[GHC] #14382: The 'impossible' happened whilst installing gi-gtk via cabal

[GHC]

#14382: The 'impossible' happened whilst installing gi-gtk via cabal
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        Reporter:  maartenjacobs  |                Owner:  (none)
            Type:  bug            |               Status:  new
        Priority:  normal         |            Milestone:
       Component:  Compiler       |              Version:  8.2.1
      Resolution:                 |             Keywords:  gtk, pango
Operating System:  Linux          |         Architecture:  x86_64 (amd64)
 Type of failure:  None/Unknown   |            Test Case:
      Blocked By:                 |             Blocking:
 Related Tickets:                 |  Differential Rev(s):
       Wiki Page:                 |
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Comment (by simonpj):

 I have no idea how to reproduce this.
 {{{
 bash$ cabal unpack gi-pango-1.0.15
 bash$ cd gi-pango-1.0.15
 bash$ cabal install --with-
 ghc=/home/simonpj/5builds/ghc-8.2-branch/inplace/bin/ghc-stage2
 Resolving dependencies...
 cabal: Could not resolve dependencies:
 trying: gi-pango-1.0.15 (user goal)
 next goal: haskell-gi (dependency of gi-pango-1.0.15)
 rejecting: haskell-gi-0.20.3, haskell-gi-0.20.2, haskell-gi-0.20.1
 (conflict:
 requires pkg-config package gobject-introspection-1.0>=1.32, not found in
 the
 pkg-config database)
 rejecting: haskell-gi-0.20, haskell-gi-0.18, haskell-gi-0.17.4,
 haskell-gi-0.17.3, haskell-gi-0.17.2, haskell-gi-0.17.1, haskell-gi-0.17,
 haskell-gi-0.15, haskell-gi-0.14, haskell-gi-0.13, haskell-gi-0.12,
 haskell-gi-0.11, haskell-gi-0.10.2, haskell-gi-0.10.1, haskell-gi-0.10,
 haskell-gi-0.9, haskell-gi-0.8 (conflict: gi-pango => haskell-gi>=0.20.1
 &&
 <1)
 Dependency tree exhaustively searched.
 }}}
 Moreover there seem be no source files.

 Try building compiler with `-DDEBUG` and add `HasDebugCallStack` to
 `tcIfaceGlobal`.

 In the panic in `tcIfaceGlobal` get hold of the `if_loc` field of the
 `IfLclEnv` and add that to the error message.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14382#comment:4>
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