[GHC] #10028: GHC Panic (The Impossible Happened)

26 Jan 2015

      #10028: GHC Panic (The Impossible Happened)
-------------------------------------+-------------------------------------
              Reporter:              |             Owner:
  archaephyrryx                      |            Status:  new
                  Type:  bug         |         Milestone:
              Priority:  normal      |           Version:  7.4.1
             Component:  Compiler    |  Operating System:  Unknown/Multiple
              Keywords:              |   Type of failure:  Compile-time
  panic,impossible,irrefutable       |  crash
          Architecture:  x86_64      |        Blocked By:
  (amd64)                            |   Related Tickets:
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
-------------------------------------+-------------------------------------
 Error message:

 {{{
 ghc: panic! (the 'impossible' happened)
   (GHC version 7.4.1 for x86_64-unknown-linux):
         compiler/rename/RnPat.lhs:535:39-79: Irrefutable pattern failed
 for pattern gres@(gre : _)
 }}}

 Cause:

 Importing a Module containing a record-syntax defined datatype, hiding one
 of the record fields, causes the use of the language pragma
 RecordWildCards to make GHC encounter a fatal error. A minimal
 reproduction case is attached to this ticket.

--
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10028
GHC http://www.haskell.org/ghc/
The Glasgow Haskell Compiler