[GHC] #12567: `ghc --make` recompiles unchanged files when using `-fplugin` OPTIONS

[GHC]

#12567: `ghc --make` recompiles unchanged files when using `-fplugin` OPTIONS
-------------------------------------+-------------------------------------
        Reporter:  heisenbug         |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.10.3
      Resolution:                    |             Keywords:  plugin,
                                     |  RecompilationCheck
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #7414             |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by Ben Gamari <ben@…>):

 In [changeset:"1d1e2b77fdc2babdf4fff72b9120c6831e7b422f/ghc" 1d1e2b7/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="1d1e2b77fdc2babdf4fff72b9120c6831e7b422f"
 Implement "An API for deciding whether plugins should cause recompilation"

 This patch implements the API proposed as pull request #108 for plugin
 authors to influence the recompilation checker.

 It adds a new field to a plugin which computes a `FingerPrint`. This is
 recorded in interface files and if it changes then we recompile the
 module. There are also helper functions such as `purePlugin` and
 `impurePlugin` for constructing plugins which have simple recompilation
 semantics but in general, an author can compute a hash as they wish.

 Fixes #12567 and #7414

 https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/002
 2-plugin-recompilation.rst

 Reviewers: bgamari, ggreif

 Reviewed By: bgamari

 Subscribers: rwbarton, thomie, carter

 GHC Trac Issues: #7414, #12567

 Differential Revision: https://phabricator.haskell.org/D4366
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12567#comment:12>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler