[GHC] #14128: Possible bug in Renamer when dealing with orphans

16 Aug 2017

      #14128: Possible bug in Renamer when dealing with orphans
-------------------------------------+-------------------------------------
           Reporter:  Shayan-Najd    |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.2.1
  (Type checker)                     |
           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:
-------------------------------------+-------------------------------------
 In a [https://github.com/shayan-najd/GrowableGHC branch] of GHC with
 [https://ghc.haskell.org/trac/ghc/wiki/ImplementingTreesThatGrow Growable
 ASTs], the code compiles with `devel2` configuration, but fails with
 `./validate`. It passes all the test cases, except two that already fail
 in HEAD (see [https://ghc.haskell.org/trac/ghc/ticket/14126 #14126]).

 Especifically, the compiler returns the following error:
 {{{
 ghc-stage1: panic! (the 'impossible' happened)
   (GHC version 8.3.20170806 for x86_64-unknown-linux):
         ASSERT failed!
   HsPat [GHC.Base, GHC.Float, Data.Binary.Generic,
          Data.ByteString.Builder, HsBinds, HsDoc, HsExpr, HsLit, HsPat,
          HsTypes, PprCore, GHC.LanguageExtensions,
          Data.Time.Calendar.Gregorian, Data.Time.Format.Parse,
          Data.Time.LocalTime.Internal.LocalTime,
          Data.Time.LocalTime.Internal.ZonedTime]
   Call stack:
       CallStack (from HasCallStack):
         prettyCurrentCallStack, called at
 compiler/utils/Outputable.hs:1133:58 in ghc:Outputable
         callStackDoc, called at compiler/utils/Outputable.hs:1188:22 in
 ghc:Outputable
         assertPprPanic, called at compiler/rename/RnNames.hs:364:99 in
 ghc:RnNames
   Call stack:
       CallStack (from HasCallStack):
         prettyCurrentCallStack, called at
 compiler/utils/Outputable.hs:1133:58 in ghc:Outputable
         callStackDoc, called at compiler/utils/Outputable.hs:1137:37 in
 ghc:Outputable
         pprPanic, called at compiler/utils/Outputable.hs:1186:5 in
 ghc:Outputable
         assertPprPanic, called at compiler/rename/RnNames.hs:364:99 in
 ghc:RnNames

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

 I suspect (as hinted above) it has to do with a bug in the renamer when
 dealing with orphan instances (and probably in conjunction with boot
 files).

-- 
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14128
GHC http://www.haskell.org/ghc/
The Glasgow Haskell Compiler