[GHC] #9815: Runtime error with RecordWildCards and a non-record constructor

[GHC]

#9815: Runtime error with RecordWildCards and a non-record constructor
-------------------------------------+-------------------------------------
       Reporter:  akio               |                   Owner:
           Type:  feature request    |                  Status:  new
       Priority:  normal             |               Milestone:
      Component:  Compiler           |                 Version:  7.8.3
       Keywords:  RecordWildCards,   |        Operating System:
  warning                            |  Unknown/Multiple
   Architecture:  Unknown/Multiple   |         Type of failure:  GHC
     Difficulty:  Unknown            |  accepts invalid program
     Blocked By:                     |               Test Case:
Related Tickets:                     |                Blocking:
                                     |  Differential Revisions:
-------------------------------------+-------------------------------------
 The following program is accepted with no warning, and crashes at runtime
 with an error:

 {{{#!hs
 {-# LANGUAGE RecordWildCards #-}
 newtype N = N Int deriving (Show)

 main = print N{..}
 }}}

 {{{
 % runghc wildcards.hs
 wildcards.hs: wildcards.hs:4:14-18: Missing field in record construction
 }}}

 I find this behavior surprising. Would it be better to either disallow it
 or have `-fwarn-missing-fields` warn it?

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9815>
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