[GHC] #9628: Add Annotations to the AST to simplify source to source conversions

[GHC]

#9628: Add Annotations to the AST to simplify source to source conversions
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              Reporter:  alanz       |            Owner:  alanz
                  Type:  feature     |           Status:  new
  request                            |        Milestone:
              Priority:  normal      |          Version:  7.9
             Component:  Compiler    |         Keywords:
            Resolution:              |     Architecture:  Unknown/Multiple
      Operating System:              |       Difficulty:  Unknown
  Unknown/Multiple                   |       Blocked By:
       Type of failure:              |  Related Tickets:
  None/Unknown                       |
             Test Case:              |
              Blocking:              |
Differential Revisions:  D297        |
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Comment (by Austin Seipp <austin@…>):

 In [changeset:"c0ad5bc03e02ce0d7d545599e4b1a68a6f727f2b/ghc"]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="c0ad5bc03e02ce0d7d545599e4b1a68a6f727f2b"
 Capture original source for literals

 Summary:
 Make HsLit and OverLitVal have original source strings, for source to
 source conversions using the GHC API

 This is part of the ongoing AST Annotations work, as captured in
 https://ghc.haskell.org/trac/ghc/wiki/GhcAstAnnotations and
 https://ghc.haskell.org/trac/ghc/ticket/9628#comment:28

 The motivations for the literals is as follows

 ```lang=haskell
 x,y :: Int
 x = 0003
 y = 0x04

 s :: String
 s = "\x20"

 c :: Char
 c = '\x20'

 d :: Double
 d = 0.00

 blah = x
   where
     charH = '\x41'#
     intH = 0004#
     wordH = 005##
     floatH = 3.20#
     doubleH = 04.16##
     x = 1
 ```

 Test Plan: ./sh validate

 Reviewers: simonpj, austin

 Reviewed By: simonpj, austin

 Subscribers: thomie, goldfire, carter, simonmar

 Differential Revision: https://phabricator.haskell.org/D412

 GHC Trac Issues: #9628
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9628#comment:42>
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