Merge pull request #911 from nspcc-dev/feature/convert

vm: implement CONVERT opcode

pkg/compiler/analysis.go

@@ -17,6 +17,7 @@ var (
 		"AppCall",
 		"FromAddress", "Equals",
 		"panic",
+		"ToBool", "ToByteArray", "ToInteger",
 	}
 )
 

pkg/compiler/codegen.go

@@ -123,7 +123,9 @@ func (c *codegen) emitLoadConst(t types.TypeAndValue) {
 
 func (c *codegen) convertBasicType(t types.TypeAndValue, typ *types.Basic) {
 	switch typ.Kind() {
-	case types.Int, types.UntypedInt, types.Uint:
+	case types.Int, types.UntypedInt, types.Uint,
+		types.Int16, types.Uint16,
+		types.Int32, types.Uint32, types.Int64, types.Uint64:
 		val, _ := constant.Int64Val(t.Value)
 		emit.Int(c.prog.BinWriter, val)
 	case types.String, types.UntypedString:
@@ -1053,6 +1055,15 @@ func (c *codegen) convertBuiltin(expr *ast.CallExpr) {
 		} else {
 			c.prog.Err = errors.New("panic should have string or nil argument")
 		}
+	case "ToInteger", "ToByteArray", "ToBool":
+		typ := vm.IntegerT
+		switch name {
+		case "ToByteArray":
+			typ = vm.ByteArrayT
+		case "ToBool":
+			typ = vm.BooleanT
+		}
+		emit.Instruction(c.prog.BinWriter, opcode.CONVERT, []byte{byte(typ)})
 	case "SHA256":
 		emit.Opcode(c.prog.BinWriter, opcode.SHA256)
 	case "SHA1":

pkg/compiler/convert_test.go

@@ -0,0 +1,62 @@
+package compiler_test
+
+import (
+	"fmt"
+	"math/big"
+	"testing"
+)
+
+type convertTestCase struct {
+	returnType string
+	argValue   string
+	result     interface{}
+}
+
+func getFunctionName(typ string) string {
+	switch typ {
+	case "bool":
+		return "Bool"
+	case "[]byte":
+		return "ByteArray"
+	case "int64":
+		return "Integer"
+	}
+	panic("invalid type")
+}
+
+func TestConvert(t *testing.T) {
+	srcTmpl := `package foo
+	import "github.com/nspcc-dev/neo-go/pkg/interop/convert"
+	func Main() %s {
+		arg := %s
+		return convert.To%s(arg)
+	}`
+
+	convertTestCases := []convertTestCase{
+		{"bool", "true", true},
+		{"bool", "false", false},
+		{"bool", "12", true},
+		{"bool", "0", false},
+		{"bool", "[]byte{0, 1, 0}", true},
+		{"bool", "[]byte{0}", false},
+		{"int64", "true", big.NewInt(1)},
+		{"int64", "false", big.NewInt(0)},
+		{"int64", "12", big.NewInt(12)},
+		{"int64", "0", big.NewInt(0)},
+		{"int64", "[]byte{0, 1, 0}", big.NewInt(256)},
+		{"int64", "[]byte{0}", big.NewInt(0)},
+		{"[]byte", "true", []byte{1}},
+		{"[]byte", "false", []byte{0}},
+		{"[]byte", "12", []byte{0x0C}},
+		{"[]byte", "0", []byte{}},
+		{"[]byte", "[]byte{0, 1, 0}", []byte{0, 1, 0}},
+	}
+
+	for _, tc := range convertTestCases {
+		name := getFunctionName(tc.returnType)
+		t.Run(tc.argValue+"->"+name, func(t *testing.T) {
+			src := fmt.Sprintf(srcTmpl, tc.returnType, tc.argValue, name)
+			eval(t, src, tc.result)
+		})
+	}
+}

pkg/compiler/return_test.go

@@ -5,6 +5,14 @@ import (
 	"testing"
 )
 
+func TestReturnInt64(t *testing.T) {
+	src := `package foo
+	func Main() int64 {
+		return 1
+	}`
+	eval(t, src, big.NewInt(1))
+}
+
 func TestMultipleReturn1(t *testing.T) {
 	src := `
 		package hello

pkg/compiler/struct_test.go

@@ -274,7 +274,7 @@ var structTestCases = []testCase{
 			vm.NewBigIntegerItem(big.NewInt(1)),
 			vm.NewBigIntegerItem(big.NewInt(2)),
 			vm.NewByteArrayItem([]byte("hello")),
-			vm.NewByteArrayItem([]byte{}),
+			vm.NewBoolItem(false),
 		},
 	},
 	{

pkg/consensus/payload.go

@@ -222,9 +222,7 @@ func (p *Payload) Verify(scriptHash util.Uint160) bool {
 		return false
 	}
 
-	res, err := v.Estack().Pop().TryBool()
+	return v.Estack().Pop().Bool()
-
-	return err == nil && res
 }
 
 // DecodeBinaryUnsigned reads payload from w excluding signature.

pkg/core/blockchain.go

@@ -1656,11 +1656,7 @@ func (bc *Blockchain) verifyHashAgainstScript(hash util.Uint160, witness *transa
 	}
 	resEl := vm.Estack().Pop()
 	if resEl != nil {
-		res, err := resEl.TryBool()
+		if !resEl.Bool() {
-		if err != nil {
-			return err
-		}
-		if !res {
 			return errors.Errorf("signature check failed")
 		}
 		if useKeys {

pkg/interop/convert/convert.go

@@ -0,0 +1,17 @@
+// Package convert provides functions for type conversion.
+package convert
+
+// ToInteger converts it's argument to an Integer.
+func ToInteger(v interface{}) int64 {
+	return 0
+}
+
+// ToByteArray converts it's argument to a ByteArray.
+func ToByteArray(v interface{}) []byte {
+	return nil
+}
+
+// ToBool converts it's argument to a Boolean.
+func ToBool(v interface{}) bool {
+	return false
+}

pkg/vm/context.go

@@ -101,7 +101,7 @@ func (c *Context) Next() (opcode.Opcode, []byte, error) {
 		}
 	case opcode.JMP, opcode.JMPIF, opcode.JMPIFNOT, opcode.JMPEQ, opcode.JMPNE,
 		opcode.JMPGT, opcode.JMPGE, opcode.JMPLT, opcode.JMPLE,
-		opcode.CALL, opcode.ISTYPE, opcode.NEWARRAYT:
+		opcode.CALL, opcode.ISTYPE, opcode.CONVERT, opcode.NEWARRAYT:
 		numtoread = 1
 	case opcode.JMPL, opcode.JMPIFL, opcode.JMPIFNOTL, opcode.JMPEQL, opcode.JMPNEL,
 		opcode.JMPGTL, opcode.JMPGEL, opcode.JMPLTL, opcode.JMPLEL,
@@ -176,6 +176,9 @@ func (c *Context) Dup() StackItem {
 	return c
 }
 
+// Bool implements StackItem interface.
+func (c *Context) Bool() bool { panic("can't convert Context to Bool") }
+
 // TryBytes implements StackItem interface.
 func (c *Context) TryBytes() ([]byte, error) {
 	return nil, errors.New("can't convert Context to ByteArray")
@@ -189,6 +192,11 @@ func (c *Context) TryInteger() (*big.Int, error) {
 // Type implements StackItem interface.
 func (c *Context) Type() StackItemType { panic("Context cannot appear on evaluation stack") }
 
+// Convert implements StackItem interface.
+func (c *Context) Convert(_ StackItemType) (StackItem, error) {
+	panic("Context cannot be converted to anything")
+}
+
 // Equals implements StackItem interface.
 func (c *Context) Equals(s StackItem) bool {
 	return c == s

pkg/vm/emit/emit.go

@@ -31,6 +31,7 @@ func Bool(w *io.BinWriter, ok bool) {
 		return
 	}
 	Opcode(w, opcode.PUSHF)
+	Instruction(w, opcode.CONVERT, []byte{0x20}) // 0x20 for Boolean type
 }
 
 func padRight(s int, buf []byte) []byte {

pkg/vm/opcode/opcode.go

@@ -73,8 +73,6 @@ const (
 	SYSCALL  Opcode = 0x68
 	TAILCALL Opcode = 0x69
 
-	ISNULL Opcode = 0x70
-
 	// Stack
 	DUPFROMALTSTACK Opcode = 0x6A
 	TOALTSTACK      Opcode = 0x6B
@@ -163,7 +161,9 @@ const (
 	CLEARITEMS   Opcode = 0xD3
 
 	// Types
+	ISNULL  Opcode = 0xD8
 	ISTYPE  Opcode = 0xD9
+	CONVERT Opcode = 0xDB
 
 	// Exceptions
 	THROW      Opcode = 0xF0

pkg/vm/opcode/opcode_string.go

@@ -64,7 +64,6 @@ func _() {
 	_ = x[APPCALL-103]
 	_ = x[SYSCALL-104]
 	_ = x[TAILCALL-105]
-	_ = x[ISNULL-112]
 	_ = x[DUPFROMALTSTACK-106]
 	_ = x[TOALTSTACK-107]
 	_ = x[FROMALTSTACK-108]
@@ -140,12 +139,14 @@ func _() {
 	_ = x[REVERSEITEMS-209]
 	_ = x[REMOVE-210]
 	_ = x[CLEARITEMS-211]
+	_ = x[ISNULL-216]
 	_ = x[ISTYPE-217]
+	_ = x[CONVERT-219]
 	_ = x[THROW-240]
 	_ = x[THROWIFNOT-241]
 }
 
-const _Opcode_name = "PUSHINT8PUSHINT16PUSHINT32PUSHINT64PUSHINT128PUSHINT256PUSHNULLPUSHDATA1PUSHDATA2PUSHDATA4PUSHM1PUSH0PUSH1PUSH2PUSH3PUSH4PUSH5PUSH6PUSH7PUSH8PUSH9PUSH10PUSH11PUSH12PUSH13PUSH14PUSH15PUSH16NOPJMPJMPLJMPIFJMPIFLJMPIFNOTJMPIFNOTLJMPEQJMPEQLJMPNEJMPNELJMPGTJMPGTLJMPGEJMPGELJMPLTJMPLTLJMPLEJMPLELCALLCALLLOLDPUSH1RETAPPCALLSYSCALLTAILCALLDUPFROMALTSTACKTOALTSTACKFROMALTSTACKXDROPISNULLXSWAPXTUCKDEPTHDROPDUPNIPOVERPICKROLLROTSWAPTUCKCATSUBSTRLEFTRIGHTINVERTANDORXOREQUALINCDECSIGNNEGATEABSNOTNZADDSUBMULDIVMODSHLSHRBOOLANDBOOLORNUMEQUALNUMNOTEQUALLTGTLTEGTEMINMAXWITHINSHA1SHA256HASH160HASH256CHECKSIGVERIFYCHECKMULTISIGPACKUNPACKNEWARRAY0NEWARRAYNEWARRAYTNEWSTRUCT0NEWSTRUCTNEWMAPSIZEHASKEYKEYSVALUESPICKITEMAPPENDSETITEMREVERSEITEMSREMOVECLEARITEMSISTYPETHROWTHROWIFNOT"
+const _Opcode_name = "PUSHINT8PUSHINT16PUSHINT32PUSHINT64PUSHINT128PUSHINT256PUSHNULLPUSHDATA1PUSHDATA2PUSHDATA4PUSHM1PUSH0PUSH1PUSH2PUSH3PUSH4PUSH5PUSH6PUSH7PUSH8PUSH9PUSH10PUSH11PUSH12PUSH13PUSH14PUSH15PUSH16NOPJMPJMPLJMPIFJMPIFLJMPIFNOTJMPIFNOTLJMPEQJMPEQLJMPNEJMPNELJMPGTJMPGTLJMPGEJMPGELJMPLTJMPLTLJMPLEJMPLELCALLCALLLOLDPUSH1RETAPPCALLSYSCALLTAILCALLDUPFROMALTSTACKTOALTSTACKFROMALTSTACKXDROPXSWAPXTUCKDEPTHDROPDUPNIPOVERPICKROLLROTSWAPTUCKCATSUBSTRLEFTRIGHTINVERTANDORXOREQUALINCDECSIGNNEGATEABSNOTNZADDSUBMULDIVMODSHLSHRBOOLANDBOOLORNUMEQUALNUMNOTEQUALLTGTLTEGTEMINMAXWITHINSHA1SHA256HASH160HASH256CHECKSIGVERIFYCHECKMULTISIGPACKUNPACKNEWARRAY0NEWARRAYNEWARRAYTNEWSTRUCT0NEWSTRUCTNEWMAPSIZEHASKEYKEYSVALUESPICKITEMAPPENDSETITEMREVERSEITEMSREMOVECLEARITEMSISNULLISTYPECONVERTTHROWTHROWIFNOT"
 
 var _Opcode_map = map[Opcode]string{
 	0:   _Opcode_name[0:8],
@@ -206,81 +207,82 @@ var _Opcode_map = map[Opcode]string{
 	107: _Opcode_name[349:359],
 	108: _Opcode_name[359:371],
 	109: _Opcode_name[371:376],
-	112: _Opcode_name[376:382],
+	114: _Opcode_name[376:381],
-	114: _Opcode_name[382:387],
+	115: _Opcode_name[381:386],
-	115: _Opcode_name[387:392],
+	116: _Opcode_name[386:391],
-	116: _Opcode_name[392:397],
+	117: _Opcode_name[391:395],
-	117: _Opcode_name[397:401],
+	118: _Opcode_name[395:398],
-	118: _Opcode_name[401:404],
+	119: _Opcode_name[398:401],
-	119: _Opcode_name[404:407],
+	120: _Opcode_name[401:405],
-	120: _Opcode_name[407:411],
+	121: _Opcode_name[405:409],
-	121: _Opcode_name[411:415],
+	122: _Opcode_name[409:413],
-	122: _Opcode_name[415:419],
+	123: _Opcode_name[413:416],
-	123: _Opcode_name[419:422],
+	124: _Opcode_name[416:420],
-	124: _Opcode_name[422:426],
+	125: _Opcode_name[420:424],
-	125: _Opcode_name[426:430],
+	126: _Opcode_name[424:427],
-	126: _Opcode_name[430:433],
+	127: _Opcode_name[427:433],
-	127: _Opcode_name[433:439],
+	128: _Opcode_name[433:437],
-	128: _Opcode_name[439:443],
+	129: _Opcode_name[437:442],
-	129: _Opcode_name[443:448],
+	131: _Opcode_name[442:448],
-	131: _Opcode_name[448:454],
+	132: _Opcode_name[448:451],
-	132: _Opcode_name[454:457],
+	133: _Opcode_name[451:453],
-	133: _Opcode_name[457:459],
+	134: _Opcode_name[453:456],
-	134: _Opcode_name[459:462],
+	135: _Opcode_name[456:461],
-	135: _Opcode_name[462:467],
+	139: _Opcode_name[461:464],
-	139: _Opcode_name[467:470],
+	140: _Opcode_name[464:467],
-	140: _Opcode_name[470:473],
+	141: _Opcode_name[467:471],
-	141: _Opcode_name[473:477],
+	143: _Opcode_name[471:477],
-	143: _Opcode_name[477:483],
+	144: _Opcode_name[477:480],
-	144: _Opcode_name[483:486],
+	145: _Opcode_name[480:483],
-	145: _Opcode_name[486:489],
+	146: _Opcode_name[483:485],
-	146: _Opcode_name[489:491],
+	147: _Opcode_name[485:488],
-	147: _Opcode_name[491:494],
+	148: _Opcode_name[488:491],
-	148: _Opcode_name[494:497],
+	149: _Opcode_name[491:494],
-	149: _Opcode_name[497:500],
+	150: _Opcode_name[494:497],
-	150: _Opcode_name[500:503],
+	151: _Opcode_name[497:500],
-	151: _Opcode_name[503:506],
+	152: _Opcode_name[500:503],
-	152: _Opcode_name[506:509],
+	153: _Opcode_name[503:506],
-	153: _Opcode_name[509:512],
+	154: _Opcode_name[506:513],
-	154: _Opcode_name[512:519],
+	155: _Opcode_name[513:519],
-	155: _Opcode_name[519:525],
+	156: _Opcode_name[519:527],
-	156: _Opcode_name[525:533],
+	158: _Opcode_name[527:538],
-	158: _Opcode_name[533:544],
+	159: _Opcode_name[538:540],
-	159: _Opcode_name[544:546],
+	160: _Opcode_name[540:542],
-	160: _Opcode_name[546:548],
+	161: _Opcode_name[542:545],
-	161: _Opcode_name[548:551],
+	162: _Opcode_name[545:548],
-	162: _Opcode_name[551:554],
+	163: _Opcode_name[548:551],
-	163: _Opcode_name[554:557],
+	164: _Opcode_name[551:554],
-	164: _Opcode_name[557:560],
+	165: _Opcode_name[554:560],
-	165: _Opcode_name[560:566],
+	167: _Opcode_name[560:564],
-	167: _Opcode_name[566:570],
+	168: _Opcode_name[564:570],
-	168: _Opcode_name[570:576],
+	169: _Opcode_name[570:577],
-	169: _Opcode_name[576:583],
+	170: _Opcode_name[577:584],
-	170: _Opcode_name[583:590],
+	172: _Opcode_name[584:592],
-	172: _Opcode_name[590:598],
+	173: _Opcode_name[592:598],
-	173: _Opcode_name[598:604],
+	174: _Opcode_name[598:611],
-	174: _Opcode_name[604:617],
+	192: _Opcode_name[611:615],
-	192: _Opcode_name[617:621],
+	193: _Opcode_name[615:621],
-	193: _Opcode_name[621:627],
+	194: _Opcode_name[621:630],
-	194: _Opcode_name[627:636],
+	195: _Opcode_name[630:638],
-	195: _Opcode_name[636:644],
+	196: _Opcode_name[638:647],
-	196: _Opcode_name[644:653],
+	197: _Opcode_name[647:657],
-	197: _Opcode_name[653:663],
+	198: _Opcode_name[657:666],
-	198: _Opcode_name[663:672],
+	200: _Opcode_name[666:672],
-	200: _Opcode_name[672:678],
+	202: _Opcode_name[672:676],
-	202: _Opcode_name[678:682],
+	203: _Opcode_name[676:682],
-	203: _Opcode_name[682:688],
+	204: _Opcode_name[682:686],
-	204: _Opcode_name[688:692],
+	205: _Opcode_name[686:692],
-	205: _Opcode_name[692:698],
+	206: _Opcode_name[692:700],
-	206: _Opcode_name[698:706],
+	207: _Opcode_name[700:706],
-	207: _Opcode_name[706:712],
+	208: _Opcode_name[706:713],
-	208: _Opcode_name[712:719],
+	209: _Opcode_name[713:725],
-	209: _Opcode_name[719:731],
+	210: _Opcode_name[725:731],
-	210: _Opcode_name[731:737],
+	211: _Opcode_name[731:741],
-	211: _Opcode_name[737:747],
+	216: _Opcode_name[741:747],
 	217: _Opcode_name[747:753],
-	240: _Opcode_name[753:758],
+	219: _Opcode_name[753:760],
-	241: _Opcode_name[758:768],
+	240: _Opcode_name[760:765],
+	241: _Opcode_name[765:775],
 }
 
 func (i Opcode) String() string {

pkg/vm/stack.go

@@ -80,38 +80,9 @@ func (e *Element) BigInt() *big.Int {
 	return val
 }
 
-// TryBool attempts to get the underlying value of the element as a boolean.
+// Bool converts an underlying value of the element to a boolean.
-// Returns error if can't convert value to boolean type.
-func (e *Element) TryBool() (bool, error) {
-	switch t := e.value.(type) {
-	case *BigIntegerItem:
-		return t.value.Int64() != 0, nil
-	case *BoolItem:
-		return t.value, nil
-	case *ArrayItem, *StructItem:
-		return true, nil
-	case *ByteArrayItem:
-		for _, b := range t.value {
-			if b != 0 {
-				return true, nil
-			}
-		}
-		return false, nil
-	case *InteropItem:
-		return t.value != nil, nil
-	default:
-		return false, fmt.Errorf("can't convert to bool: " + t.String())
-	}
-}
-
-// Bool attempts to get the underlying value of the element as a boolean.
-// Will panic if the assertion failed which will be caught by the VM.
 func (e *Element) Bool() bool {
-	val, err := e.TryBool()
+	return e.value.Bool()
-	if err != nil {
-		panic(err)
-	}
-	return val
 }
 
 // Bytes attempts to get the underlying value of the element as a byte array.

pkg/vm/stack_item.go

@@ -20,6 +20,8 @@ type StackItem interface {
 	Value() interface{}
 	// Dup duplicates current StackItem.
 	Dup() StackItem
+	// Bool converts StackItem to a boolean value.
+	Bool() bool
 	// TryBytes converts StackItem to a byte slice.
 	TryBytes() ([]byte, error)
 	// TryInteger converts StackItem to an integer.
@@ -30,8 +32,12 @@ type StackItem interface {
 	ToContractParameter(map[StackItem]bool) smartcontract.Parameter
 	// Type returns stack item type.
 	Type() StackItemType
+	// Convert converts StackItem to another type.
+	Convert(StackItemType) (StackItem, error)
 }
 
+var errInvalidConversion = errors.New("invalid conversion type")
+
 func makeStackItem(v interface{}) StackItem {
 	switch val := v.(type) {
 	case int:
@@ -106,6 +112,33 @@ func makeStackItem(v interface{}) StackItem {
 	}
 }
 
+// convertPrimitive converts primitive item to a specified type.
+func convertPrimitive(item StackItem, typ StackItemType) (StackItem, error) {
+	if item.Type() == typ {
+		return item, nil
+	}
+	switch typ {
+	case IntegerT:
+		bi, err := item.TryInteger()
+		if err != nil {
+			return nil, err
+		}
+		return NewBigIntegerItem(bi), nil
+	case ByteArrayT:
+		b, err := item.TryBytes()
+		if err != nil {
+			return nil, err
+		}
+		return NewByteArrayItem(b), nil
+	case BufferT:
+		panic("TODO") // #877
+	case BooleanT:
+		return NewBoolItem(item.Bool()), nil
+	default:
+		return nil, errInvalidConversion
+	}
+}
+
 // StructItem represents a struct on the stack.
 type StructItem struct {
 	value []StackItem
@@ -133,6 +166,9 @@ func (i *StructItem) Dup() StackItem {
 	return i
 }
 
+// Bool implements StackItem interface.
+func (i *StructItem) Bool() bool { return true }
+
 // TryBytes implements StackItem interface.
 func (i *StructItem) TryBytes() ([]byte, error) {
 	return nil, errors.New("can't convert Struct to ByteArray")
@@ -182,6 +218,20 @@ func (i *StructItem) ToContractParameter(seen map[StackItem]bool) smartcontract.
 // Type implements StackItem interface.
 func (i *StructItem) Type() StackItemType { return StructT }
 
+// Convert implements StackItem interface.
+func (i *StructItem) Convert(typ StackItemType) (StackItem, error) {
+	switch typ {
+	case StructT:
+		return i, nil
+	case ArrayT:
+		return NewArrayItem(i.value), nil
+	case BooleanT:
+		return NewBoolItem(i.Bool()), nil
+	default:
+		return nil, errInvalidConversion
+	}
+}
+
 // Clone returns a Struct with all Struct fields copied by value.
 // Array fields are still copied by reference.
 func (i *StructItem) Clone() *StructItem {
@@ -217,6 +267,9 @@ func (i NullItem) Dup() StackItem {
 	return i
 }
 
+// Bool implements StackItem interface.
+func (i NullItem) Bool() bool { return false }
+
 // TryBytes implements StackItem interface.
 func (i NullItem) TryBytes() ([]byte, error) {
 	return nil, errors.New("can't convert Null to ByteArray")
@@ -243,6 +296,14 @@ func (i NullItem) ToContractParameter(map[StackItem]bool) smartcontract.Paramete
 // Type implements StackItem interface.
 func (i NullItem) Type() StackItemType { return AnyT }
 
+// Convert implements StackItem interface.
+func (i NullItem) Convert(typ StackItemType) (StackItem, error) {
+	if typ == AnyT || !typ.IsValid() {
+		return nil, errInvalidConversion
+	}
+	return i, nil
+}
+
 // BigIntegerItem represents a big integer on the stack.
 type BigIntegerItem struct {
 	value *big.Int
@@ -260,6 +321,11 @@ func (i *BigIntegerItem) Bytes() []byte {
 	return emit.IntToBytes(i.value)
 }
 
+// Bool implements StackItem interface.
+func (i *BigIntegerItem) Bool() bool {
+	return i.value.Sign() != 0
+}
+
 // TryBytes implements StackItem interface.
 func (i *BigIntegerItem) TryBytes() ([]byte, error) {
 	return i.Bytes(), nil
@@ -311,6 +377,11 @@ func (i *BigIntegerItem) ToContractParameter(map[StackItem]bool) smartcontract.P
 // Type implements StackItem interface.
 func (i *BigIntegerItem) Type() StackItemType { return IntegerT }
 
+// Convert implements StackItem interface.
+func (i *BigIntegerItem) Convert(typ StackItemType) (StackItem, error) {
+	return convertPrimitive(i, typ)
+}
+
 // MarshalJSON implements the json.Marshaler interface.
 func (i *BigIntegerItem) MarshalJSON() ([]byte, error) {
 	return json.Marshal(i.value)
@@ -347,6 +418,9 @@ func (i *BoolItem) Dup() StackItem {
 	return &BoolItem{i.value}
 }
 
+// Bool implements StackItem interface.
+func (i *BoolItem) Bool() bool { return i.value }
+
 // Bytes converts BoolItem to bytes.
 func (i *BoolItem) Bytes() []byte {
 	if i.value {
@@ -394,6 +468,11 @@ func (i *BoolItem) ToContractParameter(map[StackItem]bool) smartcontract.Paramet
 // Type implements StackItem interface.
 func (i *BoolItem) Type() StackItemType { return BooleanT }
 
+// Convert implements StackItem interface.
+func (i *BoolItem) Convert(typ StackItemType) (StackItem, error) {
+	return convertPrimitive(i, typ)
+}
+
 // ByteArrayItem represents a byte array on the stack.
 type ByteArrayItem struct {
 	value []byte
@@ -420,6 +499,19 @@ func (i *ByteArrayItem) String() string {
 	return "ByteArray"
 }
 
+// Bool implements StackItem interface.
+func (i *ByteArrayItem) Bool() bool {
+	if len(i.value) > MaxBigIntegerSizeBits/8 {
+		return true
+	}
+	for _, b := range i.value {
+		if b != 0 {
+			return true
+		}
+	}
+	return false
+}
+
 // TryBytes implements StackItem interface.
 func (i *ByteArrayItem) TryBytes() ([]byte, error) {
 	return i.value, nil
@@ -459,6 +551,11 @@ func (i *ByteArrayItem) ToContractParameter(map[StackItem]bool) smartcontract.Pa
 // Type implements StackItem interface.
 func (i *ByteArrayItem) Type() StackItemType { return ByteArrayT }
 
+// Convert implements StackItem interface.
+func (i *ByteArrayItem) Convert(typ StackItemType) (StackItem, error) {
+	return convertPrimitive(i, typ)
+}
+
 // ArrayItem represents a new ArrayItem object.
 type ArrayItem struct {
 	value []StackItem
@@ -485,6 +582,9 @@ func (i *ArrayItem) String() string {
 	return "Array"
 }
 
+// Bool implements StackItem interface.
+func (i *ArrayItem) Bool() bool { return true }
+
 // TryBytes implements StackItem interface.
 func (i *ArrayItem) TryBytes() ([]byte, error) {
 	return nil, errors.New("can't convert Array to ByteArray")
@@ -526,6 +626,20 @@ func (i *ArrayItem) ToContractParameter(seen map[StackItem]bool) smartcontract.P
 // Type implements StackItem interface.
 func (i *ArrayItem) Type() StackItemType { return ArrayT }
 
+// Convert implements StackItem interface.
+func (i *ArrayItem) Convert(typ StackItemType) (StackItem, error) {
+	switch typ {
+	case ArrayT:
+		return i, nil
+	case StructT:
+		return NewStructItem(i.value), nil
+	case BooleanT:
+		return NewBoolItem(i.Bool()), nil
+	default:
+		return nil, errInvalidConversion
+	}
+}
+
 // MapElement is a key-value pair of StackItems.
 type MapElement struct {
 	Key   StackItem
@@ -553,6 +667,9 @@ func (i *MapItem) Value() interface{} {
 	return i.value
 }
 
+// Bool implements StackItem interface.
+func (i *MapItem) Bool() bool { return true }
+
 // TryBytes implements StackItem interface.
 func (i *MapItem) TryBytes() ([]byte, error) {
 	return nil, errors.New("can't convert Map to ByteArray")
@@ -614,6 +731,18 @@ func (i *MapItem) ToContractParameter(seen map[StackItem]bool) smartcontract.Par
 // Type implements StackItem interface.
 func (i *MapItem) Type() StackItemType { return MapT }
 
+// Convert implements StackItem interface.
+func (i *MapItem) Convert(typ StackItemType) (StackItem, error) {
+	switch typ {
+	case MapT:
+		return i, nil
+	case BooleanT:
+		return NewBoolItem(i.Bool()), nil
+	default:
+		return nil, errInvalidConversion
+	}
+}
+
 // Add adds key-value pair to the map.
 func (i *MapItem) Add(key, value StackItem) {
 	if !isValidMapKey(key) {
@@ -672,6 +801,9 @@ func (i *InteropItem) Dup() StackItem {
 	return i
 }
 
+// Bool implements StackItem interface.
+func (i *InteropItem) Bool() bool { return true }
+
 // TryBytes implements StackItem interface.
 func (i *InteropItem) TryBytes() ([]byte, error) {
 	return nil, errors.New("can't convert Interop to ByteArray")
@@ -704,6 +836,18 @@ func (i *InteropItem) ToContractParameter(map[StackItem]bool) smartcontract.Para
 // Type implements StackItem interface.
 func (i *InteropItem) Type() StackItemType { return InteropT }
 
+// Convert implements StackItem interface.
+func (i *InteropItem) Convert(typ StackItemType) (StackItem, error) {
+	switch typ {
+	case InteropT:
+		return i, nil
+	case BooleanT:
+		return NewBoolItem(i.Bool()), nil
+	default:
+		return nil, errInvalidConversion
+	}
+}
+
 // MarshalJSON implements the json.Marshaler interface.
 func (i *InteropItem) MarshalJSON() ([]byte, error) {
 	return json.Marshal(i.value)

pkg/vm/vm.go

@@ -569,6 +569,15 @@ func (v *VM) execute(ctx *Context, op opcode.Opcode, parameter []byte) (err erro
 		res := v.estack.Pop().Item()
 		v.estack.PushVal(res.Type() == StackItemType(parameter[0]))
 
+	case opcode.CONVERT:
+		typ := StackItemType(parameter[0])
+		item := v.estack.Pop().Item()
+		result, err := item.Convert(typ)
+		if err != nil {
+			panic(err)
+		}
+		v.estack.PushVal(result)
+
 	// Stack operations.
 	case opcode.TOALTSTACK:
 		v.astack.Push(v.estack.Pop())

pkg/vm/vm_test.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"encoding/binary"
 	"encoding/hex"
+	"fmt"
 	"math/big"
 	"math/rand"
 	"testing"
@@ -256,6 +257,128 @@ func TestISTYPE(t *testing.T) {
 	})
 }
 
+func testCONVERT(isErr bool, to StackItemType, item, res StackItem) func(t *testing.T) {
+	return func(t *testing.T) {
+		prog := []byte{byte(opcode.CONVERT), byte(to)}
+		v := load(prog)
+		v.estack.PushVal(item)
+		if isErr {
+			checkVMFailed(t, v)
+			return
+		}
+		runVM(t, v)
+		require.Equal(t, 1, v.estack.Len())
+		require.Equal(t, res, v.estack.Pop().value)
+	}
+}
+
+func TestCONVERT(t *testing.T) {
+	type convertTC struct {
+		item, res StackItem
+	}
+	arr := []StackItem{
+		NewBigIntegerItem(big.NewInt(7)),
+		NewByteArrayItem([]byte{4, 8, 15}),
+	}
+	m := NewMapItem()
+	m.Add(NewByteArrayItem([]byte{1}), NewByteArrayItem([]byte{2}))
+
+	getName := func(item StackItem, typ StackItemType) string { return fmt.Sprintf("%s->%s", item, typ) }
+
+	t.Run("->Bool", func(t *testing.T) {
+		testBool := func(a, b StackItem) func(t *testing.T) {
+			return testCONVERT(false, BooleanT, a, b)
+		}
+
+		trueCases := []StackItem{
+			NewBoolItem(true), NewBigIntegerItem(big.NewInt(11)), NewByteArrayItem([]byte{1, 2, 3}),
+			NewArrayItem(arr), NewArrayItem(nil),
+			NewStructItem(arr), NewStructItem(nil),
+			NewMapItem(), m, NewInteropItem(struct{}{}),
+		}
+		for i := range trueCases {
+			t.Run(getName(trueCases[i], BooleanT), testBool(trueCases[i], NewBoolItem(true)))
+		}
+
+		falseCases := []StackItem{
+			NewBigIntegerItem(big.NewInt(0)), NewByteArrayItem([]byte{0, 0}), NewBoolItem(false),
+		}
+		for i := range falseCases {
+			testBool(falseCases[i], NewBoolItem(false))
+		}
+	})
+
+	t.Run("compound/interop -> basic", func(t *testing.T) {
+		types := []StackItemType{IntegerT, ByteArrayT}
+		items := []StackItem{NewArrayItem(nil), NewStructItem(nil), NewMapItem(), NewInteropItem(struct{}{})}
+		for _, typ := range types {
+			for j := range items {
+				t.Run(getName(items[j], typ), testCONVERT(true, typ, items[j], nil))
+			}
+		}
+	})
+
+	t.Run("primitive -> Integer/ByteArray", func(t *testing.T) {
+		n := big.NewInt(42)
+		b := emit.IntToBytes(n)
+
+		itemInt := NewBigIntegerItem(n)
+		itemBytes := NewByteArrayItem(b)
+
+		trueCases := map[StackItemType][]convertTC{
+			IntegerT: {
+				{itemInt, itemInt},
+				{itemBytes, itemInt},
+				{NewBoolItem(true), NewBigIntegerItem(big.NewInt(1))},
+				{NewBoolItem(false), NewBigIntegerItem(big.NewInt(0))},
+			},
+			ByteArrayT: {
+				{itemInt, itemBytes},
+				{itemBytes, itemBytes},
+				{NewBoolItem(true), NewByteArrayItem([]byte{1})},
+				{NewBoolItem(false), NewByteArrayItem([]byte{0})},
+			},
+		}
+
+		for typ := range trueCases {
+			for _, tc := range trueCases[typ] {
+				t.Run(getName(tc.item, typ), testCONVERT(false, typ, tc.item, tc.res))
+			}
+		}
+	})
+
+	t.Run("Struct<->Array", func(t *testing.T) {
+		arrayItem := NewArrayItem(arr)
+		structItem := NewStructItem(arr)
+		t.Run("Array->Array", testCONVERT(false, ArrayT, arrayItem, arrayItem))
+		t.Run("Array->Struct", testCONVERT(false, StructT, arrayItem, structItem))
+		t.Run("Struct->Array", testCONVERT(false, ArrayT, structItem, arrayItem))
+		t.Run("Struct->Struct", testCONVERT(false, StructT, structItem, structItem))
+	})
+
+	t.Run("Map->Map", testCONVERT(false, MapT, m, m))
+
+	t.Run("Null->", func(t *testing.T) {
+		types := []StackItemType{
+			BooleanT, ByteArrayT, IntegerT, ArrayT, StructT, MapT, InteropT,
+		}
+		for i := range types {
+			t.Run(types[i].String(), testCONVERT(false, types[i], NullItem{}, NullItem{}))
+		}
+	})
+
+	t.Run("->Any", func(t *testing.T) {
+		items := []StackItem{
+			NewBigIntegerItem(big.NewInt(1)), NewByteArrayItem([]byte{1}), NewBoolItem(true),
+			NewArrayItem(arr), NewStructItem(arr), m, NewInteropItem(struct{}{}),
+		}
+
+		for i := range items {
+			t.Run(items[i].String(), testCONVERT(true, AnyT, items[i], nil))
+		}
+	})
+}
+
 // appendBigStruct returns a program which:
 // 1. pushes size Structs on stack
 // 2. packs them into a new struct