[GHC] #10021: Add "Error:" prefix for compile-time error messages

[GHC]

#10021: Add "Error:" prefix for compile-time error messages
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        Reporter:  k-bx              |                   Owner:
            Type:  feature request   |                  Status:  new
        Priority:  normal            |               Milestone:  7.12.1
       Component:  Compiler          |                 Version:  7.8.4
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  None/Unknown      |  Unknown/Multiple
      Blocked By:                    |               Test Case:
 Related Tickets:                    |                Blocking:
                                     |  Differential Revisions:
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Comment (by simonpj):

 Yes, it's horrible that these seven (''seven''!) levels of severity are
 declared in a data type with no comment whatsoever to indicate what the
 author had in mind.  One can guess from the names but it still seems like
 a huge omission.  I have no opinion about `fatal` vs `error` for
 `SevFatal`.  I'm inclined to the former, since it reflects the underlying
 truth.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10021#comment:11>
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