default roles

[Richard Eisenberg]

Please see below.

On Oct 10, 2013, at 10:09 PM, Edward Kmett wrote:

> Wait, that sounds like it induces bad semantics. 
> 
> Can't we use that as yet another way to attack the sanctity of Set?
> 
> class Ord a => Foo a where
>   badInsert :: a -> Set a -> Set a
> 
> instance Foo Int where
>   badInsert = insert
> 
> newtype Bar = Bar Int deriving (Eq,Foo)
> 
> instance Ord Bar where
>   compare (Bar x) (Bar y) = compare y x
> 
> Now you can badInsert into a Set.
> 
> If that is still in play then even with all the roles machinery then GND doesn't pass the restrictions of "SafeHaskell". =(

Hrm. Yes.

I'm out of fresh ideas at the moment.

Maybe some will arrive with sleep.

Richard