reorder parameters in makeClassy

[lingnand]

Right now makeClassy generates class for parameterized data types like this

class HasContainer container param where
    ...

I think it's actually a better idea to reorder it such that

class HasContainer param container where

A few reasons:

1. a convention is that later parameters are more important (the last one being the main parameter)
2. then we can derive newtype like

data Container t = Container { _container :: Value t }
makeClassy ''Container

newtype NewContainer = NewContainer (Container t) deriving (HasContainer t)

[louispan]

I agree that the last type param it makes intuitive sense for the last type parameter to the 'container'. Is there a more mathematical/computer science/robust theory behind type parameter ordering?

[ekmett]

Getting newtype deriving would be kind of nice.

At this point the question is is the improvement worth breaking every single user of lens that makes use of makeClassy?

I don't think so at this time. Existing users would get all sorts of weird type errors.