role signatures in libraries

Carter Schonwald carter.schonwald at
Wed Nov 27 19:14:29 UTC 2013

Roles were cooked up to address the fact that currently, its possible to
derive unsafeCoerce via  the use of Generalized Newtype Deriving. Roles
address that issue and close that type safety hole. Richard has a paper or
so on it, and theres some pretty extensive documentation/examples on the
ghc wiki/trac  (though perhaps a more extensive exposition for normal
haskellers is called for too?)

On Wed, Nov 27, 2013 at 1:18 PM, Henning Thielemann <
lemming at> wrote:

> On Wed, 27 Nov 2013, Richard Eisenberg wrote:
>  It seems that the syntax and semantics of role annotations has settled,
>> and so it's time to add role annotations to various libraries.
> This topic is completely new to me. Where can I read what it is about,
> what is its motivation?
> _______________________________________________
> Libraries mailing list
> Libraries at
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