[GHC] #12783: RecordWildCards trigger "Impossible happened" in Lucius

30 Oct 2016

      #12783: RecordWildCards trigger "Impossible happened" in Lucius
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           Reporter:  Koterpillar    |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.0.1
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 The presence of `RecordWildCards` in the following code makes GHC crash
 with "impossible happened".

 {{{#!hs
 #!/usr/bin/env stack
 -- stack --resolver lts-7.5 runghc --package shakespeare
 {-# LANGUAGE QuasiQuotes #-}
 {-# LANGUAGE RecordWildCards #-}

 import Text.Lucius

 renderPrintStylesheet = [lucius|p{}|]

 main :: IO ()
 main = return ()
 }}}

 {{{
 ghc: panic! (the 'impossible' happened)
   (GHC version 8.0.1 for x86_64-unknown-linux):
         find_tycon
   Block
   []

 Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug
 }}}

 Removing `RecordWildCards` makes the program compile.

--
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12783
GHC http://www.haskell.org/ghc/
The Glasgow Haskell Compiler