[GHC] #8448: panic with RecordWildCards: find_tycon ghc-prim:GHC.Types.[]

[GHC]

#8448: panic with RecordWildCards: find_tycon ghc-prim:GHC.Types.[]
-------------------------------------+-------------------------------------
       Reporter:  MikolajKonarski    |             Owner:
           Type:  bug                |            Status:  new
       Priority:  normal             |         Milestone:
      Component:  Compiler (Type     |           Version:  7.6.3
  checker)                           |  Operating System:  Linux
       Keywords:                     |   Type of failure:  Compile-time
   Architecture:  x86_64 (amd64)     |  crash
     Difficulty:  Unknown            |         Test Case:
     Blocked By:                     |          Blocking:
Related Tickets:                     |
-------------------------------------+-------------------------------------
 The following crashes in 7.4.2, 7.6.3, 7.7:

 {{{
 {-# LANGUAGE RecordWildCards #-}
 data R = R {r :: Int}
 f x = undefined [] {r = x}
 main = return ()
 }}}

 with the message:

 {{{
 ~/$ ghc --make tycon_panic.hs
 [1 of 1] Compiling Main             ( tycon_panic.hs, tycon_panic.o )
 ghc: panic! (the 'impossible' happened)
   (GHC version 7.4.2 for x86_64-unknown-linux):
         find_tycon
     ghc-prim:GHC.Types.[]{(w) d 6m}
     []
 }}}

 Instead it should signal a type error (as it does with no
 RecordWildCards).

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8448>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler