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The type checker doesn't support lexically scoped type variables 
unless we are using the RelaxedPolyRec option.  Reasons: see
Note [Scoped tyvars] in TcBinds.

So I've changed DynFlags to add this implication, improved the 
documentation, and simplified the code in TcBinds somewhat.
(It's longer but only because of comments!)
 

It controls the number of simplifier phases run during optimisation. These are
numbered from n to 1 (by default, n=2). Phase 0 is always run regardless of
this flag. The flag is ignored with -O0 since (practically) no optimisation is
performed in that case.

Somehow we didn't have a separate flag for impredicativity; now we do.

Furthermore, Trac #2019 showed up a missing test for monotypes in data
constructor return types.  And I realised that we were even allowing
things like
	Num (forall a. a) => ...
which we definitely should not.  

This patch insists on monotypes in several places where we were (wrongly)
too liberal before.

Could be merged to 6.8 but no big deal.

Added API support for compiling Haskell to simplified Core, and for
compiling Core to machine code. The latter, especially, should be
considered experimental and has only been given cursory testing. Also
fixed warnings in DriverPipeline. Merry Christmas.

  This patch implements generalised list comprehensions, as described in 
  the paper "Comprehensive comprehensions" (Peyton Jones & Wadler, Haskell
  Workshop 2007).  If you don't use the new comprehensions, nothing
  should change.
  
  The syntax is not exactly as in the paper; see the user manual entry 
  for details.
  
  You need an accompanying patch to the base library for this stuff 
  to work.
  
  The patch is the work of Max Bolingbroke [batterseapower@hotmail.com], 
  with some advice from Simon PJ.
  
  The related GHC Wiki page is 
    http://hackage.haskell.org/trac/ghc/wiki/SQLLikeComprehensions 

This patch replaces -fspec-threshold by -fspec-constr-threshold and
-fliberate-case-threshold. The thresholds can be disabled by
-fno-spec-constr-threshold and -fno-liberate-case-threshold.

The number of iterations during the first run of phase 0 was erroneously
hardcoded to 3. It should be *at least* 3 (see comments in code) but can be
more.

This outputs the core after each simplifier phase (i.e., it produces less
information that -ddump-simpl-iterations).

The contents of bindings show at breakpoints and by :show bindings
is rendered using the same printer that :print uses.
But sometimes the output it gives spans over too many lines and the
user may want to be able to disable it.

   
  - :browse!
    a variant of :browse that lists children separately,
    not in context, and gives import qualifiers in comments

SimonM: I also added sorting by source location for interpreted
modules in :browse, and alphabetic sorting by name otherwise.  For
:browse *M, the locally-defined names come before the external ones.

  - :{ ..lines.. :} (multiline commands)
    allow existing commands to be spread over multiple lines
    to improve readability, both interactively and in .ghci
    (includes a refactoring that unifies the previous three
    command loops into one, runCommands, fed from cmdqueue,
    file, or readline)

  - :set
      now shows GHCi-specific flag settings (printing/
      debugger), as well as non-language dynamic flag 
      settings
    :show languages
      show active language flags
    :show packages
      show active package flags as well as implicitly 
      loaded packages

This patch renames the DOC_OPTIONS pragma to OPTIONS_HADDOCK. It also
adds "-- # ..."-style Haddock option pragmas, for compatibility with
code that use them.

Another change is that both of these two pragmas behave like
OPTIONS_GHC, i.e. they are only allowed at the top of the module, they
are ignored everywhere else and they are stored in the dynflags. There is
no longer any Haddock options in HsSyn.

Please merge this to the 6.8.2 branch when 6.8.1 is out, if appropriate.

This patch implements three new features:
* view patterns (syntax: expression -> pat in a pattern)
* working versions of record wildcards and record puns
See the manual for detailed descriptions.

Other minor observable changes:
* There is a check prohibiting local fixity declarations
  when the variable being fixed is not defined in the same let
* The warn-unused-binds option now reports warnings for do and mdo stmts

Implementation notes: 

* The pattern renamer is now in its own module, RnPat, and the
implementation is now in a CPS style so that the correct context is
delivered to pattern expressions.

* These features required a fairly major upheaval to the renamer.
Whereas the old version used to collect up all the bindings from a let
(or top-level, or recursive do statement, ...) and put them into scope
before renaming anything, the new version does the collection as it
renames.  This allows us to do the right thing with record wildcard
patterns (which need to be expanded to see what names should be
collected), and it allows us to implement the desired semantics for view
patterns in lets.  This change had a bunch of domino effects brought on
by fiddling with the top-level renaming.

* Prior to this patch, there was a tricky bug in mkRecordSelId in HEAD,
which did not maintain the invariant necessary for loadDecl.  See note
[Tricky iface loop] for details.

This required moving PackageId from PackageConfig to Module

test case is driver062.5

Using -stubdir together with hierarchical modules, -fvia-C, and --make
is essentially broken in 6.6.x.  Recently discovered by Cabal's use of
-stubdir.

Test cases: driver027/driver028 (I've updated them to use -fvia-C, in
order to test for this bug).

Fixes building with -Werror (i.e. validate) and GHC < 6.6

Fix exponential-time behaviour with type synonyms; rename -XPartiallyAppliedTypeSynonyms to -XLiberalTypeSynonyms

Fixes exponential behaviour present in GHC 6.6!

I renamed the flag because the old (not very old) name wasn't
describing what it does.

When -dasm-lint is turned on the register conflict graph is checked for 
internal consistency after each build/color pass. Make sure that all 
edges point to valid nodes, that nodes are colored differently to their
neighbours, and if the graph is supposed to be colored, that all nodes
actually have a color.

    
    The flag enables the use of Show instances in :print.
    By default they are not used anymore

Iterative coalescing interleaves conservative coalesing with the regular
simplify/scan passes. This increases the chance that nodes will be coalesced
as they will have a lower degree than at the beginning of simplify. The end
result is that more register to register moves will be eliminated in the
output code, though the iterative nature of the algorithm makes it slower
compared to non-iterative coloring.

Use -fregs-iterative  for graph coloring allocation with iterative coalescing
    -fregs-graph      for non-iterative coalescing.

The plan is for iterative coalescing to be enabled with -O2 and have a 
quicker, non-iterative algorithm otherwise. The time/benefit tradeoff
between iterative and not is still being tuned - optimal graph coloring
is NP-hard, afterall..

    
    This flag works like -fbreak-on-exception, but only stops
    on uncaught exceptions.

Changes too numerous to comment on, but here is some old history that
I saved: 


Wed Aug 15 11:07:13 BST 2007  Norman Ramsey <nr@eecs.harvard.edu>
  * type synonyms made consistent with new Cmm types

    M ./compiler/nativeGen/MachInstrs.hs -2 +2

Mon Aug 20 19:22:14 BST 2007  Norman Ramsey <nr@eecs.harvard.edu>
  * pushing return info beyond cmm into codegen

    M ./compiler/codeGen/Bitmap.hs r3
    M ./compiler/codeGen/CgBindery.lhs r3
    M ./compiler/codeGen/CgCallConv.hs r3
    M ./compiler/codeGen/CgCase.lhs r3
    M ./compiler/codeGen/CgClosure.lhs r3
    M ./compiler/codeGen/CgCon.lhs r3
    M ./compiler/codeGen/CgExpr.lhs r3
    M ./compiler/codeGen/CgForeignCall.hs -6 +7 r3
    M ./compiler/codeGen/CgHeapery.lhs r3
    M ./compiler/codeGen/CgHpc.hs +1 r3
    M ./compiler/codeGen/CgInfoTbls.hs r3
    M ./compiler/codeGen/CgLetNoEscape.lhs r3
    M ./compiler/codeGen/CgMonad.lhs r3
    M ./compiler/codeGen/CgParallel.hs r3
    M ./compiler/codeGen/CgPrimOp.hs +3 r3
    M ./compiler/codeGen/CgProf.hs r3
    M ./compiler/codeGen/CgStackery.lhs r3
    M ./compiler/codeGen/CgTailCall.lhs r3
    M ./compiler/codeGen/CgTicky.hs r3
    M ./compiler/codeGen/CgUtils.hs -1 +1 r3
    M ./compiler/codeGen/ClosureInfo.lhs r3
    M ./compiler/codeGen/CodeGen.lhs r3
    M ./compiler/codeGen/SMRep.lhs r3
    M ./compiler/nativeGen/AsmCodeGen.lhs -2 +2 r1
    M ./compiler/nativeGen/MachCodeGen.hs -3 +3 r1
    M ./compiler/nativeGen/MachInstrs.hs r1
    M ./compiler/nativeGen/MachRegs.lhs r1
    M ./compiler/nativeGen/NCGMonad.hs r1
    M ./compiler/nativeGen/PositionIndependentCode.hs r1
    M ./compiler/nativeGen/PprMach.hs r1
    M ./compiler/nativeGen/RegAllocInfo.hs r1
    M ./compiler/nativeGen/RegisterAlloc.hs r1

Mon Aug 20 20:54:41 BST 2007  Norman Ramsey <nr@eecs.harvard.edu>
  * put CmmReturnInfo into a CmmCall (and related types)

    M ./compiler/cmm/Cmm.hs -2 +1 r3
    M ./compiler/cmm/CmmBrokenBlock.hs -13 +12 r1
    M ./compiler/cmm/CmmCPS.hs -3 +3
    M ./compiler/cmm/CmmCPSGen.hs -8 +6 r1
    M ./compiler/cmm/CmmLint.hs -1 +1
    M ./compiler/cmm/CmmLive.hs -1 +1
    M ./compiler/cmm/CmmOpt.hs -3 +3
    M ./compiler/cmm/CmmParse.y -6 +6 r3
    M ./compiler/cmm/PprC.hs -3 +3
    M ./compiler/cmm/PprCmm.hs -7 +4 r2
    M ./compiler/codeGen/CgForeignCall.hs -7 +6 r2
    M ./compiler/codeGen/CgHpc.hs -1 r1
    M ./compiler/codeGen/CgPrimOp.hs -3 r1
    M ./compiler/codeGen/CgUtils.hs -1 +1 r1
    M ./compiler/nativeGen/AsmCodeGen.lhs -2 +2
    M ./compiler/nativeGen/MachCodeGen.hs -3 +3 r1

Tue Aug 21 18:09:13 BST 2007  Norman Ramsey <nr@eecs.harvard.edu>
  * add call info in nativeGen

    M ./compiler/nativeGen/AsmCodeGen.lhs r1
    M ./compiler/nativeGen/MachInstrs.hs r1
    M ./compiler/nativeGen/MachRegs.lhs r1
    M ./compiler/nativeGen/NCGMonad.hs r1
    M ./compiler/nativeGen/PositionIndependentCode.hs r1
    M ./compiler/nativeGen/PprMach.hs r1
    M ./compiler/nativeGen/RegAllocInfo.hs r1

Wed Aug 22 16:41:58 BST 2007  Norman Ramsey <nr@eecs.harvard.edu>
  * ListGraph is now a newtype, not a synonym
  The resultant bookkeepping is unenviable, but the change
  greatly simplifies our ability to make Cmm things propertly
  Outputable for both list-graph and zipper-graph representations.

    M ./compiler/cmm/Cmm.hs -5 +3
    M ./compiler/cmm/CmmCPS.hs -2 +2
    M ./compiler/cmm/CmmCPSGen.hs -1 +1
    M ./compiler/cmm/CmmContFlowOpt.hs -3 +3
    M ./compiler/cmm/CmmCvt.hs -2 +2
    M ./compiler/cmm/CmmInfo.hs -2 +3
    M ./compiler/cmm/CmmLint.hs -1 +1
    M ./compiler/cmm/CmmOpt.hs -2 +2
    M ./compiler/cmm/PprC.hs -1 +1
    M ./compiler/cmm/PprCmm.hs -5 +8
    M ./compiler/cmm/PprCmmZ.hs -7 +1
    M ./compiler/codeGen/CgMonad.lhs -1 +1
    M ./compiler/nativeGen/AsmCodeGen.lhs -15 +15
    M ./compiler/nativeGen/MachCodeGen.hs -2 +2
    M ./compiler/nativeGen/PositionIndependentCode.hs -6 +6
    M ./compiler/nativeGen/PprMach.hs -3 +2
    M ./compiler/nativeGen/RegAllocColor.hs +1
    M ./compiler/nativeGen/RegAllocLinear.hs -4 +5
    M ./compiler/nativeGen/RegCoalesce.hs -6 +6
    M ./compiler/nativeGen/RegLiveness.hs -12 +12

Thu Aug 23 13:44:49 BST 2007  Norman Ramsey <nr@eecs.harvard.edu>
  * diagnostic assistance in case fromJust fails

    M ./compiler/nativeGen/MachCodeGen.hs -2 +5

Thu Aug 23 14:07:28 BST 2007  Norman Ramsey <nr@eecs.harvard.edu>
  * give every block, even the first, a label
    With branch-chain elimination, the first block of a procedure
    might be the target of a branch.  This actually happens to 
    a dozen or more procedures in the run-time system.

    M ./compiler/nativeGen/PprMach.hs -8 +3

Fri Aug 24 17:27:04 BST 2007  Norman Ramsey <nr@eecs.harvard.edu>
  * clean up the code in PprMach

    M ./compiler/nativeGen/PprMach.hs -16 +14

Fri Aug 24 19:35:03 BST 2007  Norman Ramsey <nr@eecs.harvard.edu>
  * a bunch of impedance matching to get the compiler to build, plus 
   * the plus is diagnostics for unreachable code, which required
     moving a lot of prettyprinting code

    M ./compiler/cmm/Cmm.hs -7 +5
    M ./compiler/cmm/CmmCPSZ.hs -1 +1
    M ./compiler/cmm/CmmCvt.hs -8 +8
    M ./compiler/cmm/CmmParse.y -4 +3
    M ./compiler/cmm/MkZipCfg.hs -19 +9
    M ./compiler/cmm/PprCmmZ.hs -118 +4
    M ./compiler/cmm/ZipCfg.hs -1 +13
    M ./compiler/cmm/ZipCfgCmm.hs -10 +129
    M ./compiler/main/HscMain.lhs -4 +4
    M ./compiler/nativeGen/NCGMonad.hs -2 +2
    M ./compiler/nativeGen/RegAllocInfo.hs -3 +3

Fri Aug 31 14:38:02 BST 2007  Norman Ramsey <nr@eecs.harvard.edu>
  * fix a warning about an import

    M ./compiler/nativeGen/RegAllocColor.hs -1 +1

Avoid coalescing nodes in the register conflict graph if the
new node will not be trivially colorable. Also remove the
front end aggressive coalescing pass.
  
For typical Haskell code the graph coloring allocator now does
about as well as the linear allocator.
  
For code with a large amount of register pressure it does much
better, but takes longer.
  
For SHA1.lhs from darcs on x86
   
          spills    reloads    reg-reg-moves
          inserted   inserted  left in code   compile-time
  linear    1068      1311        229            7.69(s)
  graph      387       902        340           16.12(s)

Older GHCs can't parse OPTIONS_GHC.
This also changes the URL referenced for the -w options from
WorkingConventions#Warnings to CodingStyle#Warnings for the compiler
modules.