Problems with comments.

[AnthonyJacob]

Some comments cause parse errors: -- *, -- |=, {- | -}.

If any of these are anywhere in my file, running stack hoogle will throw a parsing error!

[ndmitchell]

These are really bugs/restrictions of Haddock, and if you just do stack haddock (which generates the documentation for your package) you get the same issues. I strongly recommend fixing them, as if you don't, your package won't have documentation when you upload it to Stackage.