[GHC] #3394: Make Permissions type abstract

[GHC]

#3394: Make Permissions type abstract
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  Reporter:  igloo                |          Owner:                  
      Type:  task                 |         Status:  new             
  Priority:  normal               |      Milestone:  6.14.1          
 Component:  libraries/directory  |        Version:  6.10.4          
  Severity:  normal               |       Keywords:                  
Difficulty:  Unknown              |       Testcase:                  
        Os:  Unknown/Multiple     |   Architecture:  Unknown/Multiple
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 This task is to make a proposal to make the portable Permissions type
 abstract. We could then implement `copyPermissions` using `getPermissions`
 and `setPermissions`, for example, and functions in the unix and Win32
 packages would be able to do more with this type than the portable
 interface.

 Originally part of #2610.

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Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3394>
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