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Fixed this 6.4 TODO item listed on the wiki:

 PowerPC Linux (32bit): Fix GHCi FFI calls for arguments that are not passed on the stack (ByteCodeFFI).

Separated the code for Darwin and Linux (for PowerPC only).  Rewrote the Linux version to account for the differences in the ABIs.

All changes are inside #if powerpc_TARGET_ARCH && linux_TARGET_OS except:
  - import Data.List ( mapAccumL )      (used by my code)
  - small fix to a comment typo in Wolfgang's Darwin code
  - changed 'undefined' to a more meaningful 'error' message if
     mkMarshalCode is unimplemented

Ran regression tests.  It passes them all except for the ones that are broken because of the 'wrapper' problems currently being addressed.

system is replaced with rawSystem. This allows to use path names with embeded
spaces under Windows. This is the same story as with hsc2hs but ghc-pkg is
used only with GHC, so the change will not affect other compilers.
Cabal uses "Program Files" as default installation path and this manifests
the bug.

Fix what looks like a cut-n-pasto in retry#: the MAYBE_GC() was
specifying readTVarzh_fast as the restart point, leading to a crash if
MAYBE_GC triggered a GC in here.

Document some missing flags.

Fix for ghci on sparc.

lookupFixityRn: we should be using loadHomeInterface rather than
loadSrcInterface here, because this is a system-ish import rather than
an explicit user import.  In particular, loadSrcInterface will
complain if the module in question is hidden, but this is not what we
want.

Add Distribution.Compat to libghccompat

Mention problem with ld on Windows

Remove dead branch of #elif.

When built as a ghc utility, Compat.RawSystem is always available.
When built as an nhc98 utility, -DBUILD_NHC symbol allows for getting
the best otherwise-available version of rawSystem.

Add System.Cmd to c-files dependencies.

It seems that ghc-6.2.x doesn't have Compat.RawSystem, so should use
System.Cmd instead.  And ghc-5.04.x doesn't export rawSystem from
there either, so should use the simple inline definition.

Wibble to ambiguity reporting

Improve error message for top-level ambiguity

Remove null where

Wibble; fixes tcTyVarDetails breakage

Add assert

Don't use PK_Word64 and ASSIGN_Word64 on 64-bit machines;
they just make the .hc files harder to read without adding any benefit.

Allow trailing semicolon in GADT constructor list

------------------------
          GADTs and unification
  	------------------------

1. Adjustment to typechecking of pattern matching the call to
   gadtRefineTys in TcPat.  Now wobbly types are treated as wild
   cards in the unification process.

2. Add the WildCard possibility to the BindFlag in types/Unify.lhs

3. Some related refactoring of tcMatchTys etc.

recent non-GHCs can use System.Cmd.rawSystem

`rawSystem` is only available in GHC.

Use rawSystem where appropriate.

------------------
          Fix an mdo bug
  	------------------

Embarassingly, this bug makes GHC either panic (for some programs) or
go into a loop (on others) in a recursive mdo that involves a
polymorphic function.  Urk!

The fix is twofold:
  a) add a missing bindInstsOfLocalFuns to tcStmtAndThen (RecStmt case)
  b) bind the correct set of variables in dsRecStmt

I added some explanatory comments about RecStmt in HsExpr too.

The tests is mdo/should_compile/mdo006

ghc/mk/config.mk was never being included in ordinary Makefiles.  It
was only included in the top-level fptools/Makefile for the purposes
of obtaining binary distribution settings.

This fixes that problem, and now as a side-effect $(GhcHasReadline)
will start working again.

Import trimming

Remove redundant Subst hi-boot files

Fix to the pre-Xmas simplifier changes, which should make 
everything work again.  I'd forgotten to attend to this
corner.  Still not properly tested I fear.

Also remove dead code from SimplEnv, and simplify the remainder (hooray).

Wibble

import wibble

---------------------------
          Refactor the simplifier
  	---------------------------

Driven by a GADT bug, I have refactored the simpifier, and the way GHC
treats substitutions.  I hope I have gotten it right.  Be cautious about updating.

* coreSyn/Subst.lhs has gone

* coreSyn/CoreSubst replaces it, except that it's quite a bit simpler

* simplCore/SimplEnv is added, and contains the simplifier-specific substitution
  stuff

Previously Subst was trying to be all things to all men, and that was making
it Too Complicated.

There may be a little more code now, but it's much easier to understand.

Reset the export flag for the new bindings in LiberateCase

Further wibbles to the scoped-tyvar story.

This commit tidies up the ATyVar in TcTyThing, making it
	ATyVar Name Type
instead of the previous misleading
	ATyVar TyVar Type

But the main thing is that we must take care with definitions
like this:

	type T a = forall b. b -> (a,b)

	f :: forall c. T c
	f = ...

Here, we want only 'c' to scope over the RHS of f.  The renamer ensures
that... but we must also take care that we freshly instantiate the 
expanded type signature (forall c b. b -> (c,b)) before checking f's RHS,
so that we don't get false sharing between uses of T.

Simplifications, dead code elimination

minor nomenclature wibble

Enable scoped type variables only where there is an explicit forall

---------------------------------
          Template Haskell: names again
  	---------------------------------

On 2 Dec 04 I made this commit (1.58 in Convert.lhs)

    Fix a Template Haskell bug that meant that top-level names created
    with newName were not made properly unique.

But that just introduced a new bug!  THe trouble is that names created by
newName are NameUs; but I was *also* using NameU for names of free varaibles,
such as the 'x' in the quoted code here
	f x = $( g [| \y -> (x,y) |])

But when converting to HsSyn, the x and y must be treated diffferently.
The 'x' must convert to an Exact RdrName, so that it binds to the 'x' that's
in the type environment; but the 'y' must generate a nice unique RdrName.

So this commit adds NameL for the lexically-scoped bindings like 'x'.

----------------------------------------
	     Add more scoped type variables
	----------------------------------------

Now the top-level forall'd variables of a type signature scope
over the right hand side of that function.

	f :: a -> a
	f x = ....

The type variable 'a' is in scope in the RHS, and in f's patterns.

It's implied by -fglasgow-exts, but can also be switched off independently
using -fscoped-type-variables (and the -fno variant)

----------------------------------------
     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 -fwarn-orphans flag
	--------------------------

This gives a decent report for modules that contain 'orphan' instance and
rule declarations.  These are to be avoided, because GHC has to proactively
read the interface file every single time, just in case the instance/rule is
needed.

The flag just gives a convenient way of identifying the culprits.