stackitem: change Bool() to TryBool(), prepare for its failures

pkg/core/blockchain.go

@@ -1487,7 +1487,11 @@ func (bc *Blockchain) verifyHashAgainstScript(hash util.Uint160, witness *transa
 	}
 	resEl := vm.Estack().Pop()
 	if resEl != nil {
-		if !resEl.Bool() {
+		res, err := resEl.Item().TryBool()
+		if err != nil {
+			return fmt.Errorf("%w: invalid return value", ErrVerificationFailed)
+		}
+		if !res {
 			return fmt.Errorf("%w: invalid signature", ErrVerificationFailed)
 		}
 		if vm.Estack().Len() != 0 {

pkg/core/interop_system_test.go

@@ -577,8 +577,12 @@ func compareContractStates(t *testing.T, expected *state.Contract, actual stacki
 	require.Equal(t, 4, len(act))
 	require.Equal(t, expected.Script, act[0].Value().([]byte))
 	require.Equal(t, expectedManifest, act[1].Value().([]byte))
-	require.Equal(t, expected.HasStorage(), act[2].Bool())
-	require.Equal(t, expected.IsPayable(), act[3].Bool())
+	hasstorage, err := act[2].TryBool()
+	require.NoError(t, err)
+	ispayable, err := act[3].TryBool()
+	require.NoError(t, err)
+	require.Equal(t, expected.HasStorage(), hasstorage)
+	require.Equal(t, expected.IsPayable(), ispayable)
 }
 
 func TestContractUpdate(t *testing.T) {

pkg/core/native/native_neo_candidate.go

@@ -42,7 +42,10 @@ func (c *candidate) fromStackItem(item stackitem.Item) *candidate {
 	if err != nil {
 		panic(err)
 	}
-	c.Registered = arr[0].Bool()
+	c.Registered, err = arr[0].TryBool()
+	if err != nil {
+		panic(err)
+	}
 	c.Votes = *vs
 	return c
 }

pkg/vm/context.go

@@ -191,8 +191,8 @@ func (c *Context) Dup() stackitem.Item {
 	return c
 }
 
-// Bool implements stackitem.Item interface.
-func (c *Context) Bool() bool { panic("can't convert Context to Bool") }
+// TryBool implements stackitem.Item interface.
+func (c *Context) TryBool() (bool, error) { panic("can't convert Context to Bool") }
 
 // TryBytes implements stackitem.Item interface.
 func (c *Context) TryBytes() ([]byte, error) {

pkg/vm/exception.go

@@ -54,8 +54,8 @@ func (c *exceptionHandlingContext) Dup() stackitem.Item {
 	return c
 }
 
-// Bool implements stackitem.Item interface.
-func (c *exceptionHandlingContext) Bool() bool {
+// TryBool implements stackitem.Item interface.
+func (c *exceptionHandlingContext) TryBool() (bool, error) {
 	panic("can't convert exceptionHandlingContext to Bool")
 }
 

pkg/vm/stack.go

@@ -80,9 +80,14 @@ func (e *Element) BigInt() *big.Int {
 	return val
 }
 
-// Bool converts an underlying value of the element to a boolean.
+// Bool converts an underlying value of the element to a boolean if it's
+// possible to do so, it will panic otherwise.
 func (e *Element) Bool() bool {
-	return e.value.Bool()
+	b, err := e.value.TryBool()
+	if err != nil {
+		panic(err)
+	}
+	return b
 }
 
 // Bytes attempts to get the underlying value of the element as a byte array.

pkg/vm/stackitem/item.go

@@ -31,8 +31,8 @@ type Item interface {
 	Value() interface{}
 	// Dup duplicates current Item.
 	Dup() Item
-	// Bool converts Item to a boolean value.
-	Bool() bool
+	// TryBool converts Item to a boolean value.
+	TryBool() (bool, error)
 	// TryBytes converts Item to a byte slice.
 	TryBytes() ([]byte, error)
 	// TryInteger converts Item to an integer.
@@ -155,7 +155,11 @@ func convertPrimitive(item Item, typ Type) (Item, error) {
 		}
 		return NewByteArray(b), nil
 	case BooleanT:
-		return NewBool(item.Bool()), nil
+		b, err := item.TryBool()
+		if err != nil {
+			return nil, err
+		}
+		return NewBool(b), nil
 	default:
 		return nil, errInvalidConversion
 	}
@@ -210,8 +214,8 @@ func (i *Struct) Dup() Item {
 	return i
 }
 
-// Bool implements Item interface.
-func (i *Struct) Bool() bool { return true }
+// TryBool implements Item interface.
+func (i *Struct) TryBool() (bool, error) { return true, nil }
 
 // TryBytes implements Item interface.
 func (i *Struct) TryBytes() ([]byte, error) {
@@ -255,7 +259,7 @@ func (i *Struct) Convert(typ Type) (Item, error) {
 		copy(arr, i.value)
 		return NewArray(arr), nil
 	case BooleanT:
-		return NewBool(i.Bool()), nil
+		return NewBool(true), nil
 	default:
 		return nil, errInvalidConversion
 	}
@@ -296,8 +300,8 @@ func (i Null) Dup() Item {
 	return i
 }
 
-// Bool implements Item interface.
-func (i Null) Bool() bool { return false }
+// TryBool implements Item interface.
+func (i Null) TryBool() (bool, error) { return false, nil }
 
 // TryBytes implements Item interface.
 func (i Null) TryBytes() ([]byte, error) {
@@ -346,9 +350,9 @@ func (i *BigInteger) Bytes() []byte {
 	return bigint.ToBytes(i.value)
 }
 
-// Bool implements Item interface.
-func (i *BigInteger) Bool() bool {
-	return i.value.Sign() != 0
+// TryBool implements Item interface.
+func (i *BigInteger) TryBool() (bool, error) {
+	return i.value.Sign() != 0, nil
 }
 
 // TryBytes implements Item interface.
@@ -431,8 +435,8 @@ func (i *Bool) Dup() Item {
 	return &Bool{i.value}
 }
 
-// Bool implements Item interface.
-func (i *Bool) Bool() bool { return i.value }
+// TryBool implements Item interface.
+func (i *Bool) TryBool() (bool, error) { return i.value, nil }
 
 // Bytes converts Bool to bytes.
 func (i *Bool) Bytes() []byte {
@@ -500,17 +504,17 @@ func (i *ByteArray) String() string {
 	return "ByteString"
 }
 
-// Bool implements Item interface.
-func (i *ByteArray) Bool() bool {
+// TryBool implements Item interface.
+func (i *ByteArray) TryBool() (bool, error) {
 	if len(i.value) > MaxBigIntegerSizeBits/8 {
-		return true
+		return true, nil
 	}
 	for _, b := range i.value {
 		if b != 0 {
-			return true
+			return true, nil
 		}
 	}
-	return false
+	return false, nil
 }
 
 // TryBytes implements Item interface.
@@ -601,8 +605,8 @@ func (i *Array) String() string {
 	return "Array"
 }
 
-// Bool implements Item interface.
-func (i *Array) Bool() bool { return true }
+// TryBool implements Item interface.
+func (i *Array) TryBool() (bool, error) { return true, nil }
 
 // TryBytes implements Item interface.
 func (i *Array) TryBytes() ([]byte, error) {
@@ -638,7 +642,7 @@ func (i *Array) Convert(typ Type) (Item, error) {
 		copy(arr, i.value)
 		return NewStruct(arr), nil
 	case BooleanT:
-		return NewBool(i.Bool()), nil
+		return NewBool(true), nil
 	default:
 		return nil, errInvalidConversion
 	}
@@ -691,8 +695,8 @@ func (i *Map) Len() int {
 	return len(i.value)
 }
 
-// Bool implements Item interface.
-func (i *Map) Bool() bool { return true }
+// TryBool implements Item interface.
+func (i *Map) TryBool() (bool, error) { return true, nil }
 
 // TryBytes implements Item interface.
 func (i *Map) TryBytes() ([]byte, error) {
@@ -743,7 +747,7 @@ func (i *Map) Convert(typ Type) (Item, error) {
 	case MapT:
 		return i, nil
 	case BooleanT:
-		return NewBool(i.Bool()), nil
+		return NewBool(true), nil
 	default:
 		return nil, errInvalidConversion
 	}
@@ -807,8 +811,8 @@ func (i *Interop) Dup() Item {
 	return i
 }
 
-// Bool implements Item interface.
-func (i *Interop) Bool() bool { return true }
+// TryBool implements Item interface.
+func (i *Interop) TryBool() (bool, error) { return true, nil }
 
 // TryBytes implements Item interface.
 func (i *Interop) TryBytes() ([]byte, error) {
@@ -840,7 +844,7 @@ func (i *Interop) Convert(typ Type) (Item, error) {
 	case InteropT:
 		return i, nil
 	case BooleanT:
-		return NewBool(i.Bool()), nil
+		return NewBool(true), nil
 	default:
 		return nil, errInvalidConversion
 	}
@@ -886,9 +890,9 @@ func (p *Pointer) Dup() Item {
 	}
 }
 
-// Bool implements Item interface.
-func (p *Pointer) Bool() bool {
-	return true
+// TryBool implements Item interface.
+func (p *Pointer) TryBool() (bool, error) {
+	return true, nil
 }
 
 // TryBytes implements Item interface.
@@ -921,7 +925,7 @@ func (p *Pointer) Convert(typ Type) (Item, error) {
 	case PointerT:
 		return p, nil
 	case BooleanT:
-		return NewBool(p.Bool()), nil
+		return NewBool(true), nil
 	default:
 		return nil, errInvalidConversion
 	}
@@ -959,9 +963,9 @@ func (i *Buffer) String() string {
 	return "Buffer"
 }
 
-// Bool implements Item interface.
-func (i *Buffer) Bool() bool {
-	return true
+// TryBool implements Item interface.
+func (i *Buffer) TryBool() (bool, error) {
+	return true, nil
 }
 
 // TryBytes implements Item interface.
@@ -998,7 +1002,7 @@ func (i *Buffer) Type() Type { return BufferT }
 func (i *Buffer) Convert(typ Type) (Item, error) {
 	switch typ {
 	case BooleanT:
-		return NewBool(i.Bool()), nil
+		return NewBool(true), nil
 	case BufferT:
 		return i, nil
 	case ByteArrayT: