This change allows you to write
	f :: (Eq a) => (Ord b) => a -> b -> b
Previously you could only have a forall and context after '->'
but not after '=>' which is strange and inconsistent.

Making the parser a bit more generous didn't change the number
of shift/reduce conflicts.

tc236 tests.

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.

You now say
    deriving instance Cxt => Head

It looks like this was an experiment that accidentally got committed,
somewhere between 6.0 and 6.2.

f () = do { x :: Bool <- return True; ... }

For some reason the production for 'pat' required 'infixexp' on the
LHS of a do-notation binding.  This patch makes it an 'exp', which 
thereby allows an expression with a type sig.

Happily, there are no new shift-reduce errors, so I don't think this
will break anything else.

1. Record disambiguation (-fdisambiguate-record-fields)

In record construction and pattern matching (although not
in record updates) it is clear which field name is intended
even if there are several in scope.  This extension uses
the constructor to disambiguate.  Thus
	C { x=3 }
uses the 'x' field from constructor C (assuming there is one)
even if there are many x's in scope.


2. Record punning (-frecord-puns)

In a record construction or pattern match or update you can 
omit the "=" part, thus
	C { x, y }
This is just syntactic sugar for
	C { x=x, y=y }


3.  Dot-dot notation for records (-frecord-dot-dot)

In record construction or pattern match (but not update) 
you can use ".." to mean "all the remaining fields".  So

	C { x=v, .. }

means to fill in the remaining fields to give

	C { x=v, y=y }

(assuming C has fields x and y).  This might reasonably
considered very dodgy stuff.  For pattern-matching it brings
into scope a bunch of things that are not explictly mentioned;
and in record construction it just picks whatver 'y' is in
scope for the 'y' field.   Still, Lennart Augustsson really
wants it, and it's a feature that is extremely easy to explain.


Implementation
~~~~~~~~~~~~~~
I thought of using the "parent" field in the GlobalRdrEnv, but
that's really used for import/export and just isn't right for this.
For example, for import/export a field is a subordinate of the *type
constructor* whereas here we need to know what fields belong to a
particular *data* constructor.

The main thing is that we need to map a data constructor to its
fields, and we need to do so in the renamer.   For imported modules
it's easy: just look in the imported TypeEnv.  For the module being
compiled, we make a new field tcg_field_env in the TcGblEnv.
The important functions are
	RnEnv.lookupRecordBndr
	RnEnv.lookupConstructorFields

There is still a significant infelicity in the way the renamer
works on patterns, which I'll tackle next.


I also did quite a bit of refactoring in the representation of
record fields (mainly in HsPat).***END OF DESCRIPTION***

Place the long patch description above the ***END OF DESCRIPTION*** marker.
The first line of this file will be the patch name.


This patch contains the following changes:

M ./compiler/deSugar/Check.lhs -3 +5
M ./compiler/deSugar/Coverage.lhs -6 +7
M ./compiler/deSugar/DsExpr.lhs -6 +13
M ./compiler/deSugar/DsMeta.hs -8 +8
M ./compiler/deSugar/DsUtils.lhs -1 +1
M ./compiler/deSugar/MatchCon.lhs -2 +2
M ./compiler/hsSyn/Convert.lhs -3 +3
M ./compiler/hsSyn/HsDecls.lhs -9 +25
M ./compiler/hsSyn/HsExpr.lhs -13 +3
M ./compiler/hsSyn/HsPat.lhs -25 +63
M ./compiler/hsSyn/HsUtils.lhs -3 +3
M ./compiler/main/DynFlags.hs +6
M ./compiler/parser/Parser.y.pp -13 +17
M ./compiler/parser/RdrHsSyn.lhs -16 +18
M ./compiler/rename/RnBinds.lhs -2 +2
M ./compiler/rename/RnEnv.lhs -22 +82
M ./compiler/rename/RnExpr.lhs -34 +12
M ./compiler/rename/RnHsSyn.lhs -3 +2
M ./compiler/rename/RnSource.lhs -50 +78
M ./compiler/rename/RnTypes.lhs -50 +84
M ./compiler/typecheck/TcExpr.lhs -18 +18
M ./compiler/typecheck/TcHsSyn.lhs -20 +21
M ./compiler/typecheck/TcPat.lhs -8 +6
M ./compiler/typecheck/TcRnMonad.lhs -6 +15
M ./compiler/typecheck/TcRnTypes.lhs -2 +11
M ./compiler/typecheck/TcTyClsDecls.lhs -3 +4
M ./docs/users_guide/flags.xml +7
M ./docs/users_guide/glasgow_exts.xml +42

- This patch removes "newtype family" declarations.
- "newtype instance" declarations can now be instances of data families
- This also fixes bug #1331

  ** This patch changes the interface format.  All libraries and all of **
  ** Stage 2 & 3 need to be re-compiled from scratch.                   **

This fixes Trac #1065.  The fix is just to emit a decent error message
rather than crash.  The situation is this:

  f x = ... [d| $(..stuff..); 
                f x = v :: T |] ...

TH wants to rename and typecheck the bracket; but it can't run the 
nested splice yet.  That seems hard, because we know nothing about v, T,
which are, presumably bound by the splice.

The original TH paper says this isn't allowed, and now it's checked for
properly (in the parser, in fact) rather than causing a crash.  In the
fullness of time we might want to do something more flexible, but not now.

The class is named IsString with the single method fromString.
Overloaded strings work the same way as overloaded numeric literals.
In expressions a string literals gets a fromString applied to it.
In a pattern there will be an equality comparison with the fromString:ed literal.

Use -foverloaded-strings to enable this extension.
 

- This patch cleans up the HsSyn representation of type family declarations.
- The new representation is not only less delicate, it also simplified teh code
  a bit.
- I took the opportunity of stream lining the terminology and function names
  at the same time.
- I also updated the description on the wiki at
  <http://hackage.haskell.org/trac/ghc/wiki/TypeFunctionsSyntax>

This tidy-up, triggered by Trac #1068, re-factors the way that 'deriving' 
happens.  It took me way longer than I had intended.  The main changes,
by far are to TcDeriv; everyting else is a minor consequence.

While I was at it, I changed the syntax for standalone deriving, so that
it goes
	derive instance Show (T a)

(instead of "derive Show for T").  However, there's still an implicit
context, generated by the deriving code, and I wonder if it shouldn't really
be
	derive instance (..) => Show (T a)
but I have left it simple for now.

I also added a function Type.substTyVars, and used it here and there, which
led to some one-line changes otherwise unrelated (sorry).

Loose ends:
  * 'deriving Typeable' for indexed data types is still not right
  * standalone deriving should be documented

Adding a {-# GENERATED "SourceFile" SourceSpan #-} <expr> pragma.
This will be used to generate coverage for tool generated (or quoted) code.
The pragma states the the expression was generated/quoted from the stated
source file and source span.

- With -findexed-types, equational constraints can appear in contexts 
  wherever class predicates are allowed.
- The two argument types need to be boxed and rank 0.

* This is only a slight generalisation of the parser, so that family
  declarations on the toplevel and in classes are uniform.
* I didn't allow that right away as it is a bit tricky to avoid reduce/reduce 
  conflicts.

Push this further along, and fix build problems in the first patch.

Linear implicit parameters have been in GHC quite a while,
but we decided they were a mis-feature and scheduled them for
removal.  This patch does the job.

Mon Sep 18 19:13:47 EDT 2006  Manuel M T Chakravarty <chak@cse.unsw.edu.au>
  * Kind sig for toplevel family decls is optional
  Sat Aug 26 19:03:50 EDT 2006  Manuel M T Chakravarty <chak@cse.unsw.edu.au>
    * Kind sig for toplevel family decls is optional
    - Kind sigs are still compulsory for AT family decls.  Changing this is more 
      tricky, as AT decls don't have the family keyword and hence look like empty 
      data decls.  That impacts reduce/reduce conflicts and/or the criteria for 
      checking whether a TyData variant is a family signature.
    - Also removed iso from the syntax (it's still in the lexer in case we want to
      resurrect it). 

Mon Sep 18 18:58:51 EDT 2006  Manuel M T Chakravarty <chak@cse.unsw.edu.au>
  * Extend Class.Class to include the TyCons of ATs
  Wed Aug 16 16:15:31 EDT 2006  Manuel M T Chakravarty <chak@cse.unsw.edu.au>
    * Extend Class.Class to include the TyCons of ATs

Tue Sep 12 16:57:32 EDT 2006  Manuel M T Chakravarty <chak@cse.unsw.edu.au>
  * Type tags in import/export lists
  - To write something like GMapKey(type GMap, empty, lookup, insert)
  - Requires -findexed-types

Tue Aug 15 20:16:00 EDT 2006  Manuel M T Chakravarty <chak@cse.unsw.edu.au>
  * Use family and instance keyword to identify indexed types

Tue Aug 15 17:02:53 EDT 2006  Manuel M T Chakravarty <chak@cse.unsw.edu.au>
  * Remove checkTopTypeD

Thu Aug  3 19:29:38 EDT 2006  Manuel M T Chakravarty <chak@cse.unsw.edu.au>
  * Added error checks & fixed bugs

Tue Aug  1 14:10:39 EDT 2006  Manuel M T Chakravarty <chak@cse.unsw.edu.au>
  * Revised kind signatures