[GHC] #13211: NegativeLiterals -0.0 :: Double

[GHC]

#13211: NegativeLiterals -0.0 :: Double
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        Reporter:  rwbarton          |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.1
      Resolution:                    |             Keywords:  newcomer
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Changes (by Nolan):

 * Attachment "patchToLexer.x" added.

 I fixed this error. Now it works as expected. It passes tests but 3 of
 them report slight performance drop(I forgot their ids, now retesting...).
 Here's patch to ```compiler/parser/Lexer.x```

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13211>
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