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

[GHC]

#10843: Allow do blocks without dollar signs as arguments
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        Reporter:  agibiansky        |                Owner:  agibiansky
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.10.2
  (Parser)                           |
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #11706            |  Differential Rev(s):  Phab:D1219
       Wiki Page:                    |
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Comment (by Iceland_jack):

 Lambda motivation

 {{{#!hs
 -- phoas :: Phoas v (x -> y -> x)
 -- phoas = PLam (\x -> PLam (\y -> PVar x))

 phoas :: Phoas v (x -> y -> x)
 phoas = PLam \x -> PLam \y -> PVar x
 }}}

 {{{#!hs
 -- ex = λ (\x -> λ (\y -> x))

 ex = λ \x -> λ \y -> x
 }}}

 Would this parse?

 {{{#!hs
 ex = λ\ x -> λ\ y -> x
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10843#comment:32>
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