[GHC] #10884: Indentation requirements for parsing seem inconsistent

[GHC]

#10884: Indentation requirements for parsing seem inconsistent
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        Reporter:  Samvh             |                   Owner:
            Type:  bug               |                  Status:  closed
        Priority:  normal            |               Milestone:
       Component:  Compiler          |                 Version:  7.10.2
  (Parser)                           |                Keywords:  parsing,
      Resolution:  invalid           |  indentation, do-notation
Operating System:  Unknown/Multiple  |            Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:
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Changes (by ezyang):

 * status:  new => closed
 * resolution:   => invalid


Comment:

 This is due to `NonDecreasingIndentation`, which is not per Haskell98 but
 useful in cases where you want to open a do-block without increasing
 indentation.  This will parse fail:

 {{{
 {-# LANGUAGE NoNondecreasingIndentation #-}

 f = let y = do
         Just 1
     in y
 }}}

 Non-decreasing indentation doesn't work at the top level, because if you
 applied it there, there would be no indentation you could drop back in
 order to get out of a do-block.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10884#comment:1>
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