[GHC] #8051: GHCi: confusing `:set +m`/`:{` interaction & wrong line-numbers in multi-line input

[GHC]

#8051: GHCi: confusing `:set +m`/`:{` interaction & wrong line-numbers in multi-
line input
------------------------------------+-------------------------------------
       Reporter:  hvr               |             Owner:
           Type:  bug               |            Status:  new
       Priority:  normal            |         Milestone:
      Component:  GHCi              |           Version:  7.6.3
       Keywords:                    |  Operating System:  Unknown/Multiple
   Architecture:  Unknown/Multiple  |   Type of failure:  None/Unknown
     Difficulty:  Unknown           |         Test Case:
     Blocked By:                    |          Blocking:
Related Tickets:                    |
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 As mentioned in ticket:8047#comment:1 GHCi exhibits a line-numbering
 offset bug when multi-line input is evaluated.

 Morever, when `:set +m` is active, `:{`-entered multi-input may trigger
 multi-line input continuation, e.g.:

 {{{
 Prelude> :set +m
 Prelude> :{
 Prelude| let x = ()
 Prelude|     y = ()
 Prelude| :}
 Prelude|     z = ()
 Prelude|
 Prelude>
 }}}

 The attached patch fixes both issues, but does so in an admittedly hacky
 way...

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8051>
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