Back-porting pattern synonym type signature syntax for GHC 7.8.4 [Re: ANNOUNCE: GHC 7.8.4 Release Candidate 1]

[Simon Peyton Jones]

Harump.  

a) We do not generally make user-visible changes in a patch-level
   release, so we would not normally do this in 7.8.2, let alone 7.8.4

b) The 7.8.4 release candidate is out already

c) It would take a little care to back-port the syntax changes to 7.8
   without pattern signature (which we definitely don't want).  And
   there would be a knock on effect in Haddock perhaps?

d) BUT pattern synonyms are a brand new feature in 7.8
   and minimising differences between 7.8 and 7.10 would be good.

My instinct is that (a)-(c) overwhelm (d); i.e. let sleeping dogs lie.  But what do others think?

Simon

|  -----Original Message-----
|  From: ghc-devs [mailto:ghc-devs-bounces at haskell.org] On Behalf Of Dr.
|  ERDI Gergo
|  Sent: 26 November 2014 00:59
|  To: Austin Seipp
|  Cc: ghc-devs at haskell.org
|  Subject: Back-porting pattern synonym type signature syntax for GHC
|  7.8.4 [Re: ANNOUNCE: GHC 7.8.4 Release Candidate 1]
|  
|  Hi,
|  
|  Now that we know what the syntax of pattern synonym type signatures is
|  going to be for GHC 7.10, would it make sense / is it not too late to
|  backport that same syntax to 7.8.4?
|  
|  To recap, 7.8 doesn't support adding type signatures to pattern
|  synonyms, but GHCi's ":i" and Haddock both need to produce output
|  which has them.
|  There's a horrible hacked-together syntax in 7.8 which is very much
|  *not* the syntax that will be used in 7.10.
|  
|  Thanks,
|   	Gergo
|  
|  --
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