[GHC] #10942: CPP pragma ignored if top comments and Opt_KeepRawTokenStream

[GHC]

#10942: CPP pragma ignored if top comments and Opt_KeepRawTokenStream
-------------------------------------+-------------------------------------
           Reporter:  alanz          |             Owner:  alanz
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:  8.0.1
          Component:  Compiler       |           Version:  7.10.2
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |
-------------------------------------+-------------------------------------
 HaRe sets `Opt_KeepRawTokenStream` to be able to round trip the source
 code.

 If we have a module starting

 {{{#!hs
 {-

 A normal comment, to check if we can still pick up the CPP directive after
 it.

 -}
 {-# LANGUAGE FlexibleInstances #-}
 {-# LANGUAGE CPP #-}
 -- Check that we can parse a file which requires CPP
 module BCpp where
 bob :: Int -> Int -> Int
 #if __GLASGOW_HASKELL__ > 704
 bob x y = x + y
 #else
 bob x y = x + y * 2
 #endif

 }}}

 then the call to `loadTargets` via the GHC API fails with

 `SourceError (lexical error at character 'i'` which is the normal error
 when `#if` is hit and CPP is not enabled.

 If `Opt_KeepRawTokenStream` is not set it loads without problems.

 Also, files using CPP but not having a top comment load properly too.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10942>
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