[GHC] #7828: RebindableSyntax and Arrow

[GHC]

#7828: RebindableSyntax and Arrow
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              Reporter:              |            Owner:  jstolarek
  AlessandroVermeulen                |           Status:  new
                  Type:  bug         |        Milestone:  7.10.1
              Priority:  normal      |          Version:  7.6.2
             Component:  Compiler    |         Keywords:
  (Type checker)                     |     Architecture:  Unknown/Multiple
            Resolution:              |       Difficulty:  Unknown
      Operating System:              |       Blocked By:
  Unknown/Multiple                   |  Related Tickets:  #1537, #3613
       Type of failure:  GHC         |
  rejects valid program              |
             Test Case:              |
              Blocking:              |
Differential Revisions:  Phab:D72    |
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Comment (by simonpj):

 I'm sorry Jan I'm struggling with this one.  My main difficulty is that I
 don't understand arrows well enough, and I do not have a stand-alone
 document giving the typing rules they are supposed to obey, one that
 matches the syntax and deguaring used in GHC.  (There are some changes
 described above, and I do not know how they fit in either.)

 What would be really helpful would be a wiki page or Latex document that
 gave
  * The syntax for arrows, including a clear indication of how it is
 represented in !HsSyn
  * The static semantics as typing rules
  * The desugaring into Core
 The second and third of these are connected, because the type checker must
 generate the evidence that will be used by the desugarer to translate to
 Core.

 I believe that the static semantics may be specified (perhaps only in
 part), as comment:17 suggests, by translation into some simpler
 combinators.

 In short, it's a nice, cleanly-separable problem; and has clear
 intellectual challenge; but I feel unable to contribute much at the
 moment.

 Simon

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7828#comment:46>
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