[GHC] #694: lawbreaker in HughesPJ

[GHC]

#694: lawbreaker in HughesPJ
-------------------------------------+---------------------------------
        Reporter:  maeder@…          |         Owner:
            Type:  bug               |        Status:  closed
        Priority:  normal            |     Milestone:  6.4.2
       Component:  libraries/base    |       Version:  6.4.1
      Resolution:  fixed             |      Keywords:
Operating System:  Unknown/Multiple  |  Architecture:  Unknown/Multiple
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Comment (by Thomas Miedema <thomasmiedema@…>):

 In [changeset:"5d57087e314bd484dbe14958f9b422be3ac6641a/ghc" 5d57087/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="5d57087e314bd484dbe14958f9b422be3ac6641a"
 Pretty: fix a broken invariant (#10735)

 This is a backport of a bug fix from
 6cfbd0444981c074bae10a3cf72733bcb8597bef in libraries/pretty:

     Fix a broken invariant
     Patch from #694,  for the problem "empty is an identity for <> and $$"
 is
     currently broken by eg. isEmpty (empty<>empty)"
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/694#comment:5>
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