[Haskell-cafe] Haskell interface files: Why used? What about same data in object files?

[Malcolm Wallace]

>> for some changes of .hs file (where just
>> the implementation changes) the .o file can be regenerated without
>> touching the .hi file. This allows more accurate build dependencies
>> and less recompilation.
>
> Is that really the case?  I thought that GHC may add code to the
> interface files for cross-module inlining purposes, which means that
> changing the implementation might change the interface too.

Indeed, GHC _may_ change the interface file for such reasons, but it  
may equally decide to leave the interface untouched, e.g. if there are  
no new inlinings.

Regards,
     Malcolm