Permitting trailing commas for record syntax ADT declarations

Simon Peyton Jones simonpj at
Mon Sep 22 19:07:16 UTC 2014

I’m all for it.  To progress it you need to

·        open a Trac ticket,

·        start a wiki page to describe the design specifically (e.g give all the changed syntax rules)

·        have a language extension TrailingCommas (or something) to enable the extension

·        perhaps suggest switching on the extension if the program parses with it, but fails without

·        develop a patch

Easy really!  I doubt it’s controversial.


From: ghc-devs [mailto:ghc-devs-bounces at] On Behalf Of Johan Tibell
Sent: 22 September 2014 14:28
To: Alexander Berntsen
Cc: ghc-devs at
Subject: Re: Permitting trailing commas for record syntax ADT declarations


I think this makes sense and we should allow trailing commas wherever the syntax allows it without adding ambiguity (e.g. tuple sections prevent trailing commas for tuple declarations.)

P.S. Last time we tried to discuss something like this (on libraries@ I believe) the whole discussion devolved into a "lets rewrite all of Haskell". Lets not do that here. Thanks!
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