[GHC] #12627: build sytem feature request: persist warnings

[GHC]

#12627: build sytem feature request: persist warnings
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           Reporter:  nomeata        |             Owner:
               Type:  feature        |            Status:  new
  request                            |
           Priority:  normal         |         Milestone:
          Component:  Build System   |           Version:  8.0.1
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 I often have this pattern: I hack on GHC in `devel2` mode, introducing a
 few changes that cause warnings all over the place (usually related to
 imports). I ignore them while I work on the feature.

 Now I want to clean the warnings up. I basically only have one option:
 Switch the settings to make warnings errors, make clean, re-build
 everything, see where it aborts, fix it, restart the build.

 This is annoying.

 I would prefer if the build system (in any more) would keep, for every
 file, the output of the compiler on disc, e.g. with a suffix of `.comp-
 out` or something. This way, after a complete build, even without
 `-Werror`, I can simply run `cat **/*.comp-out` (or whatever suffix is
 suitable), fix all these error in one go, and be done with it.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12627>
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