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The trouble here is that given

    {-# LANGUAGE DataKinds, TypeFamilies #-}
    data instance Foo a = Bar (Bar a)

we want to get a sensible message that we can't use the promoted 'Bar'
constructor until after its definition; it's a staging error.  Bud the
staging mechanism that we use for vanilla data declarations don't work
here.

Solution is to perform strongly-connected component analysis on the
instance declarations. But that in turn means that we need to track
free-variable information on more HsSyn declarations, which is why
so many files are touched.  All the changes are boiler-platey except
the ones in TcInstDcls.

Not only does this fix Trac #5853, but it also eliminate
the horrid SimplEqsOnly part of the constraint simplifier.

The new plan is described in TcRules
 Note [Simplifying RULE constraints]

There was an ASSERT which does not hold during type checking (and
should not) which is later checked by Core Lint

This is the last major addition to the kind-polymorphism story,
by allowing (Trac #5938)

 type family F a   -- F :: forall k. k -> *
 data T a          -- T :: forall k. k -> *
 type instance F (T (a :: Maybe k)) = Char

The new thing is the explicit 'k' in the type signature on 'a',
which itself is inside a type pattern for F.

Main changes are:

* HsTypes.HsBSig now has a *pair* (kvs, tvs) of binders,
  the kind variables and the type variables

* extractHsTyRdrTyVars returns a pair (kvs, tvs)
  and the function itself has moved from RdrHsSyn to RnTypes

* Quite a bit of fiddling with
     TcHsType.tcHsPatSigType and tcPatSig
  which have become a bit simpler.  I'm still not satisfied
  though.  There's some consequential fiddling in TcRules too.

* Removed the unused HsUtils.collectSigTysFromPats

There's a consequential wibble to Haddock too

Two problems, for now at any rate
  a) Breaks the build with lots of errors like
        No instance for (Show (IO ())) arising from a use of `print'
  b) Discussion of the approache hasn't converged yet
     (Simon M had a number of suggestions)

This reverts commit eecd7c98.

This command allows you to lift user stmts in GHCi into an IO monad
that implements the GHC.GHCi.GHCiSandboxIO type class. This allows for
easy sandboxing of GHCi using :runmonad and Safe Haskell.

Longer term it would be nice to allow a more general model for the Monad
than GHCiSandboxIO but delaying this for the moment.

This is a partial fix for #2786.  It seems we still don't get
NonTermination exceptions for interpreted computations, but we do now
get the BlockedIndefinitely family.

Display class method signature instead of user-provided signature.

Patch by Sam Anklesaria <amsay@amsay.net>

This reverts commit 991f1419.

Firstly, we were rounding up too much, such that the smallest delay
was 20ms.  Secondly, there is no need to use millisecond resolution on
a 64-bit machine where we have room in the TSO to use the normal
nanosecond resolution that we use elsewhere in the RTS.

The threaded RTS had a fix for this a long time ago (#1623) but this
patch applies a similar fix to the non-threaded RTS.

decomposition in the constraint solver.

* The following commits made validate fail on OS X (Lion):
65aaa9b2 and c294d95d
* I just commented out all offending code until it validated again. The original authors need to clean this up.

constraint generation during solveInteractCts, needed for polytype
equality decomposition. More commentary to follow.

this was the reason for the regression of T3064.

so that it does not print a quote in front of a promoted
TyCon in a Kind.

I also systematically renamed
   PromotedTypeTyCon  -->   PromotedTyCon
   PromotedDataTyCon  -->   PromotedDataCon

It is still Not Right, but can't readily be fixed until
the major overhaul of TH described in Simon PJ's 2011
GHC blog post.  (Then type splices will be done in
the renamer.)

Sometimes when a variable is out of scope in the type-checker,
it's not a GHC bug, but rather a TH staging error.  See
Note [Out of scope might be a staging error] in TcEnv.

This showed up as Trac #5795.