Hi Simon,
On 13 February 2015 at 18:12, Simon Peyton Jones
I don’t think it would be difficult to recover the old behaviour, but it's not clear to me that it would be a Good Thing. A program that works today, and then does not work tomorrow because of some incidental change to the way type inference works, would not be a happy state of affairs.
In much the same way, programs that rely on the memory representation that GHC uses for objects can be written with the provided unsafe functions. In my view, if you make this danger clear, having those functions is much better than not having them. And it seems like the Haskell environment generally agree with this view. In any case, if I think of some reasonable but more permissive restriction, I'll write it up.
Meanwhile, if you would care to draft the bit of user-manual material that you wish had been there, I could review it and put it in.
I'll try to get some writing done regarding this and the FFI wiki page next week. Francesco