<p dir="ltr">"While were in there", it occurred to me that one `coerce` per constructor argument ideally ought to suffice.</p>
<br><div class="gmail_quote"><div dir="ltr">On Mon, Aug 15, 2016, 07:17 GHC <<a href="mailto:ghc-devs@haskell.org">ghc-devs@haskell.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">#8516: Add (->) representation and the Invariant class to GHC.Generics<br>
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        Reporter:  nfrisby           |                Owner:<br>
            Type:  feature request   |               Status:  new<br>
        Priority:  low               |            Milestone:<br>
       Component:  Compiler (Type    |              Version:  7.7<br>
  checker)                           |<br>
      Resolution:                    |             Keywords:  Generics<br>
Operating System:  Unknown/Multiple  |         Architecture:<br>
                                     |  Unknown/Multiple<br>
 Type of failure:  None/Unknown      |            Test Case:<br>
      Blocked By:                    |             Blocking:<br>
 Related Tickets:                    |  Differential Rev(s):<br>
       Wiki Page:                    |<br>
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Comment (by RyanGlScott):<br>
<br>
 And as it turns out, goldfire has a separate ticket (#8177) for the<br>
 proposed idea of being able to give explicit role signatures to type<br>
 families, which might make the potential regression in<br>
 [<a href="https://ghc.haskell.org/trac/ghc/ticket/8516#comment:7" rel="noreferrer" target="_blank">https://ghc.haskell.org/trac/ghc/ticket/8516#comment:7</a> this comment] not<br>
 an actual regression. See my comment<br>
 [<a href="https://ghc.haskell.org/trac/ghc/ticket/8177#comment:31" rel="noreferrer" target="_blank">https://ghc.haskell.org/trac/ghc/ticket/8177#comment:31</a> here].<br>
<br>
--<br>
Ticket URL: <<a href="http://ghc.haskell.org/trac/ghc/ticket/8516#comment:11" rel="noreferrer" target="_blank">http://ghc.haskell.org/trac/ghc/ticket/8516#comment:11</a>><br>
GHC <<a href="http://www.haskell.org/ghc/" rel="noreferrer" target="_blank">http://www.haskell.org/ghc/</a>><br>
The Glasgow Haskell Compiler<br>
</blockquote></div>