Implement -XConstraintKind

Basically as documented in http://hackage.haskell.org/trac/ghc/wiki/KindFact,
this patch adds a new kind Constraint such that:

  Show :: * -> Constraint
  (?x::Int) :: Constraint
  (Int ~ a) :: Constraint

And you can write *any* type with kind Constraint to the left of (=>):
even if that type is a type synonym, type variable, indexed type or so on.

The following (somewhat related) changes are also made:
 1. We now box equality evidence. This is required because we want
    to give (Int ~ a) the *lifted* kind Constraint
 2. For similar reasons, implicit parameters can now only be of
    a lifted kind. (?x::Int#) => ty is now ruled out
 3. Implicit parameter constraints are now allowed in superclasses
    and instance contexts (this just falls out as OK with the new
    constraint solver)

Internally the following major changes were made:
 1. There is now no PredTy in the Type data type. Instead
    GHC checks the kind of a type to figure out if it is a predicate
 2. There is now no AClass TyThing: we represent classes as TyThings
    just as a ATyCon (classes had TyCons anyway)
 3. What used to be (~) is now pretty-printed as (~#). The box
    constructor EqBox :: (a ~# b) -> (a ~ b)
 4. The type LCoercion is used internally in the constraint solver
    and type checker to represent coercions with free variables
    of type (a ~ b) rather than (a ~# b)

1 files changed, 7 insertions, 7 deletions

diff --git a/compiler/rename/RnPat.lhs b/compiler/rename/RnPat.lhs
index 975969d0b1..a6f619a447 100644
--- a/compiler/rename/RnPat.lhs
+++ b/compiler/rename/RnPat.lhs
@@ -155,15 +155,15 @@ matchNameMaker ctxt = LamMk report_unused
                       StmtCtxt GhciStmt -> False
                       _                 -> True
 
-newName :: NameMaker -> Located RdrName -> CpsRn Name
-newName (LamMk report_unused) rdr_name
+newPatName :: NameMaker -> Located RdrName -> CpsRn Name
+newPatName (LamMk report_unused) rdr_name
   = CpsRn (\ thing_inside -> 
 	do { name <- newLocalBndrRn rdr_name
 	   ; (res, fvs) <- bindLocalName name (thing_inside name)
 	   ; when report_unused $ warnUnusedMatches [name] fvs
 	   ; return (res, name `delFV` fvs) })
 
-newName (LetMk is_top fix_env) rdr_name
+newPatName (LetMk is_top fix_env) rdr_name
   = CpsRn (\ thing_inside -> 
         do { name <- case is_top of
                        NotTopLevel -> newLocalBndrRn rdr_name
@@ -253,7 +253,7 @@ rnPat ctxt pat thing_inside
   = rnPats ctxt [pat] (\pats' -> let [pat'] = pats' in thing_inside pat')
 
 applyNameMaker :: NameMaker -> Located RdrName -> RnM Name
-applyNameMaker mk rdr = do { (n, _fvs) <- runCps (newName mk rdr); return n }
+applyNameMaker mk rdr = do { (n, _fvs) <- runCps (newPatName mk rdr); return n }
 
 -- ----------- Entry point 2: rnBindPat -------------------
 -- Binds local names; in a recursive scope that involves other bound vars
@@ -298,7 +298,7 @@ rnPatAndThen mk (ParPat pat)  = do { pat' <- rnLPatAndThen mk pat; return (ParPa
 rnPatAndThen mk (LazyPat pat) = do { pat' <- rnLPatAndThen mk pat; return (LazyPat pat') }
 rnPatAndThen mk (BangPat pat) = do { pat' <- rnLPatAndThen mk pat; return (BangPat pat') }
 rnPatAndThen mk (VarPat rdr)  = do { loc <- liftCps getSrcSpanM
-                                   ; name <- newName mk (L loc rdr)
+                                   ; name <- newPatName mk (L loc rdr)
                                    ; return (VarPat name) }
      -- we need to bind pattern variables for view pattern expressions
      -- (e.g. in the pattern (x, x -> y) x needs to be bound in the rhs of the tuple)
@@ -334,7 +334,7 @@ rnPatAndThen _ (NPat lit mb_neg _eq)
        ; return (NPat lit' mb_neg' eq') }
 
 rnPatAndThen mk (NPlusKPat rdr lit _ _)
-  = do { new_name <- newName mk rdr
+  = do { new_name <- newPatName mk rdr
        ; lit'  <- liftCpsFV $ rnOverLit lit
        ; minus <- liftCpsFV $ lookupSyntaxName minusName
        ; ge    <- liftCpsFV $ lookupSyntaxName geName
@@ -342,7 +342,7 @@ rnPatAndThen mk (NPlusKPat rdr lit _ _)
 	   	-- The Report says that n+k patterns must be in Integral
 
 rnPatAndThen mk (AsPat rdr pat)
-  = do { new_name <- newName mk rdr
+  = do { new_name <- newPatName mk rdr
        ; pat' <- rnLPatAndThen mk pat
        ; return (AsPat (L (nameSrcSpan new_name) new_name) pat') }