[GHC] #9398: Data.List.cycle is not a good producer

[GHC]

#9398: Data.List.cycle is not a good producer
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              Reporter:  dfeuer      |            Owner:
                  Type:  bug         |           Status:  new
              Priority:  normal      |        Milestone:  7.8.4
             Component:              |          Version:  7.8.3
  libraries/base                     |         Keywords:
            Resolution:              |     Architecture:  Unknown/Multiple
      Operating System:              |       Difficulty:  Easy (less than 1
  Unknown/Multiple                   |  hour)
       Type of failure:  Runtime     |       Blocked By:
  performance bug                    |  Related Tickets:
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
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Comment (by nomeata):

 I think you meant
  {{{#!hs
  cycle [] = let cyc = augment cycle' cyc in cyc
    where
      cycle' c n = foldr c n []

  cycle [] = let cyc = augment (\c n -> n) cyc in cyc

  cycle [] = let cyc = cyc in cyc

  cycle [] = ⊥
  }}}
 so you turned a helpful error message into nontermination

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9398#comment:7>
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