[GHC] #14709: Extend the plugin mechanism to access program representation

[GHC]

#14709: Extend the plugin mechanism to access program representation
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        Reporter:  lazac             |                Owner:  (none)
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  GHC API           |              Version:  8.2.2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |  https://phabricator.haskell.org/D4342
  https://ghc.haskell.org/trac/ghc/wiki/ExtendedPluginsProposal|
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Comment (by alanz):

 As a fellow tool-writer, in principle I am in favour of this patch.

 One thing that confuses me though, is the motivating examples are to
 extract information, but the plugins allow changes on the fly.

 I am concerned that we open a pandora's box of arbitrary transformations
 via plugins, that will make it ***harder*** for tool writers, as we now
 need to know what other things are happening under the hood.

 That said, I do believe it would be incredibly useful to be able to make
 changes to some part of a given AST, and push it down the pipeline to
 either validate a proposed change to the code, or to gather type
 information based on the change.  And to do that modification is required.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14709#comment:11>
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