[GHC] #10843: Allow do blocks without dollar signs as arguments

[GHC]

#10843: Allow do blocks without dollar signs as arguments
-------------------------------------+-------------------------------------
              Reporter:  agibiansky  |             Owner:  agibiansky
                  Type:  feature     |            Status:  new
  request                            |
              Priority:  normal      |         Milestone:
             Component:  Compiler    |           Version:  7.10.2
  (Parser)                           |
              Keywords:              |  Operating System:  Unknown/Multiple
          Architecture:              |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
             Test Case:              |        Blocked By:
              Blocking:              |   Related Tickets:
Differential Revisions:              |
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 I would like the following to be valid Haskell code:

 {{{#!hs
 main = when True do
   putStrLn "Hello!"
 }}}

 Instead of requiring a dollar sign before the "do". This would parse as


 {{{#!hs
 main = when True (do
   putStrLn "Hello!")
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10843>
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