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Fix compilation breakage with GHC 4.08.x.

Three Template Haskell improvements

a) Add type synonyms to THSyntax (and DsMeta, Convert)

b) Make Q into a newtype instead of a type synonym

c) Eliminate tiresome and error prone argument to DsMeta.wrapGenSyms
   and similarly addTyVarBinds

More tidy up

deja vu all over again

Fix build on GHC < 5.00

Restore interrupt/quit signal handlers after every evaluation in GHCi,
just in case the program set its own.

Don't need to export Exception.try or Exception.throwDyn here.

make it compile again with 4.08.x

Compatibility fixes for Exception.try

Fix up exception handling when reading an interface file, and make it
compile with 4.08.x again.

GhcExceptions weren't being caught by readIface, so an error when
reading an interface could be unintentionally fatal (errors should be
soft when reading the old interface file for the current module).
Also, the Interrupted exception should not be caught by readIface,
because we want ^C to behave as normal when reading interface files
(currently it causes an interface-file read error rather than
interrupting the whole compiler).

Some exception-related compatibility functions have been moved from
Util to Panic.

--------------------------------------
	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
itself).

* 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
	Language/Haskell/THSyntax
  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.

So:
	HsPat.InPat	--> HsPat.Pat
	HsPat.OutPat	--> HsPat.Pat
	No 'pat' type parameter in HsExpr, HsBinds, etc

	Constructor patterns are nicer now: they use
		HsPat.HsConDetails
	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.

Housekeeping:

  - The main goal is to remove dependencies on hslibs for a
    bootstrapped compiler, leaving only a requirement that the
    packages base, haskell98 and readline are built in stage 1 in
    order to bootstrap.  We're almost there: Posix is still required
    for signal handling, but all other dependencies on hslibs are now
    gone.

    Uses of Addr and ByteArray/MutableByteArray array are all gone
    from the compiler.  PrimPacked defines the Ptr type for GHC 4.08
    (which didn't have it), and it defines simple BA and MBA types to
    replace uses of ByteArray and MutableByteArray respectively.

  - Clean up import lists.  HsVersions.h now defines macros for some
    modules which have moved between GHC versions.  eg. one now
    imports 'GLAEXTS' to get at unboxed types and primops in the
    compiler.

    Many import lists have been sorted as per the recommendations in
    the new style guidelines in the commentary.

I've built the compiler with GHC 4.08.2, 5.00.2, 5.02.3, 5.04 and
itself, and everything still works here.  Doubtless I've got something
wrong, though.

oops, changes not tested with a stage2 build

reuse Panic.showGhcException

Clean up GHC's error reporting

  - the GhcException type has some more constructors: CmdLineError,
    ProgramError, and InstallationError.  OtherError has gone.

  - most error messages should begin with "<location>:".  When the
    error is on the command-line or in GHC itself, <location> is
    "ghc", for consistency with std Unix semantics.

print GHC's version in the panic message

Clean up the error handling a bit; the exception type is moved to
Panic, and a new exception for panics has been added.

Move FAST_INT and FAST_BOOL into their own module FastTypes, replacing
the macro definitions in HsVersions.h with real definitions.  Change
most of the names in the process.

Now we don't get bogus imports of GlaExts all over the place, and
-fwarn-unused-imports is less noisy.

glasgow-haskell-{bugs,users} has moved.

import list tweak

Add utils/Panic.lhs