[GHC] #1974: length "foo" doesn't work with -XOverloadedStrings

[GHC]

#1974: length "foo" doesn't work with -XOverloadedStrings
--------------------------------+-------------------------------------------
    Reporter:  ganesh           |       Owner:         
        Type:  feature request  |      Status:  new    
    Priority:  low              |   Milestone:         
   Component:  Compiler         |     Version:  6.8.1  
    Severity:  minor            |    Keywords:         
  Difficulty:  Unknown          |    Testcase:         
Architecture:  Unknown          |          Os:  Unknown
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 The extensions to the defaulting rule for -XOverloadedStrings aren't
 sufficient to make {{{length "foo"}}} typecheck without an annotation. The
 reason is that we end up with a constraint {{{IsString [a]}}}, and we
 would somehow have to decide to instantiate a to Char to get the hoped-for
 behaviour.

 It would be nice if this could be made to work (perhaps just with
 -XExtendedDefaultRules), if a solution can be found without too much
 hacking.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1974>
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