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  • Simon Peyton Jones's avatar
    [project @ 2002-09-13 15:02:25 by simonpj] · 9af77fa4
    Simon Peyton Jones authored
    	Make Template Haskell into the HEAD
    This massive commit transfers to the HEAD all the stuff that
    Simon and Tim have been doing on Template Haskell.  The
    meta-haskell-branch is no more!
    WARNING: make sure that you
      * Update your links if you are using link trees.
        Some modules have been added, some have gone away.
      * Do 'make clean' in all library trees.
        The interface file format has changed, and you can
        get strange panics (sadly) if GHC tries to read old interface files:
        e.g.  ghc-5.05: panic! (the `impossible' happened, GHC version 5.05):
    	  Binary.get(TyClDecl): ForeignType
      * You need to recompile the rts too; Linker.c has changed
    However the libraries are almost unaltered; just a tiny change in
    Base, and to the exports in Prelude.
    NOTE: so far as TH itself is concerned, expression splices work
    fine, but declaration splices are not complete.
    		The main change
    The main structural change: renaming and typechecking have to be
    interleaved, because we can't rename stuff after a declaration splice
    until after we've typechecked the stuff before (and the splice
    * Combine the renamer and typecheker monads into one
    	(TcRnMonad, TcRnTypes)
      These two replace TcMonad and RnMonad
    * Give them a single 'driver' (TcRnDriver).  This driver
      replaces TcModule.lhs and Rename.lhs
    * The haskell-src library package has a module
      which defines the Haskell data type seen by the TH programmer.
    * New modules:
    	hsSyn/Convert.hs 	converts THSyntax -> HsSyn
    	deSugar/DsMeta.hs 	converts HsSyn -> THSyntax
    * New module typecheck/TcSplice type-checks Template Haskell splices.
    		Linking stuff
    * ByteCodeLink has been split into
    	ByteCodeLink	(which links)
    	ByteCodeAsm	(which assembles)
    * New module ghci/ObjLink is the object-code linker.
    * compMan/CmLink is removed entirely (was out of place)
      Ditto CmTypes (which was tiny)
    * Linker.c initialises the linker when it is first used (no need to call
      initLinker any more).  Template Haskell makes it harder to know when
      and whether to initialise the linker.
    	Gathering the LIE in the type checker
    * Instead of explicitly gathering constraints in the LIE
    	tcExpr :: RenamedExpr -> TcM (TypecheckedExpr, LIE)
      we now dump the constraints into a mutable varabiable carried
      by the monad, so we get
    	tcExpr :: RenamedExpr -> TcM TypecheckedExpr
      Much less clutter in the code, and more efficient too.
      (Originally suggested by Mark Shields.)
    		Remove "SysNames"
    Because the renamer and the type checker were entirely separate,
    we had to carry some rather tiresome implicit binders (or "SysNames")
    along inside some of the HsDecl data structures.  They were both
    tiresome and fragile.
    Now that the typechecker and renamer are more intimately coupled,
    we can eliminate SysNames (well, mostly... default methods still
    carry something similar).
    		Clean up HsPat
    One big clean up is this: instead of having two HsPat types (InPat and
    OutPat), they are now combined into one.  This is more consistent with
    the way that HsExpr etc is handled; there are some 'Out' constructors
    for the type checker output.
    	HsPat.InPat	--> HsPat.Pat
    	HsPat.OutPat	--> HsPat.Pat
    	No 'pat' type parameter in HsExpr, HsBinds, etc
    	Constructor patterns are nicer now: they use
    	for the three cases of constructor patterns:
    		prefix, infix, and record-bindings
    	The *same* data type HsConDetails is used in the type
    	declaration of the data type (HsDecls.TyData)
    Lots of associated clean-up operations here and there.  Less code.
    Everything is wonderful.