Re: [GHC] #11184: panic tcMonoExpr _ with bad indentation in TH code

25 Mar 2016

      #11184: panic tcMonoExpr _ with bad indentation in TH code
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        Reporter:  TeroLaitinen      |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.10.2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  Runtime crash     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by mgsloan):

 Perhaps this is worth another bug report, but here's another case:

 {{{
 {-# LANGUAGE TemplateHaskell #-}

 -- A realistic example, demonstrating how this can be baffling in real
 code.
 $(mapM (n -> [d| foo = n |]) [1])

 -- Minimal example
 $((x -> x))
 }}}

 causes

 {{{
 ghc: panic! (the 'impossible' happened)
   (GHC version 7.10.3 for x86_64-unknown-linux):
         tcMonoExpr _
 }}}

 Similarly, this is likely due to expressions and patterns sharing parsing.
 We just need to do the same checks that are applied to normal user code.

--
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11184#comment:5
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