[commit: ghc] master: Define TypeVar (like KindVar), isTypeVar, isKindVar, and use them (c676a15)

[Simon Peyton Jones]

Repository : ssh://darcs.haskell.org//srv/darcs/ghc

On branch  : master

http://hackage.haskell.org/trac/ghc/changeset/c676a15e9b0ead9d9322d036d9cf2f4df734bb01

>---------------------------------------------------------------

commit c676a15e9b0ead9d9322d036d9cf2f4df734bb01
Author: Simon Peyton Jones <simonpj at microsoft.com>
Date:   Fri Feb 17 13:55:03 2012 +0000

    Define TypeVar (like KindVar), isTypeVar, isKindVar, and use them
    
    This is the start of more global renaming

>---------------------------------------------------------------

 compiler/basicTypes/Var.lhs |   35 +++++++++++++++++++++--------------
 compiler/types/TypeRep.lhs  |   18 ++++++++++++++++--
 2 files changed, 37 insertions(+), 16 deletions(-)

diff --git a/compiler/basicTypes/Var.lhs b/compiler/basicTypes/Var.lhs
index 6b58305..af7cb35 100644
--- a/compiler/basicTypes/Var.lhs
+++ b/compiler/basicTypes/Var.lhs
@@ -39,7 +39,8 @@
 
 module Var (
         -- * The main data type and synonyms
-        Var, TyVar, CoVar, Id, KindVar, DictId, DFunId, EvVar, EqVar, EvId, IpId,
+        Var, CoVar, Id, DictId, DFunId, EvVar, EqVar, EvId, IpId,
+        TyVar, TypeVar, KindVar, TKVar,
 
 	-- ** Taking 'Var's apart
 	varName, varUnique, varType, 
@@ -54,7 +55,7 @@ module Var (
 	setIdExported, setIdNotExported,
 
         -- ** Predicates
-        isId, isTyVar, isTcTyVar,
+        isId, isTKVar, isTyVar, isTcTyVar,
         isLocalVar, isLocalId,
 	isGlobalId, isExportedId,
 	mustHaveLocalBinding,
@@ -102,7 +103,10 @@ import Data.Data
 \begin{code}
 type Id    = Var       -- A term-level identifier
 
-type TyVar   = Var     -- Type *or* kind variable
+type TyVar   = Var     -- Type *or* kind variable (historical)
+
+type TKVar   = Var     -- Type *or* kind variable (historical)
+type TypeVar = Var     -- Definitely a type variable
 type KindVar = Var     -- Definitely a kind variable
      	       	       -- See Note [Kind and type variables]
 
@@ -136,8 +140,8 @@ Before kind polymorphism, TyVar were used to mean type variables. Now
 they are use to mean kind *or* type variables. KindVar is used when we
 know for sure that it is a kind variable. In future, we might want to
 go over the whole compiler code to use:
-   - KiTyVar to mean kind or type variables
-   - TyVar   to mean         type variables only
+   - TKVar   to mean kind or type variables
+   - TypeVar to mean         type variables only
    - KindVar to mean kind         variables
 
 
@@ -157,13 +161,13 @@ in its @VarDetails at .
 -- | Essentially a typed 'Name', that may also contain some additional information
 -- about the 'Var' and it's use sites.
 data Var
-  = TyVar {  -- type and kind variables
+  = TyVar {  -- Type and kind variables
              -- see Note [Kind and type variables]
 	varName    :: !Name,
-	realUnique :: FastInt,		-- Key for fast comparison
-					-- Identical to the Unique in the name,
-					-- cached here for speed
-	varType       :: Kind           -- ^ The type or kind of the 'Var' in question
+	realUnique :: FastInt,	     -- Key for fast comparison
+				     -- Identical to the Unique in the name,
+				     -- cached here for speed
+	varType    :: Kind           -- ^ The type or kind of the 'Var' in question
  }
 
   | TcTyVar { 				-- Used only during type inference
@@ -411,10 +415,13 @@ setIdNotExported id = ASSERT( isLocalId id )
 %************************************************************************
 
 \begin{code}
-isTyVar :: Var -> Bool          -- True of both type variables only
-isTyVar (TyVar {})   = True
-isTyVar (TcTyVar {}) = True
-isTyVar _            = False
+isTyVar :: Var -> Bool
+isTyVar = isTKVar     -- Historical
+
+isTKVar :: Var -> Bool  -- True of both type and kind variables
+isTKVar (TyVar {})   = True
+isTKVar (TcTyVar {}) = True
+isTKVar _            = False
 
 isTcTyVar :: Var -> Bool
 isTcTyVar (TcTyVar {}) = True
diff --git a/compiler/types/TypeRep.lhs b/compiler/types/TypeRep.lhs
index 3bc1b23..9c1a1d7 100644
--- a/compiler/types/TypeRep.lhs
+++ b/compiler/types/TypeRep.lhs
@@ -23,7 +23,7 @@ module TypeRep (
 
         -- Functions over types
         mkTyConApp, mkTyConTy, mkTyVarTy, mkTyVarTys,
-        isLiftedTypeKind,
+        isLiftedTypeKind, isSuperKind, isTypeVar, isKindVar,
         
         -- Pretty-printing
 	pprType, pprParendType, pprTypeApp,
@@ -257,11 +257,25 @@ mkTyConApp tycon tys
 -- | Create the plain type constructor type which has been applied to no type arguments at all.
 mkTyConTy :: TyCon -> Type
 mkTyConTy tycon = mkTyConApp tycon []
+\end{code}
+
+Some basic functions, put here to break loops eg with the pretty printer
 
+\begin{code}
 isLiftedTypeKind :: Kind -> Bool
--- This function is here because it's used in the pretty printer
 isLiftedTypeKind (TyConApp tc []) = tc `hasKey` liftedTypeKindTyConKey
 isLiftedTypeKind _                = False
+
+-- | Is this a super-kind (i.e. a type-of-kinds)?
+isSuperKind :: Type -> Bool
+isSuperKind (TyConApp skc []) = skc `hasKey` superKindTyConKey
+isSuperKind _                 = False
+
+isTypeVar :: Var -> Bool
+isTypeVar v = isTKVar v && not (isSuperKind (varType v))
+
+isKindVar :: Var -> Bool 
+isKindVar v = isTKVar v && isSuperKind (varType v)
 \end{code}