accounts/abi: Prevent recalculation of internal fields (#20895)

* accounts/abi: prevent recalculation of ID, Sig and String

* accounts/abi: fixed unpacking of no values

* accounts/abi: multiple fixes to arguments

* accounts/abi: refactored methodName and eventName

This commit moves the complicated logic of how we assign method names
and event names if they already exist into their own functions for
better readability.

* accounts/abi: prevent recalculation of internal

In this commit, I changed the way we calculate the string
representations, sig representations and the id's of methods. Before
that these fields would be recalculated everytime someone called .Sig()
.String() or .ID() on a method or an event.

Additionally this commit fixes issue #20856 as we assign names to inputs
with no name (input with name "" becomes "arg0")

* accounts/abi: added unnamed event params test

* accounts/abi: fixed rebasing errors in method sig

* accounts/abi: fixed rebasing errors in method sig

* accounts/abi: addressed comments

* accounts/abi: added FunctionType enumeration

* accounts/abi/bind: added test for unnamed arguments

* accounts/abi: improved readability in NewMethod, nitpicks

* accounts/abi: method/eventName -> overloadedMethodName

accounts/abi/abi.go

@@ -76,7 +76,7 @@ func (abi ABI) Pack(name string, args ...interface{}) ([]byte, error) {
 		return nil, err
 	}
 	// Pack up the method ID too if not a constructor and return
-	return append(method.ID(), arguments...), nil
+	return append(method.ID, arguments...), nil
 }
 
 // Unpack output in v according to the abi specification
@@ -139,59 +139,17 @@ func (abi *ABI) UnmarshalJSON(data []byte) error {
 	for _, field := range fields {
 		switch field.Type {
 		case "constructor":
-			abi.Constructor = Method{
-				Inputs: field.Inputs,
-
-				// Note for constructor the `StateMutability` can only
-				// be payable or nonpayable according to the output of
-				// compiler. So constant is always false.
-				StateMutability: field.StateMutability,
-
-				// Legacy fields, keep them for backward compatibility
-				Constant: field.Constant,
-				Payable:  field.Payable,
-			}
+			abi.Constructor = NewMethod("", "", Constructor, field.StateMutability, field.Constant, field.Payable, field.Inputs, nil)
 		case "function":
-			name := field.Name
-			_, ok := abi.Methods[name]
-			for idx := 0; ok; idx++ {
-				name = fmt.Sprintf("%s%d", field.Name, idx)
-				_, ok = abi.Methods[name]
-			}
-			abi.Methods[name] = Method{
-				Name:            name,
-				RawName:         field.Name,
-				StateMutability: field.StateMutability,
-				Inputs:          field.Inputs,
-				Outputs:         field.Outputs,
-
-				// Legacy fields, keep them for backward compatibility
-				Constant: field.Constant,
-				Payable:  field.Payable,
-			}
+			name := abi.overloadedMethodName(field.Name)
+			abi.Methods[name] = NewMethod(name, field.Name, Function, field.StateMutability, field.Constant, field.Payable, field.Inputs, field.Outputs)
 		case "fallback":
 			// New introduced function type in v0.6.0, check more detail
 			// here https://solidity.readthedocs.io/en/v0.6.0/contracts.html#fallback-function
 			if abi.HasFallback() {
 				return errors.New("only single fallback is allowed")
 			}
-			abi.Fallback = Method{
-				Name:    "",
-				RawName: "",
-
-				// The `StateMutability` can only be payable or nonpayable,
-				// so the constant is always false.
-				StateMutability: field.StateMutability,
-				IsFallback:      true,
-
-				// Fallback doesn't have any input or output
-				Inputs:  nil,
-				Outputs: nil,
-
-				// Legacy fields, keep them for backward compatibility
-				Constant: field.Constant,
-				Payable:  field.Payable,
-			}
+			abi.Fallback = NewMethod("", "", Fallback, field.StateMutability, field.Constant, field.Payable, nil, nil)
 		case "receive":
 			// New introduced function type in v0.6.0, check more detail
 			// here https://solidity.readthedocs.io/en/v0.6.0/contracts.html#fallback-function
@@ -201,39 +159,45 @@ func (abi *ABI) UnmarshalJSON(data []byte) error {
 			if field.StateMutability != "payable" {
 				return errors.New("the statemutability of receive can only be payable")
 			}
-			abi.Receive = Method{
-				Name:    "",
-				RawName: "",
-
-				// The `StateMutability` can only be payable, so constant
-				// is always true while payable is always false.
-				StateMutability: field.StateMutability,
-				IsReceive:       true,
-
-				// Receive doesn't have any input or output
-				Inputs:  nil,
-				Outputs: nil,
+			abi.Receive = NewMethod("", "", Receive, field.StateMutability, field.Constant, field.Payable, nil, nil)
+		case "event":
+			name := abi.overloadedEventName(field.Name)
+			abi.Events[name] = NewEvent(name, field.Name, field.Anonymous, field.Inputs)
+		default:
+			return fmt.Errorf("abi: could not recognize type %v of field %v", field.Type, field.Name)
+		}
+	}
+	return nil
+}
 
-				// Legacy fields, keep them for backward compatibility
-				Constant: field.Constant,
-				Payable:  field.Payable,
+// overloadedMethodName returns the next available name for a given function.
+// Needed since solidity allows for function overload.
+//
+// e.g. if the abi contains Methods send, send1
+// overloadedMethodName would return send2 for input send.
+func (abi *ABI) overloadedMethodName(rawName string) string {
+	name := rawName
+	_, ok := abi.Methods[name]
+	for idx := 0; ok; idx++ {
+		name = fmt.Sprintf("%s%d", rawName, idx)
+		_, ok = abi.Methods[name]
 	}
-		case "event":
-			name := field.Name
+	return name
+}
+
+// overloadedEventName returns the next available name for a given event.
+// Needed since solidity allows for event overload.
+//
+// e.g. if the abi contains events received, received1
+// overloadedEventName would return received2 for input received.
+func (abi *ABI) overloadedEventName(rawName string) string {
+	name := rawName
 	_, ok := abi.Events[name]
 	for idx := 0; ok; idx++ {
-				name = fmt.Sprintf("%s%d", field.Name, idx)
+		name = fmt.Sprintf("%s%d", rawName, idx)
 		_, ok = abi.Events[name]
 	}
-			abi.Events[name] = Event{
-				Name:      name,
-				RawName:   field.Name,
-				Anonymous: field.Anonymous,
-				Inputs:    field.Inputs,
-			}
-		}
-	}
-	return nil
+	return name
 }
 
 // MethodById looks up a method by the 4-byte id
@@ -243,7 +207,7 @@ func (abi *ABI) MethodById(sigdata []byte) (*Method, error) {
 		return nil, fmt.Errorf("data too short (%d bytes) for abi method lookup", len(sigdata))
 	}
 	for _, method := range abi.Methods {
-		if bytes.Equal(method.ID(), sigdata[:4]) {
+		if bytes.Equal(method.ID, sigdata[:4]) {
 			return &method, nil
 		}
 	}
@@ -254,7 +218,7 @@ func (abi *ABI) MethodById(sigdata []byte) (*Method, error) {
 // ABI and returns nil if none found.
 func (abi *ABI) EventByID(topic common.Hash) (*Event, error) {
 	for _, event := range abi.Events {
-		if bytes.Equal(event.ID().Bytes(), topic.Bytes()) {
+		if bytes.Equal(event.ID.Bytes(), topic.Bytes()) {
 			return &event, nil
 		}
 	}
@@ -263,10 +227,10 @@ func (abi *ABI) EventByID(topic common.Hash) (*Event, error) {
 
 // HasFallback returns an indicator whether a fallback function is included.
 func (abi *ABI) HasFallback() bool {
-	return abi.Fallback.IsFallback
+	return abi.Fallback.Type == Fallback
 }
 
 // HasReceive returns an indicator whether a receive function is included.
 func (abi *ABI) HasReceive() bool {
-	return abi.Receive.IsReceive
+	return abi.Receive.Type == Receive
 }

accounts/abi/abi_test.go

@@ -58,20 +58,14 @@ const jsondata2 = `
 
 func TestReader(t *testing.T) {
 	Uint256, _ := NewType("uint256", "", nil)
-	exp := ABI{
+	abi := ABI{
 		Methods: map[string]Method{
-			"balance": {
-				"balance", "balance", "view", false, false, false, false, nil, nil,
-			},
-			"send": {
-				"send", "send", "", false, false, false, false, []Argument{
-					{"amount", Uint256, false},
-				}, nil,
-			},
+			"balance": NewMethod("balance", "balance", Function, "view", false, false, nil, nil),
+			"send":    NewMethod("send", "send", Function, "", false, false, []Argument{{"amount", Uint256, false}}, nil),
 		},
 	}
 
-	abi, err := JSON(strings.NewReader(jsondata))
+	exp, err := JSON(strings.NewReader(jsondata))
 	if err != nil {
 		t.Error(err)
 	}
@@ -173,22 +167,22 @@ func TestTestSlice(t *testing.T) {
 
 func TestMethodSignature(t *testing.T) {
 	String, _ := NewType("string", "", nil)
-	m := Method{"foo", "foo", "", false, false, false, false, []Argument{{"bar", String, false}, {"baz", String, false}}, nil}
+	m := NewMethod("foo", "foo", Function, "", false, false, []Argument{{"bar", String, false}, {"baz", String, false}}, nil)
 	exp := "foo(string,string)"
-	if m.Sig() != exp {
-		t.Error("signature mismatch", exp, "!=", m.Sig())
+	if m.Sig != exp {
+		t.Error("signature mismatch", exp, "!=", m.Sig)
 	}
 
 	idexp := crypto.Keccak256([]byte(exp))[:4]
-	if !bytes.Equal(m.ID(), idexp) {
-		t.Errorf("expected ids to match %x != %x", m.ID(), idexp)
+	if !bytes.Equal(m.ID, idexp) {
+		t.Errorf("expected ids to match %x != %x", m.ID, idexp)
 	}
 
 	uintt, _ := NewType("uint256", "", nil)
-	m = Method{"foo", "foo", "", false, false, false, false, []Argument{{"bar", uintt, false}}, nil}
+	m = NewMethod("foo", "foo", Function, "", false, false, []Argument{{"bar", uintt, false}}, nil)
 	exp = "foo(uint256)"
-	if m.Sig() != exp {
-		t.Error("signature mismatch", exp, "!=", m.Sig())
+	if m.Sig != exp {
+		t.Error("signature mismatch", exp, "!=", m.Sig)
 	}
 
 	// Method with tuple arguments
@@ -204,10 +198,10 @@ func TestMethodSignature(t *testing.T) {
 			{Name: "y", Type: "int256"},
 		}},
 	})
-	m = Method{"foo", "foo", "", false, false, false, false, []Argument{{"s", s, false}, {"bar", String, false}}, nil}
+	m = NewMethod("foo", "foo", Function, "", false, false, []Argument{{"s", s, false}, {"bar", String, false}}, nil)
 	exp = "foo((int256,int256[],(int256,int256)[],(int256,int256)[2]),string)"
-	if m.Sig() != exp {
-		t.Error("signature mismatch", exp, "!=", m.Sig())
+	if m.Sig != exp {
+		t.Error("signature mismatch", exp, "!=", m.Sig)
 	}
 }
 
@@ -219,12 +213,12 @@ func TestOverloadedMethodSignature(t *testing.T) {
 	}
 	check := func(name string, expect string, method bool) {
 		if method {
-			if abi.Methods[name].Sig() != expect {
-				t.Fatalf("The signature of overloaded method mismatch, want %s, have %s", expect, abi.Methods[name].Sig())
+			if abi.Methods[name].Sig != expect {
+				t.Fatalf("The signature of overloaded method mismatch, want %s, have %s", expect, abi.Methods[name].Sig)
 			}
 		} else {
-			if abi.Events[name].Sig() != expect {
-				t.Fatalf("The signature of overloaded event mismatch, want %s, have %s", expect, abi.Events[name].Sig())
+			if abi.Events[name].Sig != expect {
+				t.Fatalf("The signature of overloaded event mismatch, want %s, have %s", expect, abi.Events[name].Sig)
 			}
 		}
 	}
@@ -921,13 +915,13 @@ func TestABI_MethodById(t *testing.T) {
 	}
 	for name, m := range abi.Methods {
 		a := fmt.Sprintf("%v", m)
-		m2, err := abi.MethodById(m.ID())
+		m2, err := abi.MethodById(m.ID)
 		if err != nil {
 			t.Fatalf("Failed to look up ABI method: %v", err)
 		}
 		b := fmt.Sprintf("%v", m2)
 		if a != b {
-			t.Errorf("Method %v (id %x) not 'findable' by id in ABI", name, m.ID())
+			t.Errorf("Method %v (id %x) not 'findable' by id in ABI", name, m.ID)
 		}
 	}
 	// Also test empty
@@ -995,8 +989,8 @@ func TestABI_EventById(t *testing.T) {
 			t.Errorf("We should find a event for topic %s, test #%d", topicID.Hex(), testnum)
 		}
 
-		if event.ID() != topicID {
-			t.Errorf("Event id %s does not match topic %s, test #%d", event.ID().Hex(), topicID.Hex(), testnum)
+		if event.ID != topicID {
+			t.Errorf("Event id %s does not match topic %s, test #%d", event.ID.Hex(), topicID.Hex(), testnum)
 		}
 
 		unknowntopicID := crypto.Keccak256Hash([]byte("unknownEvent"))
@@ -1051,3 +1045,28 @@ func TestDoubleDuplicateMethodNames(t *testing.T) {
 		t.Fatalf("Should not have found extra method")
 	}
 }
+
+// TestUnnamedEventParam checks that an event with unnamed parameters is
+// correctly handled
+// The test runs the abi of the following contract.
+// 	contract TestEvent {
+//		event send(uint256, uint256);
+//	}
+func TestUnnamedEventParam(t *testing.T) {
+	abiJSON := `[{ "anonymous": false, "inputs": [{	"indexed": false,"internalType": "uint256",	"name": "","type": "uint256"},{"indexed": false,"internalType": "uint256","name": "","type": "uint256"}],"name": "send","type": "event"}]`
+	contractAbi, err := JSON(strings.NewReader(abiJSON))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	event, ok := contractAbi.Events["send"]
+	if !ok {
+		t.Fatalf("Could not find event")
+	}
+	if event.Inputs[0].Name != "arg0" {
+		t.Fatalf("Could not find input")
+	}
+	if event.Inputs[1].Name != "arg1" {
+		t.Fatalf("Could not find input")
+	}
+}

accounts/abi/argument.go

@@ -92,9 +92,8 @@ 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
 		}
+		return nil // Nothing to unmarshal, return
 	}
 	// make sure the passed value is arguments pointer
 	if reflect.Ptr != reflect.ValueOf(v).Kind() {
@@ -104,6 +103,9 @@ func (arguments Arguments) Unpack(v interface{}, data []byte) error {
 	if err != nil {
 		return err
 	}
+	if len(marshalledValues) == 0 {
+		return fmt.Errorf("abi: Unpack(no-values unmarshalled %T)", v)
+	}
 	if arguments.isTuple() {
 		return arguments.unpackTuple(v, marshalledValues)
 	}
@@ -112,18 +114,24 @@ 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 {
+	// Make sure map is not nil
+	if v == nil {
+		return fmt.Errorf("abi: cannot unpack into a nil map")
+	}
 	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
 		}
+		return nil // Nothing to unmarshal, return
 	}
 	marshalledValues, err := arguments.UnpackValues(data)
 	if err != nil {
 		return err
 	}
-	return arguments.unpackIntoMap(v, marshalledValues)
+	for i, arg := range arguments.NonIndexed() {
+		v[arg.Name] = marshalledValues[i]
+	}
+	return nil
 }
 
 // unpack sets the unmarshalled value to go format.
@@ -195,19 +203,6 @@ func unpack(t *Type, dst interface{}, src interface{}) error {
 	return nil
 }
 
-// unpackIntoMap unpacks marshalledValues into the provided map[string]interface{}
-func (arguments Arguments) unpackIntoMap(v map[string]interface{}, marshalledValues []interface{}) error {
-	// Make sure map is not nil
-	if v == nil {
-		return fmt.Errorf("abi: cannot unpack into a nil map")
-	}
-
-	for i, arg := range arguments.NonIndexed() {
-		v[arg.Name] = marshalledValues[i]
-	}
-	return nil
-}
-
 // unpackAtomic unpacks ( hexdata -> go ) a single value
 func (arguments Arguments) unpackAtomic(v interface{}, marshalledValues interface{}) error {
 	if arguments.LengthNonIndexed() == 0 {
@@ -236,27 +231,25 @@ func (arguments Arguments) unpackTuple(v interface{}, marshalledValues []interfa
 		value          = reflect.ValueOf(v).Elem()
 		typ            = value.Type()
 		kind           = value.Kind()
+		nonIndexedArgs = arguments.NonIndexed()
 	)
-	if err := requireUnpackKind(value, typ, kind, arguments); err != nil {
+	if err := requireUnpackKind(value, len(nonIndexedArgs), arguments); err != nil {
 		return err
 	}
 
 	// If the interface is a struct, get of abi->struct_field mapping
 	var abi2struct map[string]string
 	if kind == reflect.Struct {
-		var (
-			argNames []string
-			err      error
-		)
-		for _, arg := range arguments.NonIndexed() {
-			argNames = append(argNames, arg.Name)
+		argNames := make([]string, len(nonIndexedArgs))
+		for i, arg := range nonIndexedArgs {
+			argNames[i] = arg.Name
 		}
-		abi2struct, err = mapArgNamesToStructFields(argNames, value)
-		if err != nil {
+		var err error
+		if abi2struct, err = mapArgNamesToStructFields(argNames, value); err != nil {
 			return err
 		}
 	}
-	for i, arg := range arguments.NonIndexed() {
+	for i, arg := range nonIndexedArgs {
 		switch kind {
 		case reflect.Struct:
 			field := value.FieldByName(abi2struct[arg.Name])

accounts/abi/bind/base.go

@@ -264,7 +264,7 @@ func (c *BoundContract) FilterLogs(opts *FilterOpts, name string, query ...[]int
 		opts = new(FilterOpts)
 	}
 	// Append the event selector to the query parameters and construct the topic set
-	query = append([][]interface{}{{c.abi.Events[name].ID()}}, query...)
+	query = append([][]interface{}{{c.abi.Events[name].ID}}, query...)
 
 	topics, err := makeTopics(query...)
 	if err != nil {
@@ -313,7 +313,7 @@ func (c *BoundContract) WatchLogs(opts *WatchOpts, name string, query ...[]inter
 		opts = new(WatchOpts)
 	}
 	// Append the event selector to the query parameters and construct the topic set
-	query = append([][]interface{}{{c.abi.Events[name].ID()}}, query...)
+	query = append([][]interface{}{{c.abi.Events[name].ID}}, query...)
 
 	topics, err := makeTopics(query...)
 	if err != nil {

accounts/abi/bind/bind.go

@@ -639,9 +639,9 @@ func formatMethod(method abi.Method, structs map[string]*tmplStruct) string {
 		state = state + " "
 	}
 	identity := fmt.Sprintf("function %v", method.RawName)
-	if method.IsFallback {
+	if method.Type == abi.Fallback {
 		identity = "fallback"
-	} else if method.IsReceive {
+	} else if method.Type == abi.Receive {
 		identity = "receive"
 	}
 	return fmt.Sprintf("%s(%v) %sreturns(%v)", identity, strings.Join(inputs, ", "), state, strings.Join(outputs, ", "))

accounts/abi/bind/bind_test.go

@@ -199,7 +199,8 @@ var bindTests = []struct {
 				{"type":"event","name":"indexed","inputs":[{"name":"addr","type":"address","indexed":true},{"name":"num","type":"int256","indexed":true}]},
 				{"type":"event","name":"mixed","inputs":[{"name":"addr","type":"address","indexed":true},{"name":"num","type":"int256"}]},
 				{"type":"event","name":"anonymous","anonymous":true,"inputs":[]},
-				{"type":"event","name":"dynamic","inputs":[{"name":"idxStr","type":"string","indexed":true},{"name":"idxDat","type":"bytes","indexed":true},{"name":"str","type":"string"},{"name":"dat","type":"bytes"}]}
+				{"type":"event","name":"dynamic","inputs":[{"name":"idxStr","type":"string","indexed":true},{"name":"idxDat","type":"bytes","indexed":true},{"name":"str","type":"string"},{"name":"dat","type":"bytes"}]},
+				{"type":"event","name":"unnamed","inputs":[{"name":"","type":"uint256","indexed": true},{"name":"","type":"uint256","indexed":true}]}
 			]
 		`},
 		`
@@ -249,6 +250,12 @@ var bindTests = []struct {
 			 fmt.Println(event.Addr)          // Make sure the reconstructed indexed fields are present
 
 			 fmt.Println(res, str, dat, hash, err)
+
+			 oit, err := e.FilterUnnamed(nil, []*big.Int{}, []*big.Int{})
+
+			 arg0  := oit.Event.Arg0    // Make sure unnamed arguments are handled correctly
+			 arg1  := oit.Event.Arg1    // Make sure unnamed arguments are handled correctly
+			 fmt.Println(arg0, arg1)
 		 }
 		 // Run a tiny reflection test to ensure disallowed methods don't appear
 		 if _, ok := reflect.TypeOf(&EventChecker{}).MethodByName("FilterAnonymous"); ok {

accounts/abi/event.go

@@ -42,36 +42,59 @@ type Event struct {
 	RawName   string
 	Anonymous bool
 	Inputs    Arguments
+	str       string
+	// Sig contains the string signature according to the ABI spec.
+	// e.g.	 event foo(uint32 a, int b) = "foo(uint32,int256)"
+	// Please note that "int" is substitute for its canonical representation "int256"
+	Sig string
+	// ID returns the canonical representation of the event's signature used by the
+	// abi definition to identify event names and types.
+	ID common.Hash
 }
 
-func (e Event) String() string {
-	inputs := make([]string, len(e.Inputs))
-	for i, input := range e.Inputs {
-		inputs[i] = fmt.Sprintf("%v %v", input.Type, input.Name)
+// NewEvent creates a new Event.
+// It sanitizes the input arguments to remove unnamed arguments.
+// It also precomputes the id, signature and string representation
+// of the event.
+func NewEvent(name, rawName string, anonymous bool, inputs Arguments) Event {
+	// sanitize inputs to remove inputs without names
+	// and precompute string and sig representation.
+	names := make([]string, len(inputs))
+	types := make([]string, len(inputs))
+	for i, input := range inputs {
+		if input.Name == "" {
+			inputs[i] = Argument{
+				Name:    fmt.Sprintf("arg%d", i),
+				Indexed: input.Indexed,
+				Type:    input.Type,
+			}
+		} else {
+			inputs[i] = input
+		}
+		// string representation
+		names[i] = fmt.Sprintf("%v %v", input.Type, inputs[i].Name)
 		if input.Indexed {
-			inputs[i] = fmt.Sprintf("%v indexed %v", input.Type, input.Name)
+			names[i] = fmt.Sprintf("%v indexed %v", input.Type, inputs[i].Name)
 		}
+		// sig representation
+		types[i] = input.Type.String()
 	}
-	return fmt.Sprintf("event %v(%v)", e.RawName, strings.Join(inputs, ", "))
-}
 
-// Sig returns the event string signature according to the ABI spec.
-//
-// Example
-//
-//     event foo(uint32 a, int b) = "foo(uint32,int256)"
-//
-// Please note that "int" is substitute for its canonical representation "int256"
-func (e Event) Sig() string {
-	types := make([]string, len(e.Inputs))
-	for i, input := range e.Inputs {
-		types[i] = input.Type.String()
+	str := fmt.Sprintf("event %v(%v)", rawName, strings.Join(names, ", "))
+	sig := fmt.Sprintf("%v(%v)", rawName, strings.Join(types, ","))
+	id := common.BytesToHash(crypto.Keccak256([]byte(sig)))
+
+	return Event{
+		Name:      name,
+		RawName:   rawName,
+		Anonymous: anonymous,
+		Inputs:    inputs,
+		str:       str,
+		Sig:       sig,
+		ID:        id,
 	}
-	return fmt.Sprintf("%v(%v)", e.RawName, strings.Join(types, ","))
 }
 
-// ID returns the canonical representation of the event's signature used by the
-// abi definition to identify event names and types.
-func (e Event) ID() common.Hash {
-	return common.BytesToHash(crypto.Keccak256([]byte(e.Sig())))
+func (e Event) String() string {
+	return e.str
 }

accounts/abi/event_test.go

@@ -104,8 +104,8 @@ func TestEventId(t *testing.T) {
 		}
 
 		for name, event := range abi.Events {
-			if event.ID() != test.expectations[name] {
-				t.Errorf("expected id to be %x, got %x", test.expectations[name], event.ID())
+			if event.ID != test.expectations[name] {
+				t.Errorf("expected id to be %x, got %x", test.expectations[name], event.ID)
 			}
 		}
 	}

accounts/abi/method.go

@@ -23,6 +23,24 @@ import (
 	"github.com/ethereum/go-ethereum/crypto"
 )
 
+// FunctionType represents different types of functions a contract might have.
+type FunctionType int
+
+const (
+	// Constructor represents the constructor of the contract.
+	// The constructor function is called while deploying a contract.
+	Constructor FunctionType = iota
+	// Fallback represents the fallback function.
+	// This function is executed if no other function matches the given function
+	// signature and no receive function is specified.
+	Fallback
+	// Receive represents the receive function.
+	// This function is executed on plain Ether transfers.
+	Receive
+	// Function represents a normal function.
+	Function
+)
+
 // Method represents a callable given a `Name` and whether the method is a constant.
 // If the method is `Const` no transaction needs to be created for this
 // particular Method call. It can easily be simulated using a local VM.
@@ -44,6 +62,10 @@ type Method struct {
 	Name    string
 	RawName string // RawName is the raw method name parsed from ABI
 
+	// Type indicates whether the method is a
+	// special fallback introduced in solidity v0.6.0
+	Type FunctionType
+
 	// StateMutability indicates the mutability state of method,
 	// the default value is nonpayable. It can be empty if the abi
 	// is generated by legacy compiler.
@@ -53,69 +75,84 @@ type Method struct {
 	Constant bool
 	Payable  bool
 
-	// The following two flags indicates whether the method is a
-	// special fallback introduced in solidity v0.6.0
-	IsFallback bool
-	IsReceive  bool
-
 	Inputs  Arguments
 	Outputs Arguments
+	str     string
+	// Sig returns the methods string signature according to the ABI spec.
+	// e.g.		function foo(uint32 a, int b) = "foo(uint32,int256)"
+	// Please note that "int" is substitute for its canonical representation "int256"
+	Sig string
+	// ID returns the canonical representation of the method's signature used by the
+	// abi definition to identify method names and types.
+	ID []byte
 }
 
-// Sig returns the methods string signature according to the ABI spec.
-//
-// Example
-//
-//     function foo(uint32 a, int b) = "foo(uint32,int256)"
-//
-// Please note that "int" is substitute for its canonical representation "int256"
-func (method Method) Sig() string {
-	// Short circuit if the method is special. Fallback
-	// and Receive don't have signature at all.
-	if method.IsFallback || method.IsReceive {
-		return ""
-	}
-	types := make([]string, len(method.Inputs))
-	for i, input := range method.Inputs {
+// NewMethod creates a new Method.
+// A method should always be created using NewMethod.
+// It also precomputes the sig representation and the string representation
+// of the method.
+func NewMethod(name string, rawName string, funType FunctionType, mutability string, isConst, isPayable bool, inputs Arguments, outputs Arguments) Method {
+	var (
+		types       = make([]string, len(inputs))
+		inputNames  = make([]string, len(inputs))
+		outputNames = make([]string, len(outputs))
+	)
+	for i, input := range inputs {
+		inputNames[i] = fmt.Sprintf("%v %v", input.Type, input.Name)
 		types[i] = input.Type.String()
 	}
-	return fmt.Sprintf("%v(%v)", method.RawName, strings.Join(types, ","))
-}
-
-func (method Method) String() string {
-	inputs := make([]string, len(method.Inputs))
-	for i, input := range method.Inputs {
-		inputs[i] = fmt.Sprintf("%v %v", input.Type, input.Name)
-	}
-	outputs := make([]string, len(method.Outputs))
-	for i, output := range method.Outputs {
-		outputs[i] = output.Type.String()
+	for i, output := range outputs {
+		outputNames[i] = output.Type.String()
 		if len(output.Name) > 0 {
-			outputs[i] += fmt.Sprintf(" %v", output.Name)
+			outputNames[i] += fmt.Sprintf(" %v", output.Name)
 		}
 	}
+	// calculate the signature and method id. Note only function
+	// has meaningful signature and id.
+	var (
+		sig string
+		id  []byte
+	)
+	if funType == Function {
+		sig = fmt.Sprintf("%v(%v)", rawName, strings.Join(types, ","))
+		id = crypto.Keccak256([]byte(sig))[:4]
+	}
 	// Extract meaningful state mutability of solidity method.
 	// If it's default value, never print it.
-	state := method.StateMutability
+	state := mutability
 	if state == "nonpayable" {
 		state = ""
 	}
 	if state != "" {
 		state = state + " "
 	}
-	identity := fmt.Sprintf("function %v", method.RawName)
-	if method.IsFallback {
+	identity := fmt.Sprintf("function %v", rawName)
+	if funType == Fallback {
 		identity = "fallback"
-	} else if method.IsReceive {
+	} else if funType == Receive {
 		identity = "receive"
+	} else if funType == Constructor {
+		identity = "constructor"
+	}
+	str := fmt.Sprintf("%v(%v) %sreturns(%v)", identity, strings.Join(inputNames, ", "), state, strings.Join(outputNames, ", "))
+
+	return Method{
+		Name:            name,
+		RawName:         rawName,
+		Type:            funType,
+		StateMutability: mutability,
+		Constant:        isConst,
+		Payable:         isPayable,
+		Inputs:          inputs,
+		Outputs:         outputs,
+		str:             str,
+		Sig:             sig,
+		ID:              id,
 	}
-	return fmt.Sprintf("%v(%v) %sreturns(%v)", identity, strings.Join(inputs, ", "), state, strings.Join(outputs, ", "))
 }
 
-// ID returns the canonical representation of the method's signature used by the
-// abi definition to identify method names and types.
-func (method Method) ID() []byte {
-	return crypto.Keccak256([]byte(method.Sig()))[:4]
+func (method Method) String() string {
+	return method.str
 }
 
 // IsConstant returns the indicator whether the method is read-only.

accounts/abi/method_test.go

@@ -137,7 +137,7 @@ func TestMethodSig(t *testing.T) {
 	}
 
 	for _, test := range cases {
-		got := abi.Methods[test.method].Sig()
+		got := abi.Methods[test.method].Sig
 		if got != test.expect {
 			t.Errorf("expected string to be %s, got %s", test.expect, got)
 		}

accounts/abi/pack_test.go

@@ -634,7 +634,7 @@ func TestMethodPack(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	sig := abi.Methods["slice"].ID()
+	sig := abi.Methods["slice"].ID
 	sig = append(sig, common.LeftPadBytes([]byte{1}, 32)...)
 	sig = append(sig, common.LeftPadBytes([]byte{2}, 32)...)
 
@@ -648,7 +648,7 @@ func TestMethodPack(t *testing.T) {
 	}
 
 	var addrA, addrB = common.Address{1}, common.Address{2}
-	sig = abi.Methods["sliceAddress"].ID()
+	sig = abi.Methods["sliceAddress"].ID
 	sig = append(sig, common.LeftPadBytes([]byte{32}, 32)...)
 	sig = append(sig, common.LeftPadBytes([]byte{2}, 32)...)
 	sig = append(sig, common.LeftPadBytes(addrA[:], 32)...)
@@ -663,7 +663,7 @@ func TestMethodPack(t *testing.T) {
 	}
 
 	var addrC, addrD = common.Address{3}, common.Address{4}
-	sig = abi.Methods["sliceMultiAddress"].ID()
+	sig = abi.Methods["sliceMultiAddress"].ID
 	sig = append(sig, common.LeftPadBytes([]byte{64}, 32)...)
 	sig = append(sig, common.LeftPadBytes([]byte{160}, 32)...)
 	sig = append(sig, common.LeftPadBytes([]byte{2}, 32)...)
@@ -681,7 +681,7 @@ func TestMethodPack(t *testing.T) {
 		t.Errorf("expected %x got %x", sig, packed)
 	}
 
-	sig = abi.Methods["slice256"].ID()
+	sig = abi.Methods["slice256"].ID
 	sig = append(sig, common.LeftPadBytes([]byte{1}, 32)...)
 	sig = append(sig, common.LeftPadBytes([]byte{2}, 32)...)
 
@@ -695,7 +695,7 @@ func TestMethodPack(t *testing.T) {
 	}
 
 	a := [2][2]*big.Int{{big.NewInt(1), big.NewInt(1)}, {big.NewInt(2), big.NewInt(0)}}
-	sig = abi.Methods["nestedArray"].ID()
+	sig = abi.Methods["nestedArray"].ID
 	sig = append(sig, common.LeftPadBytes([]byte{1}, 32)...)
 	sig = append(sig, common.LeftPadBytes([]byte{1}, 32)...)
 	sig = append(sig, common.LeftPadBytes([]byte{2}, 32)...)
@@ -712,7 +712,7 @@ func TestMethodPack(t *testing.T) {
 		t.Errorf("expected %x got %x", sig, packed)
 	}
 
-	sig = abi.Methods["nestedArray2"].ID()
+	sig = abi.Methods["nestedArray2"].ID
 	sig = append(sig, common.LeftPadBytes([]byte{0x20}, 32)...)
 	sig = append(sig, common.LeftPadBytes([]byte{0x40}, 32)...)
 	sig = append(sig, common.LeftPadBytes([]byte{0x80}, 32)...)
@@ -728,7 +728,7 @@ func TestMethodPack(t *testing.T) {
 		t.Errorf("expected %x got %x", sig, packed)
 	}
 
-	sig = abi.Methods["nestedSlice"].ID()
+	sig = abi.Methods["nestedSlice"].ID
 	sig = append(sig, common.LeftPadBytes([]byte{0x20}, 32)...)
 	sig = append(sig, common.LeftPadBytes([]byte{0x02}, 32)...)
 	sig = append(sig, common.LeftPadBytes([]byte{0x40}, 32)...)

accounts/abi/reflect.go

@@ -118,18 +118,16 @@ func requireAssignable(dst, src reflect.Value) error {
 }
 
 // requireUnpackKind verifies preconditions for unpacking `args` into `kind`
-func requireUnpackKind(v reflect.Value, t reflect.Type, k reflect.Kind,
-	args Arguments) error {
-
-	switch k {
+func requireUnpackKind(v reflect.Value, minLength int, args Arguments) error {
+	switch v.Kind() {
 	case reflect.Struct:
 	case reflect.Slice, reflect.Array:
-		if minLen := args.LengthNonIndexed(); v.Len() < minLen {
+		if v.Len() < minLength {
 			return fmt.Errorf("abi: insufficient number of elements in the list/array for unpack, want %d, got %d",
-				minLen, v.Len())
+				minLength, v.Len())
 		}
 	default:
-		return fmt.Errorf("abi: cannot unmarshal tuple into %v", t)
+		return fmt.Errorf("abi: cannot unmarshal tuple into %v", v.Type())
 	}
 	return nil
 }
@@ -156,9 +154,8 @@ func mapArgNamesToStructFields(argNames []string, value reflect.Value) (map[stri
 			continue
 		}
 		// skip fields that have no abi:"" tag.
-		var ok bool
-		var tagName string
-		if tagName, ok = typ.Field(i).Tag.Lookup("abi"); !ok {
+		tagName, ok := typ.Field(i).Tag.Lookup("abi")
+		if !ok {
 			continue
 		}
 		// check if tag is empty.

signer/fourbyte/abi.go

@@ -140,7 +140,7 @@ func parseCallData(calldata []byte, abidata string) (*decodedCallData, error) {
 		return nil, fmt.Errorf("signature %q matches, but arguments mismatch: %v", method.String(), err)
 	}
 	// Everything valid, assemble the call infos for the signer
-	decoded := decodedCallData{signature: method.Sig(), name: method.RawName}
+	decoded := decodedCallData{signature: method.Sig, name: method.RawName}
 	for i := 0; i < len(method.Inputs); i++ {
 		decoded.inputs = append(decoded.inputs, decodedArgument{
 			soltype: method.Inputs[i],
@@ -158,7 +158,7 @@ func parseCallData(calldata []byte, abidata string) (*decodedCallData, error) {
 	if !bytes.Equal(encoded, argdata) {
 		was := common.Bytes2Hex(encoded)
 		exp := common.Bytes2Hex(argdata)
-		return nil, fmt.Errorf("WARNING: Supplied data is stuffed with extra data. \nWant %s\nHave %s\nfor method %v", exp, was, method.Sig())
+		return nil, fmt.Errorf("WARNING: Supplied data is stuffed with extra data. \nWant %s\nHave %s\nfor method %v", exp, was, method.Sig)
 	}
 	return &decoded, nil
 }

signer/fourbyte/fourbyte_test.go

@@ -48,8 +48,8 @@ func TestEmbeddedDatabase(t *testing.T) {
 			t.Errorf("Failed to get method by id (%s): %v", id, err)
 			continue
 		}
-		if m.Sig() != selector {
-			t.Errorf("Selector mismatch: have %v, want %v", m.Sig(), selector)
+		if m.Sig != selector {
+			t.Errorf("Selector mismatch: have %v, want %v", m.Sig, selector)
 		}
 	}
 }