[GHC] #12584: Bug (or Unhelpful Error) with TemplateHaskell

[GHC]

#12584: Bug (or Unhelpful Error) with TemplateHaskell
-------------------------------------+-------------------------------------
           Reporter:  Shayan-Najd    |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.1
           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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 To recreate this make a Haskell file say named 'T.hs', with the following
 code:

 {{{#!hs
 {-# LANGUAGE TemplateHaskell #-}
 (() -> ())
 }}}

 Then try to compile it:

 {{{
 $> ghc-stage2 T.hs
 [...]
 ghc-stage2: panic! (the 'impossible' happened)
   (GHC version 8.1.20160617 for x86_64-unknown-linux):
         tcMonoExpr _
 [...]
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12584>
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