[GHC] #14172: GHC hangs during type-checking

[GHC]

#14172: GHC hangs during type-checking
-------------------------------------+-------------------------------------
           Reporter:  lightandlight  |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.0.2
           Keywords:                 |  Operating System:  Linux
       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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 GHC 8.0.2 doesn't terminate when type checking this file:

 {{{#!hs
 import           Control.Lens
 import           Data.Functor.Compose

 traverseCompose :: (a -> f b) -> g a -> f (h _)
 traverseCompose = _Wrapping Compose . traverse
 }}}

 This is the smallest type signature I could find that still causes the
 problem. GHCi infers the type without issue, and when I annotate it with
 the correct type signature, the file is successfully compiled.

 Using base-4.9.1.0, lens-4.14.1, and transformers-0.5.2.0

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14172>
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