We need to add role annotations for 7.8

Mikhail Glushenkov the.dead.shall.rise at gmail.com
Fri Mar 14 17:45:16 UTC 2014

Hi Richard,

On 14 March 2014 17:25, Richard Eisenberg <eir at cis.upenn.edu> wrote:
> This is an even thornier corner of a thorny design decision. As one can discover from various public sources, I have advocated for adding extra checks under -XSafe, essentially closing this hole, as described in the paper and in those tickets. However, due to trouble *inferring* safe mode with the extra checks, and the fact that there was no clear design goal to attend to, we decided to drop the checks, with Simon PJ consistently advocating against the checks. There's nothing insurmountable here, just more engineering overhead. Is it worth it?

I think that you were right. IIUC, omitting these checks essentially
makes the MinList example from the Safe Haskell paper legal (provided
that there are no role annotations), which was the reason for
prohibiting GND in Safe Haskell code.

I agree with Brandon that it'd be nice to have some kind of warning.

> The real trouble with making this decision is that we have no real guidance. We've tried contacting David Terei (the originator of Safe Haskell) several times to no avail. If you are an actual consumer of Safe Haskell and would like to share your opinion on this front, I do encourage you to make a ticket, essentially requesting a resurrection of the extra Safe checks.

Yes, it would be nice if David Terei or David Mazières (CC:ed) could comment.

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