[GHC] #13803: Panic while forcing the thunk for TyThing IsFile (regression)

[GHC]

#13803: Panic while forcing the thunk for TyThing IsFile (regression)
-------------------------------------+-------------------------------------
           Reporter:  inaki          |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.2.1-rc2
           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:
-------------------------------------+-------------------------------------
 (Apologies in advance for the very non-minimal testcase. I have been
 unsuccessfully trying to reduce the testcase for a few hours now, but I am
 flying blind, and the bug seems to depend on the interaction of various
 modules. The panic is very reproducible for me, so I figured that better
 reporting even if I failed to obtain a simplified testcase. Maybe someone
 else has more luck isolating the issue.)

 When compiling `gi-gio-2.0.12` I consistently get the following GHC panic:
 {{{
 [259 of 293] Compiling GI.Gio.Interfaces.File ( GI/Gio/Interfaces/File.hs,
 dist/build/GI/Gio/Interfaces/File.o )
 ghc: panic! (the 'impossible' happened)
   (GHC version 8.2.0.20170507 for x86_64-unknown-linux):
         tcIfaceGlobal (local): not found
   You are in a maze of twisty little passages, all alike.
   While forcing the thunk for TyThing IsFile
   which was lazily initialized by initIfaceCheck typecheckLoop,
   I tried to tie the knot, but I couldn't find IsFile
   in the current type environment.
   If you are developing GHC, please read Note [Tying the knot]
   and Note [Type-checking inside the knot].
   Consider rebuilding GHC with profiling for a better stack trace.
   Contents of current type environment: []
   Call stack:
       CallStack (from HasCallStack):
         prettyCurrentCallStack, called at
 compiler/utils/Outputable.hs:1134:58 in ghc:Outputable
         callStackDoc, called at compiler/utils/Outputable.hs:1138:37 in
 ghc:Outputable
         pprPanic, called at compiler/iface/TcIface.hs:1689:23 in
 ghc:TcIface

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

 To compile this code you will need the `glib2-devel` package installed. To
 compile
 {{{
 $ cabal get gi-gio-2.0.12
 $ cd gi-gio-2.0.12
 $ cabal sandbox init
 $ cabal install --dependencies-only
 $ cabal build
 }}}

 I am running version `8.2.0.20170507`, from
 https://copr.fedorainfracloud.org/coprs/petersen/ghc-8.2.1/ .

 The same code compiles in versions `7.8.x`, `7.10.x` and `8.0.x`.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13803>
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