[GHC] #16219: Backpack - TH+indefinite module interface file error

[GHC]

#16219: Backpack - TH+indefinite module interface file error
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           Reporter:  lightandlight  |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.7
           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:
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 Repro: https://github.com/LightAndLight/backpack-test

 I've been stuck on this for a while now. There's a weird interaction
 between the Template Haskell pragma and indefinite modules. When Template
 Haskell is enabled in this particular file (but TH features aren't used) I
 get an interface error. When I remove the pragma, the project successfully
 compiles.

 I hope I haven't made some trivial .cabal blunder.

 Anyway, I'm interested in potentially trying to fix this, but I've been
 digging around in GHC for a couple of days and figured it was time to ask
 for help.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16219>
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