[GHC] #7447: Stale .hi files affect compilation.

[GHC]

#7447: Stale .hi files affect compilation.
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    Reporter:  int-e           |       Owner:                                   
        Type:  bug             |      Status:  new                              
    Priority:  high            |   Milestone:  7.6.2                            
   Component:  Compiler        |     Version:  7.6.1                            
    Keywords:                  |          Os:  Linux                            
Architecture:  x86_64 (amd64)  |     Failure:  Incorrect warning at compile-time
  Difficulty:  Unknown         |    Testcase:                                   
   Blockedby:                  |    Blocking:                                   
     Related:                  |  
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Changes (by simonmar):

  * priority:  normal => high
  * difficulty:  => Unknown
  * milestone:  => 7.6.2
  * failure:  None/Unknown => Incorrect warning at compile-time


Comment:

 Reproduced, and it still happens with HEAD. Here's the relevant bit:

 {{{
 > echo 'module Peaker(L(..)) where{ data V = V {-# UNPACK #-} !L; data L =
 L V }' > Peaker.hs
 > ghc -fforce-recomp -O1 Peaker.hs
 [1 of 1] Compiling Peaker           ( Peaker.hs, Peaker.o )

 Peaker.hs:1:38: Warning:
     Ignoring unusable UNPACK pragma on the first argument of `V'
     In the definition of data constructor `V'
     In the data declaration for `V'
 > ghc -fforce-recomp -O1 Peaker.hs
 [1 of 1] Compiling Peaker           ( Peaker.hs, Peaker.o )
 >
 }}}

 The warning should have been produced the second time.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7447#comment:1>
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