Haskell Foldable Wats

[Henning Thielemann]

On Thu, 25 Feb 2016, Augustsson, Lennart wrote:

> Yes, at this point I think the best we can do is to make sure we get good warnings.
> I'd suggest that we can attach a warning to a method in each instance.
> So when using length on a tuple we'd get a warning.
> I don't even want to upgrade ghc to get the FTP until such a warning is in place (we are still on 7.8).

Me too.

I have earlier written about the wish for such warnings.

A general solution would be close to explicit import of instances and is 
certainly far away. If we can agree on warnings on 'length' on tuples this 
would be simpler and might already help.