[GHC] #14163: Stack Overflow with ApplicativeDo

[GHC]

#14163: Stack Overflow with ApplicativeDo
-------------------------------------+-------------------------------------
           Reporter:  lippling       |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.2.1
           Keywords:                 |  Operating System:  MacOS X
       Architecture:  x86_64         |   Type of failure:  Compile-time
  (amd64)                            |  crash or panic
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 I tried to compile one of our server applications with 8.2.1 (which
 compiles fine with 8.0.2).

 The compilation runs smooth, but when it reaches a specific file, the RAM
 usage goes up to > 20GB pretty fast on my 16GB machine and the GHC process
 gets terminated with a stack overflow error.

 I tried to find a minimal example that causes this behavior:

 {{{
 #!/usr/bin/env stack
 -- stack --resolver nightly-2017-08-25 script

 {-# LANGUAGE ApplicativeDo #-}

 x = do
     (a, _) <- undefined
     (b, _) <- undefined
     (c, _) <- undefined
     undefined

 main = undefined
 }}}

 It only happens with at least 3 of these pattern matches.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14163>
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