From b774f31c2da7dfb8ef0cd676d03f336774fa6927 Mon Sep 17 00:00:00 2001
From: Richard Wilkes <wilkes@me.com>
Date: Tue, 9 Jul 2024 21:24:40 -0700
Subject: [PATCH] Sync with Go 1.22.5

---
 bench_test.go   | 201 ++++++++++++--
 decode.go       | 165 +++++-------
 encode.go       | 539 ++++++++++++++----------------------
 encode_test.go  | 705 +++++++++++++++++++++++++-----------------------
 example_test.go |   2 +-
 fold.go         | 149 ++--------
 fold_test.go    | 138 +++-------
 fuzz.go         |  43 ---
 fuzz_test.go    |  83 ++++++
 go.mod          |   2 +-
 indent.go       | 119 +++++---
 number_test.go  |  15 --
 scanner.go      |   6 +-
 scanner_test.go | 233 ++++++++--------
 stream.go       |  49 ++--
 stream_test.go  | 452 +++++++++++++++++--------------
 tagkey_test.go  | 107 +++-----
 tags.go         |  16 +-
 tags_test.go    |   2 +-
 19 files changed, 1491 insertions(+), 1535 deletions(-)
 delete mode 100644 fuzz.go
 create mode 100644 fuzz_test.go

diff --git a/bench_test.go b/bench_test.go
index 2feb2c1..c37687b 100644
--- a/bench_test.go
+++ b/bench_test.go
@@ -17,6 +17,7 @@ import (
 	"io"
 	"os"
 	"reflect"
+	"regexp"
 	"runtime"
 	"strings"
 	"sync"
@@ -91,7 +92,37 @@ func BenchmarkCodeEncoder(b *testing.B) {
 		enc := NewEncoder(io.Discard)
 		for pb.Next() {
 			if err := enc.Encode(&codeStruct); err != nil {
-				b.Fatal("Encode:", err)
+				b.Fatalf("Encode error: %v", err)
+			}
+		}
+	})
+	b.SetBytes(int64(len(codeJSON)))
+}
+
+func BenchmarkCodeEncoderError(b *testing.B) {
+	b.ReportAllocs()
+	if codeJSON == nil {
+		b.StopTimer()
+		codeInit()
+		b.StartTimer()
+	}
+
+	// Trigger an error in Marshal with cyclic data.
+	type Dummy struct {
+		Name string
+		Next *Dummy
+	}
+	dummy := Dummy{Name: "Dummy"}
+	dummy.Next = &dummy
+
+	b.RunParallel(func(pb *testing.PB) {
+		enc := NewEncoder(io.Discard)
+		for pb.Next() {
+			if err := enc.Encode(&codeStruct); err != nil {
+				b.Fatalf("Encode error: %v", err)
+			}
+			if _, err := Marshal(dummy); err == nil {
+				b.Fatal("Marshal error: got nil, want non-nil")
 			}
 		}
 	})
@@ -108,7 +139,36 @@ func BenchmarkCodeMarshal(b *testing.B) {
 	b.RunParallel(func(pb *testing.PB) {
 		for pb.Next() {
 			if _, err := Marshal(&codeStruct); err != nil {
-				b.Fatal("Marshal:", err)
+				b.Fatalf("Marshal error: %v", err)
+			}
+		}
+	})
+	b.SetBytes(int64(len(codeJSON)))
+}
+
+func BenchmarkCodeMarshalError(b *testing.B) {
+	b.ReportAllocs()
+	if codeJSON == nil {
+		b.StopTimer()
+		codeInit()
+		b.StartTimer()
+	}
+
+	// Trigger an error in Marshal with cyclic data.
+	type Dummy struct {
+		Name string
+		Next *Dummy
+	}
+	dummy := Dummy{Name: "Dummy"}
+	dummy.Next = &dummy
+
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			if _, err := Marshal(&codeStruct); err != nil {
+				b.Fatalf("Marshal error: %v", err)
+			}
+			if _, err := Marshal(dummy); err == nil {
+				b.Fatal("Marshal error: got nil, want non-nil")
 			}
 		}
 	})
@@ -127,7 +187,37 @@ func benchMarshalBytes(n int) func(*testing.B) {
 	return func(b *testing.B) {
 		for i := 0; i < b.N; i++ {
 			if _, err := Marshal(v); err != nil {
-				b.Fatal("Marshal:", err)
+				b.Fatalf("Marshal error: %v", err)
+			}
+		}
+	}
+}
+
+func benchMarshalBytesError(n int) func(*testing.B) {
+	sample := []byte("hello world")
+	// Use a struct pointer, to avoid an allocation when passing it as an
+	// interface parameter to Marshal.
+	v := &struct {
+		Bytes []byte
+	}{
+		bytes.Repeat(sample, (n/len(sample))+1)[:n],
+	}
+
+	// Trigger an error in Marshal with cyclic data.
+	type Dummy struct {
+		Name string
+		Next *Dummy
+	}
+	dummy := Dummy{Name: "Dummy"}
+	dummy.Next = &dummy
+
+	return func(b *testing.B) {
+		for i := 0; i < b.N; i++ {
+			if _, err := Marshal(v); err != nil {
+				b.Fatalf("Marshal error: %v", err)
+			}
+			if _, err := Marshal(dummy); err == nil {
+				b.Fatal("Marshal error: got nil, want non-nil")
 			}
 		}
 	}
@@ -144,6 +234,33 @@ func BenchmarkMarshalBytes(b *testing.B) {
 	b.Run("4096", benchMarshalBytes(4096))
 }
 
+func BenchmarkMarshalBytesError(b *testing.B) {
+	b.ReportAllocs()
+	// 32 fits within encodeState.scratch.
+	b.Run("32", benchMarshalBytesError(32))
+	// 256 doesn't fit in encodeState.scratch, but is small enough to
+	// allocate and avoid the slower base64.NewEncoder.
+	b.Run("256", benchMarshalBytesError(256))
+	// 4096 is large enough that we want to avoid allocating for it.
+	b.Run("4096", benchMarshalBytesError(4096))
+}
+
+func BenchmarkMarshalMap(b *testing.B) {
+	b.ReportAllocs()
+	m := map[string]int{
+		"key3": 3,
+		"key2": 2,
+		"key1": 1,
+	}
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			if _, err := Marshal(m); err != nil {
+				b.Fatal("Marshal:", err)
+			}
+		}
+	})
+}
+
 func BenchmarkCodeDecoder(b *testing.B) {
 	b.ReportAllocs()
 	if codeJSON == nil {
@@ -162,7 +279,7 @@ func BenchmarkCodeDecoder(b *testing.B) {
 			buf.WriteByte('\n')
 			buf.WriteByte('\n')
 			if err := dec.Decode(&r); err != nil {
-				b.Fatal("Decode:", err)
+				b.Fatalf("Decode error: %v", err)
 			}
 		}
 	})
@@ -179,7 +296,7 @@ func BenchmarkUnicodeDecoder(b *testing.B) {
 	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
 		if err := dec.Decode(&out); err != nil {
-			b.Fatal("Decode:", err)
+			b.Fatalf("Decode error: %v", err)
 		}
 		r.Seek(0, 0)
 	}
@@ -191,9 +308,9 @@ func BenchmarkDecoderStream(b *testing.B) {
 	var buf bytes.Buffer
 	dec := NewDecoder(&buf)
 	buf.WriteString(`"` + strings.Repeat("x", 1000000) + `"` + "\n\n\n")
-	var x interface{}
+	var x any
 	if err := dec.Decode(&x); err != nil {
-		b.Fatal("Decode:", err)
+		b.Fatalf("Decode error: %v", err)
 	}
 	ones := strings.Repeat(" 1\n", 300000) + "\n\n\n"
 	b.StartTimer()
@@ -202,8 +319,11 @@ func BenchmarkDecoderStream(b *testing.B) {
 			buf.WriteString(ones)
 		}
 		x = nil
-		if err := dec.Decode(&x); err != nil || x != 1.0 {
-			b.Fatalf("Decode: %v after %d", err, i)
+		switch err := dec.Decode(&x); {
+		case err != nil:
+			b.Fatalf("Decode error: %v", err)
+		case x != 1.0:
+			b.Fatalf("Decode: got %v want 1.0", i)
 		}
 	}
 }
@@ -219,7 +339,7 @@ func BenchmarkCodeUnmarshal(b *testing.B) {
 		for pb.Next() {
 			var r codeResponse
 			if err := Unmarshal(codeJSON, &r); err != nil {
-				b.Fatal("Unmarshal:", err)
+				b.Fatalf("Unmarshal error: %v", err)
 			}
 		}
 	})
@@ -237,7 +357,7 @@ func BenchmarkCodeUnmarshalReuse(b *testing.B) {
 		var r codeResponse
 		for pb.Next() {
 			if err := Unmarshal(codeJSON, &r); err != nil {
-				b.Fatal("Unmarshal:", err)
+				b.Fatalf("Unmarshal error: %v", err)
 			}
 		}
 	})
@@ -251,7 +371,7 @@ func BenchmarkUnmarshalString(b *testing.B) {
 		var s string
 		for pb.Next() {
 			if err := Unmarshal(data, &s); err != nil {
-				b.Fatal("Unmarshal:", err)
+				b.Fatalf("Unmarshal error: %v", err)
 			}
 		}
 	})
@@ -264,7 +384,7 @@ func BenchmarkUnmarshalFloat64(b *testing.B) {
 		var f float64
 		for pb.Next() {
 			if err := Unmarshal(data, &f); err != nil {
-				b.Fatal("Unmarshal:", err)
+				b.Fatalf("Unmarshal error: %v", err)
 			}
 		}
 	})
@@ -277,7 +397,20 @@ func BenchmarkUnmarshalInt64(b *testing.B) {
 		var x int64
 		for pb.Next() {
 			if err := Unmarshal(data, &x); err != nil {
-				b.Fatal("Unmarshal:", err)
+				b.Fatalf("Unmarshal error: %v", err)
+			}
+		}
+	})
+}
+
+func BenchmarkUnmarshalMap(b *testing.B) {
+	b.ReportAllocs()
+	data := []byte(`{"key1":"value1","key2":"value2","key3":"value3"}`)
+	b.RunParallel(func(pb *testing.PB) {
+		x := make(map[string]string, 3)
+		for pb.Next() {
+			if err := Unmarshal(data, &x); err != nil {
+				b.Fatalf("Unmarshal error: %v", err)
 			}
 		}
 	})
@@ -290,7 +423,7 @@ func BenchmarkIssue10335(b *testing.B) {
 		var s struct{}
 		for pb.Next() {
 			if err := Unmarshal(j, &s); err != nil {
-				b.Fatal(err)
+				b.Fatalf("Unmarshal error: %v", err)
 			}
 		}
 	})
@@ -306,7 +439,7 @@ func BenchmarkIssue34127(b *testing.B) {
 	b.RunParallel(func(pb *testing.PB) {
 		for pb.Next() {
 			if _, err := Marshal(&j); err != nil {
-				b.Fatal(err)
+				b.Fatalf("Marshal error: %v", err)
 			}
 		}
 	})
@@ -319,7 +452,7 @@ func BenchmarkUnmapped(b *testing.B) {
 		var s struct{}
 		for pb.Next() {
 			if err := Unmarshal(j, &s); err != nil {
-				b.Fatal(err)
+				b.Fatalf("Unmarshal error: %v", err)
 			}
 		}
 	})
@@ -332,7 +465,7 @@ func BenchmarkTypeFieldsCache(b *testing.B) {
 	// Dynamically generate many new types.
 	types := make([]reflect.Type, maxTypes)
 	fs := []reflect.StructField{{
-		Type:  reflect.TypeOf(""),
+		Type:  reflect.TypeFor[string](),
 		Index: []int{0},
 	}}
 	for i := range types {
@@ -399,8 +532,38 @@ func BenchmarkEncodeMarshaler(b *testing.B) {
 
 		for pb.Next() {
 			if err := enc.Encode(&m); err != nil {
-				b.Fatal("Encode:", err)
+				b.Fatalf("Encode error: %v", err)
+			}
+		}
+	})
+}
+
+func BenchmarkEncoderEncode(b *testing.B) {
+	b.ReportAllocs()
+	type T struct {
+		X, Y string
+	}
+	v := &T{"foo", "bar"}
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			if err := NewEncoder(io.Discard).Encode(v); err != nil {
+				b.Fatalf("Encode error: %v", err)
 			}
 		}
 	})
 }
+
+func BenchmarkNumberIsValid(b *testing.B) {
+	s := "-61657.61667E+61673"
+	for i := 0; i < b.N; i++ {
+		isValidNumber(s)
+	}
+}
+
+func BenchmarkNumberIsValidRegexp(b *testing.B) {
+	var jsonNumberRegexp = regexp.MustCompile(`^-?(?:0|[1-9]\d*)(?:\.\d+)?(?:[eE][+-]?\d+)?$`)
+	s := "-61657.61667E+61673"
+	for i := 0; i < b.N; i++ {
+		jsonNumberRegexp.MatchString(s)
+	}
+}
diff --git a/decode.go b/decode.go
index 2adcb26..9c73d99 100644
--- a/decode.go
+++ b/decode.go
@@ -22,10 +22,10 @@ import (
 
 // Unmarshal parses the JSON-encoded data and stores the result
 // in the value pointed to by v. If v is nil or not a pointer,
-// Unmarshal returns an InvalidUnmarshalError.
+// Unmarshal returns an [InvalidUnmarshalError].
 //
 // Unmarshal uses the inverse of the encodings that
-// Marshal uses, allocating maps, slices, and pointers as necessary,
+// [Marshal] uses, allocating maps, slices, and pointers as necessary,
 // with the following additional rules:
 //
 // To unmarshal JSON into a pointer, Unmarshal first handles the case of
@@ -34,28 +34,28 @@ import (
 // the value pointed at by the pointer. If the pointer is nil, Unmarshal
 // allocates a new value for it to point to.
 //
-// To unmarshal JSON into a value implementing the Unmarshaler interface,
-// Unmarshal calls that value's UnmarshalJSON method, including
+// To unmarshal JSON into a value implementing [Unmarshaler],
+// Unmarshal calls that value's [Unmarshaler.UnmarshalJSON] method, including
 // when the input is a JSON null.
-// Otherwise, if the value implements encoding.TextUnmarshaler
-// and the input is a JSON quoted string, Unmarshal calls that value's
-// UnmarshalText method with the unquoted form of the string.
+// Otherwise, if the value implements [encoding.TextUnmarshaler]
+// and the input is a JSON quoted string, Unmarshal calls
+// [encoding.TextUnmarshaler.UnmarshalText] with the unquoted form of the string.
 //
 // To unmarshal JSON into a struct, Unmarshal matches incoming object
-// keys to the keys used by Marshal (either the struct field name or its tag),
+// keys to the keys used by [Marshal] (either the struct field name or its tag),
 // preferring an exact match but also accepting a case-insensitive match. By
 // default, object keys which don't have a corresponding struct field are
-// ignored (see Decoder.DisallowUnknownFields for an alternative).
+// ignored (see [Decoder.DisallowUnknownFields] for an alternative).
 //
 // To unmarshal JSON into an interface value,
 // Unmarshal stores one of these in the interface value:
 //
-//	bool, for JSON booleans
-//	float64, for JSON numbers
-//	string, for JSON strings
-//	[]interface{}, for JSON arrays
-//	map[string]interface{}, for JSON objects
-//	nil for JSON null
+//   - bool, for JSON booleans
+//   - float64, for JSON numbers
+//   - string, for JSON strings
+//   - []interface{}, for JSON arrays
+//   - map[string]interface{}, for JSON objects
+//   - nil for JSON null
 //
 // To unmarshal a JSON array into a slice, Unmarshal resets the slice length
 // to zero and then appends each element to the slice.
@@ -73,14 +73,16 @@ import (
 // use. If the map is nil, Unmarshal allocates a new map. Otherwise Unmarshal
 // reuses the existing map, keeping existing entries. Unmarshal then stores
 // key-value pairs from the JSON object into the map. The map's key type must
-// either be any string type, an integer, implement json.Unmarshaler, or
-// implement encoding.TextUnmarshaler.
+// either be any string type, an integer, implement [json.Unmarshaler], or
+// implement [encoding.TextUnmarshaler].
+//
+// If the JSON-encoded data contain a syntax error, Unmarshal returns a [SyntaxError].
 //
 // If a JSON value is not appropriate for a given target type,
 // or if a JSON number overflows the target type, Unmarshal
 // skips that field and completes the unmarshaling as best it can.
 // If no more serious errors are encountered, Unmarshal returns
-// an UnmarshalTypeError describing the earliest such error. In any
+// an [UnmarshalTypeError] describing the earliest such error. In any
 // case, it's not guaranteed that all the remaining fields following
 // the problematic one will be unmarshaled into the target object.
 //
@@ -93,7 +95,7 @@ import (
 // invalid UTF-16 surrogate pairs are not treated as an error.
 // Instead, they are replaced by the Unicode replacement
 // character U+FFFD.
-func Unmarshal(data []byte, v interface{}) error {
+func Unmarshal(data []byte, v any) error {
 	// Check for well-formedness.
 	// Avoids filling out half a data structure
 	// before discovering a JSON syntax error.
@@ -108,8 +110,8 @@ func Unmarshal(data []byte, v interface{}) error {
 	return d.unmarshal(v)
 }
 
-// UnmarshalWithContext is like Unmarshal but allows a context to be passed through.
-// To take advantage of this, you must implement UnmarshalerWithContext instead of Unmarshaler.
+// UnmarshalWithContext is like [Unmarshal] but allows a context to be passed through.
+// To take advantage of this, you must implement [UnmarshalerWithContext] instead of [Unmarshaler].
 func UnmarshalWithContext(ctx context.Context, data []byte, v interface{}) error {
 	// Check for well-formedness.
 	// Avoids filling out half a data structure
@@ -135,13 +137,13 @@ func UnmarshalWithContext(ctx context.Context, data []byte, v interface{}) error
 // a JSON value. UnmarshalJSON must copy the JSON data
 // if it wishes to retain the data after returning.
 //
-// By convention, to approximate the behavior of Unmarshal itself,
+// By convention, to approximate the behavior of [Unmarshal] itself,
 // Unmarshalers implement UnmarshalJSON([]byte("null")) as a no-op.
 type Unmarshaler interface {
 	UnmarshalJSON([]byte) error
 }
 
-// UnmarshalerWithContext is a version of Unmarshaler that
+// UnmarshalerWithContext is a version of [Unmarshaler] that
 // passes a context through from the decoder.
 type UnmarshalerWithContext interface {
 	UnmarshalJSONWithContext(context.Context, []byte) error
@@ -164,8 +166,8 @@ func (e *UnmarshalTypeError) Error() string {
 	return "json: cannot unmarshal " + e.Value + " into Go value of type " + e.Type.String()
 }
 
-// An InvalidUnmarshalError describes an invalid argument passed to Unmarshal.
-// (The argument to Unmarshal must be a non-nil pointer.)
+// An InvalidUnmarshalError describes an invalid argument passed to [Unmarshal].
+// (The argument to [Unmarshal] must be a non-nil pointer.)
 type InvalidUnmarshalError struct {
 	Type reflect.Type
 }
@@ -175,15 +177,15 @@ func (e *InvalidUnmarshalError) Error() string {
 		return "json: Unmarshal(nil)"
 	}
 
-	if e.Type.Kind() != reflect.Ptr {
+	if e.Type.Kind() != reflect.Pointer {
 		return "json: Unmarshal(non-pointer " + e.Type.String() + ")"
 	}
 	return "json: Unmarshal(nil " + e.Type.String() + ")"
 }
 
-func (d *decodeState) unmarshal(v interface{}) error {
+func (d *decodeState) unmarshal(v any) error {
 	rv := reflect.ValueOf(v)
-	if rv.Kind() != reflect.Ptr || rv.IsNil() {
+	if rv.Kind() != reflect.Pointer || rv.IsNil() {
 		return &InvalidUnmarshalError{reflect.TypeOf(v)}
 	}
 
@@ -413,7 +415,7 @@ type unquotedValue struct{}
 // quoted string literal or literal null into an interface value.
 // If it finds anything other than a quoted string literal or null,
 // valueQuoted returns unquotedValue{}.
-func (d *decodeState) valueQuoted() interface{} {
+func (d *decodeState) valueQuoted() any {
 	switch d.opcode {
 	default:
 		panic(phasePanicMsg)
@@ -455,7 +457,7 @@ func indirect(v reflect.Value, decodingNull bool) (UnmarshalerWithContext, Unmar
 	// If v is a named type and is addressable,
 	// start with its address, so that if the type has pointer methods,
 	// we find them.
-	if v.Kind() != reflect.Ptr && v.Type().Name() != "" && v.CanAddr() {
+	if v.Kind() != reflect.Pointer && v.Type().Name() != "" && v.CanAddr() {
 		haveAddr = true
 		v = v.Addr()
 	}
@@ -464,14 +466,14 @@ func indirect(v reflect.Value, decodingNull bool) (UnmarshalerWithContext, Unmar
 		// usefully addressable.
 		if v.Kind() == reflect.Interface && !v.IsNil() {
 			e := v.Elem()
-			if e.Kind() == reflect.Ptr && !e.IsNil() && (!decodingNull || e.Elem().Kind() == reflect.Ptr) {
+			if e.Kind() == reflect.Pointer && !e.IsNil() && (!decodingNull || e.Elem().Kind() == reflect.Pointer) {
 				haveAddr = false
 				v = e
 				continue
 			}
 		}
 
-		if v.Kind() != reflect.Ptr {
+		if v.Kind() != reflect.Pointer {
 			break
 		}
 
@@ -562,17 +564,10 @@ func (d *decodeState) array(v reflect.Value) error {
 			break
 		}
 
-		// Get element of array, growing if necessary.
+		// Expand slice length, growing the slice if necessary.
 		if v.Kind() == reflect.Slice {
-			// Grow slice if necessary
 			if i >= v.Cap() {
-				newcap := v.Cap() + v.Cap()/2
-				if newcap < 4 {
-					newcap = 4
-				}
-				newv := reflect.MakeSlice(v.Type(), v.Len(), newcap)
-				reflect.Copy(newv, v)
-				v.Set(newv)
+				v.Grow(1)
 			}
 			if i >= v.Len() {
 				v.SetLen(i + 1)
@@ -606,13 +601,11 @@ func (d *decodeState) array(v reflect.Value) error {
 
 	if i < v.Len() {
 		if v.Kind() == reflect.Array {
-			// Array. Zero the rest.
-			z := reflect.Zero(v.Type().Elem())
 			for ; i < v.Len(); i++ {
-				v.Index(i).Set(z)
+				v.Index(i).SetZero() // zero remainder of array
 			}
 		} else {
-			v.SetLen(i)
+			v.SetLen(i) // truncate the slice
 		}
 	}
 	if i == 0 && v.Kind() == reflect.Slice {
@@ -622,7 +615,7 @@ func (d *decodeState) array(v reflect.Value) error {
 }
 
 var nullLiteral = []byte("null")
-var textUnmarshalerType = reflect.TypeOf((*encoding.TextUnmarshaler)(nil)).Elem()
+var textUnmarshalerType = reflect.TypeFor[encoding.TextUnmarshaler]()
 
 // object consumes an object from d.data[d.off-1:], decoding into v.
 // The first byte ('{') of the object has been read already.
@@ -669,7 +662,7 @@ func (d *decodeState) object(v reflect.Value) error {
 			reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
 			reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
 		default:
-			if !reflect.PtrTo(t.Key()).Implements(textUnmarshalerType) {
+			if !reflect.PointerTo(t.Key()).Implements(textUnmarshalerType) {
 				d.saveError(&UnmarshalTypeError{Value: "object", Type: t, Offset: int64(d.off)})
 				d.skip()
 				return nil
@@ -722,30 +715,19 @@ func (d *decodeState) object(v reflect.Value) error {
 			if !mapElem.IsValid() {
 				mapElem = reflect.New(elemType).Elem()
 			} else {
-				mapElem.Set(reflect.Zero(elemType))
+				mapElem.SetZero()
 			}
 			subv = mapElem
 		} else {
-			var f *field
-			if i, ok := fields.nameIndex[string(key)]; ok {
-				// Found an exact name match.
-				f = &fields.list[i]
-			} else {
-				// Fall back to the expensive case-insensitive
-				// linear search.
-				for i = range fields.list {
-					ff := &fields.list[i]
-					if ff.equalFold(ff.nameBytes, key) || (len(ff.altNameBytes) > 0 && ff.altEqualFold(ff.altNameBytes, key)) {
-						f = ff
-						break
-					}
-				}
+			f := fields.byExactName[string(key)]
+			if f == nil {
+				f = fields.byFoldedName[string(foldName(key))]
 			}
 			if f != nil {
 				subv = v
 				destring = f.quoted
 				for _, i := range f.index {
-					if subv.Kind() == reflect.Ptr {
+					if subv.Kind() == reflect.Pointer {
 						if subv.IsNil() {
 							// If a struct embeds a pointer to an unexported type,
 							// it is not possible to set a newly allocated value
@@ -809,17 +791,17 @@ func (d *decodeState) object(v reflect.Value) error {
 		if v.Kind() == reflect.Map {
 			kt := t.Key()
 			var kv reflect.Value
-			switch {
-			case reflect.PtrTo(kt).Implements(textUnmarshalerType):
+			if reflect.PointerTo(kt).Implements(textUnmarshalerType) {
 				kv = reflect.New(kt)
 				if err := d.literalStore(item, kv, true); err != nil {
 					return err
 				}
 				kv = kv.Elem()
-			case kt.Kind() == reflect.String:
-				kv = reflect.ValueOf(key).Convert(kt)
-			default:
+			} else {
 				switch kt.Kind() {
+				case reflect.String:
+					kv = reflect.New(kt).Elem()
+					kv.SetString(string(key))
 				case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
 					s := string(key)
 					n, err := strconv.ParseInt(s, 10, 64)
@@ -827,7 +809,8 @@ func (d *decodeState) object(v reflect.Value) error {
 						d.saveError(&UnmarshalTypeError{Value: "number " + s, Type: kt, Offset: int64(start + 1)})
 						break
 					}
-					kv = reflect.ValueOf(n).Convert(kt)
+					kv = reflect.New(kt).Elem()
+					kv.SetInt(n)
 				case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
 					s := string(key)
 					n, err := strconv.ParseUint(s, 10, 64)
@@ -835,7 +818,8 @@ func (d *decodeState) object(v reflect.Value) error {
 						d.saveError(&UnmarshalTypeError{Value: "number " + s, Type: kt, Offset: int64(start + 1)})
 						break
 					}
-					kv = reflect.ValueOf(n).Convert(kt)
+					kv = reflect.New(kt).Elem()
+					kv.SetUint(n)
 				default:
 					panic("json: Unexpected key type") // should never occur
 				}
@@ -868,18 +852,18 @@ func (d *decodeState) object(v reflect.Value) error {
 
 // convertNumber converts the number literal s to a float64 or a Number
 // depending on the setting of d.useNumber.
-func (d *decodeState) convertNumber(s string) (interface{}, error) {
+func (d *decodeState) convertNumber(s string) (any, error) {
 	if d.useNumber {
 		return Number(s), nil
 	}
 	f, err := strconv.ParseFloat(s, 64)
 	if err != nil {
-		return nil, &UnmarshalTypeError{Value: "number " + s, Type: reflect.TypeOf(0.0), Offset: int64(d.off)}
+		return nil, &UnmarshalTypeError{Value: "number " + s, Type: reflect.TypeFor[float64](), Offset: int64(d.off)}
 	}
 	return f, nil
 }
 
-var numberType = reflect.TypeOf(Number(""))
+var numberType = reflect.TypeFor[Number]()
 
 // literalStore decodes a literal stored in item into v.
 //
@@ -889,7 +873,7 @@ var numberType = reflect.TypeOf(Number(""))
 func (d *decodeState) literalStore(item []byte, v reflect.Value, fromQuoted bool) error {
 	// Check for unmarshaler.
 	if len(item) == 0 {
-		// Empty string given
+		// Empty string given.
 		d.saveError(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type()))
 		return nil
 	}
@@ -938,8 +922,8 @@ func (d *decodeState) literalStore(item []byte, v reflect.Value, fromQuoted bool
 			break
 		}
 		switch v.Kind() {
-		case reflect.Interface, reflect.Ptr, reflect.Map, reflect.Slice:
-			v.Set(reflect.Zero(v.Type()))
+		case reflect.Interface, reflect.Pointer, reflect.Map, reflect.Slice:
+			v.SetZero()
 			// otherwise, ignore null for primitives/string
 		}
 	case 't', 'f': // true, false
@@ -1010,13 +994,12 @@ func (d *decodeState) literalStore(item []byte, v reflect.Value, fromQuoted bool
 			}
 			panic(phasePanicMsg)
 		}
-		s := string(item)
 		switch v.Kind() {
 		default:
 			if v.Kind() == reflect.String && v.Type() == numberType {
 				// s must be a valid number, because it's
 				// already been tokenized.
-				v.SetString(s)
+				v.SetString(string(item))
 				break
 			}
 			if fromQuoted {
@@ -1024,7 +1007,7 @@ func (d *decodeState) literalStore(item []byte, v reflect.Value, fromQuoted bool
 			}
 			d.saveError(&UnmarshalTypeError{Value: "number", Type: v.Type(), Offset: int64(d.readIndex())})
 		case reflect.Interface:
-			n, err := d.convertNumber(s)
+			n, err := d.convertNumber(string(item))
 			if err != nil {
 				d.saveError(err)
 				break
@@ -1036,25 +1019,25 @@ func (d *decodeState) literalStore(item []byte, v reflect.Value, fromQuoted bool
 			v.Set(reflect.ValueOf(n))
 
 		case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
-			n, err := strconv.ParseInt(s, 10, 64)
+			n, err := strconv.ParseInt(string(item), 10, 64)
 			if err != nil || v.OverflowInt(n) {
-				d.saveError(&UnmarshalTypeError{Value: "number " + s, Type: v.Type(), Offset: int64(d.readIndex())})
+				d.saveError(&UnmarshalTypeError{Value: "number " + string(item), Type: v.Type(), Offset: int64(d.readIndex())})
 				break
 			}
 			v.SetInt(n)
 
 		case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
-			n, err := strconv.ParseUint(s, 10, 64)
+			n, err := strconv.ParseUint(string(item), 10, 64)
 			if err != nil || v.OverflowUint(n) {
-				d.saveError(&UnmarshalTypeError{Value: "number " + s, Type: v.Type(), Offset: int64(d.readIndex())})
+				d.saveError(&UnmarshalTypeError{Value: "number " + string(item), Type: v.Type(), Offset: int64(d.readIndex())})
 				break
 			}
 			v.SetUint(n)
 
 		case reflect.Float32, reflect.Float64:
-			n, err := strconv.ParseFloat(s, v.Type().Bits())
+			n, err := strconv.ParseFloat(string(item), v.Type().Bits())
 			if err != nil || v.OverflowFloat(n) {
-				d.saveError(&UnmarshalTypeError{Value: "number " + s, Type: v.Type(), Offset: int64(d.readIndex())})
+				d.saveError(&UnmarshalTypeError{Value: "number " + string(item), Type: v.Type(), Offset: int64(d.readIndex())})
 				break
 			}
 			v.SetFloat(n)
@@ -1068,7 +1051,7 @@ func (d *decodeState) literalStore(item []byte, v reflect.Value, fromQuoted bool
 // but they avoid the weight of reflection in this common case.
 
 // valueInterface is like value but returns interface{}
-func (d *decodeState) valueInterface() (val interface{}) {
+func (d *decodeState) valueInterface() (val any) {
 	switch d.opcode {
 	default:
 		panic(phasePanicMsg)
@@ -1085,8 +1068,8 @@ func (d *decodeState) valueInterface() (val interface{}) {
 }
 
 // arrayInterface is like array but returns []interface{}.
-func (d *decodeState) arrayInterface() []interface{} {
-	var v = make([]interface{}, 0)
+func (d *decodeState) arrayInterface() []any {
+	var v = make([]any, 0)
 	for {
 		// Look ahead for ] - can only happen on first iteration.
 		d.scanWhile(scanSkipSpace)
@@ -1111,8 +1094,8 @@ func (d *decodeState) arrayInterface() []interface{} {
 }
 
 // objectInterface is like object but returns map[string]interface{}.
-func (d *decodeState) objectInterface() map[string]interface{} {
-	m := make(map[string]interface{})
+func (d *decodeState) objectInterface() map[string]any {
+	m := make(map[string]any)
 	for {
 		// Read opening " of string key or closing }.
 		d.scanWhile(scanSkipSpace)
@@ -1162,7 +1145,7 @@ func (d *decodeState) objectInterface() map[string]interface{} {
 // literalInterface consumes and returns a literal from d.data[d.off-1:] and
 // it reads the following byte ahead. The first byte of the literal has been
 // read already (that's how the caller knows it's a literal).
-func (d *decodeState) literalInterface() interface{} {
+func (d *decodeState) literalInterface() any {
 	// All bytes inside literal return scanContinue op code.
 	start := d.readIndex()
 	d.rescanLiteral()
diff --git a/encode.go b/encode.go
index ba00da4..baf4a19 100644
--- a/encode.go
+++ b/encode.go
@@ -18,6 +18,7 @@ import (
 	"fmt"
 	"math"
 	"reflect"
+	"slices"
 	"sort"
 	"strconv"
 	"strings"
@@ -35,29 +36,30 @@ type Omitter interface {
 // Marshal returns the JSON encoding of v.
 //
 // Marshal traverses the value v recursively.
-// If an encountered value implements the Marshaler interface
-// and is not a nil pointer, Marshal calls its MarshalJSON method
-// to produce JSON. If no MarshalJSON method is present but the
-// value implements encoding.TextMarshaler instead, Marshal calls
-// its MarshalText method and encodes the result as a JSON string.
+// If an encountered value implements [Marshaler]
+// and is not a nil pointer, Marshal calls [Marshaler.MarshalJSON]
+// to produce JSON. If no [Marshaler.MarshalJSON] method is present but the
+// value implements [encoding.TextMarshaler] instead, Marshal calls
+// [encoding.TextMarshaler.MarshalText] and encodes the result as a JSON string.
 // The nil pointer exception is not strictly necessary
 // but mimics a similar, necessary exception in the behavior of
-// UnmarshalJSON.
+// [Unmarshaler.UnmarshalJSON].
 //
 // Otherwise, Marshal uses the following type-dependent default encodings:
 //
 // Boolean values encode as JSON booleans.
 //
-// Floating point, integer, and Number values encode as JSON numbers.
+// Floating point, integer, and [Number] values encode as JSON numbers.
+// NaN and +/-Inf values will return an [UnsupportedValueError].
 //
 // String values encode as JSON strings coerced to valid UTF-8,
 // replacing invalid bytes with the Unicode replacement rune.
 // So that the JSON will be safe to embed inside HTML <script> tags,
-// the string is encoded using HTMLEscape,
+// the string is encoded using [HTMLEscape],
 // which replaces "<", ">", "&", U+2028, and U+2029 are escaped
 // to "\u003c","\u003e", "\u0026", "\u2028", and "\u2029".
-// This replacement can be disabled when using an Encoder,
-// by calling SetEscapeHTML(false).
+// This replacement can be disabled when using an [Encoder],
+// by calling [Encoder.SetEscapeHTML](false).
 //
 // Array and slice values encode as JSON arrays, except that
 // []byte encodes as a base64-encoded string, and a nil slice
@@ -118,7 +120,7 @@ type Omitter interface {
 // only Unicode letters, digits, and ASCII punctuation except quotation
 // marks, backslash, and comma.
 //
-// Anonymous struct fields are usually marshaled as if their inner exported fields
+// Embedded struct fields are usually marshaled as if their inner exported fields
 // were fields in the outer struct, subject to the usual Go visibility rules amended
 // as described in the next paragraph.
 // An anonymous struct field with a name given in its JSON tag is treated as
@@ -145,11 +147,11 @@ type Omitter interface {
 // a JSON tag of "-".
 //
 // Map values encode as JSON objects. The map's key type must either be a
-// string, an integer type, or implement encoding.TextMarshaler. The map keys
+// string, an integer type, or implement [encoding.TextMarshaler]. The map keys
 // are sorted and used as JSON object keys by applying the following rules,
 // subject to the UTF-8 coercion described for string values above:
 //   - keys of any string type are used directly
-//   - encoding.TextMarshalers are marshaled
+//   - [encoding.TextMarshalers] are marshaled
 //   - integer keys are converted to strings
 //
 // Pointer values encode as the value pointed to.
@@ -160,13 +162,14 @@ type Omitter interface {
 //
 // Channel, complex, and function values cannot be encoded in JSON.
 // Attempting to encode such a value causes Marshal to return
-// an UnsupportedTypeError.
+// an [UnsupportedTypeError].
 //
 // JSON cannot represent cyclic data structures and Marshal does not
 // handle them. Passing cyclic structures to Marshal will result in
 // an error.
-func Marshal(v interface{}) ([]byte, error) {
+func Marshal(v any) ([]byte, error) {
 	e := newEncodeState()
+	defer encodeStatePool.Put(e)
 
 	err := e.marshal(v, encOpts{ctx: context.Background(), escapeHTML: true})
 	if err != nil {
@@ -174,15 +177,14 @@ func Marshal(v interface{}) ([]byte, error) {
 	}
 	buf := append([]byte(nil), e.Bytes()...)
 
-	encodeStatePool.Put(e)
-
 	return buf, nil
 }
 
-// MarshalWithContext is like Marshal but allows a context to be passed through.
-// To take advantage of this, you must implement MarshalerWithContext instead of Marshaler.
+// MarshalWithContext is like [Marshal] but allows a context to be passed through.
+// To take advantage of this, you must implement [MarshalerWithContext] instead of [Marshaler].
 func MarshalWithContext(ctx context.Context, v interface{}) ([]byte, error) {
 	e := newEncodeState()
+	defer encodeStatePool.Put(e)
 
 	if ctx == nil {
 		ctx = context.Background()
@@ -193,75 +195,38 @@ func MarshalWithContext(ctx context.Context, v interface{}) ([]byte, error) {
 	}
 	buf := append([]byte(nil), e.Bytes()...)
 
-	encodeStatePool.Put(e)
-
 	return buf, nil
 }
 
-// MarshalIndent is like Marshal but applies Indent to format the output.
+// MarshalIndent is like [Marshal] but applies [Indent] to format the output.
 // Each JSON element in the output will begin on a new line beginning with prefix
 // followed by one or more copies of indent according to the indentation nesting.
-func MarshalIndent(v interface{}, prefix, indent string) ([]byte, error) {
+func MarshalIndent(v any, prefix, indent string) ([]byte, error) {
 	b, err := Marshal(v)
 	if err != nil {
 		return nil, err
 	}
-	var buf bytes.Buffer
-	err = Indent(&buf, b, prefix, indent)
+	b2 := make([]byte, 0, indentGrowthFactor*len(b))
+	b2, err = appendIndent(b2, b, prefix, indent)
 	if err != nil {
 		return nil, err
 	}
-	return buf.Bytes(), nil
+	return b2, nil
 }
 
-// MarshalIndentWithContext is like MarshalIndent but allows a context to be passed through.
-// To take advantage of this, you must implement MarshalerWithContext instead of Marshaler.
+// MarshalIndentWithContext is like [MarshalIndent] but allows a context to be passed through.
+// To take advantage of this, you must implement [MarshalerWithContext] instead of [Marshaler].
 func MarshalIndentWithContext(ctx context.Context, v interface{}, prefix, indent string) ([]byte, error) {
 	b, err := MarshalWithContext(ctx, v)
 	if err != nil {
 		return nil, err
 	}
-	var buf bytes.Buffer
-	err = Indent(&buf, b, prefix, indent)
+	b2 := make([]byte, 0, indentGrowthFactor*len(b))
+	b2, err = appendIndent(b2, b, prefix, indent)
 	if err != nil {
 		return nil, err
 	}
-	return buf.Bytes(), nil
-}
-
-// HTMLEscape appends to dst the JSON-encoded src with <, >, &, U+2028 and U+2029
-// characters inside string literals changed to \u003c, \u003e, \u0026, \u2028, \u2029
-// so that the JSON will be safe to embed inside HTML <script> tags.
-// For historical reasons, web browsers don't honor standard HTML
-// escaping within <script> tags, so an alternative JSON encoding must
-// be used.
-func HTMLEscape(dst *bytes.Buffer, src []byte) {
-	// The characters can only appear in string literals,
-	// so just scan the string one byte at a time.
-	start := 0
-	for i, c := range src {
-		if c == '<' || c == '>' || c == '&' {
-			if start < i {
-				dst.Write(src[start:i])
-			}
-			dst.WriteString(`\u00`)
-			dst.WriteByte(hex[c>>4])
-			dst.WriteByte(hex[c&0xF])
-			start = i + 1
-		}
-		// Convert U+2028 and U+2029 (E2 80 A8 and E2 80 A9).
-		if c == 0xE2 && i+2 < len(src) && src[i+1] == 0x80 && src[i+2]&^1 == 0xA8 {
-			if start < i {
-				dst.Write(src[start:i])
-			}
-			dst.WriteString(`\u202`)
-			dst.WriteByte(hex[src[i+2]&0xF])
-			start = i + 3
-		}
-	}
-	if start < len(src) {
-		dst.Write(src[start:])
-	}
+	return b2, nil
 }
 
 // Marshaler is the interface implemented by types that
@@ -276,7 +241,7 @@ type MarshalerWithContext interface {
 	MarshalJSONWithContext(context.Context) ([]byte, error)
 }
 
-// An UnsupportedTypeError is returned by Marshal when attempting
+// An UnsupportedTypeError is returned by [Marshal] when attempting
 // to encode an unsupported value type.
 type UnsupportedTypeError struct {
 	Type reflect.Type
@@ -286,7 +251,7 @@ func (e *UnsupportedTypeError) Error() string {
 	return "json: unsupported type: " + e.Type.String()
 }
 
-// An UnsupportedValueError is returned by Marshal when attempting
+// An UnsupportedValueError is returned by [Marshal] when attempting
 // to encode an unsupported value.
 type UnsupportedValueError struct {
 	Value reflect.Value
@@ -297,7 +262,8 @@ func (e *UnsupportedValueError) Error() string {
 	return "json: unsupported value: " + e.Str
 }
 
-// A MarshalerError represents an error from calling a MarshalJSON or MarshalText method.
+// A MarshalerError represents an error from calling a
+// [Marshaler.MarshalJSON] or [encoding.TextMarshaler.MarshalText] method.
 type MarshalerError struct {
 	Type       reflect.Type
 	Err        error
@@ -317,12 +283,11 @@ func (e *MarshalerError) Error() string {
 // Unwrap returns the underlying error.
 func (e *MarshalerError) Unwrap() error { return e.Err }
 
-var hex = "0123456789abcdef"
+const hex = "0123456789abcdef"
 
 // An encodeState encodes JSON into a bytes.Buffer.
 type encodeState struct {
 	bytes.Buffer // accumulated output
-	scratch      [64]byte
 
 	// Keep track of what pointers we've seen in the current recursive call
 	// path, to avoid cycles that could lead to a stack overflow. Only do
@@ -330,7 +295,7 @@ type encodeState struct {
 	// startDetectingCyclesAfter, so that we skip the work if we're within a
 	// reasonable amount of nested pointers deep.
 	ptrLevel uint
-	ptrSeen  map[interface{}]struct{}
+	ptrSeen  map[any]struct{}
 }
 
 const startDetectingCyclesAfter = 1000
@@ -347,7 +312,7 @@ func newEncodeState() *encodeState {
 		e.ptrLevel = 0
 		return e
 	}
-	return &encodeState{ptrSeen: make(map[interface{}]struct{})}
+	return &encodeState{ptrSeen: make(map[any]struct{})}
 }
 
 // jsonError is an error wrapper type for internal use only.
@@ -355,7 +320,7 @@ func newEncodeState() *encodeState {
 // can distinguish intentional panics from this package.
 type jsonError struct{ error }
 
-func (e *encodeState) marshal(v interface{}, opts encOpts) (err error) {
+func (e *encodeState) marshal(v any, opts encOpts) (err error) {
 	defer func() {
 		if r := recover(); r != nil {
 			if je, ok := r.(jsonError); ok {
@@ -381,20 +346,12 @@ func isEmptyValue(v reflect.Value) bool {
 	switch v.Kind() {
 	case reflect.Array, reflect.Map, reflect.Slice, reflect.String:
 		return v.Len() == 0
-	case reflect.Bool:
-		return !v.Bool()
-	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
-		return v.Int() == 0
-	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
-		return v.Uint() == 0
-	case reflect.Float32, reflect.Float64:
-		return v.Float() == 0
-	case reflect.Ptr:
-		return v.IsNil()
-	case reflect.Interface:
-		return v.IsNil()
-	case reflect.Struct:
-
+	case reflect.Bool,
+		reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
+		reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr,
+		reflect.Float32, reflect.Float64,
+		reflect.Interface, reflect.Pointer:
+		return v.IsZero()
 	}
 	return false
 }
@@ -453,9 +410,9 @@ func typeEncoder(t reflect.Type) encoderFunc {
 }
 
 var (
-	marshalerType            = reflect.TypeOf((*Marshaler)(nil)).Elem()
-	marshalerWithContextType = reflect.TypeOf((*MarshalerWithContext)(nil)).Elem()
-	textMarshalerType        = reflect.TypeOf((*encoding.TextMarshaler)(nil)).Elem()
+	marshalerWithContextType = reflect.TypeFor[MarshalerWithContext]()
+	marshalerType            = reflect.TypeFor[Marshaler]()
+	textMarshalerType        = reflect.TypeFor[encoding.TextMarshaler]()
 )
 
 // newTypeEncoder constructs an encoderFunc for a type.
@@ -465,11 +422,11 @@ func newTypeEncoder(t reflect.Type, allowAddr bool) encoderFunc {
 	// Marshaler with a value receiver, then we're better off taking
 	// the address of the value - otherwise we end up with an
 	// allocation as we cast the value to an interface.
-	if t.Kind() != reflect.Ptr && allowAddr {
-		if reflect.PtrTo(t).Implements(marshalerWithContextType) {
+	if t.Kind() != reflect.Pointer && allowAddr {
+		if reflect.PointerTo(t).Implements(marshalerWithContextType) {
 			return newCondAddrEncoder(addrMarshalerWithContextEncoder, newTypeEncoder(t, false))
 		}
-		if reflect.PtrTo(t).Implements(marshalerType) {
+		if reflect.PointerTo(t).Implements(marshalerType) {
 			return newCondAddrEncoder(addrMarshalerEncoder, newTypeEncoder(t, false))
 		}
 	}
@@ -479,7 +436,7 @@ func newTypeEncoder(t reflect.Type, allowAddr bool) encoderFunc {
 	if t.Implements(marshalerType) {
 		return marshalerEncoder
 	}
-	if t.Kind() != reflect.Ptr && allowAddr && reflect.PtrTo(t).Implements(textMarshalerType) {
+	if t.Kind() != reflect.Pointer && allowAddr && reflect.PointerTo(t).Implements(textMarshalerType) {
 		return newCondAddrEncoder(addrTextMarshalerEncoder, newTypeEncoder(t, false))
 	}
 	if t.Implements(textMarshalerType) {
@@ -509,7 +466,7 @@ func newTypeEncoder(t reflect.Type, allowAddr bool) encoderFunc {
 		return newSliceEncoder(t)
 	case reflect.Array:
 		return newArrayEncoder(t)
-	case reflect.Ptr:
+	case reflect.Pointer:
 		return newPtrEncoder(t)
 	default:
 		return unsupportedTypeEncoder
@@ -521,7 +478,7 @@ func invalidValueEncoder(e *encodeState, v reflect.Value, _ encOpts) {
 }
 
 func marshalerEncoder(e *encodeState, v reflect.Value, opts encOpts) {
-	if v.Kind() == reflect.Ptr && v.IsNil() {
+	if v.Kind() == reflect.Pointer && v.IsNil() {
 		e.WriteString("null")
 		return
 	}
@@ -532,8 +489,10 @@ func marshalerEncoder(e *encodeState, v reflect.Value, opts encOpts) {
 	}
 	b, err := m.MarshalJSON()
 	if err == nil {
-		// copy JSON into buffer, checking validity.
-		err = compact(&e.Buffer, b, opts.escapeHTML)
+		e.Grow(len(b))
+		out := e.AvailableBuffer()
+		out, err = appendCompact(out, b, opts.escapeHTML)
+		e.Buffer.Write(out)
 	}
 	if err != nil {
 		e.error(&MarshalerError{v.Type(), err, "MarshalJSON"})
@@ -552,8 +511,10 @@ func marshalerWithContextEncoder(e *encodeState, v reflect.Value, opts encOpts)
 	}
 	b, err := m.MarshalJSONWithContext(opts.ctx)
 	if err == nil {
-		// copy JSON into buffer, checking validity.
-		err = compact(&e.Buffer, b, opts.escapeHTML)
+		e.Grow(len(b))
+		out := e.AvailableBuffer()
+		out, err = appendCompact(out, b, opts.escapeHTML)
+		e.Buffer.Write(out)
 	}
 	if err != nil {
 		e.error(&MarshalerError{v.Type(), err, "MarshalJSON"})
@@ -569,8 +530,10 @@ func addrMarshalerEncoder(e *encodeState, v reflect.Value, opts encOpts) {
 	m := va.Interface().(Marshaler)
 	b, err := m.MarshalJSON()
 	if err == nil {
-		// copy JSON into buffer, checking validity.
-		err = compact(&e.Buffer, b, opts.escapeHTML)
+		e.Grow(len(b))
+		out := e.AvailableBuffer()
+		out, err = appendCompact(out, b, opts.escapeHTML)
+		e.Buffer.Write(out)
 	}
 	if err != nil {
 		e.error(&MarshalerError{v.Type(), err, "MarshalJSON"})
@@ -586,8 +549,10 @@ func addrMarshalerWithContextEncoder(e *encodeState, v reflect.Value, opts encOp
 	m := va.Interface().(MarshalerWithContext)
 	b, err := m.MarshalJSONWithContext(opts.ctx)
 	if err == nil {
-		// copy JSON into buffer, checking validity.
-		err = compact(&e.Buffer, b, opts.escapeHTML)
+		e.Grow(len(b))
+		out := e.AvailableBuffer()
+		out, err = appendCompact(out, b, opts.escapeHTML)
+		e.Buffer.Write(out)
 	}
 	if err != nil {
 		e.error(&MarshalerError{v.Type(), err, "MarshalJSON"})
@@ -595,7 +560,7 @@ func addrMarshalerWithContextEncoder(e *encodeState, v reflect.Value, opts encOp
 }
 
 func textMarshalerEncoder(e *encodeState, v reflect.Value, opts encOpts) {
-	if v.Kind() == reflect.Ptr && v.IsNil() {
+	if v.Kind() == reflect.Pointer && v.IsNil() {
 		e.WriteString("null")
 		return
 	}
@@ -608,7 +573,7 @@ func textMarshalerEncoder(e *encodeState, v reflect.Value, opts encOpts) {
 	if err != nil {
 		e.error(&MarshalerError{v.Type(), err, "MarshalText"})
 	}
-	e.stringBytes(b, opts.escapeHTML)
+	e.Write(appendString(e.AvailableBuffer(), b, opts.escapeHTML))
 }
 
 func addrTextMarshalerEncoder(e *encodeState, v reflect.Value, opts encOpts) {
@@ -622,43 +587,31 @@ func addrTextMarshalerEncoder(e *encodeState, v reflect.Value, opts encOpts) {
 	if err != nil {
 		e.error(&MarshalerError{v.Type(), err, "MarshalText"})
 	}
-	e.stringBytes(b, opts.escapeHTML)
+	e.Write(appendString(e.AvailableBuffer(), b, opts.escapeHTML))
 }
 
 func boolEncoder(e *encodeState, v reflect.Value, opts encOpts) {
-	if opts.quoted {
-		e.WriteByte('"')
-	}
-	if v.Bool() {
-		e.WriteString("true")
-	} else {
-		e.WriteString("false")
-	}
-	if opts.quoted {
-		e.WriteByte('"')
-	}
+	b := e.AvailableBuffer()
+	b = mayAppendQuote(b, opts.quoted)
+	b = strconv.AppendBool(b, v.Bool())
+	b = mayAppendQuote(b, opts.quoted)
+	e.Write(b)
 }
 
 func intEncoder(e *encodeState, v reflect.Value, opts encOpts) {
-	b := strconv.AppendInt(e.scratch[:0], v.Int(), 10)
-	if opts.quoted {
-		e.WriteByte('"')
-	}
+	b := e.AvailableBuffer()
+	b = mayAppendQuote(b, opts.quoted)
+	b = strconv.AppendInt(b, v.Int(), 10)
+	b = mayAppendQuote(b, opts.quoted)
 	e.Write(b)
-	if opts.quoted {
-		e.WriteByte('"')
-	}
 }
 
 func uintEncoder(e *encodeState, v reflect.Value, opts encOpts) {
-	b := strconv.AppendUint(e.scratch[:0], v.Uint(), 10)
-	if opts.quoted {
-		e.WriteByte('"')
-	}
+	b := e.AvailableBuffer()
+	b = mayAppendQuote(b, opts.quoted)
+	b = strconv.AppendUint(b, v.Uint(), 10)
+	b = mayAppendQuote(b, opts.quoted)
 	e.Write(b)
-	if opts.quoted {
-		e.WriteByte('"')
-	}
 }
 
 type floatEncoder int // number of bits
@@ -674,7 +627,8 @@ func (bits floatEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
 	// See golang.org/issue/6384 and golang.org/issue/14135.
 	// Like fmt %g, but the exponent cutoffs are different
 	// and exponents themselves are not padded to two digits.
-	b := e.scratch[:0]
+	b := e.AvailableBuffer()
+	b = mayAppendQuote(b, opts.quoted)
 	abs := math.Abs(f)
 	fmt := byte('f')
 	// Note: Must use float32 comparisons for underlying float32 value to get precise cutoffs right.
@@ -692,14 +646,8 @@ func (bits floatEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
 			b = b[:n-1]
 		}
 	}
-
-	if opts.quoted {
-		e.WriteByte('"')
-	}
+	b = mayAppendQuote(b, opts.quoted)
 	e.Write(b)
-	if opts.quoted {
-		e.WriteByte('"')
-	}
 }
 
 var (
@@ -718,24 +666,18 @@ func stringEncoder(e *encodeState, v reflect.Value, opts encOpts) {
 		if !isValidNumber(numStr) {
 			e.error(fmt.Errorf("json: invalid number literal %q", numStr))
 		}
-		if opts.quoted {
-			e.WriteByte('"')
-		}
-		e.WriteString(numStr)
-		if opts.quoted {
-			e.WriteByte('"')
-		}
+		b := e.AvailableBuffer()
+		b = mayAppendQuote(b, opts.quoted)
+		b = append(b, numStr...)
+		b = mayAppendQuote(b, opts.quoted)
+		e.Write(b)
 		return
 	}
 	if opts.quoted {
-		e2 := newEncodeState()
-		// Since we encode the string twice, we only need to escape HTML
-		// the first time.
-		e2.string(v.String(), opts.escapeHTML)
-		e.stringBytes(e2.Bytes(), false)
-		encodeStatePool.Put(e2)
+		b := appendString(nil, v.String(), opts.escapeHTML)
+		e.Write(appendString(e.AvailableBuffer(), b, false)) // no need to escape again since it is already escaped
 	} else {
-		e.string(v.String(), opts.escapeHTML)
+		e.Write(appendString(e.AvailableBuffer(), v.String(), opts.escapeHTML))
 	}
 }
 
@@ -816,8 +758,9 @@ type structEncoder struct {
 }
 
 type structFields struct {
-	list      []field
-	nameIndex map[string]int
+	list         []field
+	byExactName  map[string]*field
+	byFoldedName map[string]*field
 }
 
 func (se structEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
@@ -829,7 +772,7 @@ FieldLoop:
 		// Find the nested struct field by following f.index.
 		fv := v
 		for _, i := range f.index {
-			if fv.Kind() == reflect.Ptr {
+			if fv.Kind() == reflect.Pointer {
 				if fv.IsNil() {
 					continue FieldLoop
 				}
@@ -875,7 +818,7 @@ func (me mapEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
 	if e.ptrLevel++; e.ptrLevel > startDetectingCyclesAfter {
 		// We're a large number of nested ptrEncoder.encode calls deep;
 		// start checking if we've run into a pointer cycle.
-		ptr := v.Pointer()
+		ptr := v.UnsafePointer()
 		if _, ok := e.ptrSeen[ptr]; ok {
 			e.error(&UnsupportedValueError{v, fmt.Sprintf("encountered a cycle via %s", v.Type())})
 		}
@@ -885,22 +828,26 @@ func (me mapEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
 	e.WriteByte('{')
 
 	// Extract and sort the keys.
-	sv := make([]reflectWithString, v.Len())
-	mi := v.MapRange()
+	var (
+		sv  = make([]reflectWithString, v.Len())
+		mi  = v.MapRange()
+		err error
+	)
 	for i := 0; mi.Next(); i++ {
-		sv[i].k = mi.Key()
-		sv[i].v = mi.Value()
-		if err := sv[i].resolve(); err != nil {
+		if sv[i].ks, err = resolveKeyName(mi.Key()); err != nil {
 			e.error(fmt.Errorf("json: encoding error for type %q: %q", v.Type().String(), err.Error()))
 		}
+		sv[i].v = mi.Value()
 	}
-	sort.Slice(sv, func(i, j int) bool { return sv[i].ks < sv[j].ks })
+	slices.SortFunc(sv, func(i, j reflectWithString) int {
+		return strings.Compare(i.ks, j.ks)
+	})
 
 	for i, kv := range sv {
 		if i > 0 {
 			e.WriteByte(',')
 		}
-		e.string(kv.ks, opts.escapeHTML)
+		e.Write(appendString(e.AvailableBuffer(), kv.ks, opts.escapeHTML))
 		e.WriteByte(':')
 		me.elemEnc(e, kv.v, opts)
 	}
@@ -927,29 +874,13 @@ func encodeByteSlice(e *encodeState, v reflect.Value, _ encOpts) {
 		e.WriteString("null")
 		return
 	}
+
 	s := v.Bytes()
-	e.WriteByte('"')
-	encodedLen := base64.StdEncoding.EncodedLen(len(s))
-	if encodedLen <= len(e.scratch) {
-		// If the encoded bytes fit in e.scratch, avoid an extra
-		// allocation and use the cheaper Encoding.Encode.
-		dst := e.scratch[:encodedLen]
-		base64.StdEncoding.Encode(dst, s)
-		e.Write(dst)
-	} else if encodedLen <= 1024 {
-		// The encoded bytes are short enough to allocate for, and
-		// Encoding.Encode is still cheaper.
-		dst := make([]byte, encodedLen)
-		base64.StdEncoding.Encode(dst, s)
-		e.Write(dst)
-	} else {
-		// The encoded bytes are too long to cheaply allocate, and
-		// Encoding.Encode is no longer noticeably cheaper.
-		enc := base64.NewEncoder(base64.StdEncoding, e)
-		enc.Write(s)
-		enc.Close()
-	}
-	e.WriteByte('"')
+	b := e.AvailableBuffer()
+	b = append(b, '"')
+	b = base64.StdEncoding.AppendEncode(b, s)
+	b = append(b, '"')
+	e.Write(b)
 }
 
 // sliceEncoder just wraps an arrayEncoder, checking to make sure the value isn't nil.
@@ -968,9 +899,9 @@ func (se sliceEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
 		// Here we use a struct to memorize the pointer to the first element of the slice
 		// and its length.
 		ptr := struct {
-			ptr uintptr
+			ptr interface{} // always an unsafe.Pointer, but avoids a dependency on package unsafe
 			len int
-		}{v.Pointer(), v.Len()}
+		}{v.UnsafePointer(), v.Len()}
 		if _, ok := e.ptrSeen[ptr]; ok {
 			e.error(&UnsupportedValueError{v, fmt.Sprintf("encountered a cycle via %s", v.Type())})
 		}
@@ -984,7 +915,7 @@ func (se sliceEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
 func newSliceEncoder(t reflect.Type) encoderFunc {
 	// Byte slices get special treatment; arrays don't.
 	if t.Elem().Kind() == reflect.Uint8 {
-		p := reflect.PtrTo(t.Elem())
+		p := reflect.PointerTo(t.Elem())
 		if !p.Implements(marshalerWithContextType) && !p.Implements(marshalerType) && !p.Implements(textMarshalerType) {
 			return encodeByteSlice
 		}
@@ -1080,7 +1011,7 @@ func isValidTag(s string) bool {
 
 func typeByIndex(t reflect.Type, index []int) reflect.Type {
 	for _, i := range index {
-		if t.Kind() == reflect.Ptr {
+		if t.Kind() == reflect.Pointer {
 			t = t.Elem()
 		}
 		t = t.Field(i).Type
@@ -1089,150 +1020,77 @@ func typeByIndex(t reflect.Type, index []int) reflect.Type {
 }
 
 type reflectWithString struct {
-	k  reflect.Value
 	v  reflect.Value
 	ks string
 }
 
-func (w *reflectWithString) resolve() error {
-	if w.k.Kind() == reflect.String {
-		w.ks = w.k.String()
-		return nil
+func resolveKeyName(k reflect.Value) (string, error) {
+	if k.Kind() == reflect.String {
+		return k.String(), nil
 	}
-	if tm, ok := w.k.Interface().(encoding.TextMarshaler); ok {
-		if w.k.Kind() == reflect.Ptr && w.k.IsNil() {
-			return nil
+	if tm, ok := k.Interface().(encoding.TextMarshaler); ok {
+		if k.Kind() == reflect.Pointer && k.IsNil() {
+			return "", nil
 		}
 		buf, err := tm.MarshalText()
-		w.ks = string(buf)
-		return err
+		return string(buf), err
 	}
-	switch w.k.Kind() {
+	switch k.Kind() {
 	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
-		w.ks = strconv.FormatInt(w.k.Int(), 10)
-		return nil
+		return strconv.FormatInt(k.Int(), 10), nil
 	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
-		w.ks = strconv.FormatUint(w.k.Uint(), 10)
-		return nil
+		return strconv.FormatUint(k.Uint(), 10), nil
 	}
 	panic("unexpected map key type")
 }
 
-// NOTE: keep in sync with stringBytes below.
-func (e *encodeState) string(s string, escapeHTML bool) {
-	e.WriteByte('"')
+func appendString[Bytes []byte | string](dst []byte, src Bytes, escapeHTML bool) []byte {
+	dst = append(dst, '"')
 	start := 0
-	for i := 0; i < len(s); {
-		if b := s[i]; b < utf8.RuneSelf {
+	for i := 0; i < len(src); {
+		if b := src[i]; b < utf8.RuneSelf {
 			if htmlSafeSet[b] || (!escapeHTML && safeSet[b]) {
 				i++
 				continue
 			}
-			if start < i {
-				e.WriteString(s[start:i])
-			}
-			e.WriteByte('\\')
+			dst = append(dst, src[start:i]...)
 			switch b {
 			case '\\', '"':
-				e.WriteByte(b)
+				dst = append(dst, '\\', b)
+			case '\b':
+				dst = append(dst, '\\', 'b')
+			case '\f':
+				dst = append(dst, '\\', 'f')
 			case '\n':
-				e.WriteByte('n')
+				dst = append(dst, '\\', 'n')
 			case '\r':
-				e.WriteByte('r')
+				dst = append(dst, '\\', 'r')
 			case '\t':
-				e.WriteByte('t')
+				dst = append(dst, '\\', 't')
 			default:
-				// This encodes bytes < 0x20 except for \t, \n and \r.
+				// This encodes bytes < 0x20 except for \b, \f, \n, \r and \t.
 				// If escapeHTML is set, it also escapes <, >, and &
 				// because they can lead to security holes when
 				// user-controlled strings are rendered into JSON
 				// and served to some browsers.
-				e.WriteString(`u00`)
-				e.WriteByte(hex[b>>4])
-				e.WriteByte(hex[b&0xF])
+				dst = append(dst, '\\', 'u', '0', '0', hex[b>>4], hex[b&0xF])
 			}
 			i++
 			start = i
 			continue
 		}
-		c, size := utf8.DecodeRuneInString(s[i:])
-		if c == utf8.RuneError && size == 1 {
-			if start < i {
-				e.WriteString(s[start:i])
-			}
-			e.WriteString(`\ufffd`)
-			i += size
-			start = i
-			continue
-		}
-		// U+2028 is LINE SEPARATOR.
-		// U+2029 is PARAGRAPH SEPARATOR.
-		// They are both technically valid characters in JSON strings,
-		// but don't work in JSONP, which has to be evaluated as JavaScript,
-		// and can lead to security holes there. It is valid JSON to
-		// escape them, so we do so unconditionally.
-		// See http://timelessrepo.com/json-isnt-a-javascript-subset for discussion.
-		if c == '\u2028' || c == '\u2029' {
-			if start < i {
-				e.WriteString(s[start:i])
-			}
-			e.WriteString(`\u202`)
-			e.WriteByte(hex[c&0xF])
-			i += size
-			start = i
-			continue
+		// TODO(https://go.dev/issue/56948): Use generic utf8 functionality.
+		// For now, cast only a small portion of byte slices to a string
+		// so that it can be stack allocated. This slows down []byte slightly
+		// due to the extra copy, but keeps string performance roughly the same.
+		n := len(src) - i
+		if n > utf8.UTFMax {
+			n = utf8.UTFMax
 		}
-		i += size
-	}
-	if start < len(s) {
-		e.WriteString(s[start:])
-	}
-	e.WriteByte('"')
-}
-
-// NOTE: keep in sync with string above.
-func (e *encodeState) stringBytes(s []byte, escapeHTML bool) {
-	e.WriteByte('"')
-	start := 0
-	for i := 0; i < len(s); {
-		if b := s[i]; b < utf8.RuneSelf {
-			if htmlSafeSet[b] || (!escapeHTML && safeSet[b]) {
-				i++
-				continue
-			}
-			if start < i {
-				e.Write(s[start:i])
-			}
-			e.WriteByte('\\')
-			switch b {
-			case '\\', '"':
-				e.WriteByte(b)
-			case '\n':
-				e.WriteByte('n')
-			case '\r':
-				e.WriteByte('r')
-			case '\t':
-				e.WriteByte('t')
-			default:
-				// This encodes bytes < 0x20 except for \t, \n and \r.
-				// If escapeHTML is set, it also escapes <, >, and &
-				// because they can lead to security holes when
-				// user-controlled strings are rendered into JSON
-				// and served to some browsers.
-				e.WriteString(`u00`)
-				e.WriteByte(hex[b>>4])
-				e.WriteByte(hex[b&0xF])
-			}
-			i++
-			start = i
-			continue
-		}
-		c, size := utf8.DecodeRune(s[i:])
+		c, size := utf8.DecodeRuneInString(string(src[i : i+n]))
 		if c == utf8.RuneError && size == 1 {
-			if start < i {
-				e.Write(s[start:i])
-			}
-			e.WriteString(`\ufffd`)
+			dst = append(dst, src[start:i]...)
+			dst = append(dst, `\ufffd`...)
 			i += size
 			start = i
 			continue
@@ -1243,33 +1101,27 @@ func (e *encodeState) stringBytes(s []byte, escapeHTML bool) {
 		// but don't work in JSONP, which has to be evaluated as JavaScript,
 		// and can lead to security holes there. It is valid JSON to
 		// escape them, so we do so unconditionally.
-		// See http://timelessrepo.com/json-isnt-a-javascript-subset for discussion.
+		// See https://en.wikipedia.org/wiki/JSON#Safety.
 		if c == '\u2028' || c == '\u2029' {
-			if start < i {
-				e.Write(s[start:i])
-			}
-			e.WriteString(`\u202`)
-			e.WriteByte(hex[c&0xF])
+			dst = append(dst, src[start:i]...)
+			dst = append(dst, '\\', 'u', '2', '0', '2', hex[c&0xF])
 			i += size
 			start = i
 			continue
 		}
 		i += size
 	}
-	if start < len(s) {
-		e.Write(s[start:])
-	}
-	e.WriteByte('"')
+	dst = append(dst, src[start:]...)
+	dst = append(dst, '"')
+	return dst
 }
 
 // A field represents a single field found in a struct.
 type field struct {
 	name      string
-	nameBytes []byte                 // []byte(name)
-	equalFold func(s, t []byte) bool // bytes.EqualFold or equivalent
+	nameBytes []byte // []byte(name)
 
-	altNameBytes []byte                 // []byte(altName)
-	altEqualFold func(s, t []byte) bool // bytes.EqualFold or equivalent
+	altNameBytes []byte // []byte(altName)
 
 	nameNonEsc  string // `"` + name + `":`
 	nameEscHTML string // `"` + HTMLEscape(name) + `":`
@@ -1319,8 +1171,8 @@ func typeFields(t reflect.Type) structFields {
 	// Fields found.
 	var fields []field
 
-	// Buffer to run HTMLEscape on field names.
-	var nameEscBuf bytes.Buffer
+	// Buffer to run appendHTMLEscape on field names.
+	var nameEscBuf []byte
 
 	for len(next) > 0 {
 		current, next = next, current[:0]
@@ -1337,7 +1189,7 @@ func typeFields(t reflect.Type) structFields {
 				sf := f.typ.Field(i)
 				if sf.Anonymous {
 					t := sf.Type
-					if t.Kind() == reflect.Ptr {
+					if t.Kind() == reflect.Pointer {
 						t = t.Elem()
 					}
 					if !sf.IsExported() && t.Kind() != reflect.Struct {
@@ -1363,7 +1215,7 @@ func typeFields(t reflect.Type) structFields {
 				index[len(f.index)] = i
 
 				ft := sf.Type
-				if ft.Name() == "" && ft.Kind() == reflect.Ptr {
+				if ft.Name() == "" && ft.Kind() == reflect.Pointer {
 					// Follow pointer.
 					ft = ft.Elem()
 				}
@@ -1387,7 +1239,7 @@ func typeFields(t reflect.Type) structFields {
 					if name == "" {
 						name = sf.Name
 					}
-					fld := field{
+					field := field{
 						name:      name,
 						tag:       tagged,
 						index:     index,
@@ -1395,28 +1247,23 @@ func typeFields(t reflect.Type) structFields {
 						omitEmpty: opts.Contains("omitempty"),
 						quoted:    quoted,
 					}
-					fld.nameBytes = []byte(fld.name)
-					fld.equalFold = foldFunc(fld.nameBytes)
+					field.nameBytes = []byte(field.name)
 
 					// Check for alt naming
 					if alt := opts.PrefixedValue("alt="); alt != "" {
-						fld.altNameBytes = []byte(alt)
-						fld.altEqualFold = foldFunc(fld.altNameBytes)
+						field.altNameBytes = []byte(alt)
 					}
 
 					// Build nameEscHTML and nameNonEsc ahead of time.
-					nameEscBuf.Reset()
-					nameEscBuf.WriteString(`"`)
-					HTMLEscape(&nameEscBuf, fld.nameBytes)
-					nameEscBuf.WriteString(`":`)
-					fld.nameEscHTML = nameEscBuf.String()
-					fld.nameNonEsc = `"` + fld.name + `":`
-
-					fields = append(fields, fld)
+					nameEscBuf = appendHTMLEscape(nameEscBuf[:0], field.nameBytes)
+					field.nameEscHTML = `"` + string(nameEscBuf) + `":`
+					field.nameNonEsc = `"` + field.name + `":`
+
+					fields = append(fields, field)
 					if count[f.typ] > 1 {
 						// If there were multiple instances, add a second,
 						// so that the annihilation code will see a duplicate.
-						// It only cares about the distinction between 1 or 2,
+						// It only cares about the distinction between 1 and 2,
 						// so don't bother generating any more copies.
 						fields = append(fields, fields[len(fields)-1])
 					}
@@ -1484,11 +1331,26 @@ func typeFields(t reflect.Type) structFields {
 		f := &fields[i]
 		f.encoder = typeEncoder(typeByIndex(t, f.index))
 	}
-	nameIndex := make(map[string]int, len(fields))
+	exactNameIndex := make(map[string]*field, len(fields))
+	foldedNameIndex := make(map[string]*field, len(fields))
 	for i, field := range fields {
-		nameIndex[field.name] = i
+		exactNameIndex[field.name] = &fields[i]
+		// For historical reasons, first folded match takes precedence.
+		if _, ok := foldedNameIndex[string(foldName(field.nameBytes))]; !ok {
+			foldedNameIndex[string(foldName(field.nameBytes))] = &fields[i]
+		}
+		if len(field.altNameBytes) != 0 {
+			exactNameIndex[string(field.altNameBytes)] = &fields[i]
+			if _, ok := foldedNameIndex[string(foldName(field.altNameBytes))]; !ok {
+				foldedNameIndex[string(foldName(field.altNameBytes))] = &fields[i]
+			}
+		}
+	}
+	return structFields{
+		list:         fields,
+		byExactName:  exactNameIndex,
+		byFoldedName: foldedNameIndex,
 	}
-	return structFields{fields, nameIndex}
 }
 
 // dominantField looks through the fields, all of which are known to
@@ -1517,3 +1379,10 @@ func cachedTypeFields(t reflect.Type) structFields {
 	f, _ := fieldCache.LoadOrStore(t, typeFields(t))
 	return f.(structFields)
 }
+
+func mayAppendQuote(b []byte, quoted bool) []byte {
+	if quoted {
+		b = append(b, '"')
+	}
+	return b
+}
diff --git a/encode_test.go b/encode_test.go
index 016844c..b554c6d 100644
--- a/encode_test.go
+++ b/encode_test.go
@@ -8,16 +8,15 @@ import (
 	"bytes"
 	"context"
 	"encoding"
-	"encoding/json"
 	"fmt"
 	"log"
 	"math"
 	"reflect"
 	"regexp"
+	"runtime/debug"
 	"strconv"
 	"strings"
 	"testing"
-	"unicode"
 )
 
 type Optionals struct {
@@ -31,8 +30,8 @@ type Optionals struct {
 	Slr []string `json:"slr,random"`
 	Slo []string `json:"slo,omitempty"`
 
-	Mr map[string]interface{} `json:"mr"`
-	Mo map[string]interface{} `json:",omitempty"`
+	Mr map[string]any `json:"mr"`
+	Mo map[string]any `json:",omitempty"`
 
 	Fr float64 `json:"fr"`
 	Fo float64 `json:"fo,omitempty"`
@@ -47,7 +46,8 @@ type Optionals struct {
 	Sto struct{} `json:"sto,omitempty"`
 }
 
-var optionalsExpected = `{
+func TestOmitEmpty(t *testing.T) {
+	var want = `{
  "sr": "",
  "omitempty": 0,
  "slr": null,
@@ -58,19 +58,17 @@ var optionalsExpected = `{
  "str": {},
  "sto": {}
 }`
-
-func TestOmitEmpty(t *testing.T) {
 	var o Optionals
 	o.Sw = "something"
-	o.Mr = map[string]interface{}{}
-	o.Mo = map[string]interface{}{}
+	o.Mr = map[string]any{}
+	o.Mo = map[string]any{}
 
 	got, err := MarshalIndent(&o, "", " ")
 	if err != nil {
-		t.Fatal(err)
+		t.Fatalf("MarshalIndent error: %v", err)
 	}
-	if got := string(got); got != optionalsExpected {
-		t.Errorf(" got: %s\nwant: %s\n", got, optionalsExpected)
+	if got := string(got); got != want {
+		t.Errorf("MarshalIndent:\n\tgot:  %s\n\twant: %s\n", indentNewlines(got), indentNewlines(want))
 	}
 }
 
@@ -84,62 +82,57 @@ type StringTag struct {
 
 func TestRoundtripStringTag(t *testing.T) {
 	tests := []struct {
-		name string
+		CaseName
 		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"
-			}`,
+	}{{
+		CaseName: Name("AllTypes"),
+		in: StringTag{
+			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"
-			}`,
+		want: `{
+	"BoolStr": "true",
+	"IntStr": "42",
+	"UintptrStr": "44",
+	"StrStr": "\"xzbit\"",
+	"NumberStr": "46"
+}`,
+	}, {
+		// See golang.org/issues/38173.
+		CaseName: Name("StringDoubleEscapes"),
+		in: StringTag{
+			StrStr:    "\b\f\n\r\t\"\\",
+			NumberStr: "0", // just to satisfy the roundtrip
 		},
-	}
-	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")
+		want: `{
+	"BoolStr": "false",
+	"IntStr": "0",
+	"UintptrStr": "0",
+	"StrStr": "\"\\b\\f\\n\\r\\t\\\"\\\\\"",
+	"NumberStr": "0"
+}`,
+	}}
+	for _, tt := range tests {
+		t.Run(tt.Name, func(t *testing.T) {
+			got, err := MarshalIndent(&tt.in, "", "\t")
 			if err != nil {
-				t.Fatal(err)
+				t.Fatalf("%s: MarshalIndent error: %v", tt.Where, err)
 			}
-			if got := string(got); got != test.want {
-				t.Fatalf(" got: %s\nwant: %s\n", got, test.want)
+			if got := string(got); got != tt.want {
+				t.Fatalf("%s: MarshalIndent:\n\tgot:  %s\n\twant: %s", tt.Where, stripWhitespace(got), stripWhitespace(tt.want))
 			}
 
 			// Verify that it round-trips.
 			var s2 StringTag
 			if err := Unmarshal(got, &s2); err != nil {
-				t.Fatalf("Decode: %v", err)
+				t.Fatalf("%s: Decode error: %v", tt.Where, 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)
+			if !reflect.DeepEqual(s2, tt.in) {
+				t.Fatalf("%s: Decode:\n\tinput: %s\n\tgot:  %#v\n\twant: %#v", tt.Where, indentNewlines(string(got)), s2, tt.in)
 			}
 		})
 	}
@@ -152,21 +145,21 @@ type renamedRenamedByteSlice []renamedByte
 
 func TestEncodeRenamedByteSlice(t *testing.T) {
 	s := renamedByteSlice("abc")
-	result, err := Marshal(s)
+	got, err := Marshal(s)
 	if err != nil {
-		t.Fatal(err)
+		t.Fatalf("Marshal error: %v", err)
 	}
-	expect := `"YWJj"`
-	if string(result) != expect {
-		t.Errorf(" got %s want %s", result, expect)
+	want := `"YWJj"`
+	if string(got) != want {
+		t.Errorf("Marshal:\n\tgot:  %s\n\twant: %s", got, want)
 	}
 	r := renamedRenamedByteSlice("abc")
-	result, err = Marshal(r)
+	got, err = Marshal(r)
 	if err != nil {
-		t.Fatal(err)
+		t.Fatalf("Marshal error: %v", err)
 	}
-	if string(result) != expect {
-		t.Errorf(" got %s want %s", result, expect)
+	if string(got) != want {
+		t.Errorf("Marshal:\n\tgot:  %s\n\twant: %s", got, want)
 	}
 }
 
@@ -183,16 +176,16 @@ type PointerCycle struct {
 var pointerCycle = &PointerCycle{}
 
 type PointerCycleIndirect struct {
-	Ptrs []interface{}
+	Ptrs []any
 }
 
 type RecursiveSlice []RecursiveSlice
 
 var (
 	pointerCycleIndirect = &PointerCycleIndirect{}
-	mapCycle             = make(map[string]interface{})
-	sliceCycle           = []interface{}{nil}
-	sliceNoCycle         = []interface{}{nil, nil}
+	mapCycle             = make(map[string]any)
+	sliceCycle           = []any{nil}
+	sliceNoCycle         = []any{nil, nil}
 	recursiveSliceCycle  = []RecursiveSlice{nil}
 )
 
@@ -202,49 +195,53 @@ func init() {
 	samePointerNoCycle.Ptr2 = ptr
 
 	pointerCycle.Ptr = pointerCycle
-	pointerCycleIndirect.Ptrs = []interface{}{pointerCycleIndirect}
+	pointerCycleIndirect.Ptrs = []any{pointerCycleIndirect}
 
 	mapCycle["x"] = mapCycle
 	sliceCycle[0] = sliceCycle
 	sliceNoCycle[1] = sliceNoCycle[:1]
 	for i := startDetectingCyclesAfter; i > 0; i-- {
-		sliceNoCycle = []interface{}{sliceNoCycle}
+		sliceNoCycle = []any{sliceNoCycle}
 	}
 	recursiveSliceCycle[0] = recursiveSliceCycle
 }
 
 func TestSamePointerNoCycle(t *testing.T) {
 	if _, err := Marshal(samePointerNoCycle); err != nil {
-		t.Fatalf("unexpected error: %v", err)
+		t.Fatalf("Marshal error: %v", err)
 	}
 }
 
 func TestSliceNoCycle(t *testing.T) {
 	if _, err := Marshal(sliceNoCycle); err != nil {
-		t.Fatalf("unexpected error: %v", err)
+		t.Fatalf("Marshal error: %v", err)
 	}
 }
 
-var unsupportedValues = []interface{}{
-	math.NaN(),
-	math.Inf(-1),
-	math.Inf(1),
-	pointerCycle,
-	pointerCycleIndirect,
-	mapCycle,
-	sliceCycle,
-	recursiveSliceCycle,
-}
-
 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)
+	tests := []struct {
+		CaseName
+		in any
+	}{
+		{Name(""), math.NaN()},
+		{Name(""), math.Inf(-1)},
+		{Name(""), math.Inf(1)},
+		{Name(""), pointerCycle},
+		{Name(""), pointerCycleIndirect},
+		{Name(""), mapCycle},
+		{Name(""), sliceCycle},
+		{Name(""), recursiveSliceCycle},
+	}
+	for _, tt := range tests {
+		t.Run(tt.Name, func(t *testing.T) {
+			if _, err := Marshal(tt.in); err != nil {
+				if _, ok := err.(*UnsupportedValueError); !ok {
+					t.Errorf("%s: Marshal error:\n\tgot:  %T\n\twant: %T", tt.Where, err, new(UnsupportedValueError))
+				}
+			} else {
+				t.Errorf("%s: Marshal error: got nil, want non-nil", tt.Where)
 			}
-		} else {
-			t.Errorf("for %v, expected error", v)
-		}
+		})
 	}
 }
 
@@ -256,11 +253,11 @@ func TestMarshalTextFloatMap(t *testing.T) {
 	}
 	got, err := Marshal(m)
 	if err != nil {
-		t.Errorf("Marshal() error: %v", err)
+		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)
+		t.Errorf("Marshal:\n\tgot:  %s\n\twant: %s", got, want)
 	}
 }
 
@@ -325,10 +322,10 @@ func TestRefValMarshal(t *testing.T) {
 	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)
+		t.Fatalf("Marshal error: %v", err)
 	}
 	if got := string(b); got != want {
-		t.Errorf("got %q, want %q", got, want)
+		t.Errorf("Marshal:\n\tgot:  %s\n\twant: %s", got, want)
 	}
 }
 
@@ -351,34 +348,34 @@ func TestMarshalerEscaping(t *testing.T) {
 	want := `"\u003c\u0026\u003e"`
 	b, err := Marshal(c)
 	if err != nil {
-		t.Fatalf("Marshal(c): %v", err)
+		t.Fatalf("Marshal error: %v", err)
 	}
 	if got := string(b); got != want {
-		t.Errorf("Marshal(c) = %#q, want %#q", got, want)
+		t.Errorf("Marshal:\n\tgot:  %s\n\twant: %s", got, want)
 	}
 
 	var ct CText
 	want = `"\"\u003c\u0026\u003e\""`
 	b, err = Marshal(ct)
 	if err != nil {
-		t.Fatalf("Marshal(ct): %v", err)
+		t.Fatalf("Marshal error: %v", err)
 	}
 	if got := string(b); got != want {
-		t.Errorf("Marshal(ct) = %#q, want %#q", got, want)
+		t.Errorf("Marshal:\n\tgot:  %s\n\twant: %s", got, want)
 	}
 }
 
 func TestAnonymousFields(t *testing.T) {
 	tests := []struct {
-		label     string             // Test name
-		makeInput func() interface{} // Function to create input value
-		want      string             // Expected JSON output
+		CaseName
+		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() interface{} {
+		CaseName: Name("AmbiguousField"),
+		makeInput: func() any {
 			type (
 				S1 struct{ x, X int }
 				S2 struct{ x, X int }
@@ -391,10 +388,10 @@ func TestAnonymousFields(t *testing.T) {
 		},
 		want: `{}`,
 	}, {
-		label: "DominantField",
+		CaseName: Name("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() interface{} {
+		makeInput: func() any {
 			type (
 				S1 struct{ x, X int }
 				S2 struct{ x, X int }
@@ -409,8 +406,8 @@ func TestAnonymousFields(t *testing.T) {
 		want: `{"X":6}`,
 	}, {
 		// Unexported embedded field of non-struct type should not be serialized.
-		label: "UnexportedEmbeddedInt",
-		makeInput: func() interface{} {
+		CaseName: Name("UnexportedEmbeddedInt"),
+		makeInput: func() any {
 			type (
 				myInt int
 				S     struct{ myInt }
@@ -420,8 +417,8 @@ func TestAnonymousFields(t *testing.T) {
 		want: `{}`,
 	}, {
 		// Exported embedded field of non-struct type should be serialized.
-		label: "ExportedEmbeddedInt",
-		makeInput: func() interface{} {
+		CaseName: Name("ExportedEmbeddedInt"),
+		makeInput: func() any {
 			type (
 				MyInt int
 				S     struct{ MyInt }
@@ -432,8 +429,8 @@ func TestAnonymousFields(t *testing.T) {
 	}, {
 		// Unexported embedded field of pointer to non-struct type
 		// should not be serialized.
-		label: "UnexportedEmbeddedIntPointer",
-		makeInput: func() interface{} {
+		CaseName: Name("UnexportedEmbeddedIntPointer"),
+		makeInput: func() any {
 			type (
 				myInt int
 				S     struct{ *myInt }
@@ -446,8 +443,8 @@ func TestAnonymousFields(t *testing.T) {
 	}, {
 		// Exported embedded field of pointer to non-struct type
 		// should be serialized.
-		label: "ExportedEmbeddedIntPointer",
-		makeInput: func() interface{} {
+		CaseName: Name("ExportedEmbeddedIntPointer"),
+		makeInput: func() any {
 			type (
 				MyInt int
 				S     struct{ *MyInt }
@@ -461,8 +458,8 @@ func TestAnonymousFields(t *testing.T) {
 		// 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() interface{} {
+		CaseName: Name("EmbeddedStruct"),
+		makeInput: func() any {
 			type (
 				s1 struct{ x, X int }
 				S2 struct{ y, Y int }
@@ -478,8 +475,8 @@ func TestAnonymousFields(t *testing.T) {
 		// 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() interface{} {
+		CaseName: Name("EmbeddedStructPointer"),
+		makeInput: func() any {
 			type (
 				s1 struct{ x, X int }
 				S2 struct{ y, Y int }
@@ -494,8 +491,8 @@ func TestAnonymousFields(t *testing.T) {
 	}, {
 		// Exported fields on embedded unexported structs at multiple levels
 		// of nesting should still be serialized.
-		label: "NestedStructAndInts",
-		makeInput: func() interface{} {
+		CaseName: Name("NestedStructAndInts"),
+		makeInput: func() any {
 			type (
 				MyInt1 int
 				MyInt2 int
@@ -521,8 +518,8 @@ func TestAnonymousFields(t *testing.T) {
 		// 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() interface{} {
+		CaseName: Name("EmbeddedFieldBehindNilPointer"),
+		makeInput: func() any {
 			type (
 				S2 struct{ Field string }
 				S  struct{ *S2 }
@@ -533,13 +530,13 @@ func TestAnonymousFields(t *testing.T) {
 	}}
 
 	for _, tt := range tests {
-		t.Run(tt.label, func(t *testing.T) {
+		t.Run(tt.Name, func(t *testing.T) {
 			b, err := Marshal(tt.makeInput())
 			if err != nil {
-				t.Fatalf("Marshal() = %v, want nil error", err)
+				t.Fatalf("%s: Marshal error: %v", tt.Where, err)
 			}
 			if string(b) != tt.want {
-				t.Fatalf("Marshal() = %q, want %q", b, tt.want)
+				t.Fatalf("%s: Marshal:\n\tgot:  %s\n\twant: %s", tt.Where, b, tt.want)
 			}
 		})
 	}
@@ -591,31 +588,34 @@ func (nm *nilTextMarshaler) MarshalText() ([]byte, error) {
 
 // See golang.org/issue/16042 and golang.org/issue/34235.
 func TestNilMarshal(t *testing.T) {
-	testCases := []struct {
-		v    interface{}
+	tests := []struct {
+		CaseName
+		in   any
 		want string
 	}{
-		{v: nil, want: `null`},
-		{v: new(float64), want: `0`},
-		{v: []interface{}(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 interface{} }{(*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 interface{} }{(*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
-		}
+		{Name(""), nil, `null`},
+		{Name(""), new(float64), `0`},
+		{Name(""), []any(nil), `null`},
+		{Name(""), []string(nil), `null`},
+		{Name(""), map[string]string(nil), `null`},
+		{Name(""), []byte(nil), `null`},
+		{Name(""), struct{ M string }{"gopher"}, `{"M":"gopher"}`},
+		{Name(""), struct{ M Marshaler }{}, `{"M":null}`},
+		{Name(""), struct{ M Marshaler }{(*nilJSONMarshaler)(nil)}, `{"M":"0zenil0"}`},
+		{Name(""), struct{ M any }{(*nilJSONMarshaler)(nil)}, `{"M":null}`},
+		{Name(""), struct{ M encoding.TextMarshaler }{}, `{"M":null}`},
+		{Name(""), struct{ M encoding.TextMarshaler }{(*nilTextMarshaler)(nil)}, `{"M":"0zenil0"}`},
+		{Name(""), struct{ M any }{(*nilTextMarshaler)(nil)}, `{"M":null}`},
+	}
+	for _, tt := range tests {
+		t.Run(tt.Name, func(t *testing.T) {
+			switch got, err := Marshal(tt.in); {
+			case err != nil:
+				t.Fatalf("%s: Marshal error: %v", tt.Where, err)
+			case string(got) != tt.want:
+				t.Fatalf("%s: Marshal:\n\tgot:  %s\n\twant: %s", tt.Where, got, tt.want)
+			}
+		})
 	}
 }
 
@@ -627,12 +627,12 @@ func TestEmbeddedBug(t *testing.T) {
 	}
 	b, err := Marshal(v)
 	if err != nil {
-		t.Fatal("Marshal:", err)
+		t.Fatal("Marshal error:", err)
 	}
 	want := `{"S":"B"}`
 	got := string(b)
 	if got != want {
-		t.Fatalf("Marshal: got %s want %s", got, want)
+		t.Fatalf("Marshal:\n\tgot:  %s\n\twant: %s", got, want)
 	}
 	// Now check that the duplicate field, S, does not appear.
 	x := BugX{
@@ -640,12 +640,12 @@ func TestEmbeddedBug(t *testing.T) {
 	}
 	b, err = Marshal(x)
 	if err != nil {
-		t.Fatal("Marshal:", err)
+		t.Fatal("Marshal error:", err)
 	}
 	want = `{"A":23}`
 	got = string(b)
 	if got != want {
-		t.Fatalf("Marshal: got %s want %s", got, want)
+		t.Fatalf("Marshal:\n\tgot:  %s\n\twant: %s", got, want)
 	}
 }
 
@@ -667,12 +667,12 @@ func TestTaggedFieldDominates(t *testing.T) {
 	}
 	b, err := Marshal(v)
 	if err != nil {
-		t.Fatal("Marshal:", err)
+		t.Fatal("Marshal error:", err)
 	}
 	want := `{"S":"BugD"}`
 	got := string(b)
 	if got != want {
-		t.Fatalf("Marshal: got %s want %s", got, want)
+		t.Fatalf("Marshal:\n\tgot:  %s\n\twant: %s", got, want)
 	}
 }
 
@@ -694,72 +694,58 @@ func TestDuplicatedFieldDisappears(t *testing.T) {
 	}
 	b, err := Marshal(v)
 	if err != nil {
-		t.Fatal("Marshal:", err)
+		t.Fatal("Marshal error:", err)
 	}
 	want := `{}`
 	got := string(b)
 	if got != want {
-		t.Fatalf("Marshal: got %s want %s", got, want)
+		t.Fatalf("Marshal:\n\tgot:  %s\n\twant: %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)
+func TestIssue10281(t *testing.T) {
+	type Foo struct {
+		N Number
 	}
-	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)
+	x := Foo{Number(`invalid`)}
 
-		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 _, err := Marshal(&x); err == nil {
+		t.Fatalf("Marshal error: got nil, want non-nil")
+	}
+}
 
-			if len(enc) > 20 {
-				enc = enc[:20] + "..."
-			}
-			if len(encBytes) > 20 {
-				encBytes = encBytes[:20] + "..."
-			}
+func TestMarshalErrorAndReuseEncodeState(t *testing.T) {
+	// Disable the GC temporarily to prevent encodeState's in Pool being cleaned away during the test.
+	percent := debug.SetGCPercent(-1)
+	defer debug.SetGCPercent(percent)
 
-			t.Errorf("with escapeHTML=%t, encodings differ at %#q vs %#q",
-				escapeHTML, enc, encBytes)
-		}
+	// Trigger an error in Marshal with cyclic data.
+	type Dummy struct {
+		Name string
+		Next *Dummy
+	}
+	dummy := Dummy{Name: "Dummy"}
+	dummy.Next = &dummy
+	if _, err := Marshal(dummy); err == nil {
+		t.Errorf("Marshal error: got nil, want non-nil")
 	}
-}
 
-func TestIssue10281(t *testing.T) {
-	type Foo struct {
-		N Number
+	type Data struct {
+		A string
+		I int
+	}
+	want := Data{A: "a", I: 1}
+	b, err := Marshal(want)
+	if err != nil {
+		t.Errorf("Marshal error: %v", err)
 	}
-	x := Foo{Number(`invalid`)}
 
-	b, err := Marshal(&x)
-	if err == nil {
-		t.Errorf("Marshal(&x) = %#q; want error", b)
+	var got Data
+	if err := Unmarshal(b, &got); err != nil {
+		t.Errorf("Unmarshal error: %v", err)
+	}
+	if got != want {
+		t.Errorf("Unmarshal:\n\tgot:  %v\n\twant: %v", got, want)
 	}
 }
 
@@ -769,7 +755,7 @@ func TestHTMLEscape(t *testing.T) {
 	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())
+		t.Errorf("HTMLEscape:\n\tgot:  %s\n\twant: %s", b.Bytes(), want.Bytes())
 	}
 }
 
@@ -781,21 +767,19 @@ func TestEncodePointerString(t *testing.T) {
 	var n int64 = 42
 	b, err := Marshal(stringPointer{N: &n})
 	if err != nil {
-		t.Fatalf("Marshal: %v", err)
+		t.Fatalf("Marshal error: %v", err)
 	}
 	if got, want := string(b), `{"n":"42"}`; got != want {
-		t.Errorf("Marshal = %s, want %s", got, want)
+		t.Fatalf("Marshal:\n\tgot:  %s\n\twant: %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)
+	switch err = Unmarshal(b, &back); {
+	case err != nil:
+		t.Fatalf("Unmarshal error: %v", err)
+	case back.N == nil:
+		t.Fatalf("Unmarshal: back.N = nil, want non-nil")
+	case *back.N != 42:
+		t.Fatalf("Unmarshal: *back.N = %d, want 42", *back.N)
 	}
 }
 
@@ -811,11 +795,11 @@ var encodeStringTests = []struct {
 	{"\x05", `"\u0005"`},
 	{"\x06", `"\u0006"`},
 	{"\x07", `"\u0007"`},
-	{"\x08", `"\u0008"`},
+	{"\x08", `"\b"`},
 	{"\x09", `"\t"`},
 	{"\x0a", `"\n"`},
 	{"\x0b", `"\u000b"`},
-	{"\x0c", `"\u000c"`},
+	{"\x0c", `"\f"`},
 	{"\x0d", `"\r"`},
 	{"\x0e", `"\u000e"`},
 	{"\x0f", `"\u000f"`},
@@ -841,7 +825,7 @@ 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)
+			t.Errorf("Marshal(%q) error: %v", tt.in, err)
 			continue
 		}
 		out := string(b)
@@ -867,7 +851,7 @@ type textint int
 
 func (i textint) MarshalText() ([]byte, error) { return tenc(`TI:%d`, i) }
 
-func tenc(format string, a ...interface{}) ([]byte, error) {
+func tenc(format string, a ...any) ([]byte, error) {
 	var buf bytes.Buffer
 	fmt.Fprintf(&buf, format, a...)
 	return buf.Bytes(), nil
@@ -879,65 +863,67 @@ func (f textfloat) MarshalText() ([]byte, error) { return tenc(`TF:%0.2f`, f) }
 
 // Issue 13783
 func TestEncodeBytekind(t *testing.T) {
-	testdata := []struct {
-		data interface{}
+	tests := []struct {
+		CaseName
+		in   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)
-		}
+		{Name(""), byte(7), "7"},
+		{Name(""), jsonbyte(7), `{"JB":7}`},
+		{Name(""), textbyte(4), `"TB:4"`},
+		{Name(""), jsonint(5), `{"JI":5}`},
+		{Name(""), textint(1), `"TI:1"`},
+		{Name(""), []byte{0, 1}, `"AAE="`},
+		{Name(""), []jsonbyte{0, 1}, `[{"JB":0},{"JB":1}]`},
+		{Name(""), [][]jsonbyte{{0, 1}, {3}}, `[[{"JB":0},{"JB":1}],[{"JB":3}]]`},
+		{Name(""), []textbyte{2, 3}, `["TB:2","TB:3"]`},
+		{Name(""), []jsonint{5, 4}, `[{"JI":5},{"JI":4}]`},
+		{Name(""), []textint{9, 3}, `["TI:9","TI:3"]`},
+		{Name(""), []int{9, 3}, `[9,3]`},
+		{Name(""), []textfloat{12, 3}, `["TF:12.00","TF:3.00"]`},
+	}
+	for _, tt := range tests {
+		t.Run(tt.Name, func(t *testing.T) {
+			b, err := Marshal(tt.in)
+			if err != nil {
+				t.Errorf("%s: Marshal error: %v", tt.Where, err)
+			}
+			got, want := string(b), tt.want
+			if got != want {
+				t.Errorf("%s: Marshal:\n\tgot:  %s\n\twant: %s", tt.Where, got, want)
+			}
+		})
 	}
 }
 
 func TestTextMarshalerMapKeysAreSorted(t *testing.T) {
-	b, err := Marshal(map[unmarshalerText]int{
+	got, 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)
+		t.Fatalf("Marshal error: %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)
+	if string(got) != want {
+		t.Errorf("Marshal:\n\tgot:  %s\n\twant: %s", got, want)
 	}
 }
 
 // https://golang.org/issue/33675
 func TestNilMarshalerTextMapKey(t *testing.T) {
-	b, err := Marshal(map[*unmarshalerText]int{
+	got, err := Marshal(map[*unmarshalerText]int{
 		(*unmarshalerText)(nil): 1,
 		{"A", "B"}:              2,
 	})
 	if err != nil {
-		t.Fatalf("Failed to Marshal *text.Marshaler: %v", err)
+		t.Fatalf("Marshal error: %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)
+	if string(got) != want {
+		t.Errorf("Marshal:\n\tgot:  %s\n\twant: %s", got, want)
 	}
 }
 
@@ -969,14 +955,14 @@ func TestMarshalFloat(t *testing.T) {
 	t.Parallel()
 	nfail := 0
 	test := func(f float64, bits int) {
-		vf := interface{}(f)
+		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)
+			t.Errorf("Marshal(%T(%g)) error: %v", vf, vf, err)
 			nfail++
 			return
 		}
@@ -985,12 +971,12 @@ func TestMarshalFloat(t *testing.T) {
 		// 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)
+			t.Errorf("ParseFloat(%q) error: %v", 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)
+			t.Errorf("ParseFloat(%q):\n\tgot:  %g\n\twant: %g", out, float32(g), vf)
 			nfail++
 			return
 		}
@@ -1001,7 +987,7 @@ func TestMarshalFloat(t *testing.T) {
 		}
 		for _, re := range bad {
 			if re.MatchString(out) {
-				t.Errorf("Marshal(%T(%g)) = %q, must not match /%s/", vf, vf, out, re)
+				t.Errorf("Marshal(%T(%g)) = %q; must not match /%s/", vf, vf, out, re)
 				nfail++
 				return
 			}
@@ -1065,87 +1051,90 @@ func TestMarshalRawMessageValue(t *testing.T) {
 	)
 
 	tests := []struct {
-		in   interface{}
+		CaseName
+		in   any
 		want string
 		ok   bool
 	}{
 		// Test with nil RawMessage.
-		{rawNil, "null", true},
-		{&rawNil, "null", true},
-		{[]interface{}{rawNil}, "[null]", true},
-		{&[]interface{}{rawNil}, "[null]", true},
-		{[]interface{}{&rawNil}, "[null]", true},
-		{&[]interface{}{&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]interface{}{"M": rawNil}, `{"M":null}`, true},
-		{&map[string]interface{}{"M": rawNil}, `{"M":null}`, true},
-		{map[string]interface{}{"M": &rawNil}, `{"M":null}`, true},
-		{&map[string]interface{}{"M": &rawNil}, `{"M":null}`, true},
-		{T1{rawNil}, "{}", true},
-		{T2{&rawNil}, `{"M":null}`, true},
-		{&T1{rawNil}, "{}", true},
-		{&T2{&rawNil}, `{"M":null}`, true},
+		{Name(""), rawNil, "null", true},
+		{Name(""), &rawNil, "null", true},
+		{Name(""), []any{rawNil}, "[null]", true},
+		{Name(""), &[]any{rawNil}, "[null]", true},
+		{Name(""), []any{&rawNil}, "[null]", true},
+		{Name(""), &[]any{&rawNil}, "[null]", true},
+		{Name(""), struct{ M RawMessage }{rawNil}, `{"M":null}`, true},
+		{Name(""), &struct{ M RawMessage }{rawNil}, `{"M":null}`, true},
+		{Name(""), struct{ M *RawMessage }{&rawNil}, `{"M":null}`, true},
+		{Name(""), &struct{ M *RawMessage }{&rawNil}, `{"M":null}`, true},
+		{Name(""), map[string]any{"M": rawNil}, `{"M":null}`, true},
+		{Name(""), &map[string]any{"M": rawNil}, `{"M":null}`, true},
+		{Name(""), map[string]any{"M": &rawNil}, `{"M":null}`, true},
+		{Name(""), &map[string]any{"M": &rawNil}, `{"M":null}`, true},
+		{Name(""), T1{rawNil}, "{}", true},
+		{Name(""), T2{&rawNil}, `{"M":null}`, true},
+		{Name(""), &T1{rawNil}, "{}", true},
+		{Name(""), &T2{&rawNil}, `{"M":null}`, true},
 
 		// Test with empty, but non-nil, RawMessage.
-		{rawEmpty, "", false},
-		{&rawEmpty, "", false},
-		{[]interface{}{rawEmpty}, "", false},
-		{&[]interface{}{rawEmpty}, "", false},
-		{[]interface{}{&rawEmpty}, "", false},
-		{&[]interface{}{&rawEmpty}, "", false},
-		{struct{ X RawMessage }{rawEmpty}, "", false},
-		{&struct{ X RawMessage }{rawEmpty}, "", false},
-		{struct{ X *RawMessage }{&rawEmpty}, "", false},
-		{&struct{ X *RawMessage }{&rawEmpty}, "", false},
-		{map[string]interface{}{"nil": rawEmpty}, "", false},
-		{&map[string]interface{}{"nil": rawEmpty}, "", false},
-		{map[string]interface{}{"nil": &rawEmpty}, "", false},
-		{&map[string]interface{}{"nil": &rawEmpty}, "", false},
-		{T1{rawEmpty}, "{}", true},
-		{T2{&rawEmpty}, "", false},
-		{&T1{rawEmpty}, "{}", true},
-		{&T2{&rawEmpty}, "", false},
+		{Name(""), rawEmpty, "", false},
+		{Name(""), &rawEmpty, "", false},
+		{Name(""), []any{rawEmpty}, "", false},
+		{Name(""), &[]any{rawEmpty}, "", false},
+		{Name(""), []any{&rawEmpty}, "", false},
+		{Name(""), &[]any{&rawEmpty}, "", false},
+		{Name(""), struct{ X RawMessage }{rawEmpty}, "", false},
+		{Name(""), &struct{ X RawMessage }{rawEmpty}, "", false},
+		{Name(""), struct{ X *RawMessage }{&rawEmpty}, "", false},
+		{Name(""), &struct{ X *RawMessage }{&rawEmpty}, "", false},
+		{Name(""), map[string]any{"nil": rawEmpty}, "", false},
+		{Name(""), &map[string]any{"nil": rawEmpty}, "", false},
+		{Name(""), map[string]any{"nil": &rawEmpty}, "", false},
+		{Name(""), &map[string]any{"nil": &rawEmpty}, "", false},
+		{Name(""), T1{rawEmpty}, "{}", true},
+		{Name(""), T2{&rawEmpty}, "", false},
+		{Name(""), &T1{rawEmpty}, "{}", true},
+		{Name(""), &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},
-		{[]interface{}{rawText}, `["foo"]`, true},  // Issue6458
-		{&[]interface{}{rawText}, `["foo"]`, true}, // Issue6458
-		{[]interface{}{&rawText}, `["foo"]`, true},
-		{&[]interface{}{&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]interface{}{"M": rawText}, `{"M":"foo"}`, true},  // Issue6458
-		{&map[string]interface{}{"M": rawText}, `{"M":"foo"}`, true}, // Issue6458
-		{map[string]interface{}{"M": &rawText}, `{"M":"foo"}`, true},
-		{&map[string]interface{}{"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.Errorf("test %d, unexpected success", i)
+		{Name(""), rawText, `"foo"`, true}, // Issue6458
+		{Name(""), &rawText, `"foo"`, true},
+		{Name(""), []any{rawText}, `["foo"]`, true},  // Issue6458
+		{Name(""), &[]any{rawText}, `["foo"]`, true}, // Issue6458
+		{Name(""), []any{&rawText}, `["foo"]`, true},
+		{Name(""), &[]any{&rawText}, `["foo"]`, true},
+		{Name(""), struct{ M RawMessage }{rawText}, `{"M":"foo"}`, true}, // Issue6458
+		{Name(""), &struct{ M RawMessage }{rawText}, `{"M":"foo"}`, true},
+		{Name(""), struct{ M *RawMessage }{&rawText}, `{"M":"foo"}`, true},
+		{Name(""), &struct{ M *RawMessage }{&rawText}, `{"M":"foo"}`, true},
+		{Name(""), map[string]any{"M": rawText}, `{"M":"foo"}`, true},  // Issue6458
+		{Name(""), &map[string]any{"M": rawText}, `{"M":"foo"}`, true}, // Issue6458
+		{Name(""), map[string]any{"M": &rawText}, `{"M":"foo"}`, true},
+		{Name(""), &map[string]any{"M": &rawText}, `{"M":"foo"}`, true},
+		{Name(""), T1{rawText}, `{"M":"foo"}`, true}, // Issue6458
+		{Name(""), T2{&rawText}, `{"M":"foo"}`, true},
+		{Name(""), &T1{rawText}, `{"M":"foo"}`, true},
+		{Name(""), &T2{&rawText}, `{"M":"foo"}`, true},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.Name, func(t *testing.T) {
+			b, err := Marshal(tt.in)
+			if ok := (err == nil); ok != tt.ok {
+				if err != nil {
+					t.Errorf("%s: Marshal error: %v", tt.Where, err)
+				} else {
+					t.Errorf("%s: Marshal error: got nil, want non-nil", tt.Where)
+				}
 			}
-		}
-		if got := string(b); got != tt.want {
-			t.Errorf("test %d, Marshal(%#v) = %q, want %q", i, tt.in, got, tt.want)
-		}
+			if got := string(b); got != tt.want {
+				t.Errorf("%s: Marshal:\n\tinput: %#v\n\tgot:  %s\n\twant: %s", tt.Where, tt.in, got, tt.want)
+			}
+		})
 	}
 }
 
@@ -1169,12 +1158,12 @@ func TestMarshalUncommonFieldNames(t *testing.T) {
 	}{}
 	b, err := Marshal(v)
 	if err != nil {
-		t.Fatal("Marshal:", err)
+		t.Fatal("Marshal error:", err)
 	}
 	want := `{"A0":0,"À":0,"Aβ":0}`
 	got := string(b)
 	if got != want {
-		t.Fatalf("Marshal: got %s want %s", got, want)
+		t.Fatalf("Marshal:\n\tgot:  %s\n\twant: %s", got, want)
 	}
 }
 
@@ -1184,23 +1173,51 @@ func TestMarshalerError(t *testing.T) {
 	errText := "json: test error"
 
 	tests := []struct {
+		CaseName
 		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,
-		},
+	}{{
+		Name(""),
+		&MarshalerError{st, fmt.Errorf(errText), ""},
+		"json: error calling MarshalJSON for type " + st.String() + ": " + errText,
+	}, {
+		Name(""),
+		&MarshalerError{st, fmt.Errorf(errText), "TestMarshalerError"},
+		"json: error calling TestMarshalerError for type " + st.String() + ": " + errText,
+	}}
+
+	for _, tt := range tests {
+		t.Run(tt.Name, func(t *testing.T) {
+			got := tt.err.Error()
+			if got != tt.want {
+				t.Errorf("%s: Error:\n\tgot:  %s\n\twant: %s", tt.Where, got, tt.want)
+			}
+		})
 	}
+}
+
+type marshaledValue string
+
+func (v marshaledValue) MarshalJSON() ([]byte, error) {
+	return []byte(v), nil
+}
 
-	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)
+func TestIssue63379(t *testing.T) {
+	for _, v := range []string{
+		"[]<",
+		"[]>",
+		"[]&",
+		"[]\u2028",
+		"[]\u2029",
+		"{}<",
+		"{}>",
+		"{}&",
+		"{}\u2028",
+		"{}\u2029",
+	} {
+		_, err := Marshal(marshaledValue(v))
+		if err == nil {
+			t.Errorf("expected error for %q", v)
 		}
 	}
 }
@@ -1216,7 +1233,7 @@ func (t *testMarshalContextStruct) MarshalJSONWithContext(ctx context.Context) (
 	if v == nil {
 		v = "?"
 	}
-	return json.Marshal(strings.SplitN(t.Data, "-", 2)[0] + "-" + v.(string))
+	return Marshal(strings.SplitN(t.Data, "-", 2)[0] + "-" + v.(string))
 }
 
 func TestMarshalWithContext(t *testing.T) {
diff --git a/example_test.go b/example_test.go
index fbecf1b..2261c77 100644
--- a/example_test.go
+++ b/example_test.go
@@ -200,7 +200,7 @@ func ExampleRawMessage_unmarshal() {
 	}
 
 	for _, c := range colors {
-		var dst interface{}
+		var dst any
 		switch c.Space {
 		case "RGB":
 			dst = new(RGB)
diff --git a/fold.go b/fold.go
index 9e17012..c4c671b 100644
--- a/fold.go
+++ b/fold.go
@@ -5,139 +5,44 @@
 package json
 
 import (
-	"bytes"
+	"unicode"
 	"unicode/utf8"
 )
 
-const (
-	caseMask     = ^byte(0x20) // Mask to ignore case in ASCII.
-	kelvin       = '\u212a'
-	smallLongEss = '\u017f'
-)
-
-// foldFunc returns one of four different case folding equivalence
-// functions, from most general (and slow) to fastest:
-//
-// 1) bytes.EqualFold, if the key s contains any non-ASCII UTF-8
-// 2) equalFoldRight, if s contains special folding ASCII ('k', 'K', 's', 'S')
-// 3) asciiEqualFold, no special, but includes non-letters (including _)
-// 4) simpleLetterEqualFold, no specials, no non-letters.
-//
-// The letters S and K are special because they map to 3 runes, not just 2:
-//  * S maps to s and to U+017F 'ſ' Latin small letter long s
-//  * k maps to K and to U+212A 'K' Kelvin sign
-// See https://play.golang.org/p/tTxjOc0OGo
-//
-// The returned function is specialized for matching against s and
-// should only be given s. It's not curried for performance reasons.
-func foldFunc(s []byte) func(s, t []byte) bool {
-	nonLetter := false
-	special := false // special letter
-	for _, b := range s {
-		if b >= utf8.RuneSelf {
-			return bytes.EqualFold
-		}
-		upper := b & caseMask
-		if upper < 'A' || upper > 'Z' {
-			nonLetter = true
-		} else if upper == 'K' || upper == 'S' {
-			// See above for why these letters are special.
-			special = true
-		}
-	}
-	if special {
-		return equalFoldRight
-	}
-	if nonLetter {
-		return asciiEqualFold
-	}
-	return simpleLetterEqualFold
+// foldName returns a folded string such that foldName(x) == foldName(y)
+// is identical to bytes.EqualFold(x, y).
+func foldName(in []byte) []byte {
+	// This is inlinable to take advantage of "function outlining".
+	var arr [32]byte // large enough for most JSON names
+	return appendFoldedName(arr[:0], in)
 }
 
-// equalFoldRight is a specialization of bytes.EqualFold when s is
-// known to be all ASCII (including punctuation), but contains an 's',
-// 'S', 'k', or 'K', requiring a Unicode fold on the bytes in t.
-// See comments on foldFunc.
-func equalFoldRight(s, t []byte) bool {
-	for _, sb := range s {
-		if len(t) == 0 {
-			return false
-		}
-		tb := t[0]
-		if tb < utf8.RuneSelf {
-			if sb != tb {
-				sbUpper := sb & caseMask
-				if 'A' <= sbUpper && sbUpper <= 'Z' {
-					if sbUpper != tb&caseMask {
-						return false
-					}
-				} else {
-					return false
-				}
-			}
-			t = t[1:]
-			continue
-		}
-		// sb is ASCII and t is not. t must be either kelvin
-		// sign or long s; sb must be s, S, k, or K.
-		tr, size := utf8.DecodeRune(t)
-		switch sb {
-		case 's', 'S':
-			if tr != smallLongEss {
-				return false
+func appendFoldedName(out, in []byte) []byte {
+	for i := 0; i < len(in); {
+		// Handle single-byte ASCII.
+		if c := in[i]; c < utf8.RuneSelf {
+			if 'a' <= c && c <= 'z' {
+				c -= 'a' - 'A'
 			}
-		case 'k', 'K':
-			if tr != kelvin {
-				return false
-			}
-		default:
-			return false
-		}
-		t = t[size:]
-
-	}
-	if len(t) > 0 {
-		return false
-	}
-	return true
-}
-
-// asciiEqualFold is a specialization of bytes.EqualFold for use when
-// s is all ASCII (but may contain non-letters) and contains no
-// special-folding letters.
-// See comments on foldFunc.
-func asciiEqualFold(s, t []byte) bool {
-	if len(s) != len(t) {
-		return false
-	}
-	for i, sb := range s {
-		tb := t[i]
-		if sb == tb {
+			out = append(out, c)
+			i++
 			continue
 		}
-		if ('a' <= sb && sb <= 'z') || ('A' <= sb && sb <= 'Z') {
-			if sb&caseMask != tb&caseMask {
-				return false
-			}
-		} else {
-			return false
-		}
+		// Handle multi-byte Unicode.
+		r, n := utf8.DecodeRune(in[i:])
+		out = utf8.AppendRune(out, foldRune(r))
+		i += n
 	}
-	return true
+	return out
 }
 
-// simpleLetterEqualFold is a specialization of bytes.EqualFold for
-// use when s is all ASCII letters (no underscores, etc) and also
-// doesn't contain 'k', 'K', 's', or 'S'.
-// See comments on foldFunc.
-func simpleLetterEqualFold(s, t []byte) bool {
-	if len(s) != len(t) {
-		return false
-	}
-	for i, b := range s {
-		if b&caseMask != t[i]&caseMask {
-			return false
+// foldRune is returns the smallest rune for all runes in the same fold set.
+func foldRune(r rune) rune {
+	for {
+		r2 := unicode.SimpleFold(r)
+		if r2 <= r {
+			return r2
 		}
+		r = r2
 	}
-	return true
 }
diff --git a/fold_test.go b/fold_test.go
index 9fb9464..9d6fd05 100644
--- a/fold_test.go
+++ b/fold_test.go
@@ -6,111 +6,45 @@ package json
 
 import (
 	"bytes"
-	"strings"
 	"testing"
-	"unicode/utf8"
 )
 
-var foldTests = []struct {
-	fn   func(s, t []byte) bool
-	s, t string
-	want bool
-}{
-	{equalFoldRight, "", "", true},
-	{equalFoldRight, "a", "a", true},
-	{equalFoldRight, "", "a", false},
-	{equalFoldRight, "a", "", false},
-	{equalFoldRight, "a", "A", true},
-	{equalFoldRight, "AB", "ab", true},
-	{equalFoldRight, "AB", "ac", false},
-	{equalFoldRight, "sbkKc", "ſbKKc", true},
-	{equalFoldRight, "SbKkc", "ſbKKc", true},
-	{equalFoldRight, "SbKkc", "ſbKK", false},
-	{equalFoldRight, "e", "é", false},
-	{equalFoldRight, "s", "S", true},
-
-	{simpleLetterEqualFold, "", "", true},
-	{simpleLetterEqualFold, "abc", "abc", true},
-	{simpleLetterEqualFold, "abc", "ABC", true},
-	{simpleLetterEqualFold, "abc", "ABCD", false},
-	{simpleLetterEqualFold, "abc", "xxx", false},
-
-	{asciiEqualFold, "a_B", "A_b", true},
-	{asciiEqualFold, "aa@", "aa`", false}, // verify 0x40 and 0x60 aren't case-equivalent
-}
-
-func TestFold(t *testing.T) {
-	for i, tt := range foldTests {
-		if got := tt.fn([]byte(tt.s), []byte(tt.t)); got != tt.want {
-			t.Errorf("%d. %q, %q = %v; want %v", i, tt.s, tt.t, got, tt.want)
-		}
-		truth := strings.EqualFold(tt.s, tt.t)
-		if truth != tt.want {
-			t.Errorf("strings.EqualFold doesn't agree with case %d", i)
-		}
+func FuzzEqualFold(f *testing.F) {
+	for _, ss := range [][2]string{
+		{"", ""},
+		{"123abc", "123ABC"},
+		{"αβδ", "ΑΒΔ"},
+		{"abc", "xyz"},
+		{"abc", "XYZ"},
+		{"1", "2"},
+		{"hello, world!", "hello, world!"},
+		{"hello, world!", "Hello, World!"},
+		{"hello, world!", "HELLO, WORLD!"},
+		{"hello, world!", "jello, world!"},
+		{"γειά, κόσμε!", "γειά, κόσμε!"},
+		{"γειά, κόσμε!", "Γειά, Κόσμε!"},
+		{"γειά, κόσμε!", "ΓΕΙΆ, ΚΌΣΜΕ!"},
+		{"γειά, κόσμε!", "ΛΕΙΆ, ΚΌΣΜΕ!"},
+		{"AESKey", "aesKey"},
+		{"AESKEY", "aes_key"},
+		{"aes_key", "AES_KEY"},
+		{"AES_KEY", "aes-key"},
+		{"aes-key", "AES-KEY"},
+		{"AES-KEY", "aesKey"},
+		{"aesKey", "AesKey"},
+		{"AesKey", "AESKey"},
+		{"AESKey", "aeskey"},
+		{"DESKey", "aeskey"},
+		{"AES Key", "aeskey"},
+	} {
+		f.Add([]byte(ss[0]), []byte(ss[1]))
 	}
-}
-
-func TestFoldAgainstUnicode(t *testing.T) {
-	const bufSize = 5
-	buf1 := make([]byte, 0, bufSize)
-	buf2 := make([]byte, 0, bufSize)
-	var runes []rune
-	for i := 0x20; i <= 0x7f; i++ {
-		runes = append(runes, rune(i))
-	}
-	runes = append(runes, kelvin, smallLongEss)
-
-	funcs := []struct {
-		name   string
-		fold   func(s, t []byte) bool
-		letter bool // must be ASCII letter
-		simple bool // must be simple ASCII letter (not 'S' or 'K')
-	}{
-		{
-			name: "equalFoldRight",
-			fold: equalFoldRight,
-		},
-		{
-			name:   "asciiEqualFold",
-			fold:   asciiEqualFold,
-			simple: true,
-		},
-		{
-			name:   "simpleLetterEqualFold",
-			fold:   simpleLetterEqualFold,
-			simple: true,
-			letter: true,
-		},
-	}
-
-	for _, ff := range funcs {
-		for _, r := range runes {
-			if r >= utf8.RuneSelf {
-				continue
-			}
-			if ff.letter && !isASCIILetter(byte(r)) {
-				continue
-			}
-			if ff.simple && (r == 's' || r == 'S' || r == 'k' || r == 'K') {
-				continue
-			}
-			for _, r2 := range runes {
-				buf1 := append(buf1[:0], 'x')
-				buf2 := append(buf2[:0], 'x')
-				buf1 = buf1[:1+utf8.EncodeRune(buf1[1:bufSize], r)]
-				buf2 = buf2[:1+utf8.EncodeRune(buf2[1:bufSize], r2)]
-				buf1 = append(buf1, 'x')
-				buf2 = append(buf2, 'x')
-				want := bytes.EqualFold(buf1, buf2)
-				if got := ff.fold(buf1, buf2); got != want {
-					t.Errorf("%s(%q, %q) = %v; want %v", ff.name, buf1, buf2, got, want)
-				}
-			}
+	equalFold := func(x, y []byte) bool { return string(foldName(x)) == string(foldName(y)) }
+	f.Fuzz(func(t *testing.T, x, y []byte) {
+		got := equalFold(x, y)
+		want := bytes.EqualFold(x, y)
+		if got != want {
+			t.Errorf("equalFold(%q, %q) = %v, want %v", x, y, got, want)
 		}
-	}
-}
-
-func isASCIILetter(b byte) bool {
-	return ('A' <= b && b <= 'Z') || ('a' <= b && b <= 'z')
+	})
 }
diff --git a/fuzz.go b/fuzz.go
deleted file mode 100644
index d3fa2d1..0000000
--- a/fuzz.go
+++ /dev/null
@@ -1,43 +0,0 @@
-// Copyright 2019 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.
-
-//go:build gofuzz
-// +build gofuzz
-
-package json
-
-import (
-	"fmt"
-)
-
-func Fuzz(data []byte) (score int) {
-	for _, ctor := range []func() interface{}{
-		func() interface{} { return new(interface{}) },
-		func() interface{} { return new(map[string]interface{}) },
-		func() interface{} { return new([]interface{}) },
-	} {
-		v := ctor()
-		err := Unmarshal(data, v)
-		if err != nil {
-			continue
-		}
-		score = 1
-
-		m, err := Marshal(v)
-		if err != nil {
-			fmt.Printf("v=%#v\n", v)
-			panic(err)
-		}
-
-		u := ctor()
-		err = Unmarshal(m, u)
-		if err != nil {
-			fmt.Printf("v=%#v\n", v)
-			fmt.Printf("m=%s\n", m)
-			panic(err)
-		}
-	}
-
-	return
-}
diff --git a/fuzz_test.go b/fuzz_test.go
new file mode 100644
index 0000000..778664c
--- /dev/null
+++ b/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 json
+
+import (
+	"bytes"
+	"io"
+	"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)
+			}
+		}
+	})
+}
+
+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
+			}
+		}
+	})
+}
diff --git a/go.mod b/go.mod
index 13cb9da..f911680 100644
--- a/go.mod
+++ b/go.mod
@@ -1,3 +1,3 @@
 module github.com/richardwilkes/json
 
-go 1.22.1
+go 1.22.5
diff --git a/indent.go b/indent.go
index 2924d3b..01bfdf6 100644
--- a/indent.go
+++ b/indent.go
@@ -4,38 +4,67 @@
 
 package json
 
-import (
-	"bytes"
-)
+import "bytes"
+
+// HTMLEscape appends to dst the JSON-encoded src with <, >, &, U+2028 and U+2029
+// characters inside string literals changed to \u003c, \u003e, \u0026, \u2028, \u2029
+// so that the JSON will be safe to embed inside HTML <script> tags.
+// For historical reasons, web browsers don't honor standard HTML
+// escaping within <script> tags, so an alternative JSON encoding must be used.
+func HTMLEscape(dst *bytes.Buffer, src []byte) {
+	dst.Grow(len(src))
+	dst.Write(appendHTMLEscape(dst.AvailableBuffer(), src))
+}
+
+func appendHTMLEscape(dst, src []byte) []byte {
+	// The characters can only appear in string literals,
+	// so just scan the string one byte at a time.
+	start := 0
+	for i, c := range src {
+		if c == '<' || c == '>' || c == '&' {
+			dst = append(dst, src[start:i]...)
+			dst = append(dst, '\\', 'u', '0', '0', hex[c>>4], hex[c&0xF])
+			start = i + 1
+		}
+		// Convert U+2028 and U+2029 (E2 80 A8 and E2 80 A9).
+		if c == 0xE2 && i+2 < len(src) && src[i+1] == 0x80 && src[i+2]&^1 == 0xA8 {
+			dst = append(dst, src[start:i]...)
+			dst = append(dst, '\\', 'u', '2', '0', '2', hex[src[i+2]&0xF])
+			start = i + len("\u2029")
+		}
+	}
+	return append(dst, src[start:]...)
+}
 
 // Compact appends to dst the JSON-encoded src with
 // insignificant space characters elided.
 func Compact(dst *bytes.Buffer, src []byte) error {
-	return compact(dst, src, false)
+	dst.Grow(len(src))
+	b := dst.AvailableBuffer()
+	b, err := appendCompact(b, src, false)
+	dst.Write(b)
+	return err
 }
 
-func compact(dst *bytes.Buffer, src []byte, escape bool) error {
-	origLen := dst.Len()
+func appendCompact(dst, src []byte, escape bool) ([]byte, error) {
+	origLen := len(dst)
 	scan := newScanner()
 	defer freeScanner(scan)
 	start := 0
 	for i, c := range src {
 		if escape && (c == '<' || c == '>' || c == '&') {
 			if start < i {
-				dst.Write(src[start:i])
+				dst = append(dst, src[start:i]...)
 			}
-			dst.WriteString(`\u00`)
-			dst.WriteByte(hex[c>>4])
-			dst.WriteByte(hex[c&0xF])
+			dst = append(dst, '\\', 'u', '0', '0', hex[c>>4], hex[c&0xF])
 			start = i + 1
 		}
 		// Convert U+2028 and U+2029 (E2 80 A8 and E2 80 A9).
 		if escape && c == 0xE2 && i+2 < len(src) && src[i+1] == 0x80 && src[i+2]&^1 == 0xA8 {
 			if start < i {
-				dst.Write(src[start:i])
+				dst = append(dst, src[start:i]...)
 			}
-			dst.WriteString(`\u202`)
-			dst.WriteByte(hex[src[i+2]&0xF])
+			dst = append(dst, '\\', 'u', '2', '0', '2', hex[src[i+2]&0xF])
 			start = i + 3
 		}
 		v := scan.step(scan, c)
@@ -44,29 +73,37 @@ func compact(dst *bytes.Buffer, src []byte, escape bool) error {
 				break
 			}
 			if start < i {
-				dst.Write(src[start:i])
+				dst = append(dst, src[start:i]...)
 			}
 			start = i + 1
 		}
 	}
 	if scan.eof() == scanError {
-		dst.Truncate(origLen)
-		return scan.err
+		return dst[:origLen], scan.err
 	}
 	if start < len(src) {
-		dst.Write(src[start:])
+		dst = append(dst, src[start:]...)
 	}
-	return nil
+	return dst, nil
 }
 
-func newline(dst *bytes.Buffer, prefix, indent string, depth int) {
-	dst.WriteByte('\n')
-	dst.WriteString(prefix)
+func appendNewline(dst []byte, prefix, indent string, depth int) []byte {
+	dst = append(dst, '\n')
+	dst = append(dst, prefix...)
 	for i := 0; i < depth; i++ {
-		dst.WriteString(indent)
+		dst = append(dst, indent...)
 	}
+	return dst
 }
 
+// indentGrowthFactor specifies the growth factor of indenting JSON input.
+// Empirically, the growth factor was measured to be between 1.4x to 1.8x
+// for some set of compacted JSON with the indent being a single tab.
+// Specify a growth factor slightly larger than what is observed
+// to reduce probability of allocation in appendIndent.
+// A factor no higher than 2 ensures that wasted space never exceeds 50%.
+const indentGrowthFactor = 2
+
 // Indent appends to dst an indented form of the JSON-encoded src.
 // Each element in a JSON object or array begins on a new,
 // indented line beginning with prefix followed by one or more
@@ -79,7 +116,15 @@ func newline(dst *bytes.Buffer, prefix, indent string, depth int) {
 // For example, if src has no trailing spaces, neither will dst;
 // if src ends in a trailing newline, so will dst.
 func Indent(dst *bytes.Buffer, src []byte, prefix, indent string) error {
-	origLen := dst.Len()
+	dst.Grow(indentGrowthFactor * len(src))
+	b := dst.AvailableBuffer()
+	b, err := appendIndent(b, src, prefix, indent)
+	dst.Write(b)
+	return err
+}
+
+func appendIndent(dst, src []byte, prefix, indent string) ([]byte, error) {
+	origLen := len(dst)
 	scan := newScanner()
 	defer freeScanner(scan)
 	needIndent := false
@@ -96,13 +141,13 @@ func Indent(dst *bytes.Buffer, src []byte, prefix, indent string) error {
 		if needIndent && v != scanEndObject && v != scanEndArray {
 			needIndent = false
 			depth++
-			newline(dst, prefix, indent, depth)
+			dst = appendNewline(dst, prefix, indent, depth)
 		}
 
 		// Emit semantically uninteresting bytes
 		// (in particular, punctuation in strings) unmodified.
 		if v == scanContinue {
-			dst.WriteByte(c)
+			dst = append(dst, c)
 			continue
 		}
 
@@ -111,33 +156,27 @@ func Indent(dst *bytes.Buffer, src []byte, prefix, indent string) error {
 		case '{', '[':
 			// delay indent so that empty object and array are formatted as {} and [].
 			needIndent = true
-			dst.WriteByte(c)
-
+			dst = append(dst, c)
 		case ',':
-			dst.WriteByte(c)
-			newline(dst, prefix, indent, depth)
-
+			dst = append(dst, c)
+			dst = appendNewline(dst, prefix, indent, depth)
 		case ':':
-			dst.WriteByte(c)
-			dst.WriteByte(' ')
-
+			dst = append(dst, c, ' ')
 		case '}', ']':
 			if needIndent {
 				// suppress indent in empty object/array
 				needIndent = false
 			} else {
 				depth--
-				newline(dst, prefix, indent, depth)
+				dst = appendNewline(dst, prefix, indent, depth)
 			}
-			dst.WriteByte(c)
-
+			dst = append(dst, c)
 		default:
-			dst.WriteByte(c)
+			dst = append(dst, c)
 		}
 	}
 	if scan.eof() == scanError {
-		dst.Truncate(origLen)
-		return scan.err
+		return dst[:origLen], scan.err
 	}
-	return nil
+	return dst, nil
 }
diff --git a/number_test.go b/number_test.go
index cc67018..c82e6de 100644
--- a/number_test.go
+++ b/number_test.go
@@ -116,18 +116,3 @@ func TestNumberIsValid(t *testing.T) {
 		}
 	}
 }
-
-func BenchmarkNumberIsValid(b *testing.B) {
-	s := "-61657.61667E+61673"
-	for i := 0; i < b.N; i++ {
-		isValidNumber(s)
-	}
-}
-
-func BenchmarkNumberIsValidRegexp(b *testing.B) {
-	var jsonNumberRegexp = regexp.MustCompile(`^-?(?:0|[1-9]\d*)(?:\.\d+)?(?:[eE][+-]?\d+)?$`)
-	s := "-61657.61667E+61673"
-	for i := 0; i < b.N; i++ {
-		jsonNumberRegexp.MatchString(s)
-	}
-}
diff --git a/scanner.go b/scanner.go
index 9dc1903..da6ea2a 100644
--- a/scanner.go
+++ b/scanner.go
@@ -27,6 +27,7 @@ func Valid(data []byte) bool {
 
 // checkValid verifies that data is valid JSON-encoded data.
 // scan is passed in for use by checkValid to avoid an allocation.
+// checkValid returns nil or a SyntaxError.
 func checkValid(data []byte, scan *scanner) error {
 	scan.reset()
 	for _, c := range data {
@@ -42,6 +43,7 @@ func checkValid(data []byte, scan *scanner) error {
 }
 
 // A SyntaxError is a description of a JSON syntax error.
+// [Unmarshal] will return a SyntaxError if the JSON can't be parsed.
 type SyntaxError struct {
 	msg    string // description of error
 	Offset int64  // error occurred after reading Offset bytes
@@ -83,7 +85,7 @@ type scanner struct {
 }
 
 var scannerPool = sync.Pool{
-	New: func() interface{} {
+	New: func() any {
 		return &scanner{}
 	},
 }
@@ -592,7 +594,7 @@ func (s *scanner) error(c byte, context string) int {
 	return scanError
 }
 
-// quoteChar formats c as a quoted character literal
+// quoteChar formats c as a quoted character literal.
 func quoteChar(c byte) string {
 	// special cases - different from quoted strings
 	if c == '\'' {
diff --git a/scanner_test.go b/scanner_test.go
index 3737516..068439d 100644
--- a/scanner_test.go
+++ b/scanner_test.go
@@ -9,51 +9,59 @@ import (
 	"math"
 	"math/rand"
 	"reflect"
+	"strings"
 	"testing"
 )
 
-var validTests = []struct {
-	data string
-	ok   bool
-}{
-	{`foo`, false},
-	{`}{`, false},
-	{`{]`, false},
-	{`{}`, true},
-	{`{"foo":"bar"}`, true},
-	{`{"foo":"bar","bar":{"baz":["qux"]}}`, true},
+func indentNewlines(s string) string {
+	return strings.Join(strings.Split(s, "\n"), "\n\t")
 }
 
-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)
+func stripWhitespace(s string) string {
+	return strings.Map(func(r rune) rune {
+		if r == ' ' || r == '\n' || r == '\r' || r == '\t' {
+			return -1
 		}
-	}
-}
-
-// Tests of simple examples.
-
-type example struct {
-	compact string
-	indent  string
+		return r
+	}, s)
 }
 
-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
+func TestValid(t *testing.T) {
+	tests := []struct {
+		CaseName
+		data string
+		ok   bool
+	}{
+		{Name(""), `foo`, false},
+		{Name(""), `}{`, false},
+		{Name(""), `{]`, false},
+		{Name(""), `{}`, true},
+		{Name(""), `{"foo":"bar"}`, true},
+		{Name(""), `{"foo":"bar","bar":{"baz":["qux"]}}`, true},
+	}
+	for _, tt := range tests {
+		t.Run(tt.Name, func(t *testing.T) {
+			if ok := Valid([]byte(tt.data)); ok != tt.ok {
+				t.Errorf("%s: Valid(`%s`) = %v, want %v", tt.Where, tt.data, ok, tt.ok)
+			}
+		})
+	}
 }
 
-var ex1 = `[true,false,null,"x",1,1.5,0,-5e+2]`
-
-var ex1i = `[
+func TestCompactAndIndent(t *testing.T) {
+	tests := []struct {
+		CaseName
+		compact string
+		indent  string
+	}{
+		{Name(""), `1`, `1`},
+		{Name(""), `{}`, `{}`},
+		{Name(""), `[]`, `[]`},
+		{Name(""), `{"":2}`, "{\n\t\"\": 2\n}"},
+		{Name(""), `[3]`, "[\n\t3\n]"},
+		{Name(""), `[1,2,3]`, "[\n\t1,\n\t2,\n\t3\n]"},
+		{Name(""), `{"x":1}`, "{\n\t\"x\": 1\n}"},
+		{Name(""), `[true,false,null,"x",1,1.5,0,-5e+2]`, `[
 	true,
 	false,
 	null,
@@ -62,25 +70,40 @@ var ex1i = `[
 	1.5,
 	0,
 	-5e+2
-]`
-
-func TestCompact(t *testing.T) {
+]`},
+		{Name(""), "{\"\":\"<>&\u2028\u2029\"}", "{\n\t\"\": \"<>&\u2028\u2029\"\n}"}, // See golang.org/issue/34070
+	}
 	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)
-		}
+	for _, tt := range tests {
+		t.Run(tt.Name, func(t *testing.T) {
+			buf.Reset()
+			if err := Compact(&buf, []byte(tt.compact)); err != nil {
+				t.Errorf("%s: Compact error: %v", tt.Where, err)
+			} else if got := buf.String(); got != tt.compact {
+				t.Errorf("%s: Compact:\n\tgot:  %s\n\twant: %s", tt.Where, indentNewlines(got), indentNewlines(tt.compact))
+			}
 
-		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)
-		}
+			buf.Reset()
+			if err := Compact(&buf, []byte(tt.indent)); err != nil {
+				t.Errorf("%s: Compact error: %v", tt.Where, err)
+			} else if got := buf.String(); got != tt.compact {
+				t.Errorf("%s: Compact:\n\tgot:  %s\n\twant: %s", tt.Where, indentNewlines(got), indentNewlines(tt.compact))
+			}
+
+			buf.Reset()
+			if err := Indent(&buf, []byte(tt.indent), "", "\t"); err != nil {
+				t.Errorf("%s: Indent error: %v", tt.Where, err)
+			} else if got := buf.String(); got != tt.indent {
+				t.Errorf("%s: Compact:\n\tgot:  %s\n\twant: %s", tt.Where, indentNewlines(got), indentNewlines(tt.indent))
+			}
+
+			buf.Reset()
+			if err := Indent(&buf, []byte(tt.compact), "", "\t"); err != nil {
+				t.Errorf("%s: Indent error: %v", tt.Where, err)
+			} else if got := buf.String(); got != tt.indent {
+				t.Errorf("%s: Compact:\n\tgot:  %s\n\twant: %s", tt.Where, indentNewlines(got), indentNewlines(tt.indent))
+			}
+		})
 	}
 }
 
@@ -88,38 +111,21 @@ func TestCompactSeparators(t *testing.T) {
 	// U+2028 and U+2029 should be escaped inside strings.
 	// They should not appear outside strings.
 	tests := []struct {
+		CaseName
 		in, compact string
 	}{
-		{"{\"\u2028\": 1}", "{\"\u2028\":1}"},
-		{"{\"\u2029\" :2}", "{\"\u2029\":2}"},
+		{Name(""), "{\"\u2028\": 1}", "{\"\u2028\":1}"},
+		{Name(""), "{\"\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) {
-	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)
-		}
+		t.Run(tt.Name, func(t *testing.T) {
+			var buf bytes.Buffer
+			if err := Compact(&buf, []byte(tt.in)); err != nil {
+				t.Errorf("%s: Compact error: %v", tt.Where, err)
+			} else if got := buf.String(); got != tt.compact {
+				t.Errorf("%s: Compact:\n\tgot:  %s\n\twant: %s", tt.Where, indentNewlines(got), indentNewlines(tt.compact))
+			}
+		})
 	}
 }
 
@@ -129,11 +135,11 @@ func TestCompactBig(t *testing.T) {
 	initBig()
 	var buf bytes.Buffer
 	if err := Compact(&buf, jsonBig); err != nil {
-		t.Fatalf("Compact: %v", err)
+		t.Fatalf("Compact error: %v", err)
 	}
 	b := buf.Bytes()
 	if !bytes.Equal(b, jsonBig) {
-		t.Error("Compact(jsonBig) != jsonBig")
+		t.Error("Compact:")
 		diff(t, b, jsonBig)
 		return
 	}
@@ -144,23 +150,23 @@ func TestIndentBig(t *testing.T) {
 	initBig()
 	var buf bytes.Buffer
 	if err := Indent(&buf, jsonBig, "", "\t"); err != nil {
-		t.Fatalf("Indent1: %v", err)
+		t.Fatalf("Indent error: %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")
+		t.Fatalf("Indent did not expand the input")
 	}
 
 	// should be idempotent
 	var buf1 bytes.Buffer
 	if err := Indent(&buf1, b, "", "\t"); err != nil {
-		t.Fatalf("Indent2: %v", err)
+		t.Fatalf("Indent error: %v", err)
 	}
 	b1 := buf1.Bytes()
 	if !bytes.Equal(b1, b) {
-		t.Error("Indent(Indent(jsonBig)) != Indent(jsonBig)")
+		t.Error("Indent(Indent(jsonBig)) != Indent(jsonBig):")
 		diff(t, b1, b)
 		return
 	}
@@ -168,40 +174,40 @@ func TestIndentBig(t *testing.T) {
 	// should get back to original
 	buf1.Reset()
 	if err := Compact(&buf1, b); err != nil {
-		t.Fatalf("Compact: %v", err)
+		t.Fatalf("Compact error: %v", err)
 	}
 	b1 = buf1.Bytes()
 	if !bytes.Equal(b1, jsonBig) {
-		t.Error("Compact(Indent(jsonBig)) != 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) {
-	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
+	tests := []struct {
+		CaseName
+		in  string
+		err error
+	}{
+		{Name(""), `{"X": "foo", "Y"}`, &SyntaxError{"invalid character '}' after object key", 17}},
+		{Name(""), `{"X": "foo" "Y": "bar"}`, &SyntaxError{"invalid character '\"' after object key:value pair", 13}},
+	}
+	for _, tt := range tests {
+		t.Run(tt.Name, func(t *testing.T) {
+			slice := make([]uint8, 0)
+			buf := bytes.NewBuffer(slice)
+			if err := Indent(buf, []uint8(tt.in), "", ""); err != nil {
+				if !reflect.DeepEqual(err, tt.err) {
+					t.Fatalf("%s: Indent error:\n\tgot:  %v\n\twant: %v", tt.Where, err, tt.err)
+				}
 			}
-		}
+		})
 	}
 }
 
 func diff(t *testing.T, a, b []byte) {
+	t.Helper()
 	for i := 0; ; i++ {
 		if i >= len(a) || i >= len(b) || a[i] != b[i] {
 			j := i - 10
@@ -215,10 +221,7 @@ func diff(t *testing.T, a, b []byte) {
 }
 
 func trim(b []byte) []byte {
-	if len(b) > 20 {
-		return b[0:20]
-	}
-	return b
+	return b[:min(len(b), 20)]
 }
 
 // Generate a random JSON object.
@@ -237,7 +240,7 @@ func initBig() {
 	jsonBig = b
 }
 
-func genValue(n int) interface{} {
+func genValue(n int) any {
 	if n > 1 {
 		switch rand.Intn(2) {
 		case 0:
@@ -270,7 +273,7 @@ func genString(stddev float64) string {
 	return string(c)
 }
 
-func genArray(n int) []interface{} {
+func genArray(n int) []any {
 	f := int(math.Abs(rand.NormFloat64()) * math.Min(10, float64(n/2)))
 	if f > n {
 		f = n
@@ -278,14 +281,14 @@ func genArray(n int) []interface{} {
 	if f < 1 {
 		f = 1
 	}
-	x := make([]interface{}, f)
+	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]interface{} {
+func genMap(n int) map[string]any {
 	f := int(math.Abs(rand.NormFloat64()) * math.Min(10, float64(n/2)))
 	if f > n {
 		f = n
@@ -293,7 +296,7 @@ func genMap(n int) map[string]interface{} {
 	if n > 0 && f == 0 {
 		f = 1
 	}
-	x := make(map[string]interface{})
+	x := make(map[string]any)
 	for i := 0; i < f; i++ {
 		x[genString(10)] = genValue(((i+1)*n)/f - (i*n)/f)
 	}
diff --git a/stream.go b/stream.go
index fe270cd..599a4d1 100644
--- a/stream.go
+++ b/stream.go
@@ -39,7 +39,7 @@ func NewDecoder(r io.Reader) *Decoder {
 }
 
 // UseNumber causes the Decoder to unmarshal a number into an interface{} as a
-// Number instead of as a float64.
+// [Number] instead of as a float64.
 func (dec *Decoder) UseNumber() { dec.d.useNumber = true }
 
 // DisallowUnknownFields causes the Decoder to return an error when the destination
@@ -53,9 +53,9 @@ func (dec *Decoder) SetContext(ctx context.Context) { dec.d.ctx = ctx }
 // Decode reads the next JSON-encoded value from its
 // input and stores it in the value pointed to by v.
 //
-// See the documentation for Unmarshal for details about
+// See the documentation for [Unmarshal] for details about
 // the conversion of JSON into a Go value.
-func (dec *Decoder) Decode(v interface{}) error {
+func (dec *Decoder) Decode(v any) error {
 	if dec.err != nil {
 		return dec.err
 	}
@@ -88,7 +88,7 @@ func (dec *Decoder) Decode(v interface{}) error {
 }
 
 // Buffered returns a reader of the data remaining in the Decoder's
-// buffer. The reader is valid until the next call to Decode.
+// buffer. The reader is valid until the next call to [Decoder.Decode].
 func (dec *Decoder) Buffered() io.Reader {
 	return bytes.NewReader(dec.buf[dec.scanp:])
 }
@@ -193,7 +193,7 @@ type Encoder struct {
 	err        error
 	escapeHTML bool
 
-	indentBuf    *bytes.Buffer
+	indentBuf    []byte
 	indentPrefix string
 	indentValue  string
 }
@@ -206,13 +206,16 @@ func NewEncoder(w io.Writer) *Encoder {
 // Encode writes the JSON encoding of v to the stream,
 // followed by a newline character.
 //
-// See the documentation for Marshal for details about the
+// See the documentation for [Marshal] for details about the
 // conversion of Go values to JSON.
-func (enc *Encoder) Encode(v interface{}) error {
+func (enc *Encoder) Encode(v any) error {
 	if enc.err != nil {
 		return enc.err
 	}
+
 	e := newEncodeState()
+	defer encodeStatePool.Put(e)
+
 	err := e.marshal(v, encOpts{ctx: enc.ctx, escapeHTML: enc.escapeHTML})
 	if err != nil {
 		return err
@@ -228,20 +231,15 @@ func (enc *Encoder) Encode(v interface{}) error {
 
 	b := e.Bytes()
 	if enc.indentPrefix != "" || enc.indentValue != "" {
-		if enc.indentBuf == nil {
-			enc.indentBuf = new(bytes.Buffer)
-		}
-		enc.indentBuf.Reset()
-		err = Indent(enc.indentBuf, b, enc.indentPrefix, enc.indentValue)
+		enc.indentBuf, err = appendIndent(enc.indentBuf[:0], b, enc.indentPrefix, enc.indentValue)
 		if err != nil {
 			return err
 		}
-		b = enc.indentBuf.Bytes()
+		b = enc.indentBuf
 	}
 	if _, err = enc.w.Write(b); err != nil {
 		enc.err = err
 	}
-	encodeStatePool.Put(e)
 	return err
 }
 
@@ -270,7 +268,7 @@ func (enc *Encoder) SetEscapeHTML(on bool) {
 }
 
 // RawMessage is a raw encoded JSON value.
-// It implements Marshaler and Unmarshaler and can
+// It implements [Marshaler] and [Unmarshaler] and can
 // be used to delay JSON decoding or precompute a JSON encoding.
 type RawMessage []byte
 
@@ -296,14 +294,13 @@ var _ Unmarshaler = (*RawMessage)(nil)
 
 // A Token holds a value of one of these types:
 //
-//	Delim, for the four JSON delimiters [ ] { }
-//	bool, for JSON booleans
-//	float64, for JSON numbers
-//	Number, for JSON numbers
-//	string, for JSON string literals
-//	nil, for JSON null
-//
-type Token interface{}
+//   - [Delim], for the four JSON delimiters [ ] { }
+//   - bool, for JSON booleans
+//   - float64, for JSON numbers
+//   - [Number], for JSON numbers
+//   - string, for JSON string literals
+//   - nil, for JSON null
+type Token any
 
 const (
 	tokenTopValue = iota
@@ -372,14 +369,14 @@ func (d Delim) String() string {
 }
 
 // Token returns the next JSON token in the input stream.
-// At the end of the input stream, Token returns nil, io.EOF.
+// At the end of the input stream, Token returns nil, [io.EOF].
 //
 // Token guarantees that the delimiters [ ] { } it returns are
 // properly nested and matched: if Token encounters an unexpected
 // delimiter in the input, it will return an error.
 //
 // The input stream consists of basic JSON values—bool, string,
-// number, and null—along with delimiters [ ] { } of type Delim
+// number, and null—along with delimiters [ ] { } of type [Delim]
 // to mark the start and end of arrays and objects.
 // Commas and colons are elided.
 func (dec *Decoder) Token() (Token, error) {
@@ -467,7 +464,7 @@ func (dec *Decoder) Token() (Token, error) {
 			if !dec.tokenValueAllowed() {
 				return dec.tokenError(c)
 			}
-			var x interface{}
+			var x any
 			if err := dec.Decode(&x); err != nil {
 				return nil, err
 			}
diff --git a/stream_test.go b/stream_test.go
index c284f2d..32ede8c 100644
--- a/stream_test.go
+++ b/stream_test.go
@@ -6,26 +6,54 @@ package json
 
 import (
 	"bytes"
+	"fmt"
 	"io"
 	"log"
 	"net"
 	"net/http"
 	"net/http/httptest"
+	"path"
 	"reflect"
+	"runtime"
+	"runtime/debug"
 	"strings"
 	"testing"
 )
 
+// TODO(https://go.dev/issue/52751): Replace with native testing support.
+
+// CaseName is a case name annotated with a file and line.
+type CaseName struct {
+	Name  string
+	Where CasePos
+}
+
+// Name annotates a case name with the file and line of the caller.
+func Name(s string) (c CaseName) {
+	c.Name = s
+	runtime.Callers(2, c.Where.pc[:])
+	return c
+}
+
+// CasePos represents a file and line number.
+type CasePos struct{ pc [1]uintptr }
+
+func (pos CasePos) String() string {
+	frames := runtime.CallersFrames(pos.pc[:])
+	frame, _ := frames.Next()
+	return fmt.Sprintf("%s:%d", path.Base(frame.File), frame.Line)
+}
+
 // Test values for the stream test.
 // One of each JSON kind.
-var streamTest = []interface{}{
+var streamTest = []any{
 	0.1,
 	"hello",
 	nil,
 	true,
 	false,
-	[]interface{}{"a", "b", "c"},
-	map[string]interface{}{"K": "Kelvin", "ß": "long s"},
+	[]any{"a", "b", "c"},
+	map[string]any{"K": "Kelvin", "ß": "long s"},
 	3.14, // another value to make sure something can follow map
 }
 
@@ -41,24 +69,61 @@ false
 
 func TestEncoder(t *testing.T) {
 	for i := 0; i <= len(streamTest); i++ {
-		var buf bytes.Buffer
+		var buf strings.Builder
 		enc := NewEncoder(&buf)
 		// Check that enc.SetIndent("", "") turns off indentation.
 		enc.SetIndent(">", ".")
 		enc.SetIndent("", "")
 		for j, v := range streamTest[0:i] {
 			if err := enc.Encode(v); err != nil {
-				t.Fatalf("encode #%d: %v", j, err)
+				t.Fatalf("#%d.%d Encode error: %v", i, j, err)
 			}
 		}
 		if have, want := buf.String(), nlines(streamEncoded, i); have != want {
-			t.Errorf("encoding %d items: mismatch", i)
+			t.Errorf("encoding %d items: mismatch:", i)
 			diff(t, []byte(have), []byte(want))
 			break
 		}
 	}
 }
 
+func TestEncoderErrorAndReuseEncodeState(t *testing.T) {
+	// Disable the GC temporarily to prevent encodeState's in Pool being cleaned away during the test.
+	percent := debug.SetGCPercent(-1)
+	defer debug.SetGCPercent(percent)
+
+	// Trigger an error in Marshal with cyclic data.
+	type Dummy struct {
+		Name string
+		Next *Dummy
+	}
+	dummy := Dummy{Name: "Dummy"}
+	dummy.Next = &dummy
+
+	var buf bytes.Buffer
+	enc := NewEncoder(&buf)
+	if err := enc.Encode(dummy); err == nil {
+		t.Errorf("Encode(dummy) error: got nil, want non-nil")
+	}
+
+	type Data struct {
+		A string
+		I int
+	}
+	want := Data{A: "a", I: 1}
+	if err := enc.Encode(want); err != nil {
+		t.Errorf("Marshal error: %v", err)
+	}
+
+	var got Data
+	if err := Unmarshal(buf.Bytes(), &got); err != nil {
+		t.Errorf("Unmarshal error: %v", err)
+	}
+	if got != want {
+		t.Errorf("Marshal/Unmarshal roundtrip:\n\tgot:  %v\n\twant: %v", got, want)
+	}
+}
+
 var streamEncodedIndent = `0.1
 "hello"
 null
@@ -77,14 +142,14 @@ false
 `
 
 func TestEncoderIndent(t *testing.T) {
-	var buf bytes.Buffer
+	var buf strings.Builder
 	enc := NewEncoder(&buf)
 	enc.SetIndent(">", ".")
 	for _, v := range streamTest {
 		enc.Encode(v)
 	}
 	if have, want := buf.String(), streamEncodedIndent; have != want {
-		t.Error("indented encoding mismatch")
+		t.Error("Encode mismatch:")
 		diff(t, []byte(have), []byte(want))
 	}
 }
@@ -122,50 +187,51 @@ func TestEncoderSetEscapeHTML(t *testing.T) {
 		Bar string `json:"bar,string"`
 	}{`<html>foobar</html>`}
 
-	for _, tt := range []struct {
-		name       string
-		v          interface{}
+	tests := []struct {
+		CaseName
+		v          any
 		wantEscape string
 		want       string
 	}{
-		{"c", c, `"\u003c\u0026\u003e"`, `"<&>"`},
-		{"ct", ct, `"\"\u003c\u0026\u003e\""`, `"\"<&>\""`},
-		{`"<&>"`, "<&>", `"\u003c\u0026\u003e"`, `"<&>"`},
+		{Name("c"), c, `"\u003c\u0026\u003e"`, `"<&>"`},
+		{Name("ct"), ct, `"\"\u003c\u0026\u003e\""`, `"\"<&>\""`},
+		{Name(`"<&>"`), "<&>", `"\u003c\u0026\u003e"`, `"<&>"`},
 		{
-			"tagStruct", tagStruct,
+			Name("tagStruct"), tagStruct,
 			`{"\u003c\u003e\u0026#! ":0,"Invalid":0}`,
 			`{"<>&#! ":0,"Invalid":0}`,
 		},
 		{
-			`"<str>"`, marshalerStruct,
+			Name(`"<str>"`), marshalerStruct,
 			`{"NonPtr":"\u003cstr\u003e","Ptr":"\u003cstr\u003e"}`,
 			`{"NonPtr":"<str>","Ptr":"<str>"}`,
 		},
 		{
-			"stringOption", stringOption,
+			Name("stringOption"), stringOption,
 			`{"bar":"\"\\u003chtml\\u003efoobar\\u003c/html\\u003e\""}`,
 			`{"bar":"\"<html>foobar</html>\""}`,
 		},
-	} {
-		var buf bytes.Buffer
-		enc := NewEncoder(&buf)
-		if err := enc.Encode(tt.v); err != nil {
-			t.Errorf("Encode(%s): %s", tt.name, err)
-			continue
-		}
-		if got := strings.TrimSpace(buf.String()); got != tt.wantEscape {
-			t.Errorf("Encode(%s) = %#q, want %#q", tt.name, got, tt.wantEscape)
-		}
-		buf.Reset()
-		enc.SetEscapeHTML(false)
-		if err := enc.Encode(tt.v); err != nil {
-			t.Errorf("SetEscapeHTML(false) Encode(%s): %s", tt.name, err)
-			continue
-		}
-		if got := strings.TrimSpace(buf.String()); got != tt.want {
-			t.Errorf("SetEscapeHTML(false) Encode(%s) = %#q, want %#q",
-				tt.name, got, tt.want)
-		}
+	}
+	for _, tt := range tests {
+		t.Run(tt.Name, func(t *testing.T) {
+			var buf strings.Builder
+			enc := NewEncoder(&buf)
+			if err := enc.Encode(tt.v); err != nil {
+				t.Fatalf("%s: Encode(%s) error: %s", tt.Where, tt.Name, err)
+			}
+			if got := strings.TrimSpace(buf.String()); got != tt.wantEscape {
+				t.Errorf("%s: Encode(%s):\n\tgot:  %s\n\twant: %s", tt.Where, tt.Name, got, tt.wantEscape)
+			}
+			buf.Reset()
+			enc.SetEscapeHTML(false)
+			if err := enc.Encode(tt.v); err != nil {
+				t.Fatalf("%s: SetEscapeHTML(false) Encode(%s) error: %s", tt.Where, tt.Name, err)
+			}
+			if got := strings.TrimSpace(buf.String()); got != tt.want {
+				t.Errorf("%s: SetEscapeHTML(false) Encode(%s):\n\tgot:  %s\n\twant: %s",
+					tt.Where, tt.Name, got, tt.want)
+			}
+		})
 	}
 }
 
@@ -182,18 +248,18 @@ func TestDecoder(t *testing.T) {
 				buf.WriteRune(c)
 			}
 		}
-		out := make([]interface{}, i)
+		out := make([]any, i)
 		dec := NewDecoder(&buf)
 		for j := range out {
 			if err := dec.Decode(&out[j]); err != nil {
-				t.Fatalf("decode #%d/%d: %v", j, i, err)
+				t.Fatalf("decode #%d/%d error: %v", j, i, err)
 			}
 		}
 		if !reflect.DeepEqual(out, streamTest[0:i]) {
-			t.Errorf("decoding %d items: mismatch", i)
+			t.Errorf("decoding %d items: mismatch:", i)
 			for j := range out {
 				if !reflect.DeepEqual(out[j], streamTest[j]) {
-					t.Errorf("#%d: have %v want %v", j, out[j], streamTest[j])
+					t.Errorf("#%d:\n\tgot:  %v\n\twant: %v", j, out[j], streamTest[j])
 				}
 			}
 			break
@@ -212,14 +278,14 @@ func TestDecoderBuffered(t *testing.T) {
 		t.Fatal(err)
 	}
 	if m.Name != "Gopher" {
-		t.Errorf("Name = %q; want Gopher", m.Name)
+		t.Errorf("Name = %s, want Gopher", m.Name)
 	}
 	rest, err := io.ReadAll(d.Buffered())
 	if err != nil {
 		t.Fatal(err)
 	}
-	if g, w := string(rest), " extra "; g != w {
-		t.Errorf("Remaining = %q; want %q", g, w)
+	if got, want := string(rest), " extra "; got != want {
+		t.Errorf("Remaining = %s, want %s", got, want)
 	}
 }
 
@@ -244,20 +310,20 @@ func TestRawMessage(t *testing.T) {
 		Y  float32
 	}
 	const raw = `["\u0056",null]`
-	const msg = `{"X":0.1,"Id":["\u0056",null],"Y":0.2}`
-	err := Unmarshal([]byte(msg), &data)
+	const want = `{"X":0.1,"Id":["\u0056",null],"Y":0.2}`
+	err := Unmarshal([]byte(want), &data)
 	if err != nil {
-		t.Fatalf("Unmarshal: %v", err)
+		t.Fatalf("Unmarshal error: %v", err)
 	}
 	if string([]byte(data.Id)) != raw {
-		t.Fatalf("Raw mismatch: have %#q want %#q", []byte(data.Id), raw)
+		t.Fatalf("Unmarshal:\n\tgot:  %s\n\twant: %s", []byte(data.Id), raw)
 	}
-	b, err := Marshal(&data)
+	got, err := Marshal(&data)
 	if err != nil {
-		t.Fatalf("Marshal: %v", err)
+		t.Fatalf("Marshal error: %v", err)
 	}
-	if string(b) != msg {
-		t.Fatalf("Marshal: have %#q want %#q", b, msg)
+	if string(got) != want {
+		t.Fatalf("Marshal:\n\tgot:  %s\n\twant: %s", got, want)
 	}
 }
 
@@ -268,174 +334,156 @@ func TestNullRawMessage(t *testing.T) {
 		IdPtr *RawMessage
 		Y     float32
 	}
-	const msg = `{"X":0.1,"Id":null,"IdPtr":null,"Y":0.2}`
-	err := Unmarshal([]byte(msg), &data)
+	const want = `{"X":0.1,"Id":null,"IdPtr":null,"Y":0.2}`
+	err := Unmarshal([]byte(want), &data)
 	if err != nil {
-		t.Fatalf("Unmarshal: %v", err)
+		t.Fatalf("Unmarshal error: %v", err)
 	}
 	if want, got := "null", string(data.Id); want != got {
-		t.Fatalf("Raw mismatch: have %q, want %q", got, want)
+		t.Fatalf("Unmarshal:\n\tgot:  %s\n\twant: %s", got, want)
 	}
 	if data.IdPtr != nil {
-		t.Fatalf("Raw pointer mismatch: have non-nil, want nil")
+		t.Fatalf("pointer mismatch: got non-nil, want nil")
 	}
-	b, err := Marshal(&data)
+	got, err := Marshal(&data)
 	if err != nil {
-		t.Fatalf("Marshal: %v", err)
+		t.Fatalf("Marshal error: %v", err)
 	}
-	if string(b) != msg {
-		t.Fatalf("Marshal: have %#q want %#q", b, msg)
+	if string(got) != want {
+		t.Fatalf("Marshal:\n\tgot:  %s\n\twant: %s", got, want)
 	}
 }
 
-var blockingTests = []string{
-	`{"x": 1}`,
-	`[1, 2, 3]`,
-}
-
 func TestBlocking(t *testing.T) {
-	for _, enc := range blockingTests {
-		r, w := net.Pipe()
-		go w.Write([]byte(enc))
-		var val interface{}
-
-		// If Decode reads beyond what w.Write writes above,
-		// it will block, and the test will deadlock.
-		if err := NewDecoder(r).Decode(&val); err != nil {
-			t.Errorf("decoding %s: %v", enc, err)
-		}
-		r.Close()
-		w.Close()
-	}
-}
-
-func BenchmarkEncoderEncode(b *testing.B) {
-	b.ReportAllocs()
-	type T struct {
-		X, Y string
+	tests := []struct {
+		CaseName
+		in string
+	}{
+		{Name(""), `{"x": 1}`},
+		{Name(""), `[1, 2, 3]`},
 	}
-	v := &T{"foo", "bar"}
-	b.RunParallel(func(pb *testing.PB) {
-		for pb.Next() {
-			if err := NewEncoder(io.Discard).Encode(v); err != nil {
-				b.Fatal(err)
+	for _, tt := range tests {
+		t.Run(tt.Name, func(t *testing.T) {
+			r, w := net.Pipe()
+			go w.Write([]byte(tt.in))
+			var val any
+
+			// If Decode reads beyond what w.Write writes above,
+			// it will block, and the test will deadlock.
+			if err := NewDecoder(r).Decode(&val); err != nil {
+				t.Errorf("%s: NewDecoder(%s).Decode error: %v", tt.Where, tt.in, err)
 			}
-		}
-	})
-}
-
-type tokenStreamCase struct {
-	json      string
-	expTokens []interface{}
+			r.Close()
+			w.Close()
+		})
+	}
 }
 
 type decodeThis struct {
-	v interface{}
-}
-
-var tokenStreamCases = []tokenStreamCase{
-	// streaming token cases
-	{json: `10`, expTokens: []interface{}{float64(10)}},
-	{json: ` [10] `, expTokens: []interface{}{
-		Delim('['), float64(10), Delim(']')}},
-	{json: ` [false,10,"b"] `, expTokens: []interface{}{
-		Delim('['), false, float64(10), "b", Delim(']')}},
-	{json: `{ "a": 1 }`, expTokens: []interface{}{
-		Delim('{'), "a", float64(1), Delim('}')}},
-	{json: `{"a": 1, "b":"3"}`, expTokens: []interface{}{
-		Delim('{'), "a", float64(1), "b", "3", Delim('}')}},
-	{json: ` [{"a": 1},{"a": 2}] `, expTokens: []interface{}{
-		Delim('['),
-		Delim('{'), "a", float64(1), Delim('}'),
-		Delim('{'), "a", float64(2), Delim('}'),
-		Delim(']')}},
-	{json: `{"obj": {"a": 1}}`, expTokens: []interface{}{
-		Delim('{'), "obj", Delim('{'), "a", float64(1), Delim('}'),
-		Delim('}')}},
-	{json: `{"obj": [{"a": 1}]}`, expTokens: []interface{}{
-		Delim('{'), "obj", Delim('['),
-		Delim('{'), "a", float64(1), Delim('}'),
-		Delim(']'), Delim('}')}},
-
-	// streaming tokens with intermittent Decode()
-	{json: `{ "a": 1 }`, expTokens: []interface{}{
-		Delim('{'), "a",
-		decodeThis{float64(1)},
-		Delim('}')}},
-	{json: ` [ { "a" : 1 } ] `, expTokens: []interface{}{
-		Delim('['),
-		decodeThis{map[string]interface{}{"a": float64(1)}},
-		Delim(']')}},
-	{json: ` [{"a": 1},{"a": 2}] `, expTokens: []interface{}{
-		Delim('['),
-		decodeThis{map[string]interface{}{"a": float64(1)}},
-		decodeThis{map[string]interface{}{"a": float64(2)}},
-		Delim(']')}},
-	{json: `{ "obj" : [ { "a" : 1 } ] }`, expTokens: []interface{}{
-		Delim('{'), "obj", Delim('['),
-		decodeThis{map[string]interface{}{"a": float64(1)}},
-		Delim(']'), Delim('}')}},
-
-	{json: `{"obj": {"a": 1}}`, expTokens: []interface{}{
-		Delim('{'), "obj",
-		decodeThis{map[string]interface{}{"a": float64(1)}},
-		Delim('}')}},
-	{json: `{"obj": [{"a": 1}]}`, expTokens: []interface{}{
-		Delim('{'), "obj",
-		decodeThis{[]interface{}{
-			map[string]interface{}{"a": float64(1)},
-		}},
-		Delim('}')}},
-	{json: ` [{"a": 1} {"a": 2}] `, expTokens: []interface{}{
-		Delim('['),
-		decodeThis{map[string]interface{}{"a": float64(1)}},
-		decodeThis{&SyntaxError{"expected comma after array element", 11}},
-	}},
-	{json: `{ "` + strings.Repeat("a", 513) + `" 1 }`, expTokens: []interface{}{
-		Delim('{'), strings.Repeat("a", 513),
-		decodeThis{&SyntaxError{"expected colon after object key", 518}},
-	}},
-	{json: `{ "\a" }`, expTokens: []interface{}{
-		Delim('{'),
-		&SyntaxError{"invalid character 'a' in string escape code", 3},
-	}},
-	{json: ` \a`, expTokens: []interface{}{
-		&SyntaxError{"invalid character '\\\\' looking for beginning of value", 1},
-	}},
+	v any
 }
 
 func TestDecodeInStream(t *testing.T) {
-	for ci, tcase := range tokenStreamCases {
-
-		dec := NewDecoder(strings.NewReader(tcase.json))
-		for i, etk := range tcase.expTokens {
-
-			var tk interface{}
-			var err error
-
-			if dt, ok := etk.(decodeThis); ok {
-				etk = dt.v
-				err = dec.Decode(&tk)
-			} else {
-				tk, err = dec.Token()
-			}
-			if experr, ok := etk.(error); ok {
-				if err == nil || !reflect.DeepEqual(err, experr) {
-					t.Errorf("case %v: Expected error %#v in %q, but was %#v", ci, experr, tcase.json, err)
+	tests := []struct {
+		CaseName
+		json      string
+		expTokens []any
+	}{
+		// streaming token cases
+		{CaseName: Name(""), json: `10`, expTokens: []any{float64(10)}},
+		{CaseName: Name(""), json: ` [10] `, expTokens: []any{
+			Delim('['), float64(10), Delim(']')}},
+		{CaseName: Name(""), json: ` [false,10,"b"] `, expTokens: []any{
+			Delim('['), false, float64(10), "b", Delim(']')}},
+		{CaseName: Name(""), json: `{ "a": 1 }`, expTokens: []any{
+			Delim('{'), "a", float64(1), Delim('}')}},
+		{CaseName: Name(""), json: `{"a": 1, "b":"3"}`, expTokens: []any{
+			Delim('{'), "a", float64(1), "b", "3", Delim('}')}},
+		{CaseName: Name(""), json: ` [{"a": 1},{"a": 2}] `, expTokens: []any{
+			Delim('['),
+			Delim('{'), "a", float64(1), Delim('}'),
+			Delim('{'), "a", float64(2), Delim('}'),
+			Delim(']')}},
+		{CaseName: Name(""), json: `{"obj": {"a": 1}}`, expTokens: []any{
+			Delim('{'), "obj", Delim('{'), "a", float64(1), Delim('}'),
+			Delim('}')}},
+		{CaseName: Name(""), json: `{"obj": [{"a": 1}]}`, expTokens: []any{
+			Delim('{'), "obj", Delim('['),
+			Delim('{'), "a", float64(1), Delim('}'),
+			Delim(']'), Delim('}')}},
+
+		// streaming tokens with intermittent Decode()
+		{CaseName: Name(""), json: `{ "a": 1 }`, expTokens: []any{
+			Delim('{'), "a",
+			decodeThis{float64(1)},
+			Delim('}')}},
+		{CaseName: Name(""), json: ` [ { "a" : 1 } ] `, expTokens: []any{
+			Delim('['),
+			decodeThis{map[string]any{"a": float64(1)}},
+			Delim(']')}},
+		{CaseName: Name(""), json: ` [{"a": 1},{"a": 2}] `, expTokens: []any{
+			Delim('['),
+			decodeThis{map[string]any{"a": float64(1)}},
+			decodeThis{map[string]any{"a": float64(2)}},
+			Delim(']')}},
+		{CaseName: Name(""), json: `{ "obj" : [ { "a" : 1 } ] }`, expTokens: []any{
+			Delim('{'), "obj", Delim('['),
+			decodeThis{map[string]any{"a": float64(1)}},
+			Delim(']'), Delim('}')}},
+
+		{CaseName: Name(""), json: `{"obj": {"a": 1}}`, expTokens: []any{
+			Delim('{'), "obj",
+			decodeThis{map[string]any{"a": float64(1)}},
+			Delim('}')}},
+		{CaseName: Name(""), json: `{"obj": [{"a": 1}]}`, expTokens: []any{
+			Delim('{'), "obj",
+			decodeThis{[]any{
+				map[string]any{"a": float64(1)},
+			}},
+			Delim('}')}},
+		{CaseName: Name(""), json: ` [{"a": 1} {"a": 2}] `, expTokens: []any{
+			Delim('['),
+			decodeThis{map[string]any{"a": float64(1)}},
+			decodeThis{&SyntaxError{"expected comma after array element", 11}},
+		}},
+		{CaseName: Name(""), json: `{ "` + strings.Repeat("a", 513) + `" 1 }`, expTokens: []any{
+			Delim('{'), strings.Repeat("a", 513),
+			decodeThis{&SyntaxError{"expected colon after object key", 518}},
+		}},
+		{CaseName: Name(""), json: `{ "\a" }`, expTokens: []any{
+			Delim('{'),
+			&SyntaxError{"invalid character 'a' in string escape code", 3},
+		}},
+		{CaseName: Name(""), json: ` \a`, expTokens: []any{
+			&SyntaxError{"invalid character '\\\\' looking for beginning of value", 1},
+		}},
+	}
+	for _, tt := range tests {
+		t.Run(tt.Name, func(t *testing.T) {
+			dec := NewDecoder(strings.NewReader(tt.json))
+			for i, want := range tt.expTokens {
+				var got any
+				var err error
+
+				if dt, ok := want.(decodeThis); ok {
+					want = dt.v
+					err = dec.Decode(&got)
+				} else {
+					got, err = dec.Token()
+				}
+				if errWant, ok := want.(error); ok {
+					if err == nil || !reflect.DeepEqual(err, errWant) {
+						t.Fatalf("%s:\n\tinput: %s\n\tgot error:  %v\n\twant error: %v", tt.Where, tt.json, err, errWant)
+					}
+					break
+				} else if err != nil {
+					t.Fatalf("%s:\n\tinput: %s\n\tgot error:  %v\n\twant error: nil", tt.Where, tt.json, err)
+				}
+				if !reflect.DeepEqual(got, want) {
+					t.Fatalf("%s: token %d:\n\tinput: %s\n\tgot:  %T(%v)\n\twant: %T(%v)", tt.Where, i, tt.json, got, got, want, want)
 				}
-				break
-			} else if err == io.EOF {
-				t.Errorf("case %v: Unexpected EOF in %q", ci, tcase.json)
-				break
-			} else if err != nil {
-				t.Errorf("case %v: Unexpected error '%#v' in %q", ci, err, tcase.json)
-				break
-			}
-			if !reflect.DeepEqual(tk, etk) {
-				t.Errorf(`case %v: %q @ %v expected %T(%v) was %T(%v)`, ci, tcase.json, i, etk, etk, tk, tk)
-				break
 			}
-		}
+		})
 	}
 }
 
@@ -449,7 +497,7 @@ func TestHTTPDecoding(t *testing.T) {
 	defer ts.Close()
 	res, err := http.Get(ts.URL)
 	if err != nil {
-		log.Fatalf("GET failed: %v", err)
+		log.Fatalf("http.Get error: %v", err)
 	}
 	defer res.Body.Close()
 
@@ -460,15 +508,15 @@ func TestHTTPDecoding(t *testing.T) {
 	d := NewDecoder(res.Body)
 	err = d.Decode(&foo)
 	if err != nil {
-		t.Fatalf("Decode: %v", err)
+		t.Fatalf("Decode error: %v", err)
 	}
 	if foo.Foo != "bar" {
-		t.Errorf("decoded %q; want \"bar\"", foo.Foo)
+		t.Errorf(`Decode: got %q, want "bar"`, foo.Foo)
 	}
 
 	// make sure we get the EOF the second time
 	err = d.Decode(&foo)
 	if err != io.EOF {
-		t.Errorf("err = %v; want io.EOF", err)
+		t.Errorf("Decode error:\n\tgot:  %v\n\twant: io.EOF", err)
 	}
 }
diff --git a/tagkey_test.go b/tagkey_test.go
index 75d7cd4..d432cd7 100644
--- a/tagkey_test.go
+++ b/tagkey_test.go
@@ -72,73 +72,50 @@ type unicodeTag struct {
 	W string `json:"Ελλάδα"`
 }
 
-var structTagObjectKeyTests = []struct {
-	raw   interface{}
-	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) {
-	for _, tt := range structTagObjectKeyTests {
-		b, err := Marshal(tt.raw)
-		if err != nil {
-			t.Fatalf("Marshal(%#q) failed: %v", tt.raw, err)
-		}
-		var f interface{}
-		err = Unmarshal(b, &f)
-		if err != nil {
-			t.Fatalf("Unmarshal(%#q) failed: %v", b, err)
-		}
-		for i, v := range f.(map[string]interface{}) {
-			switch i {
-			case tt.key:
-				if s, ok := v.(string); !ok || s != tt.value {
-					t.Fatalf("Unexpected value: %#q, want %v", s, tt.value)
+	tests := []struct {
+		CaseName
+		raw   any
+		value string
+		key   string
+	}{
+		{Name(""), basicLatin2xTag{"2x"}, "2x", "$%-/"},
+		{Name(""), basicLatin3xTag{"3x"}, "3x", "0123456789"},
+		{Name(""), basicLatin4xTag{"4x"}, "4x", "ABCDEFGHIJKLMO"},
+		{Name(""), basicLatin5xTag{"5x"}, "5x", "PQRSTUVWXYZ_"},
+		{Name(""), basicLatin6xTag{"6x"}, "6x", "abcdefghijklmno"},
+		{Name(""), basicLatin7xTag{"7x"}, "7x", "pqrstuvwxyz"},
+		{Name(""), miscPlaneTag{"いろはにほへと"}, "いろはにほへと", "色は匂へど"},
+		{Name(""), dashTag{"foo"}, "foo", "-"},
+		{Name(""), emptyTag{"Pour Moi"}, "Pour Moi", "W"},
+		{Name(""), misnamedTag{"Animal Kingdom"}, "Animal Kingdom", "X"},
+		{Name(""), badFormatTag{"Orfevre"}, "Orfevre", "Y"},
+		{Name(""), badCodeTag{"Reliable Man"}, "Reliable Man", "Z"},
+		{Name(""), percentSlashTag{"brut"}, "brut", "text/html%"},
+		{Name(""), punctuationTag{"Union Rags"}, "Union Rags", "!#$%&()*+-./:;<=>?@[]^_{|}~ "},
+		{Name(""), spaceTag{"Perreddu"}, "Perreddu", "With space"},
+		{Name(""), unicodeTag{"Loukanikos"}, "Loukanikos", "Ελλάδα"},
+	}
+	for _, tt := range tests {
+		t.Run(tt.Name, func(t *testing.T) {
+			b, err := Marshal(tt.raw)
+			if err != nil {
+				t.Fatalf("%s: Marshal error: %v", tt.Where, err)
+			}
+			var f any
+			err = Unmarshal(b, &f)
+			if err != nil {
+				t.Fatalf("%s: Unmarshal error: %v", tt.Where, err)
+			}
+			for k, v := range f.(map[string]any) {
+				if k == tt.key {
+					if s, ok := v.(string); !ok || s != tt.value {
+						t.Fatalf("%s: Unmarshal(%#q) value:\n\tgot:  %q\n\twant: %q", tt.Where, b, s, tt.value)
+					}
+				} else {
+					t.Fatalf("%s: Unmarshal(%#q): unexpected key: %q", tt.Where, b, k)
 				}
-			default:
-				t.Fatalf("Unexpected key: %#q, from %#q", i, b)
 			}
-		}
-	}
-}
-
-func TestAltTagKey(t *testing.T) {
-	type foo struct {
-		A int `json:"a,alt=foo,omitempty"`
-		B int `json:"b,omitempty"`
-	}
-	var f1 foo
-	input1 := []byte(`{"a":1,"b":2}`)
-	if err := Unmarshal(input1, &f1); err != nil {
-		t.Fatalf("Unmarshal(%#q) failed: %v", input1, err)
-	}
-	if f1.A != 1 || f1.B != 2 {
-		t.Fatalf("Unmarshal(%#q) failed: %v", input1, f1)
-	}
-
-	var f2 foo
-	input2 := []byte(`{"foo":3,"b":4}`)
-	if err := Unmarshal(input2, &f2); err != nil {
-		t.Fatalf("Unmarshal(%#q) failed: %v", input2, err)
-	}
-	if f2.A != 3 || f2.B != 4 {
-		t.Fatalf("Unmarshal(%#q) failed: %v", input2, f2)
+		})
 	}
 }
diff --git a/tags.go b/tags.go
index 67c0688..98a495e 100644
--- a/tags.go
+++ b/tags.go
@@ -15,10 +15,8 @@ type tagOptions string
 // parseTag splits a struct field's json tag into its name and
 // comma-separated options.
 func parseTag(tag string) (string, tagOptions) {
-	if idx := strings.Index(tag, ","); idx != -1 {
-		return tag[:idx], tagOptions(tag[idx+1:])
-	}
-	return tag, tagOptions("")
+	tag, opt, _ := strings.Cut(tag, ",")
+	return tag, tagOptions(opt)
 }
 
 // Contains reports whether a comma-separated list of options
@@ -30,15 +28,11 @@ func (o tagOptions) Contains(optionName string) bool {
 	}
 	s := string(o)
 	for s != "" {
-		var next string
-		i := strings.Index(s, ",")
-		if i >= 0 {
-			s, next = s[:i], s[i+1:]
-		}
-		if s == optionName {
+		var name string
+		name, s, _ = strings.Cut(s, ",")
+		if name == optionName {
 			return true
 		}
-		s = next
 	}
 	return false
 }
diff --git a/tags_test.go b/tags_test.go
index 8ba8ddd..1d2323d 100644
--- a/tags_test.go
+++ b/tags_test.go
@@ -22,7 +22,7 @@ func TestTagParsing(t *testing.T) {
 		{"bar", false},
 	} {
 		if opts.Contains(tt.opt) != tt.want {
-			t.Errorf("Contains(%q) = %v", tt.opt, !tt.want)
+			t.Errorf("Contains(%q) = %v, want %v", tt.opt, !tt.want, tt.want)
 		}
 	}
 }