accounts/abi: add internalType information and fix issues (#20179)

* accounts/abi: fix various issues

The fixed issues include:

(1) If there is no return in a call function, unpack should
return nil error

(2) For some functions which have struct array as parameter,
it will also be detected and generate the struct definition

(3) For event, if it has non-indexed parameter, the parameter
name will also be assigned if empty. Also the internal struct
will be detected and generate struct defition if not exist.

(4) Fix annotation generation in event function

* accounts/abi: add new abi field internalType

* accounts: address comments and add tests

* accounts/abi: replace strings.ReplaceAll with strings.Replace

accounts/abi/abi.go

@@ -75,9 +75,6 @@ func (abi ABI) Pack(name string, args ...interface{}) ([]byte, error) {
 
 // Unpack output in v according to the abi specification
 func (abi ABI) Unpack(v interface{}, name string, data []byte) (err error) {
-	if len(data) == 0 {
-		return fmt.Errorf("abi: unmarshalling empty output")
-	}
 	// since there can't be naming collisions with contracts and events,
 	// we need to decide whether we're calling a method or an event
 	if method, ok := abi.Methods[name]; ok {
@@ -94,9 +91,6 @@ func (abi ABI) Unpack(v interface{}, name string, data []byte) (err error) {
 
 // UnpackIntoMap unpacks a log into the provided map[string]interface{}
 func (abi ABI) UnpackIntoMap(v map[string]interface{}, name string, data []byte) (err error) {
-	if len(data) == 0 {
-		return fmt.Errorf("abi: unmarshalling empty output")
-	}
 	// since there can't be naming collisions with contracts and events,
 	// we need to decide whether we're calling a method or an event
 	if method, ok := abi.Methods[name]; ok {

accounts/abi/abi_test.go

@@ -57,7 +57,7 @@ const jsondata2 = `
 ]`
 
 func TestReader(t *testing.T) {
-	Uint256, _ := NewType("uint256", nil)
+	Uint256, _ := NewType("uint256", "", nil)
 	exp := ABI{
 		Methods: map[string]Method{
 			"balance": {
@@ -172,7 +172,7 @@ func TestTestSlice(t *testing.T) {
 }
 
 func TestMethodSignature(t *testing.T) {
-	String, _ := NewType("string", nil)
+	String, _ := NewType("string", "", nil)
 	m := Method{"foo", "foo", false, []Argument{{"bar", String, false}, {"baz", String, false}}, nil}
 	exp := "foo(string,string)"
 	if m.Sig() != exp {
@@ -184,7 +184,7 @@ func TestMethodSignature(t *testing.T) {
 		t.Errorf("expected ids to match %x != %x", m.ID(), idexp)
 	}
 
-	uintt, _ := NewType("uint256", nil)
+	uintt, _ := NewType("uint256", "", nil)
 	m = Method{"foo", "foo", false, []Argument{{"bar", uintt, false}}, nil}
 	exp = "foo(uint256)"
 	if m.Sig() != exp {
@@ -192,7 +192,7 @@ func TestMethodSignature(t *testing.T) {
 	}
 
 	// Method with tuple arguments
-	s, _ := NewType("tuple", []ArgumentMarshaling{
+	s, _ := NewType("tuple", "", []ArgumentMarshaling{
 		{Name: "a", Type: "int256"},
 		{Name: "b", Type: "int256[]"},
 		{Name: "c", Type: "tuple[]", Components: []ArgumentMarshaling{
@@ -602,9 +602,9 @@ func TestBareEvents(t *testing.T) {
 	{ "type" : "event", "name" : "tuple", "inputs" : [{ "indexed":false, "name":"t", "type":"tuple", "components":[{"name":"a", "type":"uint256"}] }, { "indexed":true, "name":"arg1", "type":"address" }] }
 	]`
 
-	arg0, _ := NewType("uint256", nil)
+	arg0, _ := NewType("uint256", "", nil)
-	arg1, _ := NewType("address", nil)
+	arg1, _ := NewType("address", "", nil)
-	tuple, _ := NewType("tuple", []ArgumentMarshaling{{Name: "a", Type: "uint256"}})
+	tuple, _ := NewType("tuple", "", []ArgumentMarshaling{{Name: "a", Type: "uint256"}})
 
 	expectedEvents := map[string]struct {
 		Anonymous bool

accounts/abi/argument.go

@@ -36,6 +36,7 @@ type Arguments []Argument
 type ArgumentMarshaling struct {
 	Name         string
 	Type         string
+	InternalType string
 	Components   []ArgumentMarshaling
 	Indexed      bool
 }
@@ -48,7 +49,7 @@ func (argument *Argument) UnmarshalJSON(data []byte) error {
 		return fmt.Errorf("argument json err: %v", err)
 	}
 
-	argument.Type, err = NewType(arg.Type, arg.Components)
+	argument.Type, err = NewType(arg.Type, arg.InternalType, arg.Components)
 	if err != nil {
 		return err
 	}
@@ -88,6 +89,13 @@ func (arguments Arguments) isTuple() bool {
 
 // Unpack performs the operation hexdata -> Go format
 func (arguments Arguments) Unpack(v interface{}, data []byte) error {
+	if len(data) == 0 {
+		if len(arguments) != 0 {
+			return fmt.Errorf("abi: attempting to unmarshall an empty string while arguments are expected")
+		} else {
+			return nil // Nothing to unmarshal, return
+		}
+	}
 	// make sure the passed value is arguments pointer
 	if reflect.Ptr != reflect.ValueOf(v).Kind() {
 		return fmt.Errorf("abi: Unpack(non-pointer %T)", v)
@@ -104,11 +112,17 @@ func (arguments Arguments) Unpack(v interface{}, data []byte) error {
 
 // UnpackIntoMap performs the operation hexdata -> mapping of argument name to argument value
 func (arguments Arguments) UnpackIntoMap(v map[string]interface{}, data []byte) error {
+	if len(data) == 0 {
+		if len(arguments) != 0 {
+			return fmt.Errorf("abi: attempting to unmarshall an empty string while arguments are expected")
+		} else {
+			return nil // Nothing to unmarshal, return
+		}
+	}
 	marshalledValues, err := arguments.UnpackValues(data)
 	if err != nil {
 		return err
 	}
-
 	return arguments.unpackIntoMap(v, marshalledValues)
 }
 

accounts/abi/bind/bind.go

@@ -86,7 +86,7 @@ func Bind(types []string, abis []string, bytecodes []string, fsigs []map[string]
 				if input.Name == "" {
 					normalized.Inputs[j].Name = fmt.Sprintf("arg%d", j)
 				}
-				if _, exist := structs[input.Type.String()]; input.Type.T == abi.TupleTy && !exist {
+				if hasStruct(input.Type) {
 					bindStructType[lang](input.Type, structs)
 				}
 			}
@@ -96,7 +96,7 @@ func Bind(types []string, abis []string, bytecodes []string, fsigs []map[string]
 				if output.Name != "" {
 					normalized.Outputs[j].Name = capitalise(output.Name)
 				}
-				if _, exist := structs[output.Type.String()]; output.Type.T == abi.TupleTy && !exist {
+				if hasStruct(output.Type) {
 					bindStructType[lang](output.Type, structs)
 				}
 			}
@@ -119,16 +119,13 @@ func Bind(types []string, abis []string, bytecodes []string, fsigs []map[string]
 			normalized.Inputs = make([]abi.Argument, len(original.Inputs))
 			copy(normalized.Inputs, original.Inputs)
 			for j, input := range normalized.Inputs {
-				// Indexed fields are input, non-indexed ones are outputs
-				if input.Indexed {
 				if input.Name == "" {
 					normalized.Inputs[j].Name = fmt.Sprintf("arg%d", j)
 				}
-					if _, exist := structs[input.Type.String()]; input.Type.T == abi.TupleTy && !exist {
+				if hasStruct(input.Type) {
 					bindStructType[lang](input.Type, structs)
 				}
 			}
-			}
 			// Append the event to the accumulator list
 			events[original.Name] = &tmplEvent{Original: original, Normalized: normalized}
 		}
@@ -244,7 +241,7 @@ func bindBasicTypeGo(kind abi.Type) string {
 func bindTypeGo(kind abi.Type, structs map[string]*tmplStruct) string {
 	switch kind.T {
 	case abi.TupleTy:
-		return structs[kind.String()].Name
+		return structs[kind.TupleRawName+kind.String()].Name
 	case abi.ArrayTy:
 		return fmt.Sprintf("[%d]", kind.Size) + bindTypeGo(*kind.Elem, structs)
 	case abi.SliceTy:
@@ -321,7 +318,7 @@ func pluralizeJavaType(typ string) string {
 func bindTypeJava(kind abi.Type, structs map[string]*tmplStruct) string {
 	switch kind.T {
 	case abi.TupleTy:
-		return structs[kind.String()].Name
+		return structs[kind.TupleRawName+kind.String()].Name
 	case abi.ArrayTy, abi.SliceTy:
 		return pluralizeJavaType(bindTypeJava(*kind.Elem, structs))
 	default:
@@ -340,6 +337,13 @@ var bindTopicType = map[Lang]func(kind abi.Type, structs map[string]*tmplStruct)
 // funcionality as for simple types, but dynamic types get converted to hashes.
 func bindTopicTypeGo(kind abi.Type, structs map[string]*tmplStruct) string {
 	bound := bindTypeGo(kind, structs)
+
+	// todo(rjl493456442) according solidity documentation, indexed event
+	// parameters that are not value types i.e. arrays and structs are not
+	// stored directly but instead a keccak256-hash of an encoding is stored.
+	//
+	// We only convert stringS and bytes to hash, still need to deal with
+	// array(both fixed-size and dynamic-size) and struct.
 	if bound == "string" || bound == "[]byte" {
 		bound = "common.Hash"
 	}
@@ -350,6 +354,13 @@ func bindTopicTypeGo(kind abi.Type, structs map[string]*tmplStruct) string {
 // funcionality as for simple types, but dynamic types get converted to hashes.
 func bindTopicTypeJava(kind abi.Type, structs map[string]*tmplStruct) string {
 	bound := bindTypeJava(kind, structs)
+
+	// todo(rjl493456442) according solidity documentation, indexed event
+	// parameters that are not value types i.e. arrays and structs are not
+	// stored directly but instead a keccak256-hash of an encoding is stored.
+	//
+	// We only convert stringS and bytes to hash, still need to deal with
+	// array(both fixed-size and dynamic-size) and struct.
 	if bound == "String" || bound == "byte[]" {
 		bound = "Hash"
 	}
@@ -369,7 +380,14 @@ var bindStructType = map[Lang]func(kind abi.Type, structs map[string]*tmplStruct
 func bindStructTypeGo(kind abi.Type, structs map[string]*tmplStruct) string {
 	switch kind.T {
 	case abi.TupleTy:
-		if s, exist := structs[kind.String()]; exist {
+		// We compose raw struct name and canonical parameter expression
+		// together here. The reason is before solidity v0.5.11, kind.TupleRawName
+		// is empty, so we use canonical parameter expression to distinguish
+		// different struct definition. From the consideration of backward
+		// compatibility, we concat these two together so that if kind.TupleRawName
+		// is not empty, it can have unique id.
+		id := kind.TupleRawName + kind.String()
+		if s, exist := structs[id]; exist {
 			return s.Name
 		}
 		var fields []*tmplField
@@ -377,8 +395,11 @@ func bindStructTypeGo(kind abi.Type, structs map[string]*tmplStruct) string {
 			field := bindStructTypeGo(*elem, structs)
 			fields = append(fields, &tmplField{Type: field, Name: capitalise(kind.TupleRawNames[i]), SolKind: *elem})
 		}
-		name := fmt.Sprintf("Struct%d", len(structs))
+		name := kind.TupleRawName
-		structs[kind.String()] = &tmplStruct{
+		if name == "" {
+			name = fmt.Sprintf("Struct%d", len(structs))
+		}
+		structs[id] = &tmplStruct{
 			Name:   name,
 			Fields: fields,
 		}
@@ -398,7 +419,14 @@ func bindStructTypeGo(kind abi.Type, structs map[string]*tmplStruct) string {
 func bindStructTypeJava(kind abi.Type, structs map[string]*tmplStruct) string {
 	switch kind.T {
 	case abi.TupleTy:
-		if s, exist := structs[kind.String()]; exist {
+		// We compose raw struct name and canonical parameter expression
+		// together here. The reason is before solidity v0.5.11, kind.TupleRawName
+		// is empty, so we use canonical parameter expression to distinguish
+		// different struct definition. From the consideration of backward
+		// compatibility, we concat these two together so that if kind.TupleRawName
+		// is not empty, it can have unique id.
+		id := kind.TupleRawName + kind.String()
+		if s, exist := structs[id]; exist {
 			return s.Name
 		}
 		var fields []*tmplField
@@ -406,8 +434,11 @@ func bindStructTypeJava(kind abi.Type, structs map[string]*tmplStruct) string {
 			field := bindStructTypeJava(*elem, structs)
 			fields = append(fields, &tmplField{Type: field, Name: decapitalise(kind.TupleRawNames[i]), SolKind: *elem})
 		}
-		name := fmt.Sprintf("Class%d", len(structs))
+		name := kind.TupleRawName
-		structs[kind.String()] = &tmplStruct{
+		if name == "" {
+			name = fmt.Sprintf("Class%d", len(structs))
+		}
+		structs[id] = &tmplStruct{
 			Name:   name,
 			Fields: fields,
 		}
@@ -497,6 +528,21 @@ func structured(args abi.Arguments) bool {
 	return true
 }
 
+// hasStruct returns an indicator whether the given type is struct, struct slice
+// or struct array.
+func hasStruct(t abi.Type) bool {
+	switch t.T {
+	case abi.SliceTy:
+		return hasStruct(*t.Elem)
+	case abi.ArrayTy:
+		return hasStruct(*t.Elem)
+	case abi.TupleTy:
+		return true
+	default:
+		return false
+	}
+}
+
 // resolveArgName converts a raw argument representation into a user friendly format.
 func resolveArgName(arg abi.Argument, structs map[string]*tmplStruct) string {
 	var (
@@ -512,7 +558,7 @@ loop:
 		case abi.ArrayTy:
 			prefix += fmt.Sprintf("[%d]", typ.Size)
 		default:
-			embedded = typ.String()
+			embedded = typ.TupleRawName + typ.String()
 			break loop
 		}
 		typ = typ.Elem

accounts/abi/bind/template.go

@@ -65,7 +65,7 @@ type tmplField struct {
 // tmplStruct is a wrapper around an abi.tuple contains a auto-generated
 // struct name.
 type tmplStruct struct {
-	Name   string       // Auto-generated struct name(We can't obtain the raw struct name through abi)
+	Name   string       // Auto-generated struct name(before solidity v0.5.11) or raw name.
 	Fields []*tmplField // Struct fields definition depends on the binding language.
 }
 
@@ -483,7 +483,7 @@ var (
 
 		// Parse{{.Normalized.Name}} is a log parse operation binding the contract event 0x{{printf "%x" .Original.ID}}.
 		//
-		// Solidity: {{.Original.String}}
+		// Solidity: {{formatevent .Original $structs}}
 		func (_{{$contract.Type}} *{{$contract.Type}}Filterer) Parse{{.Normalized.Name}}(log types.Log) (*{{$contract.Type}}{{.Normalized.Name}}, error) {
 			event := new({{$contract.Type}}{{.Normalized.Name}})
 			if err := _{{$contract.Type}}.contract.UnpackLog(event, "{{.Original.Name}}", log); err != nil {

accounts/abi/bind/topics.go

@@ -80,15 +80,19 @@ func makeTopics(query ...[]interface{}) ([][]common.Hash, error) {
 				copy(topic[:], hash[:])
 
 			default:
+				// todo(rjl493456442) according solidity documentation, indexed event
+				// parameters that are not value types i.e. arrays and structs are not
+				// stored directly but instead a keccak256-hash of an encoding is stored.
+				//
+				// We only convert stringS and bytes to hash, still need to deal with
+				// array(both fixed-size and dynamic-size) and struct.
+
 				// Attempt to generate the topic from funky types
 				val := reflect.ValueOf(rule)
-
 				switch {
-
 				// static byte array
 				case val.Kind() == reflect.Array && reflect.TypeOf(rule).Elem().Kind() == reflect.Uint8:
 					reflect.Copy(reflect.ValueOf(topic[:val.Len()]), val)
-
 				default:
 					return nil, fmt.Errorf("unsupported indexed type: %T", rule)
 				}
@@ -162,6 +166,7 @@ func parseTopics(out interface{}, fields abi.Arguments, topics []common.Hash) er
 
 		default:
 			// Ran out of plain primitive types, try custom types
+
 			switch field.Type() {
 			case reflectHash: // Also covers all dynamic types
 				field.Set(reflect.ValueOf(topics[0]))
@@ -178,11 +183,9 @@ func parseTopics(out interface{}, fields abi.Arguments, topics []common.Hash) er
 			default:
 				// Ran out of custom types, try the crazies
 				switch {
-
 				// static byte array
 				case arg.Type.T == abi.FixedBytesTy:
 					reflect.Copy(field, reflect.ValueOf(topics[0][:arg.Type.Size]))
-
 				default:
 					return fmt.Errorf("unsupported indexed type: %v", arg.Type)
 				}

accounts/abi/bind/topics_test.go

@@ -59,7 +59,7 @@ func TestParseTopics(t *testing.T) {
 	type bytesStruct struct {
 		StaticBytes [5]byte
 	}
-	bytesType, _ := abi.NewType("bytes5", nil)
+	bytesType, _ := abi.NewType("bytes5", "", nil)
 	type args struct {
 		createObj func() interface{}
 		resultObj func() interface{}

accounts/abi/pack_test.go

@@ -613,7 +613,7 @@ func TestPack(t *testing.T) {
 				"ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff"), // tuple[1].A[1]
 		},
 	} {
-		typ, err := NewType(test.typ, test.components)
+		typ, err := NewType(test.typ, "", test.components)
 		if err != nil {
 			t.Fatalf("%v failed. Unexpected parse error: %v", i, err)
 		}

accounts/abi/type.go

@@ -53,6 +53,7 @@ type Type struct {
 	stringKind string // holds the unparsed string for deriving signatures
 
 	// Tuple relative fields
+	TupleRawName  string   // Raw struct name defined in source code, may be empty.
 	TupleElems    []*Type  // Type information of all tuple fields
 	TupleRawNames []string // Raw field name of all tuple fields
 }
@@ -63,7 +64,7 @@ var (
 )
 
 // NewType creates a new reflection type of abi type given in t.
-func NewType(t string, components []ArgumentMarshaling) (typ Type, err error) {
+func NewType(t string, internalType string, components []ArgumentMarshaling) (typ Type, err error) {
 	// check that array brackets are equal if they exist
 	if strings.Count(t, "[") != strings.Count(t, "]") {
 		return Type{}, fmt.Errorf("invalid arg type in abi")
@@ -73,9 +74,14 @@ func NewType(t string, components []ArgumentMarshaling) (typ Type, err error) {
 	// if there are brackets, get ready to go into slice/array mode and
 	// recursively create the type
 	if strings.Count(t, "[") != 0 {
-		i := strings.LastIndex(t, "[")
+		// Note internalType can be empty here.
+		subInternal := internalType
+		if i := strings.LastIndex(internalType, "["); i != -1 {
+			subInternal = subInternal[:i]
+		}
 		// recursively embed the type
-		embeddedType, err := NewType(t[:i], components)
+		i := strings.LastIndex(t, "[")
+		embeddedType, err := NewType(t[:i], subInternal, components)
 		if err != nil {
 			return Type{}, err
 		}
@@ -173,7 +179,7 @@ func NewType(t string, components []ArgumentMarshaling) (typ Type, err error) {
 		)
 		expression += "("
 		for idx, c := range components {
-			cType, err := NewType(c.Type, c.Components)
+			cType, err := NewType(c.Type, c.InternalType, c.Components)
 			if err != nil {
 				return Type{}, err
 			}
@@ -199,6 +205,17 @@ func NewType(t string, components []ArgumentMarshaling) (typ Type, err error) {
 		typ.TupleRawNames = names
 		typ.T = TupleTy
 		typ.stringKind = expression
+
+		const structPrefix = "struct "
+		// After solidity 0.5.10, a new field of abi "internalType"
+		// is introduced. From that we can obtain the struct name
+		// user defined in the source code.
+		if internalType != "" && strings.HasPrefix(internalType, structPrefix) {
+			// Foo.Bar type definition is not allowed in golang,
+			// convert the format to FooBar
+			typ.TupleRawName = strings.Replace(internalType[len(structPrefix):], ".", "", -1)
+		}
+
 	case "function":
 		typ.Kind = reflect.Array
 		typ.T = FunctionTy

accounts/abi/type_test.go

@@ -106,7 +106,7 @@ func TestTypeRegexp(t *testing.T) {
 	}
 
 	for _, tt := range tests {
-		typ, err := NewType(tt.blob, tt.components)
+		typ, err := NewType(tt.blob, "", tt.components)
 		if err != nil {
 			t.Errorf("type %q: failed to parse type string: %v", tt.blob, err)
 		}
@@ -281,7 +281,7 @@ func TestTypeCheck(t *testing.T) {
 			B *big.Int
 		}{{big.NewInt(0), big.NewInt(0)}, {big.NewInt(0), big.NewInt(0)}}, ""},
 	} {
-		typ, err := NewType(test.typ, test.components)
+		typ, err := NewType(test.typ, "", test.components)
 		if err != nil && len(test.err) == 0 {
 			t.Fatal("unexpected parse error:", err)
 		} else if err != nil && len(test.err) != 0 {

accounts/abi/unpack_test.go

@@ -51,6 +51,7 @@ func (test unpackTest) checkError(err error) error {
 }
 
 var unpackTests = []unpackTest{
+	// Bools
 	{
 		def:  `[{ "type": "bool" }]`,
 		enc:  "0000000000000000000000000000000000000000000000000000000000000001",
@@ -73,6 +74,7 @@ var unpackTests = []unpackTest{
 		want: false,
 		err:  "abi: improperly encoded boolean value",
 	},
+	// Integers
 	{
 		def:  `[{"type": "uint32"}]`,
 		enc:  "0000000000000000000000000000000000000000000000000000000000000001",
@@ -122,11 +124,13 @@ var unpackTests = []unpackTest{
 		enc:  "ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff",
 		want: big.NewInt(-1),
 	},
+	// Address
 	{
 		def:  `[{"type": "address"}]`,
 		enc:  "0000000000000000000000000100000000000000000000000000000000000000",
 		want: common.Address{1},
 	},
+	// Bytes
 	{
 		def:  `[{"type": "bytes32"}]`,
 		enc:  "0100000000000000000000000000000000000000000000000000000000000000",
@@ -154,23 +158,39 @@ var unpackTests = []unpackTest{
 		enc:  "0100000000000000000000000000000000000000000000000000000000000000",
 		want: [32]byte{1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
 	},
+	// Functions
 	{
 		def:  `[{"type": "function"}]`,
 		enc:  "0100000000000000000000000000000000000000000000000000000000000000",
 		want: [24]byte{1},
 	},
-	// slices
+	// Slice and Array
 	{
 		def:  `[{"type": "uint8[]"}]`,
 		enc:  "0000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000000200000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000000002",
 		want: []uint8{1, 2},
 	},
+	{
+		def:  `[{"type": "uint8[]"}]`,
+		enc:  "00000000000000000000000000000000000000000000000000000000000000200000000000000000000000000000000000000000000000000000000000000000",
+		want: []uint8{},
+	},
+	{
+		def:  `[{"type": "uint256[]"}]`,
+		enc:  "00000000000000000000000000000000000000000000000000000000000000200000000000000000000000000000000000000000000000000000000000000000",
+		want: []*big.Int{},
+	},
 	{
 		def:  `[{"type": "uint8[2]"}]`,
 		enc:  "00000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000000002",
 		want: [2]uint8{1, 2},
 	},
 	// multi dimensional, if these pass, all types that don't require length prefix should pass
+	{
+		def:  `[{"type": "uint8[][]"}]`,
+		enc:  "00000000000000000000000000000000000000000000000000000000000000200000000000000000000000000000000000000000000000000000000000000000",
+		want: [][]uint8{},
+	},
 	{
 		def:  `[{"type": "uint8[][]"}]`,
 		enc:  "00000000000000000000000000000000000000000000000000000000000000200000000000000000000000000000000000000000000000000000000000000002000000000000000000000000000000000000000000000000000000000000004000000000000000000000000000000000000000000000000000000000000000a0000000000000000000000000000000000000000000000000000000000000000200000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000000002000000000000000000000000000000000000000000000000000000000000000200000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000000002",
@@ -186,11 +206,21 @@ var unpackTests = []unpackTest{
 		enc:  "0000000000000000000000000000000000000000000000000000000000000001000000000000000000000000000000000000000000000000000000000000000200000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000000002",
 		want: [2][2]uint8{{1, 2}, {1, 2}},
 	},
+	{
+		def:  `[{"type": "uint8[][2]"}]`,
+		enc:  "00000000000000000000000000000000000000000000000000000000000000200000000000000000000000000000000000000000000000000000000000000040000000000000000000000000000000000000000000000000000000000000006000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000",
+		want: [2][]uint8{{}, {}},
+	},
 	{
 		def:  `[{"type": "uint8[][2]"}]`,
 		enc:  "0000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000004000000000000000000000000000000000000000000000000000000000000000800000000000000000000000000000000000000000000000000000000000000001000000000000000000000000000000000000000000000000000000000000000100000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000000001",
 		want: [2][]uint8{{1}, {1}},
 	},
+	{
+		def:  `[{"type": "uint8[2][]"}]`,
+		enc:  "00000000000000000000000000000000000000000000000000000000000000200000000000000000000000000000000000000000000000000000000000000000",
+		want: [][2]uint8{},
+	},
 	{
 		def:  `[{"type": "uint8[2][]"}]`,
 		enc:  "0000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000000100000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000000002",
@@ -420,7 +450,7 @@ func TestUnpack(t *testing.T) {
 			}
 			encb, err := hex.DecodeString(test.enc)
 			if err != nil {
-				t.Fatalf("invalid hex: %s" + test.enc)
+				t.Fatalf("invalid hex %s: %v", test.enc, err)
 			}
 			outptr := reflect.New(reflect.TypeOf(test.want))
 			err = abi.Unpack(outptr.Interface(), "method", encb)