[GHC] #15436: Compile-time panic, Prelude.!!: negative index

[GHC]

#15436: Compile-time panic, Prelude.!!: negative index
-------------------------------------+-------------------------------------
        Reporter:  pbrisbin          |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Compiler          |              Version:  8.5
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash or panic                     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by osa1):

 The failing `!!` call is this (in PrelRules.hs):

 {{{
 get_con :: Type -> ConTagZ -> DataCon
 get_con ty tag = tyConDataCons (tyConAppTyCon ty) !! tag
 }}}

 Which is passed a negative tag in this call site probably (same file):

 {{{
 tx_con_dtt ty (LitAlt (LitNumber LitNumInt i _))
    = DataAlt (get_con ty (fromInteger i))
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15436#comment:2>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler