ooo, thats illuminating.

thanks for cooking that up

On Mon, Oct 7, 2013 at 1:13 AM, John Lato <jwlato@gmail.com> wrote:

On Sun, Oct 6, 2013 at 10:14 PM, Ryan Newton <rrnewton@gmail.com> wrote:

On Sun, Oct 6, 2013 at 6:28 PM, Ganesh Sittampalam <ganesh@earth.li> wrote:

 - Referential transparency: e.g. no unsafePerformIO

 - Module boundary control: no abstraction violation like Template
Haskell and GeneralizedNewtypeDeriving
 - Semantic consistency: importing a safe module can't change existing
code, so no OverlappingInstances and the like

Is this change necessary to preserve the existing properties, or are you
hoping to add a new one?

I'm not currently aware of ways to break these invariants *just* with GHC.Generics.  Hmm, but I would like to know why it is marked trustworthy and not inferred-safe...

How about this demo repo? https://github.com/JohnLato/safe-bugtest

I'm really not a safe haskell expert, but I believe this is a demonstration of using GHC.Generics to violate a module's abstraction boundaries with SafeHaskell enabled.

If I'm incorrect, I would appreciate if somebody could explain my error.  If, however, I'm correct, then I think that Ryan's proposal of marking GHC.Generics Unsafe is the best way to remedy the problem.

A possible stumbling block may involve base and package-trust, but I'm not certain of the current status.

John L.

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