Can you give an example of Coffeescript interacting poorly with the existing js ecosystem. I've seen complaints about the need for a build step, but since it c

Can you give an example of Coffeescript interacting poorly with the existing js ecosystem. I've seen complaints about the need for a build step, but since it compiles down to vanilla javascript, it works everywhere JS does, and its not hard to mix the 2 on a project if necessary.