Orphan Instances

[Ashley Yakeley]

Simon Peyton-Jones wrote:

 > Who is responsible for the time/ library?

I am.

> Now that orphan warnings are "proper warnings" as Duncan requested,

What is an orphan instance, and why do we care about them?

Since they weren't proper warnings before, I always assumed they were 
some weird GHC thing and not any kind of a concern with the code. But 
apparently not?

-- Ashley