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
(https://ghc.haskell.org/trac/ghc/ticket/8984#comment:6). See Note [Exotic
derived instance contexts]
(https://github.com/ghc/ghc/blob/master/compiler/typecheck/TcDeriv.hs#L1915)
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.
Thanks,
Richard
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