load().(map[reflect.Type][]field)
 	newM := make(map[reflect.Type][]field, len(m)+1)
-	for k, v := range m {
-		newM[k] = v
-	}
+	maps.Copy(newM, m)
 	newM[t] = f
 	fieldCache.value.Store(newM)
 	fieldCache.mu.Unlock()

encode_test.go

@@ -40,7 +40,7 @@ type Optionals struct {
 	Uo uint `json:"uo,omitempty"`
 
 	Str struct{} `json:"str"`
-	Sto struct{} `json:"sto,omitempty"`
+	Sto struct{} `json:"sto,omitempty"` //nolint:modernize
 }
 
 var optionalsExpected = `{

scanner_test.go

@@ -239,10 +239,7 @@ func BenchmarkSkipValue(b *testing.B) {
 func diff(t *testing.T, a, b []byte) {
 	for i := 0; ; i++ {
 		if i >= len(a) || i >= len(b) || a[i] != b[i] {
-			j := i - 10
-			if j < 0 {
-				j = 0
-			}
+			j := max(i-10, 0)
 			t.Errorf("diverge at %d: «%s» vs «%s»", i, trim(a[j:]), trim(b[j:]))
 			return
 		}
@@ -306,10 +303,7 @@ func genString(stddev float64) string {
 }
 
 func genArray(n int) []any {
-	f := int(math.Abs(rand.NormFloat64()) * math.Min(10, float64(n/2)))
-	if f > n {
-		f = n
-	}
+	f := min(int(math.Abs(rand.NormFloat64())*math.Min(10, float64(n/2))), n)
 	if f < 1 {
 		f = 1
 	}
@@ -321,10 +315,7 @@ func genArray(n int) []any {
 }
 
 func genMap(n int) map[string]any {
-	f := int(math.Abs(rand.NormFloat64()) * math.Min(10, float64(n/2)))
-	if f > n {
-		f = n
-	}
+	f := min(int(math.Abs(rand.NormFloat64())*math.Min(10, float64(n/2))), n)
 	if n > 0 && f == 0 {
 		f = 1
 	}

tags.go

@@ -15,8 +15,8 @@ type tagOptions string
 // parseTag splits a struct field's json tag into its name and
 // comma-separated options.
 func parseTag(tag string) (string, tagOptions) {
-	if idx := strings.Index(tag, ","); idx != -1 {
-		return tag[:idx], tagOptions(tag[idx+1:])
+	if before, after, ok := strings.Cut(tag, ","); ok {
+		return before, tagOptions(after)
 	}
 	return tag, tagOptions("")
 }