Why have file names with 3 components?

This looks like a bug, but please don't change it! If you have a file A.blah.hs containing a module A, ghc5.02 compiles it, producing A.hi and A.blah.o. I have an application for this, since I have just, for the first time, been reluctantly compelled to introduce recursive modules. Rather than writing .hi-boot files (which might have to be rewritten for ghc5.03) I have instead written .boot.hs files, which yield .hi files, which then get moved to .hi-boot. Thus a module A has two sources, the real source A.hs, but also the source for the .hi-boot file, A.boot.hs.