Use new reflect.TypeFor function available in Go 1.22

.github/workflows/test.yml

@@ -9,7 +9,7 @@ jobs:
     - name: Install Go
       uses: actions/setup-go@v2
       with:
-        go-version: 1.21.x
+        go-version: 1.22.x
     - name: Checkout code
       uses: actions/checkout@v2
     - name: Test
@@ -26,7 +26,7 @@ jobs:
     if: github.repository == 'go-json-experiment/json'
     strategy:
       matrix:
-        go-version: [1.21.x]
+        go-version: [1.22.x]
         os: [ubuntu-latest, macos-latest, windows-latest]
     runs-on: ${{ matrix.os }}
     steps:

arshal_default.go

@@ -30,15 +30,15 @@ const optimizeCommon = true
 
 var (
 	// Most natural Go type that correspond with each JSON type.
-	anyType          = reflect.TypeOf((*any)(nil)).Elem()            // JSON value
-	boolType         = reflect.TypeOf((*bool)(nil)).Elem()           // JSON bool
-	stringType       = reflect.TypeOf((*string)(nil)).Elem()         // JSON string
-	float64Type      = reflect.TypeOf((*float64)(nil)).Elem()        // JSON number
-	mapStringAnyType = reflect.TypeOf((*map[string]any)(nil)).Elem() // JSON object
-	sliceAnyType     = reflect.TypeOf((*[]any)(nil)).Elem()          // JSON array
-
-	bytesType       = reflect.TypeOf((*[]byte)(nil)).Elem()
-	emptyStructType = reflect.TypeOf((*struct{})(nil)).Elem()
+	anyType          = reflect.TypeFor[any]()            // JSON value
+	boolType         = reflect.TypeFor[bool]()           // JSON bool
+	stringType       = reflect.TypeFor[string]()         // JSON string
+	float64Type      = reflect.TypeFor[float64]()        // JSON number
+	mapStringAnyType = reflect.TypeFor[map[string]any]() // JSON object
+	sliceAnyType     = reflect.TypeFor[[]any]()          // JSON array
+
+	bytesType       = reflect.TypeFor[[]byte]()
+	emptyStructType = reflect.TypeFor[struct{}]()
 )
 
 const startDetectingCyclesAfter = 1000

arshal_funcs.go

@@ -166,7 +166,7 @@ func (a *typedArshalers[Coder]) lookup(fnc func(*Coder, addressableValue, *jsono
 // The value of T must not be retained outside the function call.
 // It may not return [SkipFunc].
 func MarshalFuncV1[T any](fn func(T) ([]byte, error)) *Marshalers {
-	t := reflect.TypeOf((*T)(nil)).Elem()
+	t := reflect.TypeFor[T]()
 	assertCastableTo(t, true)
 	typFnc := typedMarshaler{
 		typ: t,
@@ -200,7 +200,7 @@ func MarshalFuncV1[T any](fn func(T) ([]byte, error)) *Marshalers {
 // The pointer to [jsontext.Encoder], the value of T, and the [Options] value
 // must not be retained outside the function call.
 func MarshalFuncV2[T any](fn func(*jsontext.Encoder, T, Options) error) *Marshalers {
-	t := reflect.TypeOf((*T)(nil)).Elem()
+	t := reflect.TypeFor[T]()
 	assertCastableTo(t, true)
 	typFnc := typedMarshaler{
 		typ: t,
@@ -241,7 +241,7 @@ func MarshalFuncV2[T any](fn func(*jsontext.Encoder, T, Options) error) *Marshal
 // The input []byte and value T must not be retained outside the function call.
 // It may not return [SkipFunc].
 func UnmarshalFuncV1[T any](fn func([]byte, T) error) *Unmarshalers {
-	t := reflect.TypeOf((*T)(nil)).Elem()
+	t := reflect.TypeFor[T]()
 	assertCastableTo(t, false)
 	typFnc := typedUnmarshaler{
 		typ: t,
@@ -274,7 +274,7 @@ func UnmarshalFuncV1[T any](fn func([]byte, T) error) *Unmarshalers {
 // The pointer to [jsontext.Decoder], the value of T, and [Options] value
 // must not be retained outside the function call.
 func UnmarshalFuncV2[T any](fn func(*jsontext.Decoder, T, Options) error) *Unmarshalers {
-	t := reflect.TypeOf((*T)(nil)).Elem()
+	t := reflect.TypeFor[T]()
 	assertCastableTo(t, false)
 	typFnc := typedUnmarshaler{
 		typ: t,

arshal_inlined.go

@@ -29,7 +29,7 @@ import (
 // represent any arbitrary JSON object member. Explicitly named fields take
 // precedence over the inlined fallback. Only one inlined fallback is allowed.
 
-var jsontextValueType = reflect.TypeOf((*jsontext.Value)(nil)).Elem()
+var jsontextValueType = reflect.TypeFor[jsontext.Value]()
 
 // marshalInlinedFallbackAll marshals all the members in an inlined fallback.
 func marshalInlinedFallbackAll(enc *jsontext.Encoder, va addressableValue, mo *jsonopts.Struct, f *structField, insertUnquotedName func([]byte) bool) error {

arshal_methods.go

@@ -17,18 +17,18 @@ import (
 
 // Interfaces for custom serialization.
 var (
-	jsonMarshalerV1Type   = reflect.TypeOf((*MarshalerV1)(nil)).Elem()
-	jsonMarshalerV2Type   = reflect.TypeOf((*MarshalerV2)(nil)).Elem()
-	jsonUnmarshalerV1Type = reflect.TypeOf((*UnmarshalerV1)(nil)).Elem()
-	jsonUnmarshalerV2Type = reflect.TypeOf((*UnmarshalerV2)(nil)).Elem()
-	textAppenderType      = reflect.TypeOf((*encodingTextAppender)(nil)).Elem()
-	textMarshalerType     = reflect.TypeOf((*encoding.TextMarshaler)(nil)).Elem()
-	textUnmarshalerType   = reflect.TypeOf((*encoding.TextUnmarshaler)(nil)).Elem()
+	jsonMarshalerV1Type   = reflect.TypeFor[MarshalerV1]()
+	jsonMarshalerV2Type   = reflect.TypeFor[MarshalerV2]()
+	jsonUnmarshalerV1Type = reflect.TypeFor[UnmarshalerV1]()
+	jsonUnmarshalerV2Type = reflect.TypeFor[UnmarshalerV2]()
+	textAppenderType      = reflect.TypeFor[encodingTextAppender]()
+	textMarshalerType     = reflect.TypeFor[encoding.TextMarshaler]()
+	textUnmarshalerType   = reflect.TypeFor[encoding.TextUnmarshaler]()
 
 	// TODO(https://go.dev/issue/62384): Use encoding.TextAppender instead of this hack.
 	// This exists for now to provide performance benefits to netip types.
 	// There is no semantic difference with this change.
-	appenderToType = reflect.TypeOf((*interface{ AppendTo([]byte) []byte })(nil)).Elem()
+	appenderToType = reflect.TypeFor[interface{ AppendTo([]byte) []byte }]()
 )
 
 // TODO(https://go.dev/issue/62384): Use encoding.TextAppender instead

arshal_test.go

@@ -600,54 +600,54 @@ func (valueStringer) String() string    { return "" }
 func (*pointerStringer) String() string { return "" }
 
 var (
-	namedBoolType                = reflect.TypeOf((*namedBool)(nil)).Elem()
-	intType                      = reflect.TypeOf((*int)(nil)).Elem()
-	int8Type                     = reflect.TypeOf((*int8)(nil)).Elem()
-	int16Type                    = reflect.TypeOf((*int16)(nil)).Elem()
-	int32Type                    = reflect.TypeOf((*int32)(nil)).Elem()
-	int64Type                    = reflect.TypeOf((*int64)(nil)).Elem()
-	uintType                     = reflect.TypeOf((*uint)(nil)).Elem()
-	uint8Type                    = reflect.TypeOf((*uint8)(nil)).Elem()
-	uint16Type                   = reflect.TypeOf((*uint16)(nil)).Elem()
-	uint32Type                   = reflect.TypeOf((*uint32)(nil)).Elem()
-	uint64Type                   = reflect.TypeOf((*uint64)(nil)).Elem()
-	float32Type                  = reflect.TypeOf((*float32)(nil)).Elem()
-	sliceStringType              = reflect.TypeOf((*[]string)(nil)).Elem()
-	array1StringType             = reflect.TypeOf((*[1]string)(nil)).Elem()
-	array0ByteType               = reflect.TypeOf((*[0]byte)(nil)).Elem()
-	array1ByteType               = reflect.TypeOf((*[1]byte)(nil)).Elem()
-	array2ByteType               = reflect.TypeOf((*[2]byte)(nil)).Elem()
-	array3ByteType               = reflect.TypeOf((*[3]byte)(nil)).Elem()
-	array4ByteType               = reflect.TypeOf((*[4]byte)(nil)).Elem()
-	mapStringStringType          = reflect.TypeOf((*map[string]string)(nil)).Elem()
-	structAllType                = reflect.TypeOf((*structAll)(nil)).Elem()
-	structConflictingType        = reflect.TypeOf((*structConflicting)(nil)).Elem()
-	structNoneExportedType       = reflect.TypeOf((*structNoneExported)(nil)).Elem()
-	structMalformedTagType       = reflect.TypeOf((*structMalformedTag)(nil)).Elem()
-	structUnexportedTagType      = reflect.TypeOf((*structUnexportedTag)(nil)).Elem()
-	structUnexportedEmbeddedType = reflect.TypeOf((*structUnexportedEmbedded)(nil)).Elem()
-	structUnknownTextValueType   = reflect.TypeOf((*structUnknownTextValue)(nil)).Elem()
-	allMethodsType               = reflect.TypeOf((*allMethods)(nil)).Elem()
-	allMethodsExceptJSONv2Type   = reflect.TypeOf((*allMethodsExceptJSONv2)(nil)).Elem()
-	allMethodsExceptJSONv1Type   = reflect.TypeOf((*allMethodsExceptJSONv1)(nil)).Elem()
-	allMethodsExceptTextType     = reflect.TypeOf((*allMethodsExceptText)(nil)).Elem()
-	onlyMethodJSONv2Type         = reflect.TypeOf((*onlyMethodJSONv2)(nil)).Elem()
-	onlyMethodJSONv1Type         = reflect.TypeOf((*onlyMethodJSONv1)(nil)).Elem()
-	onlyMethodTextType           = reflect.TypeOf((*onlyMethodText)(nil)).Elem()
-	structMethodJSONv2Type       = reflect.TypeOf((*structMethodJSONv2)(nil)).Elem()
-	structMethodJSONv1Type       = reflect.TypeOf((*structMethodJSONv1)(nil)).Elem()
-	structMethodTextType         = reflect.TypeOf((*structMethodText)(nil)).Elem()
-	marshalJSONv2FuncType        = reflect.TypeOf((*marshalJSONv2Func)(nil)).Elem()
-	marshalJSONv1FuncType        = reflect.TypeOf((*marshalJSONv1Func)(nil)).Elem()
-	appendTextFuncType           = reflect.TypeOf((*appendTextFunc)(nil)).Elem()
-	marshalTextFuncType          = reflect.TypeOf((*marshalTextFunc)(nil)).Elem()
-	unmarshalJSONv2FuncType      = reflect.TypeOf((*unmarshalJSONv2Func)(nil)).Elem()
-	unmarshalJSONv1FuncType      = reflect.TypeOf((*unmarshalJSONv1Func)(nil)).Elem()
-	unmarshalTextFuncType        = reflect.TypeOf((*unmarshalTextFunc)(nil)).Elem()
-	nocaseStringType             = reflect.TypeOf((*nocaseString)(nil)).Elem()
-	ioReaderType                 = reflect.TypeOf((*io.Reader)(nil)).Elem()
-	fmtStringerType              = reflect.TypeOf((*fmt.Stringer)(nil)).Elem()
-	chanStringType               = reflect.TypeOf((*chan string)(nil)).Elem()
+	namedBoolType                = reflect.TypeFor[namedBool]()
+	intType                      = reflect.TypeFor[int]()
+	int8Type                     = reflect.TypeFor[int8]()
+	int16Type                    = reflect.TypeFor[int16]()
+	int32Type                    = reflect.TypeFor[int32]()
+	int64Type                    = reflect.TypeFor[int64]()
+	uintType                     = reflect.TypeFor[uint]()
+	uint8Type                    = reflect.TypeFor[uint8]()
+	uint16Type                   = reflect.TypeFor[uint16]()
+	uint32Type                   = reflect.TypeFor[uint32]()
+	uint64Type                   = reflect.TypeFor[uint64]()
+	float32Type                  = reflect.TypeFor[float32]()
+	sliceStringType              = reflect.TypeFor[[]string]()
+	array1StringType             = reflect.TypeFor[[1]string]()
+	array0ByteType               = reflect.TypeFor[[0]byte]()
+	array1ByteType               = reflect.TypeFor[[1]byte]()
+	array2ByteType               = reflect.TypeFor[[2]byte]()
+	array3ByteType               = reflect.TypeFor[[3]byte]()
+	array4ByteType               = reflect.TypeFor[[4]byte]()
+	mapStringStringType          = reflect.TypeFor[map[string]string]()
+	structAllType                = reflect.TypeFor[structAll]()
+	structConflictingType        = reflect.TypeFor[structConflicting]()
+	structNoneExportedType       = reflect.TypeFor[structNoneExported]()
+	structMalformedTagType       = reflect.TypeFor[structMalformedTag]()
+	structUnexportedTagType      = reflect.TypeFor[structUnexportedTag]()
+	structUnexportedEmbeddedType = reflect.TypeFor[structUnexportedEmbedded]()
+	structUnknownTextValueType   = reflect.TypeFor[structUnknownTextValue]()
+	allMethodsType               = reflect.TypeFor[allMethods]()
+	allMethodsExceptJSONv2Type   = reflect.TypeFor[allMethodsExceptJSONv2]()
+	allMethodsExceptJSONv1Type   = reflect.TypeFor[allMethodsExceptJSONv1]()
+	allMethodsExceptTextType     = reflect.TypeFor[allMethodsExceptText]()
+	onlyMethodJSONv2Type         = reflect.TypeFor[onlyMethodJSONv2]()
+	onlyMethodJSONv1Type         = reflect.TypeFor[onlyMethodJSONv1]()
+	onlyMethodTextType           = reflect.TypeFor[onlyMethodText]()
+	structMethodJSONv2Type       = reflect.TypeFor[structMethodJSONv2]()
+	structMethodJSONv1Type       = reflect.TypeFor[structMethodJSONv1]()
+	structMethodTextType         = reflect.TypeFor[structMethodText]()
+	marshalJSONv2FuncType        = reflect.TypeFor[marshalJSONv2Func]()
+	marshalJSONv1FuncType        = reflect.TypeFor[marshalJSONv1Func]()
+	appendTextFuncType           = reflect.TypeFor[appendTextFunc]()
+	marshalTextFuncType          = reflect.TypeFor[marshalTextFunc]()
+	unmarshalJSONv2FuncType      = reflect.TypeFor[unmarshalJSONv2Func]()
+	unmarshalJSONv1FuncType      = reflect.TypeFor[unmarshalJSONv1Func]()
+	unmarshalTextFuncType        = reflect.TypeFor[unmarshalTextFunc]()
+	nocaseStringType             = reflect.TypeFor[nocaseString]()
+	ioReaderType                 = reflect.TypeFor[io.Reader]()
+	fmtStringerType              = reflect.TypeFor[fmt.Stringer]()
+	chanStringType               = reflect.TypeFor[chan string]()
 )
 
 func addr[T any](v T) *T {
@@ -913,7 +913,7 @@ func TestMarshal(t *testing.T) {
 		name:    jsontest.Name("Maps/DuplicateName/NoCaseString"),
 		in:      map[nocaseString]string{"hello": "", "HELLO": ""},
 		want:    `{"hello":""`,
-		wantErr: &SemanticError{action: "marshal", JSONKind: '"', GoType: reflect.TypeOf(nocaseString("")), Err: export.NewDuplicateNameError([]byte(`"hello"`), len64(`{"hello":"",`))},
+		wantErr: &SemanticError{action: "marshal", JSONKind: '"', GoType: reflect.TypeFor[nocaseString](), Err: export.NewDuplicateNameError([]byte(`"hello"`), len64(`{"hello":"",`))},
 	}, {
 		name: jsontest.Name("Maps/DuplicateName/NaNs/Deterministic+AllowDuplicateNames"),
 		opts: []Options{
@@ -1036,7 +1036,7 @@ func TestMarshal(t *testing.T) {
 			return m
 		}(),
 		want:    strings.Repeat(`{"k":`, startDetectingCyclesAfter) + `{"k"`,
-		wantErr: &SemanticError{action: "marshal", GoType: reflect.TypeOf(recursiveMap{}), Err: errors.New("encountered a cycle")},
+		wantErr: &SemanticError{action: "marshal", GoType: reflect.TypeFor[recursiveMap](), Err: errors.New("encountered a cycle")},
 	}, {
 		name: jsontest.Name("Maps/IgnoreInvalidFormat"),
 		opts: []Options{invalidFormatOption},
@@ -1883,7 +1883,7 @@ func TestMarshal(t *testing.T) {
 			for i := 0; i < 100; i++ {
 				fields = append(fields, reflect.StructField{
 					Name: fmt.Sprintf("X%d", i),
-					Type: reflect.TypeOf(stringMarshalEmpty("")),
+					Type: reflect.TypeFor[stringMarshalEmpty](),
 					Tag:  `json:",omitempty"`,
 				})
 			}
@@ -2731,7 +2731,7 @@ func TestMarshal(t *testing.T) {
 			return s
 		}(),
 		want:    strings.Repeat(`[`, startDetectingCyclesAfter) + `[`,
-		wantErr: &SemanticError{action: "marshal", GoType: reflect.TypeOf(recursiveSlice{}), Err: errors.New("encountered a cycle")},
+		wantErr: &SemanticError{action: "marshal", GoType: reflect.TypeFor[recursiveSlice](), Err: errors.New("encountered a cycle")},
 	}, {
 		name: jsontest.Name("Slices/NonCyclicSlice"),
 		in: func() []any {
@@ -2826,7 +2826,7 @@ func TestMarshal(t *testing.T) {
 			return p
 		}(),
 		want:    strings.Repeat(`{"P":`, startDetectingCyclesAfter) + `{"P"`,
-		wantErr: &SemanticError{action: "marshal", GoType: reflect.TypeOf((*recursivePointer)(nil)), Err: errors.New("encountered a cycle")},
+		wantErr: &SemanticError{action: "marshal", GoType: reflect.TypeFor[*recursivePointer](), Err: errors.New("encountered a cycle")},
 	}, {
 		name: jsontest.Name("Pointers/IgnoreInvalidFormat"),
 		opts: []Options{invalidFormatOption},

arshal_time.go

@@ -22,8 +22,8 @@ import (
 )
 
 var (
-	timeDurationType = reflect.TypeOf((*time.Duration)(nil)).Elem()
-	timeTimeType     = reflect.TypeOf((*time.Time)(nil)).Elem()
+	timeDurationType = reflect.TypeFor[time.Duration]()
+	timeTimeType     = reflect.TypeFor[time.Time]()
 )
 
 func makeTimeArshaler(fncs *arshaler, t reflect.Type) *arshaler {

errors_test.go

@@ -34,31 +34,31 @@ func TestSemanticError(t *testing.T) {
 		err:  &SemanticError{action: "marshal", JSONKind: '"'},
 		want: "json: cannot marshal JSON string",
 	}, {
-		err:  &SemanticError{GoType: reflect.TypeOf(bool(false))},
+		err:  &SemanticError{GoType: reflect.TypeFor[bool]()},
 		want: "json: cannot handle Go value of type bool",
 	}, {
-		err:  &SemanticError{action: "marshal", GoType: reflect.TypeOf(int(0))},
+		err:  &SemanticError{action: "marshal", GoType: reflect.TypeFor[int]()},
 		want: "json: cannot marshal Go value of type int",
 	}, {
-		err:  &SemanticError{action: "unmarshal", GoType: reflect.TypeOf(uint(0))},
+		err:  &SemanticError{action: "unmarshal", GoType: reflect.TypeFor[uint]()},
 		want: "json: cannot unmarshal Go value of type uint",
 	}, {
-		err:  &SemanticError{JSONKind: '0', GoType: reflect.TypeOf(tar.Header{})},
+		err:  &SemanticError{JSONKind: '0', GoType: reflect.TypeFor[tar.Header]()},
 		want: "json: cannot handle JSON number with Go value of type tar.Header",
 	}, {
-		err:  &SemanticError{action: "marshal", JSONKind: '{', GoType: reflect.TypeOf(bytes.Buffer{})},
+		err:  &SemanticError{action: "marshal", JSONKind: '{', GoType: reflect.TypeFor[bytes.Buffer]()},
 		want: "json: cannot marshal JSON object from Go value of type bytes.Buffer",
 	}, {
-		err:  &SemanticError{action: "unmarshal", JSONKind: ']', GoType: reflect.TypeOf(strings.Reader{})},
+		err:  &SemanticError{action: "unmarshal", JSONKind: ']', GoType: reflect.TypeFor[strings.Reader]()},
 		want: "json: cannot unmarshal JSON array into Go value of type strings.Reader",
 	}, {
-		err:  &SemanticError{action: "unmarshal", JSONKind: '{', GoType: reflect.TypeOf(float64(0)), ByteOffset: 123},
+		err:  &SemanticError{action: "unmarshal", JSONKind: '{', GoType: reflect.TypeFor[float64](), ByteOffset: 123},
 		want: "json: cannot unmarshal JSON object into Go value of type float64 after byte offset 123",
 	}, {
-		err:  &SemanticError{action: "marshal", JSONKind: 'f', GoType: reflect.TypeOf(complex128(0)), ByteOffset: 123, JSONPointer: "/foo/2/bar/3"},
+		err:  &SemanticError{action: "marshal", JSONKind: 'f', GoType: reflect.TypeFor[complex128](), ByteOffset: 123, JSONPointer: "/foo/2/bar/3"},
 		want: "json: cannot marshal JSON boolean from Go value of type complex128 within JSON value at \"/foo/2/bar/3\"",
 	}, {
-		err:  &SemanticError{action: "unmarshal", JSONKind: '}', GoType: reflect.TypeOf((*io.Reader)(nil)).Elem(), ByteOffset: 123, JSONPointer: "/foo/2/bar/3", Err: errors.New("some underlying error")},
+		err:  &SemanticError{action: "unmarshal", JSONKind: '}', GoType: reflect.TypeFor[io.Reader](), ByteOffset: 123, JSONPointer: "/foo/2/bar/3", Err: errors.New("some underlying error")},
 		want: "json: cannot unmarshal JSON object into Go value of type io.Reader within JSON value at \"/foo/2/bar/3\": some underlying error",
 	}, {
 		err:  &SemanticError{Err: errors.New("some underlying error")},

fields.go

@@ -26,7 +26,7 @@ type isZeroer interface {
 	IsZero() bool
 }
 
-var isZeroerType = reflect.TypeOf((*isZeroer)(nil)).Elem()
+var isZeroerType = reflect.TypeFor[isZeroer]()
 
 type structFields struct {
 	flattened       []structField // listed in depth-first ordering

fields_test.go

@@ -197,7 +197,7 @@ func TestMakeStructFields(t *testing.T) {
 			X map[string]jsontext.Value `json:",unknown"`
 		}{},
 		want: structFields{
-			inlinedFallback: &structField{id: 0, index: []int{2}, typ: reflect.TypeOf(map[string]jsontext.Value(nil)), fieldOptions: fieldOptions{name: "X", quotedName: `"X"`, unknown: true}},
+			inlinedFallback: &structField{id: 0, index: []int{2}, typ: reflect.TypeFor[map[string]jsontext.Value](), fieldOptions: fieldOptions{name: "X", quotedName: `"X"`, unknown: true}},
 		},
 	}, {
 		name: jsontest.Name("InvalidUTF8"),

fold_test.go

@@ -120,7 +120,7 @@ func runUnmarshalUnknown(tb testing.TB) {
 		for i := 0; i < n; i++ {
 			fields = append(fields, reflect.StructField{
 				Name: fmt.Sprintf("Name%d", i),
-				Type: reflect.TypeOf(0),
+				Type: reflect.TypeFor[int](),
 				Tag:  `json:",nocase"`,
 			})
 		}