[GHC] #8340: support for generating annotations from TH

[GHC]

#8340: support for generating annotations from TH
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       Reporter:  errge                    |             Owner:
           Type:  feature request          |            Status:  new
       Priority:  normal                   |         Milestone:  7.8.1
      Component:  Compiler                 |           Version:  7.7
       Keywords:                           |  Operating System:
   Architecture:  Unknown/Multiple         |  Unknown/Multiple
     Difficulty:  Easy (less than 1 hour)  |   Type of failure:
     Blocked By:                           |  None/Unknown
Related Tickets:                           |         Test Case:
                                           |          Blocking:  7867
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 This patch adds support for template haskell generation of annotations.
 This is currently only possible directly via ```{-# ANN function "whatever
 annotation #-}```.

 The attached patch makes it possible to do the same from TH.

 Module and type annotations are supported too.

 This is part of a larger effort to make it possible to cross-module
 communicate between template haskell runs.  See #7867 for a longer
 discussion.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8340>
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