[containers] Proposal: Change to the Data.Map Monoid

[Milan Straka]

> > -----Original message-----
> > From: Andreas Abel <abela at chalmers.se>
> > Sent: 20 May 2014, 20:49
> >
> > I think the Monoid instance for Data.Map should be *removed*.
> -----Original message-----
> From: Johan Tibell <johan.tibell at gmail.com>
> Sent: 20 May 2014, 21:56
>
> -1 to removing the instance. It breaks existing code for negligible
> benefit: you still have to add newtypes to pick the instance you want.

-1 from me as well.

Although I agree that current instance is suboptimal, I do not believe
the cost of removing it is justified. After all, the instance is not
completely wrong, just not the one people usually expect.

Cheers,
Milan