[GHC] #13727: `-Wmissing-home-modules` doesn't properly recognize filepath-qualified modules

[GHC]

#13727: `-Wmissing-home-modules` doesn't properly recognize filepath-qualified
modules
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        Reporter:  hvr               |                Owner:  Yuras
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.2.1
       Component:  Compiler          |              Version:  8.2.1-rc1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Incorrect         |  Unknown/Multiple
  error/warning at compile-time      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by Yuras):

 The problem here: when file is passed to command line, we don't know yet
 the module name at the time we generate the warning. And we can't use the
 file name to guess the module name because executable main module filename
 could be anything. What if we just ignore "Main" module unconditionally,
 and don't generate the warning for it? Will it work for cabal?

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13727#comment:2>
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