[GHC] #8524: GHC is inconsistent with the Haskell Report on which Unicode characters are allowed in string and character literals

[GHC]

#8524: GHC is inconsistent with the Haskell Report on which Unicode characters are
allowed in string and character literals
-------------------------------------+-------------------------------------
        Reporter:  oerjan            |                   Owner:
                                     |  RyanGlScott
            Type:  bug               |                  Status:  new
        Priority:  low               |               Milestone:
       Component:  Compiler          |                 Version:  7.6.3
  (Parser)                           |
      Resolution:                    |                Keywords:  newcomer
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  GHC rejects       |  Unknown/Multiple
  valid program                      |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:  Phab:D1235
-------------------------------------+-------------------------------------

Comment (by oerjan):

 Replying to [comment:6 thomie]:
 > If we're going to be "as inclusive as possible", why not allow all of
 these? Are there any downsides to this? Perhaps under a new flag
 `FullUnicodeStrings`, enabled by default and disabled in Haskell98 and
 Haskell2010 mode.

 A couple thoughts:

 Allowing \n in strings severely messes with layout. I've always assumed
 that's why it was disallowed in the first place. I suppose this also
 applies to the other *Separators and perhaps "\v\f\r" too (which would
 probably be *Separators if they weren't grandfathered as Control). And \r
 has the varying newline encoding issue.

 Unless I'm severely mistaken, Surrogate only exists because of the Unicode
 multiple encodings mess, and shouldn't ever really be ''used'' in UTF-8.
 I guess including them is fairly harmless but might trip up someone doing
 a bad encoding conversion.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8524#comment:7>
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