GitLab

Worker/wrapper generation sometimes has to add a dummy void (State#) argument
to retain laziness.  But when generating the strictness signature for the
worker, I forgot to take account of the extra argument, resulting in a
bogus strictness signature.

Result, chaos.  Trac 317 shows this up, and this patch fixes it.

Mon Sep 18 17:19:19 EDT 2006  Manuel M T Chakravarty <chak@cse.unsw.edu.au>
  * Flip direction of newtype coercions, fix some comments
  Sun Aug  6 20:56:23 EDT 2006  Manuel M T Chakravarty <chak@cse.unsw.edu.au>
    * Flip direction of newtype coercions, fix some comments
    Thu Aug  3 10:53:37 EDT 2006  kevind@bu.edu

Mon Sep 18 17:17:20 EDT 2006  Manuel M T Chakravarty <chak@cse.unsw.edu.au>
  * Clean up unused imports, definitions and arguments
  Sun Aug  6 20:54:31 EDT 2006  Manuel M T Chakravarty <chak@cse.unsw.edu.au>
    * Clean up unused imports, definitions and arguments
    Wed Aug  2 11:05:33 EDT 2006  kevind@bu.edu

Mon Sep 18 14:51:33 EDT 2006  Manuel M T Chakravarty <chak@cse.unsw.edu.au>
  * fix some coercion kind representation things, extend exprIsConApp_maybe to non-vanilla
  Sat Aug  5 21:48:21 EDT 2006  Manuel M T Chakravarty <chak@cse.unsw.edu.au>
    * fix some coercion kind representation things, extend exprIsConApp_maybe to non-vanilla
    Wed Jul 19 08:06:28 EDT 2006  kevind@bu.edu

Mon Sep 18 14:48:02 EDT 2006  Manuel M T Chakravarty <chak@cse.unsw.edu.au>
  * finished product unboxing through newtypes and proper demand analysis of newtypes
  Sat Aug  5 21:45:32 EDT 2006  Manuel M T Chakravarty <chak@cse.unsw.edu.au>
    * finished product unboxing through newtypes and proper demand analysis of newtypes
    Mon Jul 17 06:52:11 EDT 2006  kevind@bu.edu

Mon Sep 18 14:44:50 EDT 2006  Manuel M T Chakravarty <chak@cse.unsw.edu.au>
  * towards unboxing through newtypes
  Sat Aug  5 21:42:05 EDT 2006  Manuel M T Chakravarty <chak@cse.unsw.edu.au>
    * towards unboxing through newtypes
    Fri Jul 14 12:02:32 EDT 2006  kevind@bu.edu

Mon Sep 18 14:24:27 EDT 2006  Manuel M T Chakravarty <chak@cse.unsw.edu.au>
  * newtype fixes, coercions for non-recursive newtypes now optional
  Sat Aug  5 21:19:58 EDT 2006  Manuel M T Chakravarty <chak@cse.unsw.edu.au>
    * newtype fixes, coercions for non-recursive newtypes now optional
    Fri Jul  7 06:11:48 EDT 2006  kevind@bu.edu

Broken up massive patch -=chak
Original log message:  
This is (sadly) all done in one patch to avoid Darcs bugs.
It's not complete work... more FC stuff to come.  A compiler
using just this patch will fail dismally.

Most of the other users of the fptools build system have migrated to
Cabal, and with the move to darcs we can now flatten the source tree
without losing history, so here goes.

The main change is that the ghc/ subdir is gone, and most of what it
contained is now at the top level.  The build system now makes no
pretense at being multi-project, it is just the GHC build system.

No doubt this will break many things, and there will be a period of
instability while we fix the dependencies.  A straightforward build
should work, but I haven't yet fixed binary/source distributions.
Changes to the Building Guide will follow, too.

Tweaks to get the GHC sources through Haddock.  Doesn't quite work
yet, because Haddock complains about the recursive modules.  Haddock
needs to understand SOURCE imports (it can probably just ignore them
as a first attempt).

Name evaldUnfolding = OtherCon [], and use it

----------------------------------------
     New Core invariant: keep case alternatives in sorted order
	----------------------------------------

We now keep the alternatives of a Case in the Core language in sorted
order.  Sorted, that is,
	by constructor tag	for DataAlt
	by literal		for LitAlt

The main reason is that it makes matching and equality testing more robust.
But in fact some lines of code vanished from SimplUtils.mkAlts.


WARNING: no change to interface file formats, but you'll need to recompile
your libraries so that they generate interface files that respect the
invariant.

------------------------------------
	Add Generalised Algebraic Data Types
	------------------------------------

This rather big commit adds support for GADTs.  For example,

    data Term a where
 	  Lit :: Int -> Term Int
	  App :: Term (a->b) -> Term a -> Term b
	  If  :: Term Bool -> Term a -> Term a
	  ..etc..

    eval :: Term a -> a
    eval (Lit i) = i
    eval (App a b) = eval a (eval b)
    eval (If p q r) | eval p    = eval q
    		    | otherwise = eval r


Lots and lots of of related changes throughout the compiler to make
this fit nicely.

One important change, only loosely related to GADTs, is that skolem
constants in the typechecker are genuinely immutable and constant, so
we often get better error messages from the type checker.  See
TcType.TcTyVarDetails.

There's a new module types/Unify.lhs, which has purely-functional
unification and matching for Type. This is used both in the typechecker
(for type refinement of GADTs) and in Core Lint (also for type refinement).

-------------------------
		GHC heart/lung transplant
		-------------------------

This major commit changes the way that GHC deals with importing
types and functions defined in other modules, during renaming and
typechecking.  On the way I've changed or cleaned up numerous other
things, including many that I probably fail to mention here.

Major benefit: GHC should suck in many fewer interface files when
compiling (esp with -O).  (You can see this with -ddump-rn-stats.)

It's also some 1500 lines of code shorter than before.

**	So expect bugs!  I can do a 3-stage bootstrap, and run
**	the test suite, but you may be doing stuff I havn't tested.
** 	Don't update if you are relying on a working HEAD.


In particular, (a) External Core and (b) GHCi are very little tested.

	But please, please DO test this version!


	------------------------
		Big things
	------------------------

Interface files, version control, and importing declarations
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
* There is a totally new data type for stuff that lives in interface files:
	Original names			IfaceType.IfaceExtName
	Types				IfaceType.IfaceType
	Declarations (type,class,id)	IfaceSyn.IfaceDecl
	Unfoldings			IfaceSyn.IfaceExpr
  (Previously we used HsSyn for type/class decls, and UfExpr for unfoldings.)
  The new data types are in iface/IfaceType and iface/IfaceSyn.  They are
  all instances of Binary, so they can be written into interface files.
  Previous engronkulation concering the binary instance of RdrName has
  gone away -- RdrName is not an instance of Binary any more.  Nor does
  Binary.lhs need to know about the ``current module'' which it used to,
  which made it specialised to GHC.

  A good feature of this is that the type checker for source code doesn't
  need to worry about the possibility that we might be typechecking interface
  file stuff.  Nor does it need to do renaming; we can typecheck direct from
  IfaceSyn, saving a whole pass (module TcIface)

* Stuff from interface files is sucked in *lazily*, rather than being eagerly
  sucked in by the renamer. Instead, we use unsafeInterleaveIO to capture
  a thunk for the unfolding of an imported function (say).  If that unfolding
  is every pulled on, TcIface will scramble over the unfolding, which may
  in turn pull in the interface files of things mentioned in the unfolding.

  The External Package State is held in a mutable variable so that it
  can be side-effected by this lazy-sucking-in process (which may happen
  way later, e.g. when the simplifier runs).   In effect, the EPS is a kind
  of lazy memo table, filled in as we suck things in.  Or you could think
  of it as a global symbol table, populated on demand.

* This lazy sucking is very cool, but it can lead to truly awful bugs. The
  intent is that updates to the symbol table happen atomically, but very bad
  things happen if you read the variable for the table, and then force a
  thunk which updates the table.  Updates can get lost that way. I regret
  this subtlety.

  One example of the way it showed up is that the top level of TidyPgm
  (which updates the global name cache) to be much more disciplined about
  those updates, since TidyPgm may itself force thunks which allocate new
  names.

* Version numbering in interface files has changed completely, fixing
  one major bug with ghc --make.  Previously, the version of A.f changed
  only if A.f's type and unfolding was textually different.  That missed
  changes to things that A.f's unfolding mentions; which was fixed by
  eagerly sucking in all of those things, and listing them in the module's
  usage list.  But that didn't work with --make, because they might have
  been already sucked in.

  Now, A.f's version changes if anything reachable from A.f (via interface
  files) changes.  A module with unchanged source code needs recompiling
  only if the versions of any of its free variables changes. [This isn't
  quite right for dictionary functions and rules, which aren't mentioned
  explicitly in the source.  There are extensive comments in module MkIface,
  where all version-handling stuff is done.]

* We don't need equality on HsDecls any more (because they aren't used in
  interface files).  Instead we have a specialised equality for IfaceSyn
  (eqIfDecl etc), which uses IfaceEq instead of Bool as its result type.
  See notes in IfaceSyn.

* The horrid bit of the renamer that tried to predict what instance decls
  would be needed has gone entirely.  Instead, the type checker simply
  sucks in whatever instance decls it needs, when it needs them.  Easy!

  Similarly, no need for 'implicitModuleFVs' and 'implicitTemplateHaskellFVs'
  etc.  Hooray!


Types and type checking
~~~~~~~~~~~~~~~~~~~~~~~
* Kind-checking of types is far far tidier (new module TcHsTypes replaces
  the badly-named TcMonoType).  Strangely, this was one of my
  original goals, because the kind check for types is the Right Place to
  do type splicing, but it just didn't fit there before.

* There's a new representation for newtypes in TypeRep.lhs.  Previously
  they were represented using "SourceTypes" which was a funny compromise.
  Now they have their own constructor in the Type datatype.  SourceType
  has turned back into PredType, which is what it used to be.

* Instance decl overlap checking done lazily.  Consider
	instance C Int b
	instance C a Int
  These were rejected before as overlapping, because when seeking
  (C Int Int) one couldn't tell which to use.  But there's no problem when
  seeking (C Bool Int); it can only be the second.

  So instead of checking for overlap when adding a new instance declaration,
  we check for overlap when looking up an Inst.  If we find more than one
  matching instance, we see if any of the candidates dominates the others
  (in the sense of being a substitution instance of all the others);
  and only if not do we report an error.



	------------------------
	     Medium things
	------------------------

* The TcRn monad is generalised a bit further.  It's now based on utils/IOEnv.lhs,
  the IO monad with an environment.  The desugarer uses the monad too,
  so that anything it needs can get faulted in nicely.

* Reduce the number of wired-in things; in particular Word and Integer
  are no longer wired in.  The latter required HsLit.HsInteger to get a
  Type argument.  The 'derivable type classes' data types (:+:, :*: etc)
  are not wired in any more either (see stuff about derivable type classes
  below).

* The PersistentComilerState is now held in a mutable variable
  in the HscEnv.  Previously (a) it was passed to and then returned by
  many top-level functions, which was painful; (b) it was invariably
  accompanied by the HscEnv.  This change tidies up top-level plumbing
  without changing anything important.

* Derivable type classes are treated much more like 'deriving' clauses.
  Previously, the Ids for the to/from functions lived inside the TyCon,
  but now the TyCon simply records their existence (with a simple boolean).
  Anyone who wants to use them must look them up in the environment.

  This in turn makes it easy to generate the to/from functions (done
  in types/Generics) using HsSyn (like TcGenDeriv for ordinary derivings)
  instead of CoreSyn, which in turn means that (a) we don't have to figure
  out all the type arguments etc; and (b) it'll be type-checked for us.
  Generally, the task of generating the code has become easier, which is
  good for Manuel, who wants to make it more sophisticated.

* A Name now says what its "parent" is. For example, the parent of a data
  constructor is its type constructor; the parent of a class op is its
  class.  This relationship corresponds exactly to the Avail data type;
  there may be other places we can exploit it.  (I made the change so that
  version comparison in interface files would be a bit easier; but in
  fact it tided up other things here and there (see calls to
  Name.nameParent).  For example, the declaration pool, of declararations
  read from interface files, but not yet used, is now keyed only by the 'main'
  name of the declaration, not the subordinate names.

* New types OccEnv and OccSet, with the usual operations.
  OccNames can be efficiently compared, because they have uniques, thanks
  to the hashing implementation of FastStrings.

* The GlobalRdrEnv is now keyed by OccName rather than RdrName.  Not only
  does this halve the size of the env (because we don't need both qualified
  and unqualified versions in the env), but it's also more efficient because
  we can use a UniqFM instead of a FiniteMap.

  Consequential changes to Provenance, which has moved to RdrName.

* External Core remains a bit of a hack, as it was before, done with a mixture
  of HsDecls (so that recursiveness and argument variance is still inferred),
  and IfaceExprs (for value declarations).  It's not thoroughly tested.


	------------------------
	     Minor things
	------------------------

* DataCon fields dcWorkId, dcWrapId combined into a single field
  dcIds, that is explicit about whether the data con is a newtype or not.
  MkId.mkDataConWorkId and mkDataConWrapId are similarly combined into
  MkId.mkDataConIds

* Choosing the boxing strategy is done for *source* type decls only, and
  hence is now in TcTyDecls, not DataCon.

* WiredIn names are distinguished by their n_sort field, not by their location,
  which was rather strange

* Define Maybes.mapCatMaybes :: (a -> Maybe b) -> [a] -> [b]
  and use it here and there

* Much better pretty-printing of interface files (--show-iface)

Many, many other small things.


	------------------------
	     File changes
	------------------------
* New iface/ subdirectory
* Much of RnEnv has moved to iface/IfaceEnv
* MkIface and BinIface have moved from main/ to iface/
* types/Variance has been absorbed into typecheck/TcTyDecls
* RnHiFiles and RnIfaces have vanished entirely.  Their
  work is done by iface/LoadIface
* hsSyn/HsCore has gone, replaced by iface/IfaceSyn
* typecheck/TcIfaceSig has gone, replaced by iface/TcIface
* typecheck/TcMonoType has been renamed to typecheck/TcHsType
* basicTypes/Var.hi-boot and basicTypes/Generics.hi-boot have gone altogether

Comments

FastString cleanup, stage 1.

The FastString type is no longer a mixture of hashed strings and
literal strings, it contains hashed strings only with O(1) comparison
(except for UnicodeStr, but that will also go away in due course).  To
create a literal instance of FastString, use FSLIT("..").

By far the most common use of the old literal version of FastString
was in the pattern

	  ptext SLIT("...")

this combination still works, although it doesn't go via FastString
any more.  The next stage will be to remove the need to use this
special combination at all, using a RULE.

To convert a FastString into an SDoc, now use 'ftext' instead of
'ptext'.

I've also removed all the FAST_STRING related macros from HsVersions.h
except for SLIT and FSLIT, just use the relevant functions from
FastString instead.

-------------------
	Mainly derived Read
	-------------------

This commit is a tangle of several things that somehow got wound up
together, I'm afraid.


The main course
~~~~~~~~~~~~~~~
Replace the derived-Read machinery with Koen's cunning new parser
combinator library.   The result should be
	* much smaller code sizes from derived Read
	* faster execution of derived Read

WARNING: I have not thoroughly tested this stuff; I'd be glad if you did!
	 All the hard work is done, but there may be a few nits.

The Read class gets two new methods, not exposed
in the H98 inteface of course:
  class Read a where
    readsPrec    :: Int -> ReadS a
    readList     :: ReadS [a]
    readPrec     :: ReadPrec a		-- NEW
    readListPrec :: ReadPrec [a]	-- NEW

There are the following new libraries:

  Text.ParserCombinators.ReadP		Koens combinator parser
  Text.ParserCombinators.ReadPrec	Ditto, but with precedences

  Text.Read.Lex				An emasculated lexical analyser
					that provides the functionality
					of H98 'lex'

TcGenDeriv is changed to generate code that uses the new libraries.
The built-in instances of Read (List, Maybe, tuples, etc) use the new
libraries.


Other stuff
~~~~~~~~~~~
1. Some fixes the the plumbing of external-core generation. Sigbjorn
did most of the work earlier, but this commit completes the renaming and
typechecking plumbing.

2. Runtime error-generation functions, such as GHC.Err.recSelErr,
GHC.Err.recUpdErr, etc, now take an Addr#, pointing to a UTF8-encoded
C string, instead of a Haskell string.  This makes the *calls* to these
functions easier to generate, and smaller too, which is a good thing.

In particular, it means that MkId.mkRecordSelectorId doesn't need to
be passed "unpackCStringId", which was GRUESOME; and that in turn means
that tcTypeAndClassDecls doesn't need to be passed unf_env, which is
a very worthwhile cleanup.   Win/win situation.

3.  GHC now faithfully translates do-notation using ">>" for statements
with no binding, just as the report says.  While I was there I tidied
up HsDo to take a list of Ids instead of 3 (but now 4) separate Ids.
Saves a bit of code here and there.  Also introduced Inst.newMethodFromName
to package a common idiom.

Friday afternoon pet peeve removal: define (Util.notNull :: [a] -> Bool) and use it

------------------------
	Kill Type.splitRepFunTys
	------------------------

splitRepFunTys was a Bad Function that split up a function type
looking through even recursive newtypes.  Alas, it diverged if
when we had a recursive newtype with a function whose result was
the newtype itself.

I've replaced it with ordinary splitFunTys, plus a new function
Type.dropForAlls, which does what you would expect.

Binary Interface Files - stage 1
--------------------------------

This commit changes the default interface file format from text to
binary, in order to improve compilation performace.

To view an interface file, use 'ghc --show-iface Foo.hi'.

utils/Binary.hs is the basic Binary I/O library, based on the nhc98
binary I/O library but much stripped-down and working in terms of
bytes rather than bits, and with some special features for GHC: it
remembers which Module is being emitted to avoid dumping too many
qualified names, and it keeps track of a "dictionary" of FastStrings
so that we don't dump the same FastString more than once into the
binary file.  I'll make a generic version of this for the libraries at
some point.

main/BinIface.hs contains most of the Binary instances.  Some
instances are in the same module as the data type (RdrName, Name,
OccName in particular).  Most instances were generated using a
modified version of DrIFT, which I'll commit later.  However, editing
them by hand isn't hard (certainly easier than modifying
ParseIface.y).

The first thing in a binary interface is the interface version, so
nice error messages will be generated if the binary format changes and
you still have old interfaces lying around.  The version also now
includes the "way" as an extra sanity check.

Other changes
-------------

I don't like the way FastStrings contain both hashed strings (with
O(1) comparison) and literal C strings (with O(n) comparison).  So as
a first step to separating these I made serveral "literal" type
strings into hashed strings.  SLIT() still generates a literal, and
now FSLIT() generates a hashed string.  With DEBUG on, you'll get a
warning if you try to compare any SLIT()s with anything, and the
compiler will fall over if you try to dump any literal C strings into
an interface file (usually indicating a use of SLIT() which should be
FSLIT()).

mkSysLocal no longer re-encodes its FastString argument each time it
is called.

I also fixed the -pgm options so that the argument can now optionally
be separted from the option.

Bugfix: PrelNames declared Names for several comparison primops, eg.
eqCharName, eqIntName etc. but these had different uniques from the
real primop names.  I've moved these to PrimOps and defined them using
mkPrimOpIdName instead, and deleted some for which we don't have real
primops (Manuel: please check that things still work for you after
this change).

comments only

------------------------------
	Don't do CPR w/w for constants
	------------------------------

We don't want to do a CPR split for a constant
function.  So if the worker will get no (value) args,
we disable the CPR transformation.

This infelicity exposed a buglet in the full laziness
transformation; we were floating an expression outside
an InlineMe context.   I've take the blunderbuss approach
now, of effectively disabling full laziness inside an
InlineMe.  Seems reasonable.

Tidy up imports

--------------------------------------
	Yet another cut at the DmdAnal domains
	--------------------------------------

This version of the domain for demand analysis was developed
in discussion with Peter Sestoft, so I think it might at last
be more or less right!

Our idea is mentally to separate
	strictness analysis
from
	absence and boxity analysis

Then we combine them back into a single domain.  The latter
is all you see in the compiler (the Demand type, as before)
but we understand it better now.

---------------------------------------
	Fix a unboxed-binding bug in SpecConstr
	---------------------------------------

	[HEAD only]

This fixes a rather obscure bug in the constructor
specialiser discovered by Ralf Hinze.  It was
generating a specialised version of the function
with no arguments --- and the function returned an
unboxed type.

Solution: same as for worker-wrapper; add a dummy
argument.

Several files are affected because I added
CoreUtils.mkPiTypes, as a useful helper function.

Correct the zero-arg stuff in worker/wrapper generation

Cosmetica

-------------------------
	Implement thunk splitting
	-------------------------

This is a rather nice transformation that I found when
optimising some nofib programs.


Suppose x is used strictly (never mind whether it has the CPR
property).

      let
	x* = x-rhs
      in body

splitThunk transforms like this:

      let
	x* = case x-rhs of { I# a -> I# a }
      in body

Now simplifier will transform to

      case x-rhs of
	I# a ->	let x* = I# b
	        in body

which is what we want. Now suppose x-rhs is itself a case:

	x-rhs = case e of { T -> I# a; F -> I# b }

The join point will abstract over a, rather than over (which is
what would have happened before) which is fine.

Notice that x certainly has the CPR property now!

In fact, splitThunk uses the function argument w/w splitting
function, so that if x's demand is deeper (say U(U(L,L),L))
then the splitting will go deeper too.



** On the way, I tidied up some of the code in WwLib.

------------------------
	Fix the demand analyser
	------------------------

A spiffy new domain for demands, and definitions for lub/both
which are actually monotonic.   Quite a bit of related jiggling
around.

One of the original motivations was to do with functions like:

	sum n []     = n
	sum n (x:xs) = sum (n+x) xs

Even though n is returned boxed from the first case, we don't want
to get strictness
	S(L)V -> T
because that means we pass the box for n, and that is TERRIBLE.
So the new version errs on the side of unboxing, more like the forwards
analyser, and only passes the box if it is *definitely* needed, rather
than if it *may* be needed.

Fix worker-wrapper generation.  See commments in WwLib.mk_ww_str

Make absent-arg errors more descriptive

---------------------------------
	Switch to the new demand analyser
	---------------------------------

This commit makes the new demand analyser the main beast,
with the old strictness analyser as a backup.  When
DEBUG is on, the old strictness analyser is run too, and the
results compared.

WARNING: this isn't thorougly tested yet, so expect glitches.
Delay updating for a few days if the HEAD is mission critical
for you.

But do try it out.  I'm away for 2.5 weeks from Thursday, so
it would be good to shake out any glaring bugs before then.

------------------------
	More newtype squashing
	------------------------

Recursive newtypes were confusing the worker/wrapper generator.
This is because I originally got rid of opaque newtypes altogether,
then put them back for recursive ones only, and forgot to reinstate
the cunning stuff in the w/w stuff.

(Discovered by Sigbjorn; thanks!)

Import wibbles

----------------
	Squash newtypes
	----------------

This commit squashes newtypes and their coerces, from the typechecker
onwards.  The original idea was that the coerces would not get in the
way of optimising transformations, but despite much effort they continue
to do so.   There's no very good reason to retain newtype information
beyond the typechecker, so now we don't.

Main points:

* The post-typechecker suite of Type-manipulating functions is in
types/Type.lhs, as before.   But now there's a new suite in types/TcType.lhs.
The difference is that in the former, newtype are transparent, while in
the latter they are opaque.  The typechecker should only import TcType,
not Type.

* The operations in TcType are all non-monadic, and most of them start with
"tc" (e.g. tcSplitTyConApp).  All the monadic operations (used exclusively
by the typechecker) are in a new module, typecheck/TcMType.lhs

* I've grouped newtypes with predicate types, thus:
	data Type = TyVarTy Tyvar | ....
		  | SourceTy SourceType

	data SourceType = NType TyCon [Type]
			| ClassP Class [Type]
			| IParam Type

[SourceType was called PredType.]  This is a little wierd in some ways,
because NTypes can't occur in qualified types.   However, the idea is that
a SourceType is a type that is opaque to the type checker, but transparent
to the rest of the compiler, and newtypes fit that as do implicit parameters
and dictionaries.

* Recursive newtypes still retain their coreces, exactly as before. If
they were transparent we'd get a recursive type, and that would make
various bits of the compiler diverge (e.g. things which do type comparison).

* I've removed types/Unify.lhs (non-monadic type unifier and matcher),
merging it into TcType.

Ditto typecheck/TcUnify.lhs (monadic unifier), merging it into TcMType.

-----------------------------
	Get unbox-strict-fields right
	-----------------------------

The problem was that when a library was compiled *without* -funbox-strict-fields,
and the main program was compiled *with* that flag, we were wrongly treating
the fields of imported data types as unboxed.

To fix this I added an extra constructor to StrictnessMark to express whether
the "!" annotation came from an interface file (don't fiddle) or a source
file (decide whether to unbox).

On the way I tided things up:

* StrictnessMark moves to Demand.lhs, and doesn't have the extra DataCon
  fields that kept it in DataCon before.

* HsDecls.BangType has one constructor, not three, with a StrictnessMark field.

* DataCon keeps track of its strictness signature (dcRepStrictness), but not
  its "user strict marks" (which were never used)

* All the functions, like getUniquesDs, that used to take an Int saying how
  many uniques to allocate, now return an infinite list. This saves arguments
  and hassle.  But it involved touching quite a few files.

* rebuildConArgs takes a list of Uniques to use as its unique supply.  This
  means I could combine DsUtils.rebuildConArgs with MkId.rebuildConArgs
  (hooray; the main point of the previous change)


I also tidied up one or two error messages

Make a better CPR wrapper when profiling is in use

Arrange that we pass the real-world token *last* when
there are no arguments to a worker.  There might still
be type arguments, and most of GHC kind-of-expects the
type arguments to be first.

Unused imports and suchlike

Small cleanups.