Datacon RULES test

Simon Peyton Jones simonpj at
Fri Feb 24 08:47:50 UTC 2017

NB: the actual ticket Trac #12689 is /not/ about rules /for/ data cons.  It's about rules that /match/ datacons.  It's only the latter I object to.  The test T12689 sort of snuck in there under false pretences :-).

Also I'm not permanently set against rules for datacons.  It's just that I think there are equally good ways to achieve the same thing, and it smells wrong to me: we should hesitate before making passive data into active stuff.  (And I think we have more urgent things to do.)  


|  -----Original Message-----
|  From: ghc-devs [mailto:ghc-devs-bounces at] On Behalf Of David
|  Feuer
|  Sent: 24 February 2017 00:30
|  To: Joachim Breitner <mail at>
|  Cc: ghc-devs at
|  Subject: Datacon RULES test
|  For good or ill, Simon doesn't want RULES for datacons. T12689 has to be
|  removed (leaving T12689a, which is still fine). But I don't know enough
|  about what you're doing with T12689broken to know how to make it express the
|  right idea after this change. Can you please advise?
|  Thanks,
|  David Feuer
|  Well-Typed LLP
|  _______________________________________________
|  ghc-devs mailing list
|  ghc-devs at
|  .org%2Fcgi-bin%2Fmailman%2Flistinfo%2Fghc-
|  devs&
|  0c%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636234930063764323&sdata=B9Z
|  ECrVpzUxDMH9EDVMMULa7VysoC6ZirvairVe0ILk%3D&reserved=0

More information about the ghc-devs mailing list