vm: make APPEND push no value on stack

pkg/vm/vm.go

@@ -633,10 +633,14 @@ func (v *VM) execute(ctx *Context, op Instruction) {
 		arrElem := v.estack.Pop()
 
 		switch t := arrElem.value.(type) {
-		case *ArrayItem, *StructItem:
+		case *ArrayItem:
 			arr := t.Value().([]StackItem)
 			arr = append(arr, itemElem.value)
-			v.estack.PushVal(arr)
+			t.value = arr
+		case *StructItem:
+			arr := t.Value().([]StackItem)
+			arr = append(arr, itemElem.value)
+			t.value = arr
 		case *ByteArrayItem:
 			newVal := append(t.value, itemElem.value.Value().([]byte)...)
 			v.estack.PushVal(newVal)

pkg/vm/vm_test.go

@@ -444,6 +444,41 @@ func TestNEWSTRUCTWrongType(t *testing.T) {
 	assert.Equal(t, true, vm.state.HasFlag(faultState))
 }
 
+func TestAPPENDArray(t *testing.T) {
+	prog := makeProgram(DUP, PUSH5, APPEND)
+	vm := load(prog)
+	vm.estack.Push(&Element{value: &ArrayItem{}})
+	vm.Run()
+	assert.Equal(t, false, vm.state.HasFlag(faultState))
+	assert.Equal(t, 1, vm.estack.Len())
+	assert.Equal(t, &ArrayItem{[]StackItem{makeStackItem(5)}}, vm.estack.Pop().value)
+}
+
+func TestAPPENDStruct(t *testing.T) {
+	prog := makeProgram(DUP, PUSH5, APPEND)
+	vm := load(prog)
+	vm.estack.Push(&Element{value: &StructItem{}})
+	vm.Run()
+	assert.Equal(t, false, vm.state.HasFlag(faultState))
+	assert.Equal(t, 1, vm.estack.Len())
+	assert.Equal(t, &StructItem{[]StackItem{makeStackItem(5)}}, vm.estack.Pop().value)
+}
+
+func TestAPPENDBadNoArguments(t *testing.T) {
+	prog := makeProgram(APPEND)
+	vm := load(prog)
+	vm.Run()
+	assert.Equal(t, true, vm.state.HasFlag(faultState))
+}
+
+func TestAPPENDBad1Argument(t *testing.T) {
+	prog := makeProgram(APPEND)
+	vm := load(prog)
+	vm.estack.PushVal(1)
+	vm.Run()
+	assert.Equal(t, true, vm.state.HasFlag(faultState))
+}
+
 func TestSIGNNoArgument(t *testing.T) {
 	prog := makeProgram(SIGN)
 	vm := load(prog)