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The I# constructor is always removed when we make a unique later
anyway, so this just saves a bit of time and allocation.

Now that the module restriction has been lifted, the auto-hiding is
mostly not required.  GHC itself automatically hides old versions of a
package.

This patch pushes through one fundamental change: a module is now
identified by the pair of its package and module name, whereas
previously it was identified by its module name alone.  This means
that now a program can contain multiple modules with the same name, as
long as they belong to different packages.

This is a language change - the Haskell report says nothing about
packages, but it is now necessary to understand packages in order to
understand GHC's module system.  For example, a type T from module M
in package P is different from a type T from module M in package Q.
Previously this wasn't an issue because there could only be a single
module M in the program.

The "module restriction" on combining packages has therefore been
lifted, and a program can contain multiple versions of the same
package.

Note that none of the proposed syntax changes have yet been
implemented, but the architecture is geared towards supporting import
declarations qualified by package name, and that is probably the next
step.

It is now necessary to specify the package name when compiling a
package, using the -package-name flag (which has been un-deprecated).
Fortunately Cabal still uses -package-name.

Certain packages are "wired in".  Currently the wired-in packages are:
base, haskell98, template-haskell and rts, and are always referred to
by these versionless names.  Other packages are referred to with full
package IDs (eg. "network-1.0").  This is because the compiler needs
to refer to entities in the wired-in packages, and we didn't want to
bake the version of these packages into the comiler.  It's conceivable
that someone might want to upgrade the base package independently of
GHC.

Internal changes:

  - There are two module-related types:

        ModuleName      just a FastString, the name of a module
        Module          a pair of a PackageId and ModuleName

    A mapping from ModuleName can be a UniqFM, but a mapping from Module
    must be a FiniteMap (we provide it as ModuleEnv).

  - The "HomeModules" type that was passed around the compiler is now
    gone, replaced in most cases by the current package name which is
    contained in DynFlags.  We can tell whether a Module comes from the
    current package by comparing its package name against the current
    package.

  - While I was here, I changed PrintUnqual to be a little more useful:
    it now returns the ModuleName that the identifier should be qualified
    with according to the current scope, rather than its original
    module.  Also, PrintUnqual tells whether to qualify module names with
    package names (currently unused).

Docs to follow.

In all cases the namespace is known from the context, so this saves 1
byte per variable binding/occurrence (a few percent per iface file).

In Haskell 98, pattern bindings are generalised.  Thus in
	(f,g) = (\x->x, \y->y)
both f and g will get polymorphic types.  I have become convinced
that generalisation for pattern-bound variables is just a bridge
toof far. It is (I claim) almost never needed, and it adds significant
complication.  (All the more so if we add bang patterns.)

So the flag -fmono-pat-binds switches off generalisation for pattern
bindings.  (A single variable is treated as a degnerate funtction
binding.)  

Furthremore, as an experiment, I'm making it the default.  I want
to see how many progarms fail with monomorphic pattern bindings.

You can recover the standard behaviour with -fno-mono-pa-binds.

Don Stewart and Duncan Coutts encountered the following situation.
	f = <rhs>
	{-# RULES f ... #-}
where f is not exported, but appears in the inlinings of other
functions that are exported.  Then what happened was that the desugarer
produced this:
	M.f = f
	f = <rhs>
where the rules get attached to the M.f. But since M.f's RHS is trivial
(just f) it was unconditionally inlinined at all its call sites, 
thereby losing the RULES attached to it.

This *is* a fragile aspect of rules. However this fix solves the 
problem by instead generating
	f = M.f
	M.f = <rhs>

A pretty small chanage to the desugarer does the job.  It still feels
a little fragile, bt it's certainly more robust than before.

Don't know how I managed to use this before... maybe a different regex
library.

	MERGE TO STABLE

I'd forgotten to compare the per-instance overlap flag when 
comparing interface files, and that meant that consequential
recompilations weren't being triggered when the only change
was to add -fallow-overlapping-instances

Fixes Trac bug #824

This experimental flag, -fdicts-cheap, makes a let-binding that bind a
value of dictionary type look cheap.  That in turn leads to more
eta expansion.  Instead of
	f = /\a. \(d1:Ord a). let d2:Ord [a] = dfOrd a d1 in
                 \(x:a). <stuff>
which has arity 1, you get
	f = /\a. \(d1:Ord a). \(x:a).
	         let d2:Ord [a] = dfOrd a d1 in <stuff>
Now f has arity 2.

This can cretainly waste dictionary-construction work, if f is
partially applied to its dictionary argument.  However it has knock-on
effects.  Because f has arity 2, we won't float (f Int d) out of
	\x. h (f Int d)
Floating f out of this lambda makes it impossible for an h/f fusion
rule to fire; and this unexpected loss of RULE application was the
immediate reason for implementing this flag. (Roman Leshchinskiy came
across this when working on array fusion.)


I've implemented the change only in CoreUtils.arityType, which
only affects eta expansion.  I thought of putting the change in
exprIsCheap, which is a more systematic place (the former calls
the latter) but

	a) I wanted this under flag control, and the flags 
	are not readily available to all callers of exprIsCheap

	b) I'm not 100% convinced that this change is a good
	idea, so it's reasonable to do the narrowest change
	that solves the immediate problem.

There are still some fixes required to get the threaded RTS compilable
with the NCG, and apparently there are problems on 32-bit archs too.

HEAD doesn't z-encode external-core output (unlike 6.4). I suppose, that
this is unwanted behaviour. It probably results from this patch:

========================================================================
Fri Jan  6 17:30:19 CET 2006  simonmar
  * [project @ 2006-01-06 16:30:17 by simonmar]
  Add support for UTF-8 source files

[...]    

Z-encoding has been moved right to the back end.  Previously we
used to Z-encode every identifier on the way in for simplicity,
and only decode when we needed to show something to the user.
Instead, we now keep every string in its UTF-8 encoding, and
Z-encode right before printing it out.

[...]
========================================================================

Greetings
Jan

Hello, this is my first patch contributed to GHC. If there are any
inadequacies about it (maybe like this introductory disclaimer), please
let me know about it.

So, the need for this patch arose, while I was involved with processing
hcr files (external core output) and I noticed, that the output didn't
fully conform to the specification [1].
No %local-tags were used, which turned out to be a real nuisance as it
was not possible to determine which VDEFs can be erased in a further
optimization process and which ones are exported by the module.

Since the specification does not define the meaning of the %local-tag, I
assume, it makes sense, that it tags all functions, that are not
exported by the module.

The patch does not fully comply to the specification, as in my
implementation a local tag may appear before a VDEF but not before a
VDEFG.

[1] An External Representation for the GHC Core Language
    (DRAFT for GHC5.02), page 3, line 1

Greetings
Jan

darcs-all may now be run with any POSIX-compatible /bin/sh.

say "{-# SOURCE #-}" rather than "{- SOURCE -}" in warning message.
Fixes http://hackage.haskell.org/trac/ghc/ticket/812

This appears to be a long-standing bug, discovered by BlueSpec 
(ravi@bluespec.com), Trac bug #795

The problem was that in an IP binding group, the dict bindings
aren't necessarily in dependency order; and if they aren't 
we get a core-lint error.

Test tc203 checks this case.  (Though whether it shows up at
all depends a bit on accidental factors of binding ordering.)

Fixes #809

static relative offsets (eg .long l1-l2) are restricted to 32 bits on
x86-64 due to lack of support in the linker.  The codegen, NCG and
runtime work around this, using 32-bit offsets instead of 64.
However, we were missing a workaround for vector tables, and it
happened to work by accident because the offsets were always positive
and resolved by the assembler.  The bug was exposed by using the NCG
to compile the RTS, where the offsets became negative, again by
accident.

So that we can build the RTS with the NCG.

so that we can calculate deterministic offsets to some of the fields
of Capability.