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

[GHC]

#14128: Possible bug in Renamer when dealing with orphans
-------------------------------------+-------------------------------------
        Reporter:  Shayan-Najd       |                Owner:  bgamari
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.2.2
       Component:  Compiler (Type    |              Version:  8.2.1
  checker)                           |
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------
Changes (by bgamari):

 * owner:  (none) => bgamari
 * milestone:   => 8.2.2


Comment:

 Surprisingly, I'm having trouble even getting as far as Shayan reports.
 Instead I'm seeing renaming failures while building stage1, namely during
 `HsExpr.hs`:
 {{{
 ghc: panic! (the 'impossible' happened)
   (GHC version 8.2.0.20170704 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 SyntaxExpr
   which was lazily initialized by initIfaceTcRn,
   I tried to tie the knot, but I couldn't find SyntaxExpr
   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
 }}}

 I am able to reproduce this with both 8.0.2 and 8.2.1-rc3.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14128#comment:5>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler