[GHC] #14490: TTG Snags

[GHC]

#14490: TTG Snags
-------------------------------------+-------------------------------------
        Reporter:  alanz             |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #14482            |  Differential Rev(s):
       Wiki Page:                    |
  ImplementingTreesThatGrow          |
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Comment (by alanz):

 My current thoughts

 1. Plan F is complex, and requires special case treatment of traversals
 into extension points that are actually used. In the parts of TTG
 introduced so far, we are already making fairly substantial use of pass-
 specific data types in a seamless way.

 2. Plan B is simple and works, and does not change the GHC API for any
 existing client users of traversals over the AST.  We are already looking
 at an earliest land of the feature in GHC 8.6 (second half of 2018?) so
 the required GHC 8.2 bootstrap compiler is not an issue.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14490#comment:42>
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