Detecting whether a file contains module Main

[nh2]

As noted in the code already:

TODO: To fully emulate GHC's behaviour, we must know whether the input module
set contains a module Main.

Consider these two invocations:

$ ghc --make Module.hs Module0.hs
[1 of 2] Compiling Module           ( Module.hs, t/Module.o )
[2 of 2] Compiling Module0          ( Module0.hs, t/Module0.o )

$ ghc --make Module.hs Main.hs
[1 of 2] Compiling Module           ( Module.hs, t/Module.o )
[2 of 2] Compiling Main             ( Main.hs, t/Main.o )
Linking Main ...

In the first case, the linking step is not performed since there is no module
called 'Main'.

Additionally, the module 'Main' can have an arbitrary source file name, not
necessary 'Main.hs'. This changes the name of the output executable:

$ ghc --make Module.hs MyProg.hs
[1 of 2] Compiling Module           ( Module.hs, t/Module.o )
[2 of 2] Compiling Main             ( MyProg.hs, t/Main.o )
Linking MyProg ...

Let's use this issue for discussion.

[nh2]

As far as I understand, only GHC can detect whether a module ends up as module Main because you can e.g. switch the module name using CPP.

[nh2]

I just realized that this is not a problem any more, since the final ghc pass we do now will detect this correctly.

I addressed it in https://github.com/23Skidoo/ghc-parmake/pull/15.