mkdir -p compat/json && mv borrowed_*_test.go compat/json/ # [ci-skip]

7 files changed, 4453 insertions, 0 deletions

diff --git a/compat/json/adapter_test.go b/compat/json/adapter_test.go
new file mode 100644
index 0000000..6c57ebc
--- /dev/null
+++ b/compat/json/adapter_test.go
@@ -0,0 +1,118 @@
+// Copyright (C) 2022  Luke Shumaker <lukeshu@lukeshu.com>
+//
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+package lowmemjson
+
+import (
+	"bytes"
+	"encoding/json"
+	"io"
+)
+
+func MarshalIndent(v any, prefix, indent string) ([]byte, error) {
+	var buf bytes.Buffer
+	formatter := &ReEncoder{
+		Out:    &buf,
+		Indent: indent,
+		prefix: prefix,
+	}
+	err := Encode(formatter, v)
+	return buf.Bytes(), err
+}
+
+func Marshal(v any) ([]byte, error) {
+	var buf bytes.Buffer
+	formatter := &ReEncoder{
+		Out:     &buf,
+		Compact: true,
+	}
+	err := Encode(formatter, v)
+	return buf.Bytes(), err
+}
+
+func HTMLEscape(dst *bytes.Buffer, src []byte) {
+	formatter := &ReEncoder{
+		Out: dst,
+	}
+	_, _ = formatter.Write(src)
+}
+
+func Compact(dst *bytes.Buffer, src []byte) error {
+	formatter := &ReEncoder{
+		Out:     dst,
+		Compact: true,
+	}
+	_, err := formatter.Write(src)
+	return err
+}
+
+func Indent(dst *bytes.Buffer, src []byte, prefix, indent string) error {
+	formatter := &ReEncoder{
+		Out:    dst,
+		Indent: indent,
+		prefix: prefix,
+	}
+	_, err := formatter.Write(src)
+	return err
+}
+
+func Valid(data []byte) bool {
+	formatter := &ReEncoder{
+		Out:     io.Discard,
+		Compact: true,
+	}
+	_, err := formatter.Write(data)
+	return err == nil
+}
+
+func Unmarshal(data []byte, ptr any) error {
+	return Decode(bytes.NewReader(data), ptr)
+}
+
+func init() {
+	forceBufio = true
+}
+
+func (dec *Decoder) Buffered() io.Reader {
+	dat, _ := dec.buf.Peek(dec.buf.Buffered())
+	return bytes.NewReader(dat)
+}
+
+//func (dec *Decoder) Token() (Token, error)
+
+/////////////////////////////////////////////////////////////////////
+
+type (
+	Number     = json.Number
+	Marshaler  = json.Marshaler
+	RawMessage = json.RawMessage
+
+	UnsupportedValueError = json.UnsupportedValueError
+	MarshalerError        = json.MarshalerError
+	UnmarshalTypeError    = json.UnmarshalTypeError
+)
+
+const (
+	startDetectingCyclesAfter = 1000
+)
+
+func isSpace(c byte) bool {
+	switch c {
+	case 0x0020, 0x000A, 0x000D, 0x0009:
+		return true
+	default:
+		return false
+	}
+}
+
+type encodeState struct {
+	bytes.Buffer
+}
+
+func (es *encodeState) string(str string, _ bool) {
+	encodeString(&es.Buffer, str)
+}
+func (es *encodeState) stringBytes(str []byte, _ bool) {
+	encodeString(&es.Buffer, str)
+}
diff --git a/compat/json/borrowed_decode_test.go b/compat/json/borrowed_decode_test.go
new file mode 100644
index 0000000..ac8594b
--- /dev/null
+++ b/compat/json/borrowed_decode_test.go
@@ -0,0 +1,2590 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package lowmemjson // MODIFIED
+
+import (
+	"bytes"
+	"encoding"
+	"errors"
+	"fmt"
+	"image"
+	"io" // MODIFIED
+	"math"
+	"math/big"
+	"net"
+	"reflect"
+	"strconv"
+	"strings"
+	"testing"
+	"time"
+)
+
+type T struct {
+	X string
+	Y int
+	Z int `json:"-"`
+}
+
+type U struct {
+	Alphabet string `json:"alpha"`
+}
+
+type V struct {
+	F1 any
+	F2 int32
+	F3 Number
+	F4 *VOuter
+}
+
+type VOuter struct {
+	V V
+}
+
+type W struct {
+	S SS
+}
+
+type P struct {
+	PP PP
+}
+
+type PP struct {
+	T  T
+	Ts []T
+}
+
+type SS string
+
+func (*SS) UnmarshalJSON(data []byte) error {
+	return &UnmarshalTypeError{Value: "number", Type: reflect.TypeOf(SS(""))}
+}
+
+// ifaceNumAsFloat64/ifaceNumAsNumber are used to test unmarshaling with and
+// without UseNumber
+var ifaceNumAsFloat64 = map[string]any{
+	"k1": float64(1),
+	"k2": "s",
+	"k3": []any{float64(1), float64(2.0), float64(3e-3)},
+	"k4": map[string]any{"kk1": "s", "kk2": float64(2)},
+}
+
+var ifaceNumAsNumber = map[string]any{
+	"k1": Number("1"),
+	"k2": "s",
+	"k3": []any{Number("1"), Number("2.0"), Number("3e-3")},
+	"k4": map[string]any{"kk1": "s", "kk2": Number("2")},
+}
+
+type tx struct {
+	x int
+}
+
+type u8 uint8
+
+// A type that can unmarshal itself.
+
+type unmarshaler struct {
+	T bool
+}
+
+func (u *unmarshaler) UnmarshalJSON(b []byte) error {
+	*u = unmarshaler{true} // All we need to see that UnmarshalJSON is called.
+	return nil
+}
+
+type ustruct struct {
+	M unmarshaler
+}
+
+type unmarshalerText struct {
+	A, B string
+}
+
+// needed for re-marshaling tests
+func (u unmarshalerText) MarshalText() ([]byte, error) {
+	return []byte(u.A + ":" + u.B), nil
+}
+
+func (u *unmarshalerText) UnmarshalText(b []byte) error {
+	pos := bytes.IndexByte(b, ':')
+	if pos == -1 {
+		return errors.New("missing separator")
+	}
+	u.A, u.B = string(b[:pos]), string(b[pos+1:])
+	return nil
+}
+
+var _ encoding.TextUnmarshaler = (*unmarshalerText)(nil)
+
+type ustructText struct {
+	M unmarshalerText
+}
+
+// u8marshal is an integer type that can marshal/unmarshal itself.
+type u8marshal uint8
+
+func (u8 u8marshal) MarshalText() ([]byte, error) {
+	return []byte(fmt.Sprintf("u%d", u8)), nil
+}
+
+var errMissingU8Prefix = errors.New("missing 'u' prefix")
+
+func (u8 *u8marshal) UnmarshalText(b []byte) error {
+	if !bytes.HasPrefix(b, []byte{'u'}) {
+		return errMissingU8Prefix
+	}
+	n, err := strconv.Atoi(string(b[1:]))
+	if err != nil {
+		return err
+	}
+	*u8 = u8marshal(n)
+	return nil
+}
+
+var _ encoding.TextUnmarshaler = (*u8marshal)(nil)
+
+var (
+	umtrue   = unmarshaler{true}
+	umslice  = []unmarshaler{{true}}
+	umstruct = ustruct{unmarshaler{true}}
+
+	umtrueXY   = unmarshalerText{"x", "y"}
+	umsliceXY  = []unmarshalerText{{"x", "y"}}
+	umstructXY = ustructText{unmarshalerText{"x", "y"}}
+
+	ummapXY = map[unmarshalerText]bool{{"x", "y"}: true}
+)
+
+// Test data structures for anonymous fields.
+
+type Point struct {
+	Z int
+}
+
+type Top struct {
+	Level0 int
+	Embed0
+	*Embed0a
+	*Embed0b `json:"e,omitempty"` // treated as named
+	Embed0c  `json:"-"`           // ignored
+	Loop
+	Embed0p // has Point with X, Y, used
+	Embed0q // has Point with Z, used
+	embed   // contains exported field
+}
+
+type Embed0 struct {
+	Level1a int // overridden by Embed0a's Level1a with json tag
+	Level1b int // used because Embed0a's Level1b is renamed
+	Level1c int // used because Embed0a's Level1c is ignored
+	Level1d int // annihilated by Embed0a's Level1d
+	Level1e int `json:"x"` // annihilated by Embed0a.Level1e
+}
+
+type Embed0a struct {
+	Level1a int `json:"Level1a,omitempty"`
+	Level1b int `json:"LEVEL1B,omitempty"`
+	Level1c int `json:"-"`
+	Level1d int // annihilated by Embed0's Level1d
+	Level1f int `json:"x"` // annihilated by Embed0's Level1e
+}
+
+type Embed0b Embed0
+
+type Embed0c Embed0
+
+type Embed0p struct {
+	image.Point
+}
+
+type Embed0q struct {
+	Point
+}
+
+type embed struct {
+	Q int
+}
+
+type Loop struct {
+	Loop1 int `json:",omitempty"`
+	Loop2 int `json:",omitempty"`
+	*Loop
+}
+
+// From reflect test:
+// The X in S6 and S7 annihilate, but they also block the X in S8.S9.
+type S5 struct {
+	S6
+	S7
+	S8
+}
+
+type S6 struct {
+	X int
+}
+
+type S7 S6
+
+type S8 struct {
+	S9
+}
+
+type S9 struct {
+	X int
+	Y int
+}
+
+// From reflect test:
+// The X in S11.S6 and S12.S6 annihilate, but they also block the X in S13.S8.S9.
+type S10 struct {
+	S11
+	S12
+	S13
+}
+
+type S11 struct {
+	S6
+}
+
+type S12 struct {
+	S6
+}
+
+type S13 struct {
+	S8
+}
+
+type Ambig struct {
+	// Given "hello", the first match should win.
+	First  int `json:"HELLO"`
+	Second int `json:"Hello"`
+}
+
+type XYZ struct {
+	X any
+	Y any
+	Z any
+}
+
+type unexportedWithMethods struct{}
+
+func (unexportedWithMethods) F() {}
+
+type byteWithMarshalJSON byte
+
+func (b byteWithMarshalJSON) MarshalJSON() ([]byte, error) {
+	return []byte(fmt.Sprintf(`"Z%.2x"`, byte(b))), nil
+}
+
+func (b *byteWithMarshalJSON) UnmarshalJSON(data []byte) error {
+	if len(data) != 5 || data[0] != '"' || data[1] != 'Z' || data[4] != '"' {
+		return fmt.Errorf("bad quoted string")
+	}
+	i, err := strconv.ParseInt(string(data[2:4]), 16, 8)
+	if err != nil {
+		return fmt.Errorf("bad hex")
+	}
+	*b = byteWithMarshalJSON(i)
+	return nil
+}
+
+type byteWithPtrMarshalJSON byte
+
+func (b *byteWithPtrMarshalJSON) MarshalJSON() ([]byte, error) {
+	return byteWithMarshalJSON(*b).MarshalJSON()
+}
+
+func (b *byteWithPtrMarshalJSON) UnmarshalJSON(data []byte) error {
+	return (*byteWithMarshalJSON)(b).UnmarshalJSON(data)
+}
+
+type byteWithMarshalText byte
+
+func (b byteWithMarshalText) MarshalText() ([]byte, error) {
+	return []byte(fmt.Sprintf(`Z%.2x`, byte(b))), nil
+}
+
+func (b *byteWithMarshalText) UnmarshalText(data []byte) error {
+	if len(data) != 3 || data[0] != 'Z' {
+		return fmt.Errorf("bad quoted string")
+	}
+	i, err := strconv.ParseInt(string(data[1:3]), 16, 8)
+	if err != nil {
+		return fmt.Errorf("bad hex")
+	}
+	*b = byteWithMarshalText(i)
+	return nil
+}
+
+type byteWithPtrMarshalText byte
+
+func (b *byteWithPtrMarshalText) MarshalText() ([]byte, error) {
+	return byteWithMarshalText(*b).MarshalText()
+}
+
+func (b *byteWithPtrMarshalText) UnmarshalText(data []byte) error {
+	return (*byteWithMarshalText)(b).UnmarshalText(data)
+}
+
+type intWithMarshalJSON int
+
+func (b intWithMarshalJSON) MarshalJSON() ([]byte, error) {
+	return []byte(fmt.Sprintf(`"Z%.2x"`, int(b))), nil
+}
+
+func (b *intWithMarshalJSON) UnmarshalJSON(data []byte) error {
+	if len(data) != 5 || data[0] != '"' || data[1] != 'Z' || data[4] != '"' {
+		return fmt.Errorf("bad quoted string")
+	}
+	i, err := strconv.ParseInt(string(data[2:4]), 16, 8)
+	if err != nil {
+		return fmt.Errorf("bad hex")
+	}
+	*b = intWithMarshalJSON(i)
+	return nil
+}
+
+type intWithPtrMarshalJSON int
+
+func (b *intWithPtrMarshalJSON) MarshalJSON() ([]byte, error) {
+	return intWithMarshalJSON(*b).MarshalJSON()
+}
+
+func (b *intWithPtrMarshalJSON) UnmarshalJSON(data []byte) error {
+	return (*intWithMarshalJSON)(b).UnmarshalJSON(data)
+}
+
+type intWithMarshalText int
+
+func (b intWithMarshalText) MarshalText() ([]byte, error) {
+	return []byte(fmt.Sprintf(`Z%.2x`, int(b))), nil
+}
+
+func (b *intWithMarshalText) UnmarshalText(data []byte) error {
+	if len(data) != 3 || data[0] != 'Z' {
+		return fmt.Errorf("bad quoted string")
+	}
+	i, err := strconv.ParseInt(string(data[1:3]), 16, 8)
+	if err != nil {
+		return fmt.Errorf("bad hex")
+	}
+	*b = intWithMarshalText(i)
+	return nil
+}
+
+type intWithPtrMarshalText int
+
+func (b *intWithPtrMarshalText) MarshalText() ([]byte, error) {
+	return intWithMarshalText(*b).MarshalText()
+}
+
+func (b *intWithPtrMarshalText) UnmarshalText(data []byte) error {
+	return (*intWithMarshalText)(b).UnmarshalText(data)
+}
+
+type mapStringToStringData struct {
+	Data map[string]string `json:"data"`
+}
+
+type unmarshalTest struct {
+	in                    string
+	ptr                   any // new(type)
+	out                   any
+	err                   error
+	useNumber             bool
+	golden                bool
+	disallowUnknownFields bool
+}
+
+type B struct {
+	B bool `json:",string"`
+}
+
+type DoublePtr struct {
+	I **int
+	J **int
+}
+
+var unmarshalTests = []unmarshalTest{
+	// basic types
+	{in: `true`, ptr: new(bool), out: true},
+	{in: `1`, ptr: new(int), out: 1},
+	{in: `1.2`, ptr: new(float64), out: 1.2},
+	{in: `-5`, ptr: new(int16), out: int16(-5)},
+	{in: `2`, ptr: new(Number), out: Number("2"), useNumber: true},
+	{in: `2`, ptr: new(Number), out: Number("2")},
+	{in: `2`, ptr: new(any), out: float64(2.0)},
+	{in: `2`, ptr: new(any), out: Number("2"), useNumber: true},
+	{in: `"a\u1234"`, ptr: new(string), out: "a\u1234"},
+	{in: `"http:\/\/"`, ptr: new(string), out: "http://"},
+	{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": 23}`, ptr: new(T), out: T{}, err: &UnmarshalTypeError{"number", reflect.TypeOf(""), 8, "T", "X"}}, {in: `{"x": 1}`, ptr: new(tx), out: tx{}},
+	{in: `{"x": 1}`, ptr: new(tx), out: tx{}},
+	{in: `{"x": 1}`, ptr: new(tx), err: fmt.Errorf("json: unknown field \"x\""), disallowUnknownFields: true},
+	{in: `{"S": 23}`, ptr: new(W), out: W{}, err: &UnmarshalTypeError{"number", reflect.TypeOf(SS("")), 0, "W", "S"}},
+	{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},
+	{in: `{"k1":1,"k2":"s","k3":[1,2.0,3e-3],"k4":{"kk1":"s","kk2":2}}`, ptr: new(any), out: ifaceNumAsFloat64},
+	{in: `{"k1":1,"k2":"s","k3":[1,2.0,3e-3],"k4":{"kk1":"s","kk2":2}}`, ptr: new(any), out: ifaceNumAsNumber, useNumber: true},
+
+	// raw values with whitespace
+	{in: "\n true ", ptr: new(bool), out: true},
+	{in: "\t 1 ", ptr: new(int), out: 1},
+	{in: "\r 1.2 ", ptr: new(float64), out: 1.2},
+	{in: "\t -5 \n", ptr: new(int16), out: int16(-5)},
+	{in: "\t \"a\\u1234\" \n", ptr: new(string), out: "a\u1234"},
+
+	// Z has a "-" tag.
+	{in: `{"Y": 1, "Z": 2}`, ptr: new(T), out: T{Y: 1}},
+	{in: `{"Y": 1, "Z": 2}`, ptr: new(T), err: fmt.Errorf("json: unknown field \"Z\""), disallowUnknownFields: true},
+
+	{in: `{"alpha": "abc", "alphabet": "xyz"}`, ptr: new(U), out: U{Alphabet: "abc"}},
+	{in: `{"alpha": "abc", "alphabet": "xyz"}`, ptr: new(U), err: fmt.Errorf("json: unknown field \"alphabet\""), disallowUnknownFields: true},
+	{in: `{"alpha": "abc"}`, ptr: new(U), out: U{Alphabet: "abc"}},
+	{in: `{"alphabet": "xyz"}`, ptr: new(U), out: U{}},
+	{in: `{"alphabet": "xyz"}`, ptr: new(U), err: fmt.Errorf("json: unknown field \"alphabet\""), disallowUnknownFields: true},
+
+	// syntax errors
+	{in: `{"X": "foo", "Y"}`, err: &SyntaxError{"invalid character '}' after object key", 17}},
+	{in: `[1, 2, 3+]`, err: &SyntaxError{"invalid character '+' after array element", 9}},
+	{in: `{"X":12x}`, err: &SyntaxError{"invalid character 'x' after object key:value pair", 8}, useNumber: true},
+	{in: `[2, 3`, err: &SyntaxError{Err: "unexpected end of JSON input", Offset: 5}},                                                       // MODIFIED
+	{in: `{"F3": -}`, ptr: new(V), out: V{F3: Number("-")}, err: &SyntaxError{Err: "invalid character '}' in numeric literal", Offset: 9}}, // MODIFIED
+
+	// raw value errors
+	{in: "\x01 42", err: &SyntaxError{"invalid character '\\x01' looking for beginning of value", 1}},
+	{in: " 42 \x01", err: &SyntaxError{"invalid character '\\x01' after top-level value", 5}},
+	{in: "\x01 true", err: &SyntaxError{"invalid character '\\x01' looking for beginning of value", 1}},
+	{in: " false \x01", err: &SyntaxError{"invalid character '\\x01' after top-level value", 8}},
+	{in: "\x01 1.2", err: &SyntaxError{"invalid character '\\x01' looking for beginning of value", 1}},
+	{in: " 3.4 \x01", err: &SyntaxError{"invalid character '\\x01' after top-level value", 6}},
+	{in: "\x01 \"string\"", err: &SyntaxError{"invalid character '\\x01' looking for beginning of value", 1}},
+	{in: " \"string\" \x01", err: &SyntaxError{"invalid character '\\x01' after top-level value", 11}},
+
+	// array tests
+	{in: `[1, 2, 3]`, ptr: new([3]int), out: [3]int{1, 2, 3}},
+	{in: `[1, 2, 3]`, ptr: new([1]int), out: [1]int{1}},
+	{in: `[1, 2, 3]`, ptr: new([5]int), out: [5]int{1, 2, 3, 0, 0}},
+	{in: `[1, 2, 3]`, ptr: new(MustNotUnmarshalJSON), err: errors.New("MustNotUnmarshalJSON was used")},
+
+	// empty array to interface test
+	{in: `[]`, ptr: new([]any), out: []any{}},
+	{in: `null`, ptr: new([]any), out: []any(nil)},
+	{in: `{"T":[]}`, ptr: new(map[string]any), out: map[string]any{"T": []any{}}},
+	{in: `{"T":null}`, ptr: new(map[string]any), out: map[string]any{"T": any(nil)}},
+
+	// composite tests
+	{in: allValueIndent, ptr: new(All), out: allValue},
+	{in: allValueCompact, ptr: new(All), out: allValue},
+	{in: allValueIndent, ptr: new(*All), out: &allValue},
+	{in: allValueCompact, ptr: new(*All), out: &allValue},
+	{in: pallValueIndent, ptr: new(All), out: pallValue},
+	{in: pallValueCompact, ptr: new(All), out: pallValue},
+	{in: pallValueIndent, ptr: new(*All), out: &pallValue},
+	{in: pallValueCompact, ptr: new(*All), out: &pallValue},
+
+	// unmarshal interface test
+	{in: `{"T":false}`, ptr: new(unmarshaler), out: umtrue}, // use "false" so test will fail if custom unmarshaler is not called
+	{in: `{"T":false}`, ptr: new(*unmarshaler), out: &umtrue},
+	{in: `[{"T":false}]`, ptr: new([]unmarshaler), out: umslice},
+	{in: `[{"T":false}]`, ptr: new(*[]unmarshaler), out: &umslice},
+	{in: `{"M":{"T":"x:y"}}`, ptr: new(ustruct), out: umstruct},
+
+	// UnmarshalText interface test
+	{in: `"x:y"`, ptr: new(unmarshalerText), out: umtrueXY},
+	{in: `"x:y"`, ptr: new(*unmarshalerText), out: &umtrueXY},
+	{in: `["x:y"]`, ptr: new([]unmarshalerText), out: umsliceXY},
+	{in: `["x:y"]`, ptr: new(*[]unmarshalerText), out: &umsliceXY},
+	{in: `{"M":"x:y"}`, ptr: new(ustructText), out: umstructXY},
+
+	// integer-keyed map test
+	{
+		in:  `{"-1":"a","0":"b","1":"c"}`,
+		ptr: new(map[int]string),
+		out: map[int]string{-1: "a", 0: "b", 1: "c"},
+	},
+	{
+		in:  `{"0":"a","10":"c","9":"b"}`,
+		ptr: new(map[u8]string),
+		out: map[u8]string{0: "a", 9: "b", 10: "c"},
+	},
+	{
+		in:  `{"-9223372036854775808":"min","9223372036854775807":"max"}`,
+		ptr: new(map[int64]string),
+		out: map[int64]string{math.MinInt64: "min", math.MaxInt64: "max"},
+	},
+	{
+		in:  `{"18446744073709551615":"max"}`,
+		ptr: new(map[uint64]string),
+		out: map[uint64]string{math.MaxUint64: "max"},
+	},
+	{
+		in:  `{"0":false,"10":true}`,
+		ptr: new(map[uintptr]bool),
+		out: map[uintptr]bool{0: false, 10: true},
+	},
+
+	// Check that MarshalText and UnmarshalText take precedence
+	// over default integer handling in map keys.
+	{
+		in:  `{"u2":4}`,
+		ptr: new(map[u8marshal]int),
+		out: map[u8marshal]int{2: 4},
+	},
+	{
+		in:  `{"2":4}`,
+		ptr: new(map[u8marshal]int),
+		err: errMissingU8Prefix,
+	},
+
+	// integer-keyed map errors
+	{
+		in:  `{"abc":"abc"}`,
+		ptr: new(map[int]string),
+		err: &UnmarshalTypeError{Value: "number abc", Type: reflect.TypeOf(0), Offset: 2},
+	},
+	{
+		in:  `{"256":"abc"}`,
+		ptr: new(map[uint8]string),
+		err: &UnmarshalTypeError{Value: "number 256", Type: reflect.TypeOf(uint8(0)), Offset: 2},
+	},
+	{
+		in:  `{"128":"abc"}`,
+		ptr: new(map[int8]string),
+		err: &UnmarshalTypeError{Value: "number 128", Type: reflect.TypeOf(int8(0)), Offset: 2},
+	},
+	{
+		in:  `{"-1":"abc"}`,
+		ptr: new(map[uint8]string),
+		err: &UnmarshalTypeError{Value: "number -1", Type: reflect.TypeOf(uint8(0)), Offset: 2},
+	},
+	{
+		in:  `{"F":{"a":2,"3":4}}`,
+		ptr: new(map[string]map[int]int),
+		err: &UnmarshalTypeError{Value: "number a", Type: reflect.TypeOf(int(0)), Offset: 7},
+	},
+	{
+		in:  `{"F":{"a":2,"3":4}}`,
+		ptr: new(map[string]map[uint]int),
+		err: &UnmarshalTypeError{Value: "number a", Type: reflect.TypeOf(uint(0)), Offset: 7},
+	},
+
+	// Map keys can be encoding.TextUnmarshalers.
+	{in: `{"x:y":true}`, ptr: new(map[unmarshalerText]bool), out: ummapXY},
+	// If multiple values for the same key exists, only the most recent value is used.
+	{in: `{"x:y":false,"x:y":true}`, ptr: new(map[unmarshalerText]bool), out: ummapXY},
+
+	{
+		in: `{
+			"Level0": 1,
+			"Level1b": 2,
+			"Level1c": 3,
+			"x": 4,
+			"Level1a": 5,
+			"LEVEL1B": 6,
+			"e": {
+				"Level1a": 8,
+				"Level1b": 9,
+				"Level1c": 10,
+				"Level1d": 11,
+				"x": 12
+			},
+			"Loop1": 13,
+			"Loop2": 14,
+			"X": 15,
+			"Y": 16,
+			"Z": 17,
+			"Q": 18
+		}`,
+		ptr: new(Top),
+		out: Top{
+			Level0: 1,
+			Embed0: Embed0{
+				Level1b: 2,
+				Level1c: 3,
+			},
+			Embed0a: &Embed0a{
+				Level1a: 5,
+				Level1b: 6,
+			},
+			Embed0b: &Embed0b{
+				Level1a: 8,
+				Level1b: 9,
+				Level1c: 10,
+				Level1d: 11,
+				Level1e: 12,
+			},
+			Loop: Loop{
+				Loop1: 13,
+				Loop2: 14,
+			},
+			Embed0p: Embed0p{
+				Point: image.Point{X: 15, Y: 16},
+			},
+			Embed0q: Embed0q{
+				Point: Point{Z: 17},
+			},
+			embed: embed{
+				Q: 18,
+			},
+		},
+	},
+	{
+		in:  `{"hello": 1}`,
+		ptr: new(Ambig),
+		out: Ambig{First: 1},
+	},
+
+	{
+		in:  `{"X": 1,"Y":2}`,
+		ptr: new(S5),
+		out: S5{S8: S8{S9: S9{Y: 2}}},
+	},
+	{
+		in:                    `{"X": 1,"Y":2}`,
+		ptr:                   new(S5),
+		err:                   fmt.Errorf("json: unknown field \"X\""),
+		disallowUnknownFields: true,
+	},
+	{
+		in:  `{"X": 1,"Y":2}`,
+		ptr: new(S10),
+		out: S10{S13: S13{S8: S8{S9: S9{Y: 2}}}},
+	},
+	{
+		in:                    `{"X": 1,"Y":2}`,
+		ptr:                   new(S10),
+		err:                   fmt.Errorf("json: unknown field \"X\""),
+		disallowUnknownFields: true,
+	},
+	{
+		in:  `{"I": 0, "I": null, "J": null}`,
+		ptr: new(DoublePtr),
+		out: DoublePtr{I: nil, J: nil},
+	},
+
+	// invalid UTF-8 is coerced to valid UTF-8.
+	{
+		in:  "\"hello\xffworld\"",
+		ptr: new(string),
+		out: "hello\ufffdworld",
+	},
+	{
+		in:  "\"hello\xc2\xc2world\"",
+		ptr: new(string),
+		out: "hello\ufffd\ufffdworld",
+	},
+	{
+		in:  "\"hello\xc2\xffworld\"",
+		ptr: new(string),
+		out: "hello\ufffd\ufffdworld",
+	},
+	{
+		in:  "\"hello\\ud800world\"",
+		ptr: new(string),
+		out: "hello\ufffdworld",
+	},
+	{
+		in:  "\"hello\\ud800\\ud800world\"",
+		ptr: new(string),
+		out: "hello\ufffd\ufffdworld",
+	},
+	{
+		in:  "\"hello\\ud800\\ud800world\"",
+		ptr: new(string),
+		out: "hello\ufffd\ufffdworld",
+	},
+	{
+		in:  "\"hello\xed\xa0\x80\xed\xb0\x80world\"",
+		ptr: new(string),
+		out: "hello\ufffd\ufffd\ufffd\ufffd\ufffd\ufffdworld",
+	},
+
+	// Used to be issue 8305, but time.Time implements encoding.TextUnmarshaler so this works now.
+	{
+		in:  `{"2009-11-10T23:00:00Z": "hello world"}`,
+		ptr: new(map[time.Time]string),
+		out: map[time.Time]string{time.Date(2009, 11, 10, 23, 0, 0, 0, time.UTC): "hello world"},
+	},
+
+	// issue 8305
+	{
+		in:  `{"2009-11-10T23:00:00Z": "hello world"}`,
+		ptr: new(map[Point]string),
+		err: &UnmarshalTypeError{Value: "object", Type: reflect.TypeOf(map[Point]string{}), Offset: 1},
+	},
+	{
+		in:  `{"asdf": "hello world"}`,
+		ptr: new(map[unmarshaler]string),
+		err: &UnmarshalTypeError{Value: "object", Type: reflect.TypeOf(map[unmarshaler]string{}), Offset: 1},
+	},
+
+	// related to issue 13783.
+	// Go 1.7 changed marshaling a slice of typed byte to use the methods on the byte type,
+	// similar to marshaling a slice of typed int.
+	// These tests check that, assuming the byte type also has valid decoding methods,
+	// either the old base64 string encoding or the new per-element encoding can be
+	// successfully unmarshaled. The custom unmarshalers were accessible in earlier
+	// versions of Go, even though the custom marshaler was not.
+	{
+		in:  `"AQID"`,
+		ptr: new([]byteWithMarshalJSON),
+		out: []byteWithMarshalJSON{1, 2, 3},
+	},
+	{
+		in:     `["Z01","Z02","Z03"]`,
+		ptr:    new([]byteWithMarshalJSON),
+		out:    []byteWithMarshalJSON{1, 2, 3},
+		golden: true,
+	},
+	{
+		in:  `"AQID"`,
+		ptr: new([]byteWithMarshalText),
+		out: []byteWithMarshalText{1, 2, 3},
+	},
+	{
+		in:     `["Z01","Z02","Z03"]`,
+		ptr:    new([]byteWithMarshalText),
+		out:    []byteWithMarshalText{1, 2, 3},
+		golden: true,
+	},
+	{
+		in:  `"AQID"`,
+		ptr: new([]byteWithPtrMarshalJSON),
+		out: []byteWithPtrMarshalJSON{1, 2, 3},
+	},
+	{
+		in:     `["Z01","Z02","Z03"]`,
+		ptr:    new([]byteWithPtrMarshalJSON),
+		out:    []byteWithPtrMarshalJSON{1, 2, 3},
+		golden: true,
+	},
+	{
+		in:  `"AQID"`,
+		ptr: new([]byteWithPtrMarshalText),
+		out: []byteWithPtrMarshalText{1, 2, 3},
+	},
+	{
+		in:     `["Z01","Z02","Z03"]`,
+		ptr:    new([]byteWithPtrMarshalText),
+		out:    []byteWithPtrMarshalText{1, 2, 3},
+		golden: true,
+	},
+
+	// ints work with the marshaler but not the base64 []byte case
+	{
+		in:     `["Z01","Z02","Z03"]`,
+		ptr:    new([]intWithMarshalJSON),
+		out:    []intWithMarshalJSON{1, 2, 3},
+		golden: true,
+	},
+	{
+		in:     `["Z01","Z02","Z03"]`,
+		ptr:    new([]intWithMarshalText),
+		out:    []intWithMarshalText{1, 2, 3},
+		golden: true,
+	},
+	{
+		in:     `["Z01","Z02","Z03"]`,
+		ptr:    new([]intWithPtrMarshalJSON),
+		out:    []intWithPtrMarshalJSON{1, 2, 3},
+		golden: true,
+	},
+	{
+		in:     `["Z01","Z02","Z03"]`,
+		ptr:    new([]intWithPtrMarshalText),
+		out:    []intWithPtrMarshalText{1, 2, 3},
+		golden: true,
+	},
+
+	{in: `0.000001`, ptr: new(float64), out: 0.000001, golden: true},
+	{in: `1e-7`, ptr: new(float64), out: 1e-7, golden: true},
+	{in: `100000000000000000000`, ptr: new(float64), out: 100000000000000000000.0, golden: true},
+	{in: `1e+21`, ptr: new(float64), out: 1e21, golden: true},
+	{in: `-0.000001`, ptr: new(float64), out: -0.000001, golden: true},
+	{in: `-1e-7`, ptr: new(float64), out: -1e-7, golden: true},
+	{in: `-100000000000000000000`, ptr: new(float64), out: -100000000000000000000.0, golden: true},
+	{in: `-1e+21`, ptr: new(float64), out: -1e21, golden: true},
+	{in: `999999999999999900000`, ptr: new(float64), out: 999999999999999900000.0, golden: true},
+	{in: `9007199254740992`, ptr: new(float64), out: 9007199254740992.0, golden: true},
+	{in: `9007199254740993`, ptr: new(float64), out: 9007199254740992.0, golden: false},
+
+	{
+		in:  `{"V": {"F2": "hello"}}`,
+		ptr: new(VOuter),
+		err: &UnmarshalTypeError{
+			Value:  "string",
+			Struct: "V",
+			Field:  "V.F2",
+			Type:   reflect.TypeOf(int32(0)),
+			Offset: 20,
+		},
+	},
+	{
+		in:  `{"V": {"F4": {}, "F2": "hello"}}`,
+		ptr: new(VOuter),
+		err: &UnmarshalTypeError{
+			Value:  "string",
+			Struct: "V",
+			Field:  "V.F2",
+			Type:   reflect.TypeOf(int32(0)),
+			Offset: 30,
+		},
+	},
+
+	// issue 15146.
+	// invalid inputs in wrongStringTests below.
+	{in: `{"B":"true"}`, ptr: new(B), out: B{true}, golden: true},
+	{in: `{"B":"false"}`, ptr: new(B), out: B{false}, golden: true},
+	{in: `{"B": "maybe"}`, ptr: new(B), err: errors.New(`json: invalid use of ,string struct tag, trying to unmarshal "maybe" into bool`)},
+	{in: `{"B": "tru"}`, ptr: new(B), err: errors.New(`json: invalid use of ,string struct tag, trying to unmarshal "tru" into bool`)},
+	{in: `{"B": "False"}`, ptr: new(B), err: errors.New(`json: invalid use of ,string struct tag, trying to unmarshal "False" into bool`)},
+	{in: `{"B": "null"}`, ptr: new(B), out: B{false}},
+	{in: `{"B": "nul"}`, ptr: new(B), err: errors.New(`json: invalid use of ,string struct tag, trying to unmarshal "nul" into bool`)},
+	{in: `{"B": [2, 3]}`, ptr: new(B), err: errors.New(`json: invalid use of ,string struct tag, trying to unmarshal unquoted value into bool`)},
+
+	// additional tests for disallowUnknownFields
+	{
+		in: `{
+			"Level0": 1,
+			"Level1b": 2,
+			"Level1c": 3,
+			"x": 4,
+			"Level1a": 5,
+			"LEVEL1B": 6,
+			"e": {
+				"Level1a": 8,
+				"Level1b": 9,
+				"Level1c": 10,
+				"Level1d": 11,
+				"x": 12
+			},
+			"Loop1": 13,
+			"Loop2": 14,
+			"X": 15,
+			"Y": 16,
+			"Z": 17,
+			"Q": 18,
+			"extra": true
+		}`,
+		ptr:                   new(Top),
+		err:                   fmt.Errorf("json: unknown field \"extra\""),
+		disallowUnknownFields: true,
+	},
+	{
+		in: `{
+			"Level0": 1,
+			"Level1b": 2,
+			"Level1c": 3,
+			"x": 4,
+			"Level1a": 5,
+			"LEVEL1B": 6,
+			"e": {
+				"Level1a": 8,
+				"Level1b": 9,
+				"Level1c": 10,
+				"Level1d": 11,
+				"x": 12,
+				"extra": null
+			},
+			"Loop1": 13,
+			"Loop2": 14,
+			"X": 15,
+			"Y": 16,
+			"Z": 17,
+			"Q": 18
+		}`,
+		ptr:                   new(Top),
+		err:                   fmt.Errorf("json: unknown field \"extra\""),
+		disallowUnknownFields: true,
+	},
+	// issue 26444
+	// UnmarshalTypeError without field & struct values
+	{
+		in:  `{"data":{"test1": "bob", "test2": 123}}`,
+		ptr: new(mapStringToStringData),
+		err: &UnmarshalTypeError{Value: "number", Type: reflect.TypeOf(""), Offset: 37, Struct: "mapStringToStringData", Field: "data"},
+	},
+	{
+		in:  `{"data":{"test1": 123, "test2": "bob"}}`,
+		ptr: new(mapStringToStringData),
+		err: &UnmarshalTypeError{Value: "number", Type: reflect.TypeOf(""), Offset: 21, Struct: "mapStringToStringData", Field: "data"},
+	},
+
+	// trying to decode JSON arrays or objects via TextUnmarshaler
+	{
+		in:  `[1, 2, 3]`,
+		ptr: new(MustNotUnmarshalText),
+		err: &UnmarshalTypeError{Value: "array", Type: reflect.TypeOf(&MustNotUnmarshalText{}), Offset: 1},
+	},
+	{
+		in:  `{"foo": "bar"}`,
+		ptr: new(MustNotUnmarshalText),
+		err: &UnmarshalTypeError{Value: "object", Type: reflect.TypeOf(&MustNotUnmarshalText{}), Offset: 1},
+	},
+	// #22369
+	{
+		in:  `{"PP": {"T": {"Y": "bad-type"}}}`,
+		ptr: new(P),
+		err: &UnmarshalTypeError{
+			Value:  "string",
+			Struct: "T",
+			Field:  "PP.T.Y",
+			Type:   reflect.TypeOf(int(0)),
+			Offset: 29,
+		},
+	},
+	{
+		in:  `{"Ts": [{"Y": 1}, {"Y": 2}, {"Y": "bad-type"}]}`,
+		ptr: new(PP),
+		err: &UnmarshalTypeError{
+			Value:  "string",
+			Struct: "T",
+			Field:  "Ts.Y",
+			Type:   reflect.TypeOf(int(0)),
+			Offset: 29,
+		},
+	},
+	// #14702
+	{
+		in:  `invalid`,
+		ptr: new(Number),
+		err: &SyntaxError{
+			Err:    "invalid character 'i' looking for beginning of value", // MODIFIED
+			Offset: 1,
+		},
+	},
+	{
+		in:  `"invalid"`,
+		ptr: new(Number),
+		err: fmt.Errorf("json: invalid number literal, trying to unmarshal %q into Number", `"invalid"`),
+	},
+	{
+		in:  `{"A":"invalid"}`,
+		ptr: new(struct{ A Number }),
+		err: fmt.Errorf("json: invalid number literal, trying to unmarshal %q into Number", `"invalid"`),
+	},
+	{
+		in: `{"A":"invalid"}`,
+		ptr: new(struct {
+			A Number `json:",string"`
+		}),
+		err: fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into json.Number", `invalid`),
+	},
+	{
+		in:  `{"A":"invalid"}`,
+		ptr: new(map[string]Number),
+		err: fmt.Errorf("json: invalid number literal, trying to unmarshal %q into Number", `"invalid"`),
+	},
+}
+
+func TestMarshal(t *testing.T) {
+	b, err := Marshal(allValue)
+	if err != nil {
+		t.Fatalf("Marshal allValue: %v", err)
+	}
+	if string(b) != allValueCompact {
+		t.Errorf("Marshal allValueCompact")
+		diff(t, b, []byte(allValueCompact))
+		return
+	}
+
+	b, err = Marshal(pallValue)
+	if err != nil {
+		t.Fatalf("Marshal pallValue: %v", err)
+	}
+	if string(b) != pallValueCompact {
+		t.Errorf("Marshal pallValueCompact")
+		diff(t, b, []byte(pallValueCompact))
+		return
+	}
+}
+
+var badUTF8 = []struct {
+	in, out string
+}{
+	{"hello\xffworld", `"hello\ufffdworld"`},
+	{"", `""`},
+	{"\xff", `"\ufffd"`},
+	{"\xff\xff", `"\ufffd\ufffd"`},
+	{"a\xffb", `"a\ufffdb"`},
+	{"\xe6\x97\xa5\xe6\x9c\xac\xff\xaa\x9e", `"日本\ufffd\ufffd\ufffd"`},
+}
+
+func TestMarshalBadUTF8(t *testing.T) {
+	for _, tt := range badUTF8 {
+		b, err := Marshal(tt.in)
+		if string(b) != tt.out || err != nil {
+			t.Errorf("Marshal(%q) = %#q, %v, want %#q, nil", tt.in, b, err, tt.out)
+		}
+	}
+}
+
+func TestMarshalNumberZeroVal(t *testing.T) {
+	var n Number
+	out, err := Marshal(n)
+	if err != nil {
+		t.Fatal(err)
+	}
+	outStr := string(out)
+	if outStr != "0" {
+		t.Fatalf("Invalid zero val for Number: %q", outStr)
+	}
+}
+
+func TestMarshalEmbeds(t *testing.T) {
+	t.Skip() // TODO
+	top := &Top{
+		Level0: 1,
+		Embed0: Embed0{
+			Level1b: 2,
+			Level1c: 3,
+		},
+		Embed0a: &Embed0a{
+			Level1a: 5,
+			Level1b: 6,
+		},
+		Embed0b: &Embed0b{
+			Level1a: 8,
+			Level1b: 9,
+			Level1c: 10,
+			Level1d: 11,
+			Level1e: 12,
+		},
+		Loop: Loop{
+			Loop1: 13,
+			Loop2: 14,
+		},
+		Embed0p: Embed0p{
+			Point: image.Point{X: 15, Y: 16},
+		},
+		Embed0q: Embed0q{
+			Point: Point{Z: 17},
+		},
+		embed: embed{
+			Q: 18,
+		},
+	}
+	b, err := Marshal(top)
+	if err != nil {
+		t.Fatal(err)
+	}
+	want := "{\"Level0\":1,\"Level1b\":2,\"Level1c\":3,\"Level1a\":5,\"LEVEL1B\":6,\"e\":{\"Level1a\":8,\"Level1b\":9,\"Level1c\":10,\"Level1d\":11,\"x\":12},\"Loop1\":13,\"Loop2\":14,\"X\":15,\"Y\":16,\"Z\":17,\"Q\":18}"
+	if string(b) != want {
+		t.Errorf("Wrong marshal result.\n got: %q\nwant: %q", b, want)
+	}
+}
+
+func equalError(a, b error) bool {
+	if a == nil {
+		return b == nil
+	}
+	if b == nil {
+		return a == nil
+	}
+	return true // a.Error() == b.Error() // MODIFIED
+}
+
+func TestUnmarshal(t *testing.T) {
+	t.Skip() // TODO
+	for i, tt := range unmarshalTests {
+		scan := &ReEncoder{
+			Out: io.Discard,
+		}
+		in := []byte(tt.in)
+		if _, err := scan.Write(in); err != nil {
+			if !equalError(err, tt.err) {
+				t.Errorf("#%d: checkValid: %#v\n\n%s", i, err, tt.in)
+				continue
+			}
+		}
+		if tt.ptr == nil {
+			continue
+		}
+
+		typ := reflect.TypeOf(tt.ptr)
+		if typ.Kind() != reflect.Pointer {
+			t.Errorf("#%d: unmarshalTest.ptr %T is not a pointer type", i, tt.ptr)
+			continue
+		}
+		typ = typ.Elem()
+
+		// v = new(right-type)
+		v := reflect.New(typ)
+
+		if !reflect.DeepEqual(tt.ptr, v.Interface()) {
+			// There's no reason for ptr to point to non-zero data,
+			// as we decode into new(right-type), so the data is
+			// discarded.
+			// This can easily mean tests that silently don't test
+			// what they should. To test decoding into existing
+			// data, see TestPrefilled.
+			t.Errorf("#%d: unmarshalTest.ptr %#v is not a pointer to a zero value", i, tt.ptr)
+			continue
+		}
+
+		dec := NewDecoder(bytes.NewReader(in))
+		if tt.useNumber {
+			dec.UseNumber()
+		}
+		if tt.disallowUnknownFields {
+			dec.DisallowUnknownFields()
+		}
+		if err := dec.Decode(v.Interface()); !equalError(err, tt.err) {
+			t.Errorf("#%d: %v, want %v", i, err, tt.err)
+			continue
+		} else if err != nil {
+			continue
+		}
+		if !reflect.DeepEqual(v.Elem().Interface(), tt.out) {
+			t.Errorf("#%d: mismatch\nhave: %#+v\nwant: %#+v\n\n%s", i, v.Elem().Interface(), tt.out, tt.in)
+			data, _ := Marshal(v.Elem().Interface())
+			println(string(data))
+			data, _ = Marshal(tt.out)
+			println(string(data))
+			continue
+		}
+
+		// Check round trip also decodes correctly.
+		if tt.err == nil {
+			enc, err := Marshal(v.Interface())
+			if err != nil {
+				t.Errorf("#%d: error re-marshaling: %v", i, err)
+				continue
+			}
+			if tt.golden && !bytes.Equal(enc, in) {
+				t.Errorf("#%d: remarshal mismatch:\nhave: %s\nwant: %s", i, enc, in)
+			}
+			vv := reflect.New(reflect.TypeOf(tt.ptr).Elem())
+			dec = NewDecoder(bytes.NewReader(enc))
+			if tt.useNumber {
+				dec.UseNumber()
+			}
+			if err := dec.Decode(vv.Interface()); err != nil {
+				t.Errorf("#%d: error re-unmarshaling %#q: %v", i, enc, err)
+				continue
+			}
+			if !reflect.DeepEqual(v.Elem().Interface(), vv.Elem().Interface()) {
+				t.Errorf("#%d: mismatch\nhave: %#+v\nwant: %#+v", i, v.Elem().Interface(), vv.Elem().Interface())
+				t.Errorf("     In: %q", strings.Map(noSpace, string(in)))
+				t.Errorf("Marshal: %q", strings.Map(noSpace, string(enc)))
+				continue
+			}
+		}
+	}
+}
+
+func TestUnmarshalMarshal(t *testing.T) {
+	initBig()
+	var v any
+	if err := Unmarshal(jsonBig, &v); err != nil {
+		t.Fatalf("Unmarshal: %v", err)
+	}
+	b, err := Marshal(v)
+	if err != nil {
+		t.Fatalf("Marshal: %v", err)
+	}
+	if !bytes.Equal(jsonBig, b) {
+		t.Errorf("Marshal jsonBig")
+		diff(t, b, jsonBig)
+		return
+	}
+}
+
+var numberTests = []struct {
+	in       string
+	i        int64
+	intErr   string
+	f        float64
+	floatErr string
+}{
+	{in: "-1.23e1", intErr: "strconv.ParseInt: parsing \"-1.23e1\": invalid syntax", f: -1.23e1},
+	{in: "-12", i: -12, f: -12.0},
+	{in: "1e1000", intErr: "strconv.ParseInt: parsing \"1e1000\": invalid syntax", floatErr: "strconv.ParseFloat: parsing \"1e1000\": value out of range"},
+}
+
+// Independent of Decode, basic coverage of the accessors in Number
+func TestNumberAccessors(t *testing.T) {
+	for _, tt := range numberTests {
+		n := Number(tt.in)
+		if s := n.String(); s != tt.in {
+			t.Errorf("Number(%q).String() is %q", tt.in, s)
+		}
+		if i, err := n.Int64(); err == nil && tt.intErr == "" && i != tt.i {
+			t.Errorf("Number(%q).Int64() is %d", tt.in, i)
+		} else if (err == nil && tt.intErr != "") || (err != nil && err.Error() != tt.intErr) {
+			t.Errorf("Number(%q).Int64() wanted error %q but got: %v", tt.in, tt.intErr, err)
+		}
+		if f, err := n.Float64(); err == nil && tt.floatErr == "" && f != tt.f {
+			t.Errorf("Number(%q).Float64() is %g", tt.in, f)
+		} else if (err == nil && tt.floatErr != "") || (err != nil && err.Error() != tt.floatErr) {
+			t.Errorf("Number(%q).Float64() wanted error %q but got: %v", tt.in, tt.floatErr, err)
+		}
+	}
+}
+
+func TestLargeByteSlice(t *testing.T) {
+	s0 := make([]byte, 2000)
+	for i := range s0 {
+		s0[i] = byte(i)
+	}
+	b, err := Marshal(s0)
+	if err != nil {
+		t.Fatalf("Marshal: %v", err)
+	}
+	var s1 []byte
+	if err := Unmarshal(b, &s1); err != nil {
+		t.Fatalf("Unmarshal: %v", err)
+	}
+	if !bytes.Equal(s0, s1) {
+		t.Errorf("Marshal large byte slice")
+		diff(t, s0, s1)
+	}
+}
+
+type Xint struct {
+	X int
+}
+
+func TestUnmarshalInterface(t *testing.T) {
+	var xint Xint
+	var i any = &xint
+	if err := Unmarshal([]byte(`{"X":1}`), &i); err != nil {
+		t.Fatalf("Unmarshal: %v", err)
+	}
+	if xint.X != 1 {
+		t.Fatalf("Did not write to xint")
+	}
+}
+
+func TestUnmarshalPtrPtr(t *testing.T) {
+	var xint Xint
+	pxint := &xint
+	if err := Unmarshal([]byte(`{"X":1}`), &pxint); err != nil {
+		t.Fatalf("Unmarshal: %v", err)
+	}
+	if xint.X != 1 {
+		t.Fatalf("Did not write to xint")
+	}
+}
+
+func TestEscape(t *testing.T) {
+	const input = `"foobar"<html>` + " [\u2028 \u2029]"
+	const expected = `"\"foobar\"\u003chtml\u003e [\u2028 \u2029]"`
+	b, err := Marshal(input)
+	if err != nil {
+		t.Fatalf("Marshal error: %v", err)
+	}
+	if s := string(b); s != expected {
+		t.Errorf("Encoding of [%s]:\n got [%s]\nwant [%s]", input, s, expected)
+	}
+}
+
+// WrongString is a struct that's misusing the ,string modifier.
+type WrongString struct {
+	Message string `json:"result,string"`
+}
+
+type wrongStringTest struct {
+	in, err string
+}
+
+var wrongStringTests = []wrongStringTest{
+	{`{"result":"x"}`, `json: invalid use of ,string struct tag, trying to unmarshal "x" into string`},
+	{`{"result":"foo"}`, `json: invalid use of ,string struct tag, trying to unmarshal "foo" into string`},
+	{`{"result":"123"}`, `json: invalid use of ,string struct tag, trying to unmarshal "123" into string`},
+	{`{"result":123}`, `json: invalid use of ,string struct tag, trying to unmarshal unquoted value into string`},
+	{`{"result":"\""}`, `json: invalid use of ,string struct tag, trying to unmarshal "\"" into string`},
+	{`{"result":"\"foo"}`, `json: invalid use of ,string struct tag, trying to unmarshal "\"foo" into string`},
+}
+
+// If people misuse the ,string modifier, the error message should be
+// helpful, telling the user that they're doing it wrong.
+func TestErrorMessageFromMisusedString(t *testing.T) {
+	for n, tt := range wrongStringTests {
+		r := strings.NewReader(tt.in)
+		var s WrongString
+		err := NewDecoder(r).Decode(&s)
+		got := fmt.Sprintf("%v", err)
+		if err == nil { // if got != tt.err { // MODIFIED
+			t.Errorf("%d. got err = %q, want %q", n, got, tt.err)
+		}
+	}
+}
+
+func noSpace(c rune) rune {
+	if isSpace(byte(c)) { //only used for ascii
+		return -1
+	}
+	return c
+}
+
+type All struct {
+	Bool    bool
+	Int     int
+	Int8    int8
+	Int16   int16
+	Int32   int32
+	Int64   int64
+	Uint    uint
+	Uint8   uint8
+	Uint16  uint16
+	Uint32  uint32
+	Uint64  uint64
+	Uintptr uintptr
+	Float32 float32
+	Float64 float64
+
+	Foo  string `json:"bar"`
+	Foo2 string `json:"bar2,dummyopt"`
+
+	IntStr     int64   `json:",string"`
+	UintptrStr uintptr `json:",string"`
+
+	PBool    *bool
+	PInt     *int
+	PInt8    *int8
+	PInt16   *int16
+	PInt32   *int32
+	PInt64   *int64
+	PUint    *uint
+	PUint8   *uint8
+	PUint16  *uint16
+	PUint32  *uint32
+	PUint64  *uint64
+	PUintptr *uintptr
+	PFloat32 *float32
+	PFloat64 *float64
+
+	String  string
+	PString *string
+
+	Map   map[string]Small
+	MapP  map[string]*Small
+	PMap  *map[string]Small
+	PMapP *map[string]*Small
+
+	EmptyMap map[string]Small
+	NilMap   map[string]Small
+
+	Slice   []Small
+	SliceP  []*Small
+	PSlice  *[]Small
+	PSliceP *[]*Small
+
+	EmptySlice []Small
+	NilSlice   []Small
+
+	StringSlice []string
+	ByteSlice   []byte
+
+	Small   Small
+	PSmall  *Small
+	PPSmall **Small
+
+	Interface  any
+	PInterface *any
+
+	unexported int
+}
+
+type Small struct {
+	Tag string
+}
+
+var allValue = All{
+	Bool:       true,
+	Int:        2,
+	Int8:       3,
+	Int16:      4,
+	Int32:      5,
+	Int64:      6,
+	Uint:       7,
+	Uint8:      8,
+	Uint16:     9,
+	Uint32:     10,
+	Uint64:     11,
+	Uintptr:    12,
+	Float32:    14.1,
+	Float64:    15.1,
+	Foo:        "foo",
+	Foo2:       "foo2",
+	IntStr:     42,
+	UintptrStr: 44,
+	String:     "16",
+	Map: map[string]Small{
+		"17": {Tag: "tag17"},
+		"18": {Tag: "tag18"},
+	},
+	MapP: map[string]*Small{
+		"19": {Tag: "tag19"},
+		"20": nil,
+	},
+	EmptyMap:    map[string]Small{},
+	Slice:       []Small{{Tag: "tag20"}, {Tag: "tag21"}},
+	SliceP:      []*Small{{Tag: "tag22"}, nil, {Tag: "tag23"}},
+	EmptySlice:  []Small{},
+	StringSlice: []string{"str24", "str25", "str26"},
+	ByteSlice:   []byte{27, 28, 29},
+	Small:       Small{Tag: "tag30"},
+	PSmall:      &Small{Tag: "tag31"},
+	Interface:   5.2,
+}
+
+var pallValue = All{
+	PBool:      &allValue.Bool,
+	PInt:       &allValue.Int,
+	PInt8:      &allValue.Int8,
+	PInt16:     &allValue.Int16,
+	PInt32:     &allValue.Int32,
+	PInt64:     &allValue.Int64,
+	PUint:      &allValue.Uint,
+	PUint8:     &allValue.Uint8,
+	PUint16:    &allValue.Uint16,
+	PUint32:    &allValue.Uint32,
+	PUint64:    &allValue.Uint64,
+	PUintptr:   &allValue.Uintptr,
+	PFloat32:   &allValue.Float32,
+	PFloat64:   &allValue.Float64,
+	PString:    &allValue.String,
+	PMap:       &allValue.Map,
+	PMapP:      &allValue.MapP,
+	PSlice:     &allValue.Slice,
+	PSliceP:    &allValue.SliceP,
+	PPSmall:    &allValue.PSmall,
+	PInterface: &allValue.Interface,
+}
+
+var allValueIndent = `{
+	"Bool": true,
+	"Int": 2,
+	"Int8": 3,
+	"Int16": 4,
+	"Int32": 5,
+	"Int64": 6,
+	"Uint": 7,
+	"Uint8": 8,
+	"Uint16": 9,
+	"Uint32": 10,
+	"Uint64": 11,
+	"Uintptr": 12,
+	"Float32": 14.1,
+	"Float64": 15.1,
+	"bar": "foo",
+	"bar2": "foo2",
+	"IntStr": "42",
+	"UintptrStr": "44",
+	"PBool": null,
+	"PInt": null,
+	"PInt8": null,
+	"PInt16": null,
+	"PInt32": null,
+	"PInt64": null,
+	"PUint": null,
+	"PUint8": null,
+	"PUint16": null,
+	"PUint32": null,
+	"PUint64": null,
+	"PUintptr": null,
+	"PFloat32": null,
+	"PFloat64": null,
+	"String": "16",
+	"PString": null,
+	"Map": {
+		"17": {
+			"Tag": "tag17"
+		},
+		"18": {
+			"Tag": "tag18"
+		}
+	},
+	"MapP": {
+		"19": {
+			"Tag": "tag19"
+		},
+		"20": null
+	},
+	"PMap": null,
+	"PMapP": null,
+	"EmptyMap": {},
+	"NilMap": null,
+	"Slice": [
+		{
+			"Tag": "tag20"
+		},
+		{
+			"Tag": "tag21"
+		}
+	],
+	"SliceP": [
+		{
+			"Tag": "tag22"
+		},
+		null,
+		{
+			"Tag": "tag23"
+		}
+	],
+	"PSlice": null,
+	"PSliceP": null,
+	"EmptySlice": [],
+	"NilSlice": null,
+	"StringSlice": [
+		"str24",
+		"str25",
+		"str26"
+	],
+	"ByteSlice": "Gxwd",
+	"Small": {
+		"Tag": "tag30"
+	},
+	"PSmall": {
+		"Tag": "tag31"
+	},
+	"PPSmall": null,
+	"Interface": 5.2,
+	"PInterface": null
+}`
+
+var allValueCompact = strings.Map(noSpace, allValueIndent)
+
+var pallValueIndent = `{
+	"Bool": false,
+	"Int": 0,
+	"Int8": 0,
+	"Int16": 0,
+	"Int32": 0,
+	"Int64": 0,
+	"Uint": 0,
+	"Uint8": 0,
+	"Uint16": 0,
+	"Uint32": 0,
+	"Uint64": 0,
+	"Uintptr": 0,
+	"Float32": 0,
+	"Float64": 0,
+	"bar": "",
+	"bar2": "",
+        "IntStr": "0",
+	"UintptrStr": "0",
+	"PBool": true,
+	"PInt": 2,
+	"PInt8": 3,
+	"PInt16": 4,
+	"PInt32": 5,
+	"PInt64": 6,
+	"PUint": 7,
+	"PUint8": 8,
+	"PUint16": 9,
+	"PUint32": 10,
+	"PUint64": 11,
+	"PUintptr": 12,
+	"PFloat32": 14.1,
+	"PFloat64": 15.1,
+	"String": "",
+	"PString": "16",
+	"Map": null,
+	"MapP": null,
+	"PMap": {
+		"17": {
+			"Tag": "tag17"
+		},
+		"18": {
+			"Tag": "tag18"
+		}
+	},
+	"PMapP": {
+		"19": {
+			"Tag": "tag19"
+		},
+		"20": null
+	},
+	"EmptyMap": null,
+	"NilMap": null,
+	"Slice": null,
+	"SliceP": null,
+	"PSlice": [
+		{
+			"Tag": "tag20"
+		},
+		{
+			"Tag": "tag21"
+		}
+	],
+	"PSliceP": [
+		{
+			"Tag": "tag22"
+		},
+		null,
+		{
+			"Tag": "tag23"
+		}
+	],
+	"EmptySlice": null,
+	"NilSlice": null,
+	"StringSlice": null,
+	"ByteSlice": null,
+	"Small": {
+		"Tag": ""
+	},
+	"PSmall": null,
+	"PPSmall": {
+		"Tag": "tag31"
+	},
+	"Interface": null,
+	"PInterface": 5.2
+}`
+
+var pallValueCompact = strings.Map(noSpace, pallValueIndent)
+
+func TestRefUnmarshal(t *testing.T) {
+	type S struct {
+		// Ref is defined in encode_test.go.
+		R0 Ref
+		R1 *Ref
+		R2 RefText
+		R3 *RefText
+	}
+	want := S{
+		R0: 12,
+		R1: new(Ref),
+		R2: 13,
+		R3: new(RefText),
+	}
+	*want.R1 = 12
+	*want.R3 = 13
+
+	var got S
+	if err := Unmarshal([]byte(`{"R0":"ref","R1":"ref","R2":"ref","R3":"ref"}`), &got); err != nil {
+		t.Fatalf("Unmarshal: %v", err)
+	}
+	if !reflect.DeepEqual(got, want) {
+		t.Errorf("got %+v, want %+v", got, want)
+	}
+}
+
+// Test that the empty string doesn't panic decoding when ,string is specified
+// Issue 3450
+func TestEmptyString(t *testing.T) {
+	type T2 struct {
+		Number1 int `json:",string"`
+		Number2 int `json:",string"`
+	}
+	data := `{"Number1":"1", "Number2":""}`
+	dec := NewDecoder(strings.NewReader(data))
+	var t2 T2
+	err := dec.Decode(&t2)
+	if err == nil {
+		t.Fatal("Decode: did not return error")
+	}
+	if t2.Number1 != 1 {
+		t.Fatal("Decode: did not set Number1")
+	}
+}
+
+// Test that a null for ,string is not replaced with the previous quoted string (issue 7046).
+// It should also not be an error (issue 2540, issue 8587).
+func TestNullString(t *testing.T) {
+	type T struct {
+		A int  `json:",string"`
+		B int  `json:",string"`
+		C *int `json:",string"`
+	}
+	data := []byte(`{"A": "1", "B": null, "C": null}`)
+	var s T
+	s.B = 1
+	s.C = new(int)
+	*s.C = 2
+	err := Unmarshal(data, &s)
+	if err != nil {
+		t.Fatalf("Unmarshal: %v", err)
+	}
+	if s.B != 1 || s.C != nil {
+		t.Fatalf("after Unmarshal, s.B=%d, s.C=%p, want 1, nil", s.B, s.C)
+	}
+}
+
+func intp(x int) *int {
+	p := new(int)
+	*p = x
+	return p
+}
+
+func intpp(x *int) **int {
+	pp := new(*int)
+	*pp = x
+	return pp
+}
+
+var interfaceSetTests = []struct {
+	pre  any
+	json string
+	post any
+}{
+	{"foo", `"bar"`, "bar"},
+	{"foo", `2`, 2.0},
+	{"foo", `true`, true},
+	{"foo", `null`, nil},
+
+	{nil, `null`, nil},
+	{new(int), `null`, nil},
+	{(*int)(nil), `null`, nil},
+	{new(*int), `null`, new(*int)},
+	{(**int)(nil), `null`, nil},
+	{intp(1), `null`, nil},
+	{intpp(nil), `null`, intpp(nil)},
+	{intpp(intp(1)), `null`, intpp(nil)},
+}
+
+func TestInterfaceSet(t *testing.T) {
+	t.Skip() // TODO
+	for _, tt := range interfaceSetTests {
+		b := struct{ X any }{tt.pre}
+		blob := `{"X":` + tt.json + `}`
+		if err := Unmarshal([]byte(blob), &b); err != nil {
+			t.Errorf("Unmarshal %#q: %v", blob, err)
+			continue
+		}
+		if !reflect.DeepEqual(b.X, tt.post) {
+			t.Errorf("Unmarshal %#q into %#v: X=%#v, want %#v", blob, tt.pre, b.X, tt.post)
+		}
+	}
+}
+
+type NullTest struct {
+	Bool      bool
+	Int       int
+	Int8      int8
+	Int16     int16
+	Int32     int32
+	Int64     int64
+	Uint      uint
+	Uint8     uint8
+	Uint16    uint16
+	Uint32    uint32
+	Uint64    uint64
+	Float32   float32
+	Float64   float64
+	String    string
+	PBool     *bool
+	Map       map[string]string
+	Slice     []string
+	Interface any
+
+	PRaw    *RawMessage
+	PTime   *time.Time
+	PBigInt *big.Int
+	PText   *MustNotUnmarshalText
+	PBuffer *bytes.Buffer // has methods, just not relevant ones
+	PStruct *struct{}
+
+	Raw    RawMessage
+	Time   time.Time
+	BigInt big.Int
+	Text   MustNotUnmarshalText
+	Buffer bytes.Buffer
+	Struct struct{}
+}
+
+// JSON null values should be ignored for primitives and string values instead of resulting in an error.
+// Issue 2540
+func TestUnmarshalNulls(t *testing.T) {
+	// Unmarshal docs:
+	// The JSON null value unmarshals into an interface, map, pointer, or slice
+	// by setting that Go value to nil. Because null is often used in JSON to mean
+	// ``not present,'' unmarshaling a JSON null into any other Go type has no effect
+	// on the value and produces no error.
+
+	jsonData := []byte(`{
+				"Bool"    : null,
+				"Int"     : null,
+				"Int8"    : null,
+				"Int16"   : null,
+				"Int32"   : null,
+				"Int64"   : null,
+				"Uint"    : null,
+				"Uint8"   : null,
+				"Uint16"  : null,
+				"Uint32"  : null,
+				"Uint64"  : null,
+				"Float32" : null,
+				"Float64" : null,
+				"String"  : null,
+				"PBool": null,
+				"Map": null,
+				"Slice": null,
+				"Interface": null,
+				"PRaw": null,
+				"PTime": null,
+				"PBigInt": null,
+				"PText": null,
+				"PBuffer": null,
+				"PStruct": null,
+				"Raw": null,
+				"Time": null,
+				"BigInt": null,
+				"Text": null,
+				"Buffer": null,
+				"Struct": null
+			}`)
+	nulls := NullTest{
+		Bool:      true,
+		Int:       2,
+		Int8:      3,
+		Int16:     4,
+		Int32:     5,
+		Int64:     6,
+		Uint:      7,
+		Uint8:     8,
+		Uint16:    9,
+		Uint32:    10,
+		Uint64:    11,
+		Float32:   12.1,
+		Float64:   13.1,
+		String:    "14",
+		PBool:     new(bool),
+		Map:       map[string]string{},
+		Slice:     []string{},
+		Interface: new(MustNotUnmarshalJSON),
+		PRaw:      new(RawMessage),
+		PTime:     new(time.Time),
+		PBigInt:   new(big.Int),
+		PText:     new(MustNotUnmarshalText),
+		PStruct:   new(struct{}),
+		PBuffer:   new(bytes.Buffer),
+		Raw:       RawMessage("123"),
+		Time:      time.Unix(123456789, 0),
+		BigInt:    *big.NewInt(123),
+	}
+
+	before := nulls.Time.String()
+
+	err := Unmarshal(jsonData, &nulls)
+	if err != nil {
+		t.Errorf("Unmarshal of null values failed: %v", err)
+	}
+	if !nulls.Bool || nulls.Int != 2 || nulls.Int8 != 3 || nulls.Int16 != 4 || nulls.Int32 != 5 || nulls.Int64 != 6 ||
+		nulls.Uint != 7 || nulls.Uint8 != 8 || nulls.Uint16 != 9 || nulls.Uint32 != 10 || nulls.Uint64 != 11 ||
+		nulls.Float32 != 12.1 || nulls.Float64 != 13.1 || nulls.String != "14" {
+		t.Errorf("Unmarshal of null values affected primitives")
+	}
+
+	if nulls.PBool != nil {
+		t.Errorf("Unmarshal of null did not clear nulls.PBool")
+	}
+	if nulls.Map != nil {
+		t.Errorf("Unmarshal of null did not clear nulls.Map")
+	}
+	if nulls.Slice != nil {
+		t.Errorf("Unmarshal of null did not clear nulls.Slice")
+	}
+	if nulls.Interface != nil {
+		t.Errorf("Unmarshal of null did not clear nulls.Interface")
+	}
+	if nulls.PRaw != nil {
+		t.Errorf("Unmarshal of null did not clear nulls.PRaw")
+	}
+	if nulls.PTime != nil {
+		t.Errorf("Unmarshal of null did not clear nulls.PTime")
+	}
+	if nulls.PBigInt != nil {
+		t.Errorf("Unmarshal of null did not clear nulls.PBigInt")
+	}
+	if nulls.PText != nil {
+		t.Errorf("Unmarshal of null did not clear nulls.PText")
+	}
+	if nulls.PBuffer != nil {
+		t.Errorf("Unmarshal of null did not clear nulls.PBuffer")
+	}
+	if nulls.PStruct != nil {
+		t.Errorf("Unmarshal of null did not clear nulls.PStruct")
+	}
+
+	if string(nulls.Raw) != "null" {
+		t.Errorf("Unmarshal of RawMessage null did not record null: %v", string(nulls.Raw))
+	}
+	if nulls.Time.String() != before {
+		t.Errorf("Unmarshal of time.Time null set time to %v", nulls.Time.String())
+	}
+	if nulls.BigInt.String() != "123" {
+		t.Errorf("Unmarshal of big.Int null set int to %v", nulls.BigInt.String())
+	}
+}
+
+type MustNotUnmarshalJSON struct{}
+
+func (x MustNotUnmarshalJSON) UnmarshalJSON(data []byte) error {
+	return errors.New("MustNotUnmarshalJSON was used")
+}
+
+type MustNotUnmarshalText struct{}
+
+func (x MustNotUnmarshalText) UnmarshalText(text []byte) error {
+	return errors.New("MustNotUnmarshalText was used")
+}
+
+func TestStringKind(t *testing.T) {
+	type stringKind string
+
+	var m1, m2 map[stringKind]int
+	m1 = map[stringKind]int{
+		"foo": 42,
+	}
+
+	data, err := Marshal(m1)
+	if err != nil {
+		t.Errorf("Unexpected error marshaling: %v", err)
+	}
+
+	err = Unmarshal(data, &m2)
+	if err != nil {
+		t.Errorf("Unexpected error unmarshaling: %v", err)
+	}
+
+	if !reflect.DeepEqual(m1, m2) {
+		t.Error("Items should be equal after encoding and then decoding")
+	}
+}
+
+// Custom types with []byte as underlying type could not be marshaled
+// and then unmarshaled.
+// Issue 8962.
+func TestByteKind(t *testing.T) {
+	type byteKind []byte
+
+	a := byteKind("hello")
+
+	data, err := Marshal(a)
+	if err != nil {
+		t.Error(err)
+	}
+	if !reflect.DeepEqual(data, []byte(`"aGVsbG8="`)) { // MODIFIED
+		t.Errorf("expected %q == %q", data, `"aGVsbG8="`) // MODIFIED
+	} // MODIFIED
+	var b byteKind
+	err = Unmarshal(data, &b)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !reflect.DeepEqual(a, b) {
+		t.Errorf("expected %v == %v", a, b)
+	}
+}
+
+// The fix for issue 8962 introduced a regression.
+// Issue 12921.
+func TestSliceOfCustomByte(t *testing.T) {
+	type Uint8 uint8
+
+	a := []Uint8("hello")
+
+	data, err := Marshal(a)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !reflect.DeepEqual(data, []byte(`"aGVsbG8="`)) { // MODIFIED
+		t.Errorf("expected %q == %q", data, `"aGVsbG8="`) // MODIFIED
+	} // MODIFIED
+	var b []Uint8
+	err = Unmarshal(data, &b)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !reflect.DeepEqual(a, b) {
+		t.Fatalf("expected %v == %v", a, b)
+	}
+}
+
+var decodeTypeErrorTests = []struct {
+	dest any
+	src  string
+}{
+	{new(string), `{"user": "name"}`}, // issue 4628.
+	{new(error), `{}`},                // issue 4222
+	{new(error), `[]`},
+	{new(error), `""`},
+	{new(error), `123`},
+	{new(error), `true`},
+}
+
+func TestUnmarshalTypeError(t *testing.T) {
+	for _, item := range decodeTypeErrorTests {
+		err := Unmarshal([]byte(item.src), item.dest)
+		if err == nil { // if _, ok := err.(*UnmarshalTypeError); !ok { // MODIFIED
+			t.Errorf("expected type error for Unmarshal(%q, type %T): got %T",
+				item.src, item.dest, err)
+		}
+	}
+}
+
+var unmarshalSyntaxTests = []string{
+	"tru",
+	"fals",
+	"nul",
+	"123e",
+	`"hello`,
+	`[1,2,3`,
+	`{"key":1`,
+	`{"key":1,`,
+}
+
+func TestUnmarshalSyntax(t *testing.T) {
+	var x any
+	for _, src := range unmarshalSyntaxTests {
+		err := Unmarshal([]byte(src), &x)
+		if err == nil { // _, ok := err.(*SyntaxError); !ok { // MODIFIED
+			t.Errorf("expected syntax error for Unmarshal(%q): got %T", src, err)
+		}
+	}
+}
+
+// Test handling of unexported fields that should be ignored.
+// Issue 4660
+type unexportedFields struct {
+	Name string
+	m    map[string]any `json:"-"`
+	m2   map[string]any `json:"abcd"`
+
+	s []int `json:"-"`
+}
+
+func TestUnmarshalUnexported(t *testing.T) {
+	input := `{"Name": "Bob", "m": {"x": 123}, "m2": {"y": 456}, "abcd": {"z": 789}, "s": [2, 3]}`
+	want := &unexportedFields{Name: "Bob"}
+
+	out := &unexportedFields{}
+	err := Unmarshal([]byte(input), out)
+	if err != nil {
+		t.Errorf("got error %v, expected nil", err)
+	}
+	if !reflect.DeepEqual(out, want) {
+		t.Errorf("got %q, want %q", out, want)
+	}
+}
+
+// Time3339 is a time.Time which encodes to and from JSON
+// as an RFC 3339 time in UTC.
+type Time3339 time.Time
+
+func (t *Time3339) UnmarshalJSON(b []byte) error {
+	if len(b) < 2 || b[0] != '"' || b[len(b)-1] != '"' {
+		return fmt.Errorf("types: failed to unmarshal non-string value %q as an RFC 3339 time", b)
+	}
+	tm, err := time.Parse(time.RFC3339, string(b[1:len(b)-1]))
+	if err != nil {
+		return err
+	}
+	*t = Time3339(tm)
+	return nil
+}
+
+func TestUnmarshalJSONLiteralError(t *testing.T) {
+	var t3 Time3339
+	err := Unmarshal([]byte(`"0000-00-00T00:00:00Z"`), &t3)
+	if err == nil {
+		t.Fatalf("expected error; got time %v", time.Time(t3))
+	}
+	if !strings.Contains(err.Error(), "range") {
+		t.Errorf("got err = %v; want out of range error", err)
+	}
+}
+
+// Test that extra object elements in an array do not result in a
+// "data changing underfoot" error.
+// Issue 3717
+func TestSkipArrayObjects(t *testing.T) {
+	json := `[{}]`
+	var dest [0]any
+
+	err := Unmarshal([]byte(json), &dest)
+	if err != nil {
+		t.Errorf("got error %q, want nil", err)
+	}
+}
+
+// Test semantics of pre-filled data, such as struct fields, map elements,
+// slices, and arrays.
+// Issues 4900 and 8837, among others.
+func TestPrefilled(t *testing.T) {
+	// Values here change, cannot reuse table across runs.
+	var prefillTests = []struct {
+		in  string
+		ptr any
+		out any
+	}{
+		{
+			in:  `{"X": 1, "Y": 2}`,
+			ptr: &XYZ{X: float32(3), Y: int16(4), Z: 1.5},
+			out: &XYZ{X: float64(1), Y: float64(2), Z: 1.5},
+		},
+		{
+			in:  `{"X": 1, "Y": 2}`,
+			ptr: &map[string]any{"X": float32(3), "Y": int16(4), "Z": 1.5},
+			out: &map[string]any{"X": float64(1), "Y": float64(2), "Z": 1.5},
+		},
+		{
+			in:  `[2]`,
+			ptr: &[]int{1},
+			out: &[]int{2},
+		},
+		{
+			in:  `[2, 3]`,
+			ptr: &[]int{1},
+			out: &[]int{2, 3},
+		},
+		{
+			in:  `[2, 3]`,
+			ptr: &[...]int{1},
+			out: &[...]int{2},
+		},
+		{
+			in:  `[3]`,
+			ptr: &[...]int{1, 2},
+			out: &[...]int{3, 0},
+		},
+	}
+
+	for _, tt := range prefillTests {
+		ptrstr := fmt.Sprintf("%v", tt.ptr)
+		err := Unmarshal([]byte(tt.in), tt.ptr) // tt.ptr edited here
+		if err != nil {
+			t.Errorf("Unmarshal: %v", err)
+		}
+		if !reflect.DeepEqual(tt.ptr, tt.out) {
+			t.Errorf("Unmarshal(%#q, %s): have %v, want %v", tt.in, ptrstr, tt.ptr, tt.out)
+		}
+	}
+}
+
+var invalidUnmarshalTests = []struct {
+	v    any
+	want string
+}{
+	{nil, "json: Unmarshal(nil)"},
+	{struct{}{}, "json: Unmarshal(non-pointer struct {})"},
+	{(*int)(nil), "json: Unmarshal(nil *int)"},
+}
+
+func TestInvalidUnmarshal(t *testing.T) {
+	buf := []byte(`{"a":"1"}`)
+	for _, tt := range invalidUnmarshalTests {
+		err := Unmarshal(buf, tt.v)
+		if err == nil {
+			t.Errorf("Unmarshal expecting error, got nil")
+			continue
+		}
+		if got := err.Error(); got != tt.want {
+			t.Errorf("Unmarshal = %q; want %q", got, tt.want)
+		}
+	}
+}
+
+var invalidUnmarshalTextTests = []struct {
+	v    any
+	want string
+}{
+	{nil, "json: Unmarshal(nil)"},
+	{struct{}{}, "json: Unmarshal(non-pointer struct {})"},
+	{(*int)(nil), "json: Unmarshal(nil *int)"},
+	{new(net.IP), "json: cannot unmarshal number into Go value of type *net.IP"},
+}
+
+func TestInvalidUnmarshalText(t *testing.T) {
+	buf := []byte(`123`)
+	for _, tt := range invalidUnmarshalTextTests {
+		err := Unmarshal(buf, tt.v)
+		if err == nil {
+			t.Errorf("Unmarshal expecting error, got nil")
+			continue
+		}
+		// if got := err.Error(); got != tt.want { // MODIFIED
+		// 	t.Errorf("Unmarshal = %q; want %q", got, tt.want) // MODIFIED
+		// } // MODIFIED
+	}
+}
+
+// Test that string option is ignored for invalid types.
+// Issue 9812.
+func TestInvalidStringOption(t *testing.T) {
+	num := 0
+	item := struct {
+		T time.Time         `json:",string"`
+		M map[string]string `json:",string"`
+		S []string          `json:",string"`
+		A [1]string         `json:",string"`
+		I any               `json:",string"`
+		P *int              `json:",string"`
+	}{M: make(map[string]string), S: make([]string, 0), I: num, P: &num}
+
+	data, err := Marshal(item)
+	if err != nil {
+		t.Fatalf("Marshal: %v", err)
+	}
+
+	err = Unmarshal(data, &item)
+	if err != nil {
+		t.Fatalf("Unmarshal: %v", err)
+	}
+}
+
+// Test unmarshal behavior with regards to embedded unexported structs.
+//
+// (Issue 21357) If the embedded struct is a pointer and is unallocated,
+// this returns an error because unmarshal cannot set the field.
+//
+// (Issue 24152) If the embedded struct is given an explicit name,
+// ensure that the normal unmarshal logic does not panic in reflect.
+//
+// (Issue 28145) If the embedded struct is given an explicit name and has
+// exported methods, don't cause a panic trying to get its value.
+func TestUnmarshalEmbeddedUnexported(t *testing.T) {
+	t.Skip() // TODO
+	type (
+		embed1 struct{ Q int }
+		embed2 struct{ Q int }
+		embed3 struct {
+			Q int64 `json:",string"`
+		}
+		S1 struct {
+			*embed1
+			R int
+		}
+		S2 struct {
+			*embed1
+			Q int
+		}
+		S3 struct {
+			embed1
+			R int
+		}
+		S4 struct {
+			*embed1
+			embed2
+		}
+		S5 struct {
+			*embed3
+			R int
+		}
+		S6 struct {
+			embed1 `json:"embed1"`
+		}
+		S7 struct {
+			embed1 `json:"embed1"`
+			embed2
+		}
+		S8 struct {
+			embed1 `json:"embed1"`
+			embed2 `json:"embed2"`
+			Q      int
+		}
+		S9 struct {
+			unexportedWithMethods `json:"embed"`
+		}
+	)
+
+	tests := []struct {
+		in  string
+		ptr any
+		out any
+		err error
+	}{{
+		// Error since we cannot set S1.embed1, but still able to set S1.R.
+		in:  `{"R":2,"Q":1}`,
+		ptr: new(S1),
+		out: &S1{R: 2},
+		err: fmt.Errorf("json: cannot set embedded pointer to unexported struct: json.embed1"),
+	}, {
+		// The top level Q field takes precedence.
+		in:  `{"Q":1}`,
+		ptr: new(S2),
+		out: &S2{Q: 1},
+	}, {
+		// No issue with non-pointer variant.
+		in:  `{"R":2,"Q":1}`,
+		ptr: new(S3),
+		out: &S3{embed1: embed1{Q: 1}, R: 2},
+	}, {
+		// No error since both embedded structs have field R, which annihilate each other.
+		// Thus, no attempt is made at setting S4.embed1.
+		in:  `{"R":2}`,
+		ptr: new(S4),
+		out: new(S4),
+	}, {
+		// Error since we cannot set S5.embed1, but still able to set S5.R.
+		in:  `{"R":2,"Q":1}`,
+		ptr: new(S5),
+		out: &S5{R: 2},
+		err: fmt.Errorf("json: cannot set embedded pointer to unexported struct: json.embed3"),
+	}, {
+		// Issue 24152, ensure decodeState.indirect does not panic.
+		in:  `{"embed1": {"Q": 1}}`,
+		ptr: new(S6),
+		out: &S6{embed1{1}},
+	}, {
+		// Issue 24153, check that we can still set forwarded fields even in
+		// the presence of a name conflict.
+		//
+		// This relies on obscure behavior of reflect where it is possible
+		// to set a forwarded exported field on an unexported embedded struct
+		// even though there is a name conflict, even when it would have been
+		// impossible to do so according to Go visibility rules.
+		// Go forbids this because it is ambiguous whether S7.Q refers to
+		// S7.embed1.Q or S7.embed2.Q. Since embed1 and embed2 are unexported,
+		// it should be impossible for an external package to set either Q.
+		//
+		// It is probably okay for a future reflect change to break this.
+		in:  `{"embed1": {"Q": 1}, "Q": 2}`,
+		ptr: new(S7),
+		out: &S7{embed1{1}, embed2{2}},
+	}, {
+		// Issue 24153, similar to the S7 case.
+		in:  `{"embed1": {"Q": 1}, "embed2": {"Q": 2}, "Q": 3}`,
+		ptr: new(S8),
+		out: &S8{embed1{1}, embed2{2}, 3},
+	}, {
+		// Issue 228145, similar to the cases above.
+		in:  `{"embed": {}}`,
+		ptr: new(S9),
+		out: &S9{},
+	}}
+
+	for i, tt := range tests {
+		err := Unmarshal([]byte(tt.in), tt.ptr)
+		if !equalError(err, tt.err) {
+			t.Errorf("#%d: %v, want %v", i, err, tt.err)
+		}
+		if !reflect.DeepEqual(tt.ptr, tt.out) {
+			t.Errorf("#%d: mismatch\ngot:  %#+v\nwant: %#+v", i, tt.ptr, tt.out)
+		}
+	}
+}
+
+func TestUnmarshalErrorAfterMultipleJSON(t *testing.T) {
+	t.Skip() // TODO
+	tests := []struct {
+		in  string
+		err error
+	}{{
+		in:  `1 false null :`,
+		err: &SyntaxError{"invalid character ':' looking for beginning of value", 14},
+	}, {
+		in:  `1 [] [,]`,
+		err: &SyntaxError{"invalid character ',' looking for beginning of value", 7},
+	}, {
+		in:  `1 [] [true:]`,
+		err: &SyntaxError{"invalid character ':' after array element", 11},
+	}, {
+		in:  `1  {}    {"x"=}`,
+		err: &SyntaxError{"invalid character '=' after object key", 14},
+	}, {
+		in:  `falsetruenul#`,
+		err: &SyntaxError{"invalid character '#' in literal null (expecting 'l')", 13},
+	}}
+	for i, tt := range tests {
+		dec := NewDecoder(strings.NewReader(tt.in))
+		var err error
+		for {
+			var v any
+			if err = dec.Decode(&v); err != nil {
+				break
+			}
+		}
+		if !reflect.DeepEqual(err, tt.err) {
+			t.Errorf("#%d: got %#v, want %#v", i, err, tt.err)
+		}
+	}
+}
+
+type unmarshalPanic struct{}
+
+func (unmarshalPanic) UnmarshalJSON([]byte) error { panic(0xdead) }
+
+func TestUnmarshalPanic(t *testing.T) {
+	defer func() {
+		if got := recover(); !reflect.DeepEqual(got, 0xdead) {
+			t.Errorf("panic() = (%T)(%v), want 0xdead", got, got)
+		}
+	}()
+	Unmarshal([]byte("{}"), &unmarshalPanic{})
+	t.Fatalf("Unmarshal should have panicked")
+}
+
+// The decoder used to hang if decoding into an interface pointing to its own address.
+// See golang.org/issues/31740.
+func TestUnmarshalRecursivePointer(t *testing.T) {
+	t.Skip() // TODO
+	var v any
+	v = &v
+	data := []byte(`{"a": "b"}`)
+
+	if err := Unmarshal(data, v); err != nil {
+		t.Fatal(err)
+	}
+}
+
+type textUnmarshalerString string
+
+func (m *textUnmarshalerString) UnmarshalText(text []byte) error {
+	*m = textUnmarshalerString(strings.ToLower(string(text)))
+	return nil
+}
+
+// Test unmarshal to a map, where the map key is a user defined type.
+// See golang.org/issues/34437.
+func TestUnmarshalMapWithTextUnmarshalerStringKey(t *testing.T) {
+	var p map[textUnmarshalerString]string
+	if err := Unmarshal([]byte(`{"FOO": "1"}`), &p); err != nil {
+		t.Fatalf("Unmarshal unexpected error: %v", err)
+	}
+
+	if _, ok := p["foo"]; !ok {
+		t.Errorf(`Key "foo" does not exist in map: %v`, p)
+	}
+}
+
+func TestUnmarshalRescanLiteralMangledUnquote(t *testing.T) {
+	// See golang.org/issues/38105.
+	var p map[textUnmarshalerString]string
+	if err := Unmarshal([]byte(`{"开源":"12345开源"}`), &p); err != nil {
+		t.Fatalf("Unmarshal unexpected error: %v", err)
+	}
+	if _, ok := p["开源"]; !ok {
+		t.Errorf(`Key "开源" does not exist in map: %v`, p)
+	}
+
+	// See golang.org/issues/38126.
+	type T struct {
+		F1 string `json:"F1,string"`
+	}
+	t1 := T{"aaa\tbbb"}
+
+	b, err := Marshal(t1)
+	if err != nil {
+		t.Fatalf("Marshal unexpected error: %v", err)
+	}
+	var t2 T
+	if err := Unmarshal(b, &t2); err != nil {
+		t.Fatalf("Unmarshal unexpected error: %v", err)
+	}
+	if t1 != t2 {
+		t.Errorf("Marshal and Unmarshal roundtrip mismatch: want %q got %q", t1, t2)
+	}
+
+	// See golang.org/issues/39555.
+	input := map[textUnmarshalerString]string{"FOO": "", `"`: ""}
+
+	encoded, err := Marshal(input)
+	if err != nil {
+		t.Fatalf("Marshal unexpected error: %v", err)
+	}
+	var got map[textUnmarshalerString]string
+	if err := Unmarshal(encoded, &got); err != nil {
+		t.Fatalf("Unmarshal unexpected error: %v", err)
+	}
+	want := map[textUnmarshalerString]string{"foo": "", `"`: ""}
+	if !reflect.DeepEqual(want, got) {
+		t.Fatalf("Unexpected roundtrip result:\nwant: %q\ngot:  %q", want, got)
+	}
+}
+
+func TestUnmarshalMaxDepth(t *testing.T) {
+	t.Skip() // TODO
+	testcases := []struct {
+		name        string
+		data        string
+		errMaxDepth bool
+	}{
+		{
+			name:        "ArrayUnderMaxNestingDepth",
+			data:        `{"a":` + strings.Repeat(`[`, 10000-1) + strings.Repeat(`]`, 10000-1) + `}`,
+			errMaxDepth: false,
+		},
+		{
+			name:        "ArrayOverMaxNestingDepth",
+			data:        `{"a":` + strings.Repeat(`[`, 10000) + strings.Repeat(`]`, 10000) + `}`,
+			errMaxDepth: true,
+		},
+		{
+			name:        "ArrayOverStackDepth",
+			data:        `{"a":` + strings.Repeat(`[`, 3000000) + strings.Repeat(`]`, 3000000) + `}`,
+			errMaxDepth: true,
+		},
+		{
+			name:        "ObjectUnderMaxNestingDepth",
+			data:        `{"a":` + strings.Repeat(`{"a":`, 10000-1) + `0` + strings.Repeat(`}`, 10000-1) + `}`,
+			errMaxDepth: false,
+		},
+		{
+			name:        "ObjectOverMaxNestingDepth",
+			data:        `{"a":` + strings.Repeat(`{"a":`, 10000) + `0` + strings.Repeat(`}`, 10000) + `}`,
+			errMaxDepth: true,
+		},
+		{
+			name:        "ObjectOverStackDepth",
+			data:        `{"a":` + strings.Repeat(`{"a":`, 3000000) + `0` + strings.Repeat(`}`, 3000000) + `}`,
+			errMaxDepth: true,
+		},
+	}
+
+	targets := []struct {
+		name     string
+		newValue func() any
+	}{
+		{
+			name: "unstructured",
+			newValue: func() any {
+				var v any
+				return &v
+			},
+		},
+		{
+			name: "typed named field",
+			newValue: func() any {
+				v := struct {
+					A any `json:"a"`
+				}{}
+				return &v
+			},
+		},
+		{
+			name: "typed missing field",
+			newValue: func() any {
+				v := struct {
+					B any `json:"b"`
+				}{}
+				return &v
+			},
+		},
+		{
+			name: "custom unmarshaler",
+			newValue: func() any {
+				v := unmarshaler{}
+				return &v
+			},
+		},
+	}
+
+	for _, tc := range testcases {
+		for _, target := range targets {
+			t.Run(target.name+"-"+tc.name, func(t *testing.T) {
+				err := Unmarshal([]byte(tc.data), target.newValue())
+				if !tc.errMaxDepth {
+					if err != nil {
+						t.Errorf("unexpected error: %v", err)
+					}
+				} else {
+					if err == nil {
+						t.Errorf("expected error containing 'exceeded max depth', got none")
+					} else if !strings.Contains(err.Error(), "exceeded max depth") {
+						t.Errorf("expected error containing 'exceeded max depth', got: %v", err)
+					}
+				}
+			})
+		}
+	}
+}
diff --git a/compat/json/borrowed_encode_test.go b/compat/json/borrowed_encode_test.go
new file mode 100644
index 0000000..9659910
--- /dev/null
+++ b/compat/json/borrowed_encode_test.go
@@ -0,0 +1,1208 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package lowmemjson // MODIFIED
+
+import (
+	"bytes"
+	"encoding"
+	"fmt"
+	"log"
+	"math"
+	"reflect"
+	"regexp"
+	"strconv"
+	"testing"
+	"unicode"
+)
+
+type Optionals struct {
+	Sr string `json:"sr"`
+	So string `json:"so,omitempty"`
+	Sw string `json:"-"`
+
+	Ir int `json:"omitempty"` // actually named omitempty, not an option
+	Io int `json:"io,omitempty"`
+
+	Slr []string `json:"slr,random"` //nolint:staticcheck // testing handling of unknown options // MODIFIED
+	Slo []string `json:"slo,omitempty"`
+
+	Mr map[string]any `json:"mr"`
+	Mo map[string]any `json:",omitempty"`
+
+	Fr float64 `json:"fr"`
+	Fo float64 `json:"fo,omitempty"`
+
+	Br bool `json:"br"`
+	Bo bool `json:"bo,omitempty"`
+
+	Ur uint `json:"ur"`
+	Uo uint `json:"uo,omitempty"`
+
+	Str struct{} `json:"str"`
+	Sto struct{} `json:"sto,omitempty"`
+}
+
+var optionalsExpected = `{
+ "sr": "",
+ "omitempty": 0,
+ "slr": null,
+ "mr": {},
+ "fr": 0,
+ "br": false,
+ "ur": 0,
+ "str": {},
+ "sto": {}
+}`
+
+func TestOmitEmpty(t *testing.T) {
+	var o Optionals
+	o.Sw = "something"
+	o.Mr = map[string]any{}
+	o.Mo = map[string]any{}
+
+	got, err := MarshalIndent(&o, "", " ")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got := string(got); got != optionalsExpected {
+		t.Errorf(" got: %s\nwant: %s\n", got, optionalsExpected)
+	}
+}
+
+type StringTag struct {
+	BoolStr    bool    `json:",string"`
+	IntStr     int64   `json:",string"`
+	UintptrStr uintptr `json:",string"`
+	StrStr     string  `json:",string"`
+	NumberStr  Number  `json:",string"`
+}
+
+func TestRoundtripStringTag(t *testing.T) {
+	tests := []struct {
+		name string
+		in   StringTag
+		want string // empty to just test that we roundtrip
+	}{
+		{
+			name: "AllTypes",
+			in: StringTag{
+				BoolStr:    true,
+				IntStr:     42,
+				UintptrStr: 44,
+				StrStr:     "xzbit",
+				NumberStr:  "46",
+			},
+			want: `{
+				"BoolStr": "true",
+				"IntStr": "42",
+				"UintptrStr": "44",
+				"StrStr": "\"xzbit\"",
+				"NumberStr": "46"
+			}`,
+		},
+		{
+			// See golang.org/issues/38173.
+			name: "StringDoubleEscapes",
+			in: StringTag{
+				StrStr:    "\b\f\n\r\t\"\\",
+				NumberStr: "0", // just to satisfy the roundtrip
+			},
+			want: `{
+				"BoolStr": "false",
+				"IntStr": "0",
+				"UintptrStr": "0",
+				"StrStr": "\"\\u0008\\u000c\\n\\r\\t\\\"\\\\\"",
+				"NumberStr": "0"
+			}`,
+		},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			// Indent with a tab prefix to make the multi-line string
+			// literals in the table nicer to read.
+			got, err := MarshalIndent(&test.in, "\t\t\t", "\t")
+			if err != nil {
+				t.Fatal(err)
+			}
+			if got := string(got); got != test.want {
+				t.Fatalf(" got: %s\nwant: %s\n", got, test.want)
+			}
+
+			// Verify that it round-trips.
+			var s2 StringTag
+			if err := Unmarshal(got, &s2); err != nil {
+				t.Fatalf("Decode: %v", err)
+			}
+			if !reflect.DeepEqual(test.in, s2) {
+				t.Fatalf("decode didn't match.\nsource: %#v\nEncoded as:\n%s\ndecode: %#v", test.in, string(got), s2)
+			}
+		})
+	}
+}
+
+// byte slices are special even if they're renamed types.
+type renamedByte byte
+type renamedByteSlice []byte
+type renamedRenamedByteSlice []renamedByte
+
+func TestEncodeRenamedByteSlice(t *testing.T) {
+	s := renamedByteSlice("abc")
+	result, err := Marshal(s)
+	if err != nil {
+		t.Fatal(err)
+	}
+	expect := `"YWJj"`
+	if string(result) != expect {
+		t.Errorf(" got %s want %s", result, expect)
+	}
+	r := renamedRenamedByteSlice("abc")
+	result, err = Marshal(r)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if string(result) != expect {
+		t.Errorf(" got %s want %s", result, expect)
+	}
+}
+
+type SamePointerNoCycle struct {
+	Ptr1, Ptr2 *SamePointerNoCycle
+}
+
+var samePointerNoCycle = &SamePointerNoCycle{}
+
+type PointerCycle struct {
+	Ptr *PointerCycle
+}
+
+var pointerCycle = &PointerCycle{}
+
+type PointerCycleIndirect struct {
+	Ptrs []any
+}
+
+type RecursiveSlice []RecursiveSlice
+
+var (
+	pointerCycleIndirect = &PointerCycleIndirect{}
+	mapCycle             = make(map[string]any)
+	sliceCycle           = []any{nil}
+	sliceNoCycle         = []any{nil, nil}
+	recursiveSliceCycle  = []RecursiveSlice{nil}
+)
+
+func init() {
+	ptr := &SamePointerNoCycle{}
+	samePointerNoCycle.Ptr1 = ptr
+	samePointerNoCycle.Ptr2 = ptr
+
+	pointerCycle.Ptr = pointerCycle
+	pointerCycleIndirect.Ptrs = []any{pointerCycleIndirect}
+
+	mapCycle["x"] = mapCycle
+	sliceCycle[0] = sliceCycle
+	sliceNoCycle[1] = sliceNoCycle[:1]
+	for i := startDetectingCyclesAfter; i > 0; i-- {
+		sliceNoCycle = []any{sliceNoCycle}
+	}
+	recursiveSliceCycle[0] = recursiveSliceCycle
+}
+
+func TestSamePointerNoCycle(t *testing.T) {
+	if _, err := Marshal(samePointerNoCycle); err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+}
+
+func TestSliceNoCycle(t *testing.T) {
+	if _, err := Marshal(sliceNoCycle); err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+}
+
+var unsupportedValues = []any{
+	math.NaN(),
+	math.Inf(-1),
+	math.Inf(1),
+	//pointerCycle, // MODIFIED
+	//pointerCycleIndirect, // MODIFIED
+	//mapCycle, // MODIFIED
+	//sliceCycle, // MODIFIED
+	//recursiveSliceCycle, // MODIFIED
+}
+
+func TestUnsupportedValues(t *testing.T) {
+	for _, v := range unsupportedValues {
+		if _, err := Marshal(v); err != nil {
+			if _, ok := err.(*UnsupportedValueError); !ok {
+				t.Errorf("for %v, got %T want UnsupportedValueError", v, err)
+			}
+		} else {
+			t.Errorf("for %v, expected error", v)
+		}
+	}
+}
+
+// Issue 43207
+func TestMarshalTextFloatMap(t *testing.T) {
+	m := map[textfloat]string{
+		textfloat(math.NaN()): "1",
+		textfloat(math.NaN()): "1",
+	}
+	got, err := Marshal(m)
+	if err != nil {
+		t.Errorf("Marshal() error: %v", err)
+	}
+	want := `{"TF:NaN":"1","TF:NaN":"1"}`
+	if string(got) != want {
+		t.Errorf("Marshal() = %s, want %s", got, want)
+	}
+}
+
+// Ref has Marshaler and Unmarshaler methods with pointer receiver.
+type Ref int
+
+func (*Ref) MarshalJSON() ([]byte, error) {
+	return []byte(`"ref"`), nil
+}
+
+func (r *Ref) UnmarshalJSON([]byte) error {
+	*r = 12
+	return nil
+}
+
+// Val has Marshaler methods with value receiver.
+type Val int
+
+func (Val) MarshalJSON() ([]byte, error) {
+	return []byte(`"val"`), nil
+}
+
+// RefText has Marshaler and Unmarshaler methods with pointer receiver.
+type RefText int
+
+func (*RefText) MarshalText() ([]byte, error) {
+	return []byte(`"ref"`), nil
+}
+
+func (r *RefText) UnmarshalText([]byte) error {
+	*r = 13
+	return nil
+}
+
+// ValText has Marshaler methods with value receiver.
+type ValText int
+
+func (ValText) MarshalText() ([]byte, error) {
+	return []byte(`"val"`), nil
+}
+
+func TestRefValMarshal(t *testing.T) {
+	var s = struct {
+		R0 Ref
+		R1 *Ref
+		R2 RefText
+		R3 *RefText
+		V0 Val
+		V1 *Val
+		V2 ValText
+		V3 *ValText
+	}{
+		R0: 12,
+		R1: new(Ref),
+		R2: 14,
+		R3: new(RefText),
+		V0: 13,
+		V1: new(Val),
+		V2: 15,
+		V3: new(ValText),
+	}
+	const want = `{"R0":"ref","R1":"ref","R2":"\"ref\"","R3":"\"ref\"","V0":"val","V1":"val","V2":"\"val\"","V3":"\"val\""}`
+	b, err := Marshal(&s)
+	if err != nil {
+		t.Fatalf("Marshal: %v", err)
+	}
+	if got := string(b); got != want {
+		t.Errorf("got %q, want %q", got, want)
+	}
+}
+
+// C implements Marshaler and returns unescaped JSON.
+type C int
+
+func (C) MarshalJSON() ([]byte, error) {
+	return []byte(`"<&>"`), nil
+}
+
+// CText implements Marshaler and returns unescaped text.
+type CText int
+
+func (CText) MarshalText() ([]byte, error) {
+	return []byte(`"<&>"`), nil
+}
+
+func TestMarshalerEscaping(t *testing.T) {
+	t.Skip() // MODIFIED
+	var c C
+	want := `"\u003c\u0026\u003e"`
+	b, err := Marshal(c)
+	if err != nil {
+		t.Fatalf("Marshal(c): %v", err)
+	}
+	if got := string(b); got != want {
+		t.Errorf("Marshal(c) = %#q, want %#q", got, want)
+	}
+
+	var ct CText
+	want = `"\"\u003c\u0026\u003e\""`
+	b, err = Marshal(ct)
+	if err != nil {
+		t.Fatalf("Marshal(ct): %v", err)
+	}
+	if got := string(b); got != want {
+		t.Errorf("Marshal(ct) = %#q, want %#q", got, want)
+	}
+}
+
+func TestAnonymousFields(t *testing.T) {
+	tests := []struct {
+		label     string     // Test name
+		makeInput func() any // Function to create input value
+		want      string     // Expected JSON output
+	}{{
+		// Both S1 and S2 have a field named X. From the perspective of S,
+		// it is ambiguous which one X refers to.
+		// This should not serialize either field.
+		label: "AmbiguousField",
+		makeInput: func() any {
+			type (
+				S1 struct{ x, X int }
+				S2 struct{ x, X int }
+				S  struct {
+					S1
+					S2
+				}
+			)
+			return S{S1{1, 2}, S2{3, 4}}
+		},
+		want: `{}`,
+	}, {
+		label: "DominantField",
+		// Both S1 and S2 have a field named X, but since S has an X field as
+		// well, it takes precedence over S1.X and S2.X.
+		makeInput: func() any {
+			type (
+				S1 struct{ x, X int }
+				S2 struct{ x, X int }
+				S  struct {
+					S1
+					S2
+					x, X int
+				}
+			)
+			return S{S1{1, 2}, S2{3, 4}, 5, 6}
+		},
+		want: `{"X":6}`,
+	}, {
+		// Unexported embedded field of non-struct type should not be serialized.
+		label: "UnexportedEmbeddedInt",
+		makeInput: func() any {
+			type (
+				myInt int
+				S     struct{ myInt }
+			)
+			return S{5}
+		},
+		want: `{}`,
+	}, {
+		// Exported embedded field of non-struct type should be serialized.
+		label: "ExportedEmbeddedInt",
+		makeInput: func() any {
+			type (
+				MyInt int
+				S     struct{ MyInt }
+			)
+			return S{5}
+		},
+		want: `{"MyInt":5}`,
+	}, {
+		// Unexported embedded field of pointer to non-struct type
+		// should not be serialized.
+		label: "UnexportedEmbeddedIntPointer",
+		makeInput: func() any {
+			type (
+				myInt int
+				S     struct{ *myInt }
+			)
+			s := S{new(myInt)}
+			*s.myInt = 5
+			return s
+		},
+		want: `{}`,
+	}, {
+		// Exported embedded field of pointer to non-struct type
+		// should be serialized.
+		label: "ExportedEmbeddedIntPointer",
+		makeInput: func() any {
+			type (
+				MyInt int
+				S     struct{ *MyInt }
+			)
+			s := S{new(MyInt)}
+			*s.MyInt = 5
+			return s
+		},
+		want: `{"MyInt":5}`,
+	}, {
+		// Exported fields of embedded structs should have their
+		// exported fields be serialized regardless of whether the struct types
+		// themselves are exported.
+		label: "EmbeddedStruct",
+		makeInput: func() any {
+			type (
+				s1 struct{ x, X int }
+				S2 struct{ y, Y int }
+				S  struct {
+					s1
+					S2
+				}
+			)
+			return S{s1{1, 2}, S2{3, 4}}
+		},
+		want: `{"X":2,"Y":4}`,
+	}, {
+		// Exported fields of pointers to embedded structs should have their
+		// exported fields be serialized regardless of whether the struct types
+		// themselves are exported.
+		label: "EmbeddedStructPointer",
+		makeInput: func() any {
+			type (
+				s1 struct{ x, X int }
+				S2 struct{ y, Y int }
+				S  struct {
+					*s1
+					*S2
+				}
+			)
+			return S{&s1{1, 2}, &S2{3, 4}}
+		},
+		want: `{"X":2,"Y":4}`,
+	}, {
+		// Exported fields on embedded unexported structs at multiple levels
+		// of nesting should still be serialized.
+		label: "NestedStructAndInts",
+		makeInput: func() any {
+			type (
+				MyInt1 int
+				MyInt2 int
+				myInt  int
+				s2     struct {
+					MyInt2
+					myInt
+				}
+				s1 struct {
+					MyInt1
+					myInt
+					s2
+				}
+				S struct {
+					s1
+					myInt
+				}
+			)
+			return S{s1{1, 2, s2{3, 4}}, 6}
+		},
+		want: `{"MyInt1":1,"MyInt2":3}`,
+	}, {
+		// If an anonymous struct pointer field is nil, we should ignore
+		// the embedded fields behind it. Not properly doing so may
+		// result in the wrong output or reflect panics.
+		label: "EmbeddedFieldBehindNilPointer",
+		makeInput: func() any {
+			type (
+				S2 struct{ Field string }
+				S  struct{ *S2 }
+			)
+			return S{}
+		},
+		want: `{}`,
+	}}
+
+	for _, tt := range tests {
+		t.Run(tt.label, func(t *testing.T) {
+			b, err := Marshal(tt.makeInput())
+			if err != nil {
+				t.Fatalf("Marshal() = %v, want nil error", err)
+			}
+			if string(b) != tt.want {
+				t.Fatalf("Marshal() = %q, want %q", b, tt.want)
+			}
+		})
+	}
+}
+
+type BugA struct {
+	S string
+}
+
+type BugB struct {
+	BugA
+	S string
+}
+
+type BugC struct {
+	S string
+}
+
+// Legal Go: We never use the repeated embedded field (S).
+type BugX struct {
+	A int
+	BugA
+	BugB
+}
+
+// golang.org/issue/16042.
+// Even if a nil interface value is passed in, as long as
+// it implements Marshaler, it should be marshaled.
+type nilJSONMarshaler string
+
+func (nm *nilJSONMarshaler) MarshalJSON() ([]byte, error) {
+	if nm == nil {
+		return Marshal("0zenil0")
+	}
+	return Marshal("zenil:" + string(*nm))
+}
+
+// golang.org/issue/34235.
+// Even if a nil interface value is passed in, as long as
+// it implements encoding.TextMarshaler, it should be marshaled.
+type nilTextMarshaler string
+
+func (nm *nilTextMarshaler) MarshalText() ([]byte, error) {
+	if nm == nil {
+		return []byte("0zenil0"), nil
+	}
+	return []byte("zenil:" + string(*nm)), nil
+}
+
+// See golang.org/issue/16042 and golang.org/issue/34235.
+func TestNilMarshal(t *testing.T) {
+	testCases := []struct {
+		v    any
+		want string
+	}{
+		{v: nil, want: `null`},
+		{v: new(float64), want: `0`},
+		{v: []any(nil), want: `null`},
+		{v: []string(nil), want: `null`},
+		{v: map[string]string(nil), want: `null`},
+		{v: []byte(nil), want: `null`},
+		{v: struct{ M string }{"gopher"}, want: `{"M":"gopher"}`},
+		{v: struct{ M Marshaler }{}, want: `{"M":null}`},
+		{v: struct{ M Marshaler }{(*nilJSONMarshaler)(nil)}, want: `{"M":"0zenil0"}`},
+		{v: struct{ M any }{(*nilJSONMarshaler)(nil)}, want: `{"M":null}`},
+		{v: struct{ M encoding.TextMarshaler }{}, want: `{"M":null}`},
+		{v: struct{ M encoding.TextMarshaler }{(*nilTextMarshaler)(nil)}, want: `{"M":"0zenil0"}`},
+		{v: struct{ M any }{(*nilTextMarshaler)(nil)}, want: `{"M":null}`},
+	}
+
+	for _, tt := range testCases {
+		out, err := Marshal(tt.v)
+		if err != nil || string(out) != tt.want {
+			t.Errorf("Marshal(%#v) = %#q, %#v, want %#q, nil", tt.v, out, err, tt.want)
+			continue
+		}
+	}
+}
+
+// Issue 5245.
+func TestEmbeddedBug(t *testing.T) {
+	v := BugB{
+		BugA{"A"},
+		"B",
+	}
+	b, err := Marshal(v)
+	if err != nil {
+		t.Fatal("Marshal:", err)
+	}
+	want := `{"S":"B"}`
+	got := string(b)
+	if got != want {
+		t.Fatalf("Marshal: got %s want %s", got, want)
+	}
+	// Now check that the duplicate field, S, does not appear.
+	x := BugX{
+		A: 23,
+	}
+	b, err = Marshal(x)
+	if err != nil {
+		t.Fatal("Marshal:", err)
+	}
+	want = `{"A":23}`
+	got = string(b)
+	if got != want {
+		t.Fatalf("Marshal: got %s want %s", got, want)
+	}
+}
+
+type BugD struct { // Same as BugA after tagging.
+	XXX string `json:"S"`
+}
+
+// BugD's tagged S field should dominate BugA's.
+type BugY struct {
+	BugA
+	BugD
+}
+
+// Test that a field with a tag dominates untagged fields.
+func TestTaggedFieldDominates(t *testing.T) {
+	v := BugY{
+		BugA{"BugA"},
+		BugD{"BugD"},
+	}
+	b, err := Marshal(v)
+	if err != nil {
+		t.Fatal("Marshal:", err)
+	}
+	want := `{"S":"BugD"}`
+	got := string(b)
+	if got != want {
+		t.Fatalf("Marshal: got %s want %s", got, want)
+	}
+}
+
+// There are no tags here, so S should not appear.
+type BugZ struct {
+	BugA
+	BugC
+	BugY // Contains a tagged S field through BugD; should not dominate.
+}
+
+func TestDuplicatedFieldDisappears(t *testing.T) {
+	v := BugZ{
+		BugA{"BugA"},
+		BugC{"BugC"},
+		BugY{
+			BugA{"nested BugA"},
+			BugD{"nested BugD"},
+		},
+	}
+	b, err := Marshal(v)
+	if err != nil {
+		t.Fatal("Marshal:", err)
+	}
+	want := `{}`
+	got := string(b)
+	if got != want {
+		t.Fatalf("Marshal: got %s want %s", got, want)
+	}
+}
+
+func TestStringBytes(t *testing.T) {
+	t.Parallel()
+	// Test that encodeState.stringBytes and encodeState.string use the same encoding.
+	var r []rune
+	for i := '\u0000'; i <= unicode.MaxRune; i++ {
+		if testing.Short() && i > 1000 {
+			i = unicode.MaxRune
+		}
+		r = append(r, i)
+	}
+	s := string(r) + "\xff\xff\xffhello" // some invalid UTF-8 too
+
+	for _, escapeHTML := range []bool{true, false} {
+		es := &encodeState{}
+		es.string(s, escapeHTML)
+
+		esBytes := &encodeState{}
+		esBytes.stringBytes([]byte(s), escapeHTML)
+
+		enc := es.Buffer.String()
+		encBytes := esBytes.Buffer.String()
+		if enc != encBytes {
+			i := 0
+			for i < len(enc) && i < len(encBytes) && enc[i] == encBytes[i] {
+				i++
+			}
+			enc = enc[i:]
+			encBytes = encBytes[i:]
+			i = 0
+			for i < len(enc) && i < len(encBytes) && enc[len(enc)-i-1] == encBytes[len(encBytes)-i-1] {
+				i++
+			}
+			enc = enc[:len(enc)-i]
+			encBytes = encBytes[:len(encBytes)-i]
+
+			if len(enc) > 20 {
+				enc = enc[:20] + "..."
+			}
+			if len(encBytes) > 20 {
+				encBytes = encBytes[:20] + "..."
+			}
+
+			t.Errorf("with escapeHTML=%t, encodings differ at %#q vs %#q",
+				escapeHTML, enc, encBytes)
+		}
+	}
+}
+
+func TestIssue10281(t *testing.T) {
+	type Foo struct {
+		N Number
+	}
+	x := Foo{Number(`invalid`)}
+
+	b, err := Marshal(&x)
+	if err == nil {
+		t.Errorf("Marshal(&x) = %#q; want error", b)
+	}
+}
+
+func TestHTMLEscape(t *testing.T) {
+	var b, want bytes.Buffer
+	m := `{"M":"<html>foo &` + "\xe2\x80\xa8 \xe2\x80\xa9" + `</html>"}`
+	want.Write([]byte(`{"M":"\u003chtml\u003efoo \u0026\u2028 \u2029\u003c/html\u003e"}`))
+	HTMLEscape(&b, []byte(m))
+	if !bytes.Equal(b.Bytes(), want.Bytes()) {
+		t.Errorf("HTMLEscape(&b, []byte(m)) = %s; want %s", b.Bytes(), want.Bytes())
+	}
+}
+
+// golang.org/issue/8582
+func TestEncodePointerString(t *testing.T) {
+	type stringPointer struct {
+		N *int64 `json:"n,string"`
+	}
+	var n int64 = 42
+	b, err := Marshal(stringPointer{N: &n})
+	if err != nil {
+		t.Fatalf("Marshal: %v", err)
+	}
+	if got, want := string(b), `{"n":"42"}`; got != want {
+		t.Errorf("Marshal = %s, want %s", got, want)
+	}
+	var back stringPointer
+	err = Unmarshal(b, &back)
+	if err != nil {
+		t.Fatalf("Unmarshal: %v", err)
+	}
+	if back.N == nil {
+		t.Fatalf("Unmarshaled nil N field")
+	}
+	if *back.N != 42 {
+		t.Fatalf("*N = %d; want 42", *back.N)
+	}
+}
+
+var encodeStringTests = []struct {
+	in  string
+	out string
+}{
+	{"\x00", `"\u0000"`},
+	{"\x01", `"\u0001"`},
+	{"\x02", `"\u0002"`},
+	{"\x03", `"\u0003"`},
+	{"\x04", `"\u0004"`},
+	{"\x05", `"\u0005"`},
+	{"\x06", `"\u0006"`},
+	{"\x07", `"\u0007"`},
+	{"\x08", `"\u0008"`},
+	{"\x09", `"\t"`},
+	{"\x0a", `"\n"`},
+	{"\x0b", `"\u000b"`},
+	{"\x0c", `"\u000c"`},
+	{"\x0d", `"\r"`},
+	{"\x0e", `"\u000e"`},
+	{"\x0f", `"\u000f"`},
+	{"\x10", `"\u0010"`},
+	{"\x11", `"\u0011"`},
+	{"\x12", `"\u0012"`},
+	{"\x13", `"\u0013"`},
+	{"\x14", `"\u0014"`},
+	{"\x15", `"\u0015"`},
+	{"\x16", `"\u0016"`},
+	{"\x17", `"\u0017"`},
+	{"\x18", `"\u0018"`},
+	{"\x19", `"\u0019"`},
+	{"\x1a", `"\u001a"`},
+	{"\x1b", `"\u001b"`},
+	{"\x1c", `"\u001c"`},
+	{"\x1d", `"\u001d"`},
+	{"\x1e", `"\u001e"`},
+	{"\x1f", `"\u001f"`},
+}
+
+func TestEncodeString(t *testing.T) {
+	for _, tt := range encodeStringTests {
+		b, err := Marshal(tt.in)
+		if err != nil {
+			t.Errorf("Marshal(%q): %v", tt.in, err)
+			continue
+		}
+		out := string(b)
+		if out != tt.out {
+			t.Errorf("Marshal(%q) = %#q, want %#q", tt.in, out, tt.out)
+		}
+	}
+}
+
+type jsonbyte byte
+
+func (b jsonbyte) MarshalJSON() ([]byte, error) { return tenc(`{"JB":%d}`, b) }
+
+type textbyte byte
+
+func (b textbyte) MarshalText() ([]byte, error) { return tenc(`TB:%d`, b) }
+
+type jsonint int
+
+func (i jsonint) MarshalJSON() ([]byte, error) { return tenc(`{"JI":%d}`, i) }
+
+type textint int
+
+func (i textint) MarshalText() ([]byte, error) { return tenc(`TI:%d`, i) }
+
+func tenc(format string, a ...any) ([]byte, error) {
+	var buf bytes.Buffer
+	fmt.Fprintf(&buf, format, a...)
+	return buf.Bytes(), nil
+}
+
+type textfloat float64
+
+func (f textfloat) MarshalText() ([]byte, error) { return tenc(`TF:%0.2f`, f) }
+
+// Issue 13783
+func TestEncodeBytekind(t *testing.T) {
+	t.Skip() // TODO
+	testdata := []struct {
+		data any
+		want string
+	}{
+		{byte(7), "7"},
+		{jsonbyte(7), `{"JB":7}`},
+		{textbyte(4), `"TB:4"`},
+		{jsonint(5), `{"JI":5}`},
+		{textint(1), `"TI:1"`},
+		{[]byte{0, 1}, `"AAE="`},
+		{[]jsonbyte{0, 1}, `[{"JB":0},{"JB":1}]`},
+		{[][]jsonbyte{{0, 1}, {3}}, `[[{"JB":0},{"JB":1}],[{"JB":3}]]`},
+		{[]textbyte{2, 3}, `["TB:2","TB:3"]`},
+		{[]jsonint{5, 4}, `[{"JI":5},{"JI":4}]`},
+		{[]textint{9, 3}, `["TI:9","TI:3"]`},
+		{[]int{9, 3}, `[9,3]`},
+		{[]textfloat{12, 3}, `["TF:12.00","TF:3.00"]`},
+	}
+	for _, d := range testdata {
+		js, err := Marshal(d.data)
+		if err != nil {
+			t.Error(err)
+			continue
+		}
+		got, want := string(js), d.want
+		if got != want {
+			t.Errorf("got %s, want %s", got, want)
+		}
+	}
+}
+
+func TestTextMarshalerMapKeysAreSorted(t *testing.T) {
+	b, err := Marshal(map[unmarshalerText]int{
+		{"x", "y"}: 1,
+		{"y", "x"}: 2,
+		{"a", "z"}: 3,
+		{"z", "a"}: 4,
+	})
+	if err != nil {
+		t.Fatalf("Failed to Marshal text.Marshaler: %v", err)
+	}
+	const want = `{"a:z":3,"x:y":1,"y:x":2,"z:a":4}`
+	if string(b) != want {
+		t.Errorf("Marshal map with text.Marshaler keys: got %#q, want %#q", b, want)
+	}
+}
+
+// https://golang.org/issue/33675
+func TestNilMarshalerTextMapKey(t *testing.T) {
+	b, err := Marshal(map[*unmarshalerText]int{
+		(*unmarshalerText)(nil): 1,
+		{"A", "B"}:              2,
+	})
+	if err != nil {
+		t.Fatalf("Failed to Marshal *text.Marshaler: %v", err)
+	}
+	const want = `{"":1,"A:B":2}`
+	if string(b) != want {
+		t.Errorf("Marshal map with *text.Marshaler keys: got %#q, want %#q", b, want)
+	}
+}
+
+var re = regexp.MustCompile
+
+// syntactic checks on form of marshaled floating point numbers.
+var badFloatREs = []*regexp.Regexp{
+	re(`p`),                     // no binary exponential notation
+	re(`^\+`),                   // no leading + sign
+	re(`^-?0[^.]`),              // no unnecessary leading zeros
+	re(`^-?\.`),                 // leading zero required before decimal point
+	re(`\.(e|$)`),               // no trailing decimal
+	re(`\.[0-9]+0(e|$)`),        // no trailing zero in fraction
+	re(`^-?(0|[0-9]{2,})\..*e`), // exponential notation must have normalized mantissa
+	re(`e[0-9]`),                // positive exponent must be signed
+	re(`e[+-]0`),                // exponent must not have leading zeros
+	re(`e-[1-6]$`),              // not tiny enough for exponential notation
+	re(`e+(.|1.|20)$`),          // not big enough for exponential notation
+	re(`^-?0\.0000000`),         // too tiny, should use exponential notation
+	re(`^-?[0-9]{22}`),          // too big, should use exponential notation
+	re(`[1-9][0-9]{16}[1-9]`),   // too many significant digits in integer
+	re(`[1-9][0-9.]{17}[1-9]`),  // too many significant digits in decimal
+	// below here for float32 only
+	re(`[1-9][0-9]{8}[1-9]`),  // too many significant digits in integer
+	re(`[1-9][0-9.]{9}[1-9]`), // too many significant digits in decimal
+}
+
+func TestMarshalFloat(t *testing.T) {
+	t.Parallel()
+	nfail := 0
+	test := func(f float64, bits int) {
+		vf := any(f)
+		if bits == 32 {
+			f = float64(float32(f)) // round
+			vf = float32(f)
+		}
+		bout, err := Marshal(vf)
+		if err != nil {
+			t.Errorf("Marshal(%T(%g)): %v", vf, vf, err)
+			nfail++
+			return
+		}
+		out := string(bout)
+
+		// result must convert back to the same float
+		g, err := strconv.ParseFloat(out, bits)
+		if err != nil {
+			t.Errorf("Marshal(%T(%g)) = %q, cannot parse back: %v", vf, vf, out, err)
+			nfail++
+			return
+		}
+		if f != g || fmt.Sprint(f) != fmt.Sprint(g) { // fmt.Sprint handles ±0
+			t.Errorf("Marshal(%T(%g)) = %q (is %g, not %g)", vf, vf, out, float32(g), vf)
+			nfail++
+			return
+		}
+
+		bad := badFloatREs
+		if bits == 64 {
+			bad = bad[:len(bad)-2]
+		}
+		for _, re := range bad {
+			if re.MatchString(out) {
+				t.Errorf("Marshal(%T(%g)) = %q, must not match /%s/", vf, vf, out, re)
+				nfail++
+				return
+			}
+		}
+	}
+
+	var (
+		bigger  = math.Inf(+1)
+		smaller = math.Inf(-1)
+	)
+
+	var digits = "1.2345678901234567890123"
+	for i := len(digits); i >= 2; i-- {
+		if testing.Short() && i < len(digits)-4 {
+			break
+		}
+		for exp := -30; exp <= 30; exp++ {
+			for _, sign := range "+-" {
+				for bits := 32; bits <= 64; bits += 32 {
+					s := fmt.Sprintf("%c%se%d", sign, digits[:i], exp)
+					f, err := strconv.ParseFloat(s, bits)
+					if err != nil {
+						log.Fatal(err)
+					}
+					next := math.Nextafter
+					if bits == 32 {
+						next = func(g, h float64) float64 {
+							return float64(math.Nextafter32(float32(g), float32(h)))
+						}
+					}
+					test(f, bits)
+					test(next(f, bigger), bits)
+					test(next(f, smaller), bits)
+					if nfail > 50 {
+						t.Fatalf("stopping test early")
+					}
+				}
+			}
+		}
+	}
+	test(0, 64)
+	test(math.Copysign(0, -1), 64)
+	test(0, 32)
+	test(math.Copysign(0, -1), 32)
+}
+
+func TestMarshalRawMessageValue(t *testing.T) {
+	type (
+		T1 struct {
+			M RawMessage `json:",omitempty"`
+		}
+		T2 struct {
+			M *RawMessage `json:",omitempty"`
+		}
+	)
+
+	var (
+		rawNil   = RawMessage(nil)
+		rawEmpty = RawMessage([]byte{})
+		rawText  = RawMessage([]byte(`"foo"`))
+	)
+
+	tests := []struct {
+		in   any
+		want string
+		ok   bool
+	}{
+		// Test with nil RawMessage.
+		{rawNil, "null", true},
+		{&rawNil, "null", true},
+		{[]any{rawNil}, "[null]", true},
+		{&[]any{rawNil}, "[null]", true},
+		{[]any{&rawNil}, "[null]", true},
+		{&[]any{&rawNil}, "[null]", true},
+		{struct{ M RawMessage }{rawNil}, `{"M":null}`, true},
+		{&struct{ M RawMessage }{rawNil}, `{"M":null}`, true},
+		{struct{ M *RawMessage }{&rawNil}, `{"M":null}`, true},
+		{&struct{ M *RawMessage }{&rawNil}, `{"M":null}`, true},
+		{map[string]any{"M": rawNil}, `{"M":null}`, true},
+		{&map[string]any{"M": rawNil}, `{"M":null}`, true},
+		{map[string]any{"M": &rawNil}, `{"M":null}`, true},
+		{&map[string]any{"M": &rawNil}, `{"M":null}`, true},
+		{T1{rawNil}, "{}", true},
+		{T2{&rawNil}, `{"M":null}`, true},
+		{&T1{rawNil}, "{}", true},
+		{&T2{&rawNil}, `{"M":null}`, true},
+
+		// Test with empty, but non-nil, RawMessage.
+		{rawEmpty, "", false},
+		{&rawEmpty, "", false},
+		{[]any{rawEmpty}, "", false},
+		{&[]any{rawEmpty}, "", false},
+		{[]any{&rawEmpty}, "", false},
+		{&[]any{&rawEmpty}, "", false},
+		{struct{ X RawMessage }{rawEmpty}, "", false},
+		{&struct{ X RawMessage }{rawEmpty}, "", false},
+		{struct{ X *RawMessage }{&rawEmpty}, "", false},
+		{&struct{ X *RawMessage }{&rawEmpty}, "", false},
+		{map[string]any{"nil": rawEmpty}, "", false},
+		{&map[string]any{"nil": rawEmpty}, "", false},
+		{map[string]any{"nil": &rawEmpty}, "", false},
+		{&map[string]any{"nil": &rawEmpty}, "", false},
+		{T1{rawEmpty}, "{}", true},
+		{T2{&rawEmpty}, "", false},
+		{&T1{rawEmpty}, "{}", true},
+		{&T2{&rawEmpty}, "", false},
+
+		// Test with RawMessage with some text.
+		//
+		// The tests below marked with Issue6458 used to generate "ImZvbyI=" instead "foo".
+		// This behavior was intentionally changed in Go 1.8.
+		// See https://golang.org/issues/14493#issuecomment-255857318
+		{rawText, `"foo"`, true}, // Issue6458
+		{&rawText, `"foo"`, true},
+		{[]any{rawText}, `["foo"]`, true},  // Issue6458
+		{&[]any{rawText}, `["foo"]`, true}, // Issue6458
+		{[]any{&rawText}, `["foo"]`, true},
+		{&[]any{&rawText}, `["foo"]`, true},
+		{struct{ M RawMessage }{rawText}, `{"M":"foo"}`, true}, // Issue6458
+		{&struct{ M RawMessage }{rawText}, `{"M":"foo"}`, true},
+		{struct{ M *RawMessage }{&rawText}, `{"M":"foo"}`, true},
+		{&struct{ M *RawMessage }{&rawText}, `{"M":"foo"}`, true},
+		{map[string]any{"M": rawText}, `{"M":"foo"}`, true},  // Issue6458
+		{&map[string]any{"M": rawText}, `{"M":"foo"}`, true}, // Issue6458
+		{map[string]any{"M": &rawText}, `{"M":"foo"}`, true},
+		{&map[string]any{"M": &rawText}, `{"M":"foo"}`, true},
+		{T1{rawText}, `{"M":"foo"}`, true}, // Issue6458
+		{T2{&rawText}, `{"M":"foo"}`, true},
+		{&T1{rawText}, `{"M":"foo"}`, true},
+		{&T2{&rawText}, `{"M":"foo"}`, true},
+	}
+
+	for i, tt := range tests {
+		b, err := Marshal(tt.in)
+		if ok := (err == nil); ok != tt.ok {
+			if err != nil {
+				t.Errorf("test %d, unexpected failure: %v", i, err)
+			} else {
+				t.Skip() // MODIFIED
+				t.Errorf("test %d, unexpected success", i)
+			}
+		}
+		if got := string(b); got != tt.want {
+			t.Errorf("test %d, Marshal(%#v) = %q, want %q", i, tt.in, got, tt.want)
+		}
+	}
+}
+
+type marshalPanic struct{}
+
+func (marshalPanic) MarshalJSON() ([]byte, error) { panic(0xdead) }
+
+func TestMarshalPanic(t *testing.T) {
+	defer func() {
+		if got := recover(); !reflect.DeepEqual(got, 0xdead) {
+			t.Errorf("panic() = (%T)(%v), want 0xdead", got, got)
+		}
+	}()
+	_, _ = Marshal(&marshalPanic{}) // MODIFIED
+	t.Error("Marshal should have panicked")
+}
+
+func TestMarshalUncommonFieldNames(t *testing.T) {
+	v := struct {
+		A0, À, Aβ int
+	}{}
+	b, err := Marshal(v)
+	if err != nil {
+		t.Fatal("Marshal:", err)
+	}
+	want := `{"A0":0,"À":0,"Aβ":0}`
+	got := string(b)
+	if got != want {
+		t.Fatalf("Marshal: got %s want %s", got, want)
+	}
+}
+
+/* // MODIFIED
+func TestMarshalerError(t *testing.T) {
+	s := "test variable"
+	st := reflect.TypeOf(s)
+	errText := "json: test error"
+
+	tests := []struct {
+		err  *MarshalerError
+		want string
+	}{
+		{
+			&MarshalerError{st, fmt.Errorf(errText), ""},
+			"json: error calling MarshalJSON for type " + st.String() + ": " + errText,
+		},
+		{
+			&MarshalerError{st, fmt.Errorf(errText), "TestMarshalerError"},
+			"json: error calling TestMarshalerError for type " + st.String() + ": " + errText,
+		},
+	}
+
+	for i, tt := range tests {
+		got := tt.err.Error()
+		if got != tt.want {
+			t.Errorf("MarshalerError test %d, got: %s, want: %s", i, got, tt.want)
+		}
+	}
+}
+*/ // MODIFIED
diff --git a/compat/json/borrowed_fuzz_test.go b/compat/json/borrowed_fuzz_test.go
new file mode 100644
index 0000000..21756a7
--- /dev/null
+++ b/compat/json/borrowed_fuzz_test.go
@@ -0,0 +1,83 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package lowmemjson // MODIFIED
+
+import (
+	"testing"
+)
+
+func FuzzUnmarshalJSON(f *testing.F) {
+	f.Add([]byte(`{
+"object": {
+	"slice": [
+		1,
+		2.0,
+		"3",
+		[4],
+		{5: {}}
+	]
+},
+"slice": [[]],
+"string": ":)",
+"int": 1e5,
+"float": 3e-9"
+}`))
+
+	f.Fuzz(func(t *testing.T, b []byte) {
+		for _, typ := range []func() interface{}{
+			func() interface{} { return new(interface{}) },
+			func() interface{} { return new(map[string]interface{}) },
+			func() interface{} { return new([]interface{}) },
+		} {
+			i := typ()
+			if err := Unmarshal(b, i); err != nil {
+				return
+			}
+
+			encoded, err := Marshal(i)
+			if err != nil {
+				t.Fatalf("failed to marshal: %s", err)
+			}
+
+			if err := Unmarshal(encoded, i); err != nil {
+				t.Fatalf("failed to roundtrip: %s", err)
+			}
+		}
+	})
+}
+
+/* // MODIFIED
+func FuzzDecoderToken(f *testing.F) {
+	f.Add([]byte(`{
+"object": {
+	"slice": [
+		1,
+		2.0,
+		"3",
+		[4],
+		{5: {}}
+	]
+},
+"slice": [[]],
+"string": ":)",
+"int": 1e5,
+"float": 3e-9"
+}`))
+
+	f.Fuzz(func(t *testing.T, b []byte) {
+		r := bytes.NewReader(b)
+		d := NewDecoder(r)
+		for {
+			_, err := d.Token()
+			if err != nil {
+				if err == io.EOF {
+					break
+				}
+				return
+			}
+		}
+	})
+}
+*/ // MODIFIED
diff --git a/compat/json/borrowed_scanner_test.go b/compat/json/borrowed_scanner_test.go
new file mode 100644
index 0000000..c5d67e6
--- /dev/null
+++ b/compat/json/borrowed_scanner_test.go
@@ -0,0 +1,305 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package lowmemjson // MODIFIED
+
+import (
+	"bytes"
+	"math"
+	"math/rand"
+	"reflect"
+	"testing"
+)
+
+var validTests = []struct {
+	data string
+	ok   bool
+}{
+	{`foo`, false},
+	{`}{`, false},
+	{`{]`, false},
+	{`{}`, true},
+	{`{"foo":"bar"}`, true},
+	{`{"foo":"bar","bar":{"baz":["qux"]}}`, true},
+}
+
+func TestValid(t *testing.T) {
+	for _, tt := range validTests {
+		if ok := Valid([]byte(tt.data)); ok != tt.ok {
+			t.Errorf("Valid(%#q) = %v, want %v", tt.data, ok, tt.ok)
+		}
+	}
+}
+
+// Tests of simple examples.
+
+type example struct {
+	compact string
+	indent  string
+}
+
+var examples = []example{
+	{`1`, `1`},
+	{`{}`, `{}`},
+	{`[]`, `[]`},
+	{`{"":2}`, "{\n\t\"\": 2\n}"},
+	{`[3]`, "[\n\t3\n]"},
+	{`[1,2,3]`, "[\n\t1,\n\t2,\n\t3\n]"},
+	{`{"x":1}`, "{\n\t\"x\": 1\n}"},
+	{ex1, ex1i},
+	{"{\"\":\"<>&\u2028\u2029\"}", "{\n\t\"\": \"<>&\u2028\u2029\"\n}"}, // See golang.org/issue/34070
+}
+
+var ex1 = `[true,false,null,"x",1,1.5,0,-5e+2]`
+
+var ex1i = `[
+	true,
+	false,
+	null,
+	"x",
+	1,
+	1.5,
+	0,
+	-5e+2
+]`
+
+func TestCompact(t *testing.T) {
+	t.Skip() // TODO
+	var buf bytes.Buffer
+	for _, tt := range examples {
+		buf.Reset()
+		if err := Compact(&buf, []byte(tt.compact)); err != nil {
+			t.Errorf("Compact(%#q): %v", tt.compact, err)
+		} else if s := buf.String(); s != tt.compact {
+			t.Errorf("Compact(%#q) = %#q, want original", tt.compact, s)
+		}
+
+		buf.Reset()
+		if err := Compact(&buf, []byte(tt.indent)); err != nil {
+			t.Errorf("Compact(%#q): %v", tt.indent, err)
+			continue
+		} else if s := buf.String(); s != tt.compact {
+			t.Errorf("Compact(%#q) = %#q, want %#q", tt.indent, s, tt.compact)
+		}
+	}
+}
+
+func TestCompactSeparators(t *testing.T) {
+	t.Skip() // TODO
+	// U+2028 and U+2029 should be escaped inside strings.
+	// They should not appear outside strings.
+	tests := []struct {
+		in, compact string
+	}{
+		{"{\"\u2028\": 1}", "{\"\u2028\":1}"},
+		{"{\"\u2029\" :2}", "{\"\u2029\":2}"},
+	}
+	for _, tt := range tests {
+		var buf bytes.Buffer
+		if err := Compact(&buf, []byte(tt.in)); err != nil {
+			t.Errorf("Compact(%q): %v", tt.in, err)
+		} else if s := buf.String(); s != tt.compact {
+			t.Errorf("Compact(%q) = %q, want %q", tt.in, s, tt.compact)
+		}
+	}
+}
+
+func TestIndent(t *testing.T) {
+	t.Skip() // TODO
+	var buf bytes.Buffer
+	for _, tt := range examples {
+		buf.Reset()
+		if err := Indent(&buf, []byte(tt.indent), "", "\t"); err != nil {
+			t.Errorf("Indent(%#q): %v", tt.indent, err)
+		} else if s := buf.String(); s != tt.indent {
+			t.Errorf("Indent(%#q) = %#q, want original", tt.indent, s)
+		}
+
+		buf.Reset()
+		if err := Indent(&buf, []byte(tt.compact), "", "\t"); err != nil {
+			t.Errorf("Indent(%#q): %v", tt.compact, err)
+			continue
+		} else if s := buf.String(); s != tt.indent {
+			t.Errorf("Indent(%#q) = %#q, want %#q", tt.compact, s, tt.indent)
+		}
+	}
+}
+
+// Tests of a large random structure.
+
+func TestCompactBig(t *testing.T) {
+	initBig()
+	var buf bytes.Buffer
+	if err := Compact(&buf, jsonBig); err != nil {
+		t.Fatalf("Compact: %v", err)
+	}
+	b := buf.Bytes()
+	if !bytes.Equal(b, jsonBig) {
+		t.Error("Compact(jsonBig) != jsonBig")
+		diff(t, b, jsonBig)
+		return
+	}
+}
+
+func TestIndentBig(t *testing.T) {
+	t.Parallel()
+	initBig()
+	var buf bytes.Buffer
+	if err := Indent(&buf, jsonBig, "", "\t"); err != nil {
+		t.Fatalf("Indent1: %v", err)
+	}
+	b := buf.Bytes()
+	if len(b) == len(jsonBig) {
+		// jsonBig is compact (no unnecessary spaces);
+		// indenting should make it bigger
+		t.Fatalf("Indent(jsonBig) did not get bigger")
+	}
+
+	// should be idempotent
+	var buf1 bytes.Buffer
+	if err := Indent(&buf1, b, "", "\t"); err != nil {
+		t.Fatalf("Indent2: %v", err)
+	}
+	b1 := buf1.Bytes()
+	if !bytes.Equal(b1, b) {
+		t.Error("Indent(Indent(jsonBig)) != Indent(jsonBig)")
+		diff(t, b1, b)
+		return
+	}
+
+	// should get back to original
+	buf1.Reset()
+	if err := Compact(&buf1, b); err != nil {
+		t.Fatalf("Compact: %v", err)
+	}
+	b1 = buf1.Bytes()
+	if !bytes.Equal(b1, jsonBig) {
+		t.Error("Compact(Indent(jsonBig)) != jsonBig")
+		diff(t, b1, jsonBig)
+		return
+	}
+}
+
+type indentErrorTest struct {
+	in  string
+	err error
+}
+
+var indentErrorTests = []indentErrorTest{
+	{`{"X": "foo", "Y"}`, &SyntaxError{"invalid character '}' after object key", 17}},
+	{`{"X": "foo" "Y": "bar"}`, &SyntaxError{"invalid character '\"' after object key:value pair", 13}},
+}
+
+func TestIndentErrors(t *testing.T) {
+	t.Skip() // TODO
+	for i, tt := range indentErrorTests {
+		slice := make([]uint8, 0)
+		buf := bytes.NewBuffer(slice)
+		if err := Indent(buf, []uint8(tt.in), "", ""); err != nil {
+			if !reflect.DeepEqual(err, tt.err) {
+				t.Errorf("#%d: Indent: %#v", i, err)
+				continue
+			}
+		}
+	}
+}
+
+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
+			}
+			t.Errorf("diverge at %d: «%s» vs «%s»", i, trim(a[j:]), trim(b[j:]))
+			return
+		}
+	}
+}
+
+func trim(b []byte) []byte {
+	if len(b) > 20 {
+		return b[0:20]
+	}
+	return b
+}
+
+// Generate a random JSON object.
+
+var jsonBig []byte
+
+func initBig() {
+	n := 10000
+	if testing.Short() {
+		n = 100
+	}
+	b, err := Marshal(genValue(n))
+	if err != nil {
+		panic(err)
+	}
+	jsonBig = b
+}
+
+func genValue(n int) any {
+	if n > 1 {
+		switch rand.Intn(2) {
+		case 0:
+			return genArray(n)
+		case 1:
+			return genMap(n)
+		}
+	}
+	switch rand.Intn(3) {
+	case 0:
+		return rand.Intn(2) == 0
+	case 1:
+		return rand.NormFloat64()
+	case 2:
+		return genString(30)
+	}
+	panic("unreachable")
+}
+
+func genString(stddev float64) string {
+	n := int(math.Abs(rand.NormFloat64()*stddev + stddev/2))
+	c := make([]rune, n)
+	for i := range c {
+		f := math.Abs(rand.NormFloat64()*64 + 32)
+		if f > 0x10ffff {
+			f = 0x10ffff
+		}
+		c[i] = rune(f)
+	}
+	return string(c)
+}
+
+func genArray(n int) []any {
+	f := int(math.Abs(rand.NormFloat64()) * math.Min(10, float64(n/2)))
+	if f > n {
+		f = n
+	}
+	if f < 1 {
+		f = 1
+	}
+	x := make([]any, f)
+	for i := range x {
+		x[i] = genValue(((i+1)*n)/f - (i*n)/f)
+	}
+	return x
+}
+
+func genMap(n int) map[string]any {
+	f := int(math.Abs(rand.NormFloat64()) * math.Min(10, float64(n/2)))
+	if f > n {
+		f = n
+	}
+	if n > 0 && f == 0 {
+		f = 1
+	}
+	x := make(map[string]any)
+	for i := 0; i < f; i++ {
+		x[genString(10)] = genValue(((i+1)*n)/f - (i*n)/f)
+	}
+	return x
+}
diff --git a/compat/json/borrowed_tagkey_test.go b/compat/json/borrowed_tagkey_test.go
new file mode 100644
index 0000000..2d4d2c0
--- /dev/null
+++ b/compat/json/borrowed_tagkey_test.go
@@ -0,0 +1,121 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package lowmemjson // MODIFIED
+
+import (
+	"testing"
+)
+
+type basicLatin2xTag struct {
+	V string `json:"$%-/"`
+}
+
+type basicLatin3xTag struct {
+	V string `json:"0123456789"`
+}
+
+type basicLatin4xTag struct {
+	V string `json:"ABCDEFGHIJKLMO"`
+}
+
+type basicLatin5xTag struct {
+	V string `json:"PQRSTUVWXYZ_"`
+}
+
+type basicLatin6xTag struct {
+	V string `json:"abcdefghijklmno"`
+}
+
+type basicLatin7xTag struct {
+	V string `json:"pqrstuvwxyz"`
+}
+
+type miscPlaneTag struct {
+	V string `json:"色は匂へど"`
+}
+
+type percentSlashTag struct {
+	V string `json:"text/html%"` // https://golang.org/issue/2718
+}
+
+type punctuationTag struct {
+	V string `json:"!#$%&()*+-./:;<=>?@[]^_{|}~ "` // https://golang.org/issue/3546
+}
+
+type dashTag struct {
+	V string `json:"-,"`
+}
+
+type emptyTag struct {
+	W string
+}
+
+type misnamedTag struct {
+	X string `jsom:"Misnamed"`
+}
+
+type badFormatTag struct {
+	Y string `:"BadFormat"`
+}
+
+type badCodeTag struct {
+	Z string `json:" !\"#&'()*+,."`
+}
+
+type spaceTag struct {
+	Q string `json:"With space"`
+}
+
+type unicodeTag struct {
+	W string `json:"Ελλάδα"`
+}
+
+var structTagObjectKeyTests = []struct {
+	raw   any
+	value string
+	key   string
+}{
+	{basicLatin2xTag{"2x"}, "2x", "$%-/"},
+	{basicLatin3xTag{"3x"}, "3x", "0123456789"},
+	{basicLatin4xTag{"4x"}, "4x", "ABCDEFGHIJKLMO"},
+	{basicLatin5xTag{"5x"}, "5x", "PQRSTUVWXYZ_"},
+	{basicLatin6xTag{"6x"}, "6x", "abcdefghijklmno"},
+	{basicLatin7xTag{"7x"}, "7x", "pqrstuvwxyz"},
+	{miscPlaneTag{"いろはにほへと"}, "いろはにほへと", "色は匂へど"},
+	{dashTag{"foo"}, "foo", "-"},
+	{emptyTag{"Pour Moi"}, "Pour Moi", "W"},
+	{misnamedTag{"Animal Kingdom"}, "Animal Kingdom", "X"},
+	{badFormatTag{"Orfevre"}, "Orfevre", "Y"},
+	{badCodeTag{"Reliable Man"}, "Reliable Man", "Z"},
+	{percentSlashTag{"brut"}, "brut", "text/html%"},
+	{punctuationTag{"Union Rags"}, "Union Rags", "!#$%&()*+-./:;<=>?@[]^_{|}~ "},
+	{spaceTag{"Perreddu"}, "Perreddu", "With space"},
+	{unicodeTag{"Loukanikos"}, "Loukanikos", "Ελλάδα"},
+}
+
+func TestStructTagObjectKey(t *testing.T) {
+	t.Skip() // TODO
+	for _, tt := range structTagObjectKeyTests {
+		b, err := Marshal(tt.raw)
+		if err != nil {
+			t.Fatalf("Marshal(%#q) failed: %v", tt.raw, err)
+		}
+		var f any
+		err = Unmarshal(b, &f)
+		if err != nil {
+			t.Fatalf("Unmarshal(%#q) failed: %v", b, err)
+		}
+		for i, v := range f.(map[string]any) {
+			switch i {
+			case tt.key:
+				if s, ok := v.(string); !ok || s != tt.value {
+					t.Fatalf("Unexpected value: %#q, want %v", s, tt.value)
+				}
+			default:
+				t.Fatalf("Unexpected key: %#q, from %#q", i, b)
+			}
+		}
+	}
+}
diff --git a/compat/json/borrowed_tags_test.go b/compat/json/borrowed_tags_test.go
new file mode 100644
index 0000000..28d76e9
--- /dev/null
+++ b/compat/json/borrowed_tags_test.go
@@ -0,0 +1,28 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package lowmemjson // MODIFIED
+
+import (
+	"testing"
+)
+
+func TestTagParsing(t *testing.T) {
+	name, opts := parseTag("field,foobar,foo")
+	if name != "field" {
+		t.Fatalf("name = %q, want field", name)
+	}
+	for _, tt := range []struct {
+		opt  string
+		want bool
+	}{
+		{"foobar", true},
+		{"foo", true},
+		{"bar", false},
+	} {
+		if opts.Contains(tt.opt) != tt.want {
+			t.Errorf("Contains(%q) = %v", tt.opt, !tt.want)
+		}
+	}
+}