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

8 Jun 2017

      #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
      Resolution:                    |             Keywords:  hs-boot
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:                    |
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Comment (by RyanGlScott):

 Minimizing this bug is probably going to take off a couple years of my
 life...

 But in any case, I've managed to reduce this down to six (!) files with
 one external dependency (`haskell-gi-base`):

 {{{#!hs
 module GIGioInterfacesFile where

 import Data.GI.Base.ShortPrelude -- from haskell-gi-base
 import {-# SOURCE #-} qualified GIGioObjectsFileEnumerator as
 Gio.FileEnumerator
 import {-# SOURCE #-} qualified GIGioObjectsMountOperation as
 Gio.MountOperation

 class IsFile o
 }}}
 {{{#!hs
 module GIGioInterfacesFile where

 class IsFile o
 }}}
 {{{#!hs
 {-# LANGUAGE ConstraintKinds #-}
 {-# LANGUAGE DataKinds #-}
 {-# LANGUAGE TypeFamilies #-}
 module GIGioObjectsFileEnumerator where

 import GHC.Exts (Constraint)
 import {-# SOURCE #-} qualified GIGioInterfacesFile as Gio.File

 class IsFileEnumerator o

 class AttrInfo info where
   type family AttrSetTypeConstraint info :: * -> Constraint

 data FileEnumeratorContainerPropertyInfo
 instance AttrInfo FileEnumeratorContainerPropertyInfo where
     type AttrSetTypeConstraint FileEnumeratorContainerPropertyInfo =
 Gio.File.IsFile
 }}}
 {{{#!hs
 module GIGioObjectsFileEnumerator where

 class IsFileEnumerator o
 }}}
 {{{#!hs
 module GIGioObjectsMountOperation where

 class IsMountOperation o
 }}}
 {{{#!hs
 module GIGioObjectsMountOperation where

 class IsMountOperation o
 }}}
 {{{
 $ /opt/ghc/8.2.1/bin/ghci GIGioInterfacesFile.hs
 GHCi, version 8.2.0.20170522: http://www.haskell.org/ghc/  :? for help
 Loaded GHCi configuration from /home/rgscott/.ghci
 [1 of 6] Compiling GIGioInterfacesFile[boot] ( GIGioInterfacesFile.hs-
 boot, interpreted )
 [2 of 6] Compiling GIGioObjectsFileEnumerator[boot] (
 GIGioObjectsFileEnumerator.hs-boot, interpreted )
 [3 of 6] Compiling GIGioObjectsFileEnumerator (
 GIGioObjectsFileEnumerator.hs, interpreted )
 [4 of 6] Compiling GIGioObjectsMountOperation[boot] (
 GIGioObjectsMountOperation.hs-boot, interpreted )
 [5 of 6] Compiling GIGioInterfacesFile ( GIGioInterfacesFile.hs,
 interpreted )
 ghc: panic! (the 'impossible' happened)
   (GHC version 8.2.0.20170522 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:1133:58 in ghc:Outputable
         callStackDoc, called at compiler/utils/Outputable.hs:1137:37 in
 ghc:Outputable
         pprPanic, called at compiler/iface/TcIface.hs:1689:23 in
 ghc:TcIface
 }}}

 The annoying bit is that I haven't figure out how to eliminate that
 `import Data.GI.Base.ShortPrelude` from the `haskell-gi-base` library.

--
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13803#comment:4
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