[GHC] #13450: Better parse error for empy character literal

[GHC]

#13450: Better parse error for empy character literal
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        Reporter:  parsonsmatt       |                Owner:  (none)
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Poor/confusing    |  Unknown/Multiple
  error message                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by Simon Peyton Jones <simonpj@…>):

 In [changeset:"74cd1be0b2778ad99566cde085328bde2090294a/ghc"
 74cd1be0/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="74cd1be0b2778ad99566cde085328bde2090294a"
 Don't deeply expand insolubles

 Trac #13450 went bananas if we expand insoluble constraints.
 Better just to leave them un-expanded.

 I'm not sure in detail about why it goes so badly wrong; but
 regardless, the less we mess around with insoluble contraints
 the better the error messages will be.
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13450#comment:1>
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