[project @ 2005-01-27 10:45:47 by simonpj]

--------------------------------------------
          Replace hi-boot files with hs-boot files
  	--------------------------------------------

This major commit completely re-organises the way that recursive modules
are dealt with.

  * It should have NO EFFECT if you do not use recursive modules

  * It is a BREAKING CHANGE if you do

====== Warning: .hi-file format has changed, so if you are
======		updating into an existing HEAD build, you'll
======		need to make clean and re-make


The details:  [documentation still to be done]

* Recursive loops are now broken with Foo.hs-boot (or Foo.lhs-boot),
  not Foo.hi-boot

* An hs-boot files is a proper source file.  It is compiled just like
  a regular Haskell source file:
	ghc Foo.hs		generates Foo.hi, Foo.o
	ghc Foo.hs-boot		generates Foo.hi-boot, Foo.o-boot

* hs-boot files are precisely a subset of Haskell. In particular:
	- they have the same import, export, and scoping rules
	- errors (such as kind errors) in hs-boot files are checked
  You do *not* need to mention the "original" name of something in
  an hs-boot file, any more than you do in any other Haskell module.

* The Foo.hi-boot file generated by compiling Foo.hs-boot is a machine-
  generated interface file, in precisely the same format as Foo.hi

* When compiling Foo.hs, its exports are checked for compatibility with
  Foo.hi-boot (previously generated by compiling Foo.hs-boot)

* The dependency analyser (ghc -M) knows about Foo.hs-boot files, and
  generates appropriate dependencies.  For regular source files it
  generates
	Foo.o : Foo.hs
	Foo.o : Baz.hi		-- Foo.hs imports Baz
	Foo.o : Bog.hi-boot	-- Foo.hs source-imports Bog

  For a hs-boot file it generates similar dependencies
	Bog.o-boot : Bog.hs-boot
	Bog.o-boot : Nib.hi	-- Bog.hs-boto imports Nib

* ghc -M is also enhanced to use the compilation manager dependency
  chasing, so that
	ghc -M Main
  will usually do the job.  No need to enumerate all the source files.

* The -c flag is no longer a "compiler mode". It simply means "omit the
  link step", and synonymous with -no-link.