inferred contexts from `deriving`

Richard Eisenberg eir at
Mon Dec 8 03:41:47 UTC 2014

Hi devs,

I've just hit on (what I view to be) a design wart in what is allowed in an instance context inferred through the use of non-standalone `deriving`. I've posed a problem and potential solution in #8984 ( See Note [Exotic derived instance contexts] ( for some background info. I would love input on this issue, as it all boils down to a simple design choice. The implementation is dead easy no matter what.

Please post any further comments to the ticket, but I wanted to bleat here because it seems easy to ignore emails from #8984, whose title is about tweaking an error message.

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