[GHC] #13801: Make -main-is work with {thing} from arbitrary installed packages

[GHC]

#13801: Make -main-is work with {thing} from arbitrary installed packages
-------------------------------------+-------------------------------------
        Reporter:  SimonHengel       |                Owner:  (none)
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------
Changes (by bgamari):

 * cc: ezyang (added)


Comment:

 CCing ezyang due to his interest in package system concerns.

 > I haven't looked at any code, but my assumption is that GHC generates a
 driver module, similar to the one we have to write by hand if we don't use
 -main-is. Can somebody confirm (or negate) this?

 I believe this is partially true. However, it's a bit tricky; we don't
 actually generate a module. We merely emit a binding which claims to be
 from another module when typechecking what the user says should be the
 main module. Have a look at `Note [Root-main Id]` for details.


 On the whole this sounds fairly easy to do.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13801#comment:2>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler