Proposal to extend FieldPat in Template Haskell

Simon Peyton-Jones simonpj at
Wed Jan 30 09:43:28 CET 2013

Fine with me!  We need people to update TH.

We plan to release 7.8 in mid Feb, and then have a TH upheaval shortly thereafter (I hope). So let’s put this in afterwards.


From: glasgow-haskell-users-bounces at [mailto:glasgow-haskell-users-bounces at] On Behalf Of Iavor Diatchki
Sent: 29 January 2013 21:25
To: GHC Users Mailing List; Eric Mertens
Subject: Proposal to extend FieldPat in Template Haskell

(sorry for the repost, I forgot to add a subject.)

I was just doing some work with Template Haskell and I noticed that the AST does not have support for record puns and wild-cards.  I know that these could be desugared into ordinary record patterns but I think that it would be more convenient for users (and also more consistent with the rest of the AST) if we provided direct support for them.

So I propose to change:

type FieldPat = (Name, Pat)


data FieldPat = RecordFileldP Name Pat  -- x = P
              | RecordPunP Name         -- x
              | RecordWildP             -- ..

Would there be any objections to doing so?  If not, I'd be happy to have a go at making the change.


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