the editor in coding task sometimes acting weird

Hi all, so when I paste my code to task editor from playground and click on "check", it pops up a bummer warning (not always but sometimes).

I am 100% sure my code is the right answer to the question like, for example :

// this isn't working for editor

struct Dog :Pet { }

// if I put a space between ":" and "Pet", it then works

struct Dog : Pet { }

( for the examples sake, keep the body empty)

it is kinda frustrating that I need to tackle problems like this every time. since I'm new to treeHouse, I wonder if its just me having this kind of problem or is it a bug in the editor ?

any comment are appreciated