Newtype wrappers

[Johan Tibell]

On Mon, Jan 14, 2013 at 3:40 PM, Evan Laforge <qdunkan at gmail.com> wrote:
> Wait, what's the runtime error?  Do you mean messing up Set's invariants?

Yes.

> If you as the library writer don't want to allow unsafe things, then
> don't export the constructor.  Then no one can break your invariants,
> even with newtype malarky.  If you as the the library user go and
> explicitly import the bare Set constructor from (theoretical)
> Data.Set.Unsafe, then you are in the position to break Set's internal
> invariants anyway, and have already accepted the great power / great
> responsibility tradeoff.

If it's explicit that this is what you're doing I'm fine with it. I
just don't want magic coercing depending on what's in scope.