implemented nullable type notation

src/lib/runtime/runtime.c

@@ -653,6 +653,32 @@ static _Bool step(Runtime *runtime, Error *error)
 			return 1;
 		}
 
+		case OPCODE_NLB:
+		{
+			ASSERT(opc == 0);
+
+			if(runtime->frame->used == 0)
+			{
+				Error_Report(error, 1, "Frame doesn't have enough items on the stack to execute NLB");
+				return 0;
+			}
+
+			Object *top = Stack_Top(runtime->stack, 0);
+
+			if(!Runtime_Pop(runtime, error, 1))
+				return 0;
+			
+			ASSERT(top != NULL);
+
+			Object *nullable = Object_NewNullable(top, runtime->heap, error);
+			if(nullable == NULL)
+				return 0;
+
+			if(!Runtime_Push(runtime, error, nullable))
+				return 0;
+			return 1;
+		}
+
 		case OPCODE_ADD:
 		case OPCODE_SUB:
 		case OPCODE_MUL: