[GHC] #13875: ApplicativeDo desugaring is lazier than standard desugaring

[GHC]

#13875: ApplicativeDo desugaring is lazier than standard desugaring
-------------------------------------+-------------------------------------
        Reporter:  dfeuer            |                Owner:  simonmar
            Type:  bug               |               Status:  closed
        Priority:  high              |            Milestone:  8.2.1
       Component:  Compiler          |              Version:  8.3
      Resolution:  fixed             |             Keywords:  ApplicativeDo
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  Other             |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D3681
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by ElvishJerricco):

 Replying to [comment:6 dfeuer]:
 > While I'm mentioning idle thoughts: monad comprehension syntax seems to
 handle the `pure`/`return`/`pure $`/whatever issue a lot more cleanly than
 anything `do`-like. Has anyone considered applicative comprehensions?

 This may no longer be the right place to answer this question, but I do
 think that using `in` would be better than special casing `return`,
 `pure`, and `$`.


 {{{
 do
   a <- foo
   b <- bar
   in a + b
 }}}

 Seems more consistent with `let`-binding syntax. Though there is
 definitely some value in desugarring those functions since it means
 `ApplicativeDo` can be a drop-in optimization.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13875#comment:16>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler