[project @ 2000-10-11 16:31:27 by simonpj]

Beginnings of renamer and typechecker stuff

5 files changed, 265 insertions, 131 deletions

diff --git a/ghc/compiler/ghci/CmCompile.lhs b/ghc/compiler/ghci/CmCompile.lhs
index b61d1b5ac5..0a7863728c 100644
--- a/ghc/compiler/ghci/CmCompile.lhs
+++ b/ghc/compiler/ghci/CmCompile.lhs
@@ -68,6 +68,102 @@ cmCompile finder summary old_iface hst pcs
                        []
                )
 
+data CompResult
+   = CompOK   ModDetails  -- new details (HST additions)
+              (Maybe (ModIFace, Linkable))
+                       -- summary and code; Nothing => compilation not reqd
+                       -- (old summary and code are still valid)
+              PersistentCompilerState -- updated PCS
+              [SDoc]                  -- warnings
+
+   | CompErrs PersistentCompilerState -- updated PCS
+              [SDoc]                  -- errors
+              [SDoc]                  -- warnings
+
+
+-- These two are only here to avoid recursion between CmCompile and
+-- CompManager.  They really ought to be in the latter.
+type ModuleEnv a = UniqFM a   -- Domain is Module
+
+type HomeModMap         = FiniteMap ModuleName Module -- domain: home mods only
+type HomeSymbolTable    = ModuleEnv ModDetails        -- ditto
+type HomeInterfaceTable = ModuleEnv ModIFace
+\end{code}
+
+
+%************************************************************************
+%*									*
+\subsection{Module details}
+%*									*
+%************************************************************************
+
+A @ModDetails@ summarises everything we know about a compiled module
+
+\begin{code}
+data ModDetails
+   = ModDetails {
+        moduleExports :: Avails,		-- What it exports
+        moduleEnv     :: GlobalRdrEnv,		-- Its top level environment
+
+        fixityEnv     :: NameEnv Fixity,
+	deprecEnv     :: NameEnv DeprecTxt,
+        typeEnv       :: NameEnv TcEnv.TyThing,
+
+        instEnv       :: InstEnv,
+        ruleEnv       :: IdEnv [CoreRule]	-- Domain includes Ids from other modules
+     }
+\end{code}
+
+Auxiliary definitions
+
+\begin{code}
+type DeprecationEnv = NameEnv DeprecTxt		-- Give reason for deprecation
+
+type GlobalRdrEnv = RdrNameEnv [Name]	-- The list is because there may be name clashes
+					-- These only get reported on lookup,
+					-- not on construction
+
+data GenAvailInfo name	= Avail name	 -- An ordinary identifier
+			| AvailTC name 	 -- The name of the type or class
+				  [name] -- The available pieces of type/class.
+					 -- NB: If the type or class is itself
+					 -- to be in scope, it must be in this list.
+					 -- Thus, typically: AvailTC Eq [Eq, ==, /=]
+			deriving( Eq )
+			-- Equality used when deciding if the interface has changed
+
+type AvailEnv	  = NameEnv AvailInfo	-- Maps a Name to the AvailInfo that contains it
+type AvailInfo    = GenAvailInfo Name
+type RdrAvailInfo = GenAvailInfo OccName
+type Avails	  = [AvailInfo]
+\end{code}
+
+
+%************************************************************************
+%*									*
+\subsection{The persistent compiler state}
+%*									*
+%************************************************************************
+
+\begin{code}
+data PersistentCompilerState 
+   = PCS {
+        pcsPST    :: PackageSymbolTable,	-- Domain = non-home-package modules
+        pcsHP     :: RnMonad.HoldingPen, 	-- Pre-slurped interface bits and pieces
+	pcsNS	  :: NameSupply			-- Allocate uniques for names
+     }
+
+type PackageSymbolTable = ModuleEnv ModDetails
+
+data NameSupply
+ = NS { nsUniqs  :: UniqSupply,
+	nsNames  :: FiniteMap (Module,OccName) Name	-- Ensures that one original name gets one unique
+	nsIParam :: FiniteMap OccName Name		-- Ensures that one implicit parameter name gets one unique
+   }
+=======
+>>>>>>> 1.9
+=======
+
 -- should be somewhere else?
 emptyPCS :: IO PersistentCompilerState
 emptyPCS = return (PersistentCompilerState 
@@ -75,5 +171,6 @@ emptyPCS = return (PersistentCompilerState
                         pcs_pit    = emptyPIT,
                         pcs_pst    = emptyPST,
                         pcs_hp     = emptyHoldingPen })
+>>>>>>> 1.10
 \end{code}
 
diff --git a/ghc/compiler/main/HscTypes.lhs b/ghc/compiler/main/HscTypes.lhs
index e274124a8a..64e2a6b6a7 100644
--- a/ghc/compiler/main/HscTypes.lhs
+++ b/ghc/compiler/main/HscTypes.lhs
@@ -13,7 +13,7 @@ where
 
 %************************************************************************
 %*									*
-\subsection{Module details}
+\subsection{Symbol tables and Module details}
 %*									*
 %************************************************************************
 
@@ -34,9 +34,22 @@ data ModDetails
      }
 \end{code}
 
+Symbol tables map modules to ModDetails:
+
+\begin{code}
+type HomeSymbolTable    = ModuleEnv ModDetails	-- Domain = modules in the home package
+type PackageSymbolTable = ModuleEnv ModDetails	-- Domain = modules in the some other package
+type GlobalSymbolTable  = ModuleEnv ModDetails	-- Domain = all modules
+\end{code}
+
+
 Auxiliary definitions
 
 \begin{code}
+data TyThing = AnId   Id
+	     | ATyCon TyCon
+	     | AClass Class
+
 type DeprecationEnv = NameEnv DeprecTxt		-- Give reason for deprecation
 
 type GlobalRdrEnv = RdrNameEnv [Name]	-- The list is because there may be name clashes
@@ -84,6 +97,7 @@ data ModIFace
      }
 \end{code}
 
+
 %************************************************************************
 %*									*
 \subsection{The persistent compiler state}
@@ -93,20 +107,47 @@ data ModIFace
 \begin{code}
 data PersistentCompilerState 
    = PCS {
-        pcsPST    :: PackageSymbolTable,	-- Domain = non-home-package modules
-        pcsHP     :: HoldingPen, 		-- Pre-slurped interface bits and pieces
-	pcsNS	  :: NameSupply			-- Allocate uniques for names
+        pcsPST :: PackageSymbolTable,		-- Domain = non-home-package modules
+        pcsPRS :: PersistentRenamerState
      }
+\end{code}
+
+The @PersistentRenamerState@ persists across successive calls to the
+compiler.
 
-type PackageSymbolTable = ModuleEnv ModDetails
+It contains:
+  * a name supply, which deals with allocating unique names to
+    (Module,OccName) original names, 
+ 
+  * a "holding pen" for declarations that have been read out of
+    interface files but not yet sucked in, renamed, and typechecked
+
+\begin{code}
+data PersistentRenamerState
+  = PRS { prsNS	   :: NameSupply,
+	  prsDecls :: DeclsMap,
+	  prsInsts :: IfaceInsts,
+	  prsRules :: IfaceRules,
+    }
 
 data NameSupply
  = NS { nsUniqs  :: UniqSupply,
 	nsNames  :: FiniteMap (Module,OccName) Name	-- Ensures that one original name gets one unique
 	nsIParam :: FiniteMap OccName Name		-- Ensures that one implicit parameter name gets one unique
    }
+
+type DeclsMap = NameEnv (Version, AvailInfo, Bool, (Module, RdrNameHsDecl))
+		-- A DeclsMap contains a binding for each Name in the declaration
+		-- including the constructors of a type decl etc.
+		-- The Bool is True just for the 'main' Name.
+
+type IfaceInsts = Bag GatedDecl
+type IfaceRules = Bag GatedDecl
+
+type GatedDecl = (NameSet, (Module, RdrNameHsDecl))
 \end{code}
 
+
 %************************************************************************
 %*									*
 \subsection{The result of compiling one module}
@@ -119,12 +160,12 @@ data CompResult
               (Maybe (ModIFace, Linkable))
                        -- summary and code; Nothing => compilation not reqd
                        -- (old summary and code are still valid)
-              PersistentCompilerState -- updated PCS
-              [SDoc]                  -- warnings
+              PersistentCompilerState	-- updated PCS
+              (Bag WarnMsg) 		-- warnings
 
-   | CompErrs PersistentCompilerState -- updated PCS
-              [SDoc]                  -- errors
-              [SDoc]                  -- warnings
+   | CompErrs PersistentCompilerState	-- updated PCS
+              (Bag ErrMsg)		-- errors
+              (Bag WarnMsg)             -- warnings
 
 
 -- The driver sits between 'compile' and 'hscMain', translating calls
@@ -146,15 +187,12 @@ data HscResult
              [SDoc]                  	-- warnings
 
 	
-
 -- These two are only here to avoid recursion between CmCompile and
 -- CompManager.  They really ought to be in the latter.
 type ModuleEnv a = UniqFM a   -- Domain is Module
 
 type HomeModMap         = FiniteMap ModuleName Module -- domain: home mods only
-type HomeSymbolTable    = ModuleEnv ModDetails        -- ditto
 type HomeInterfaceTable = ModuleEnv ModIFace
-
 \end{code}
 
 
diff --git a/ghc/compiler/rename/Rename.lhs b/ghc/compiler/rename/Rename.lhs
index 93437ca20e..cc228aed9a 100644
--- a/ghc/compiler/rename/Rename.lhs
+++ b/ghc/compiler/rename/Rename.lhs
@@ -80,12 +80,13 @@ type RenameResult = ( Module		-- This module
 		    , FixityEnv		-- The fixity environment; for derivings
 		    , [Module])		-- Imported modules
 		   
-renameModule :: UniqSupply -> RdrNameHsModule -> IO (Maybe RenameResult)
-renameModule us this_mod@(HsModule mod_name vers exports imports local_decls _ loc)
+renameModule :: PersistentCompilerState -> RdrNameHsModule -> IO (Maybe RenameResult)
+renameModule pcs this_mod@(HsModule mod_name vers exports imports local_decls _ loc)
   = 	-- Initialise the renamer monad
     do {
 	((maybe_rn_stuff, dump_action), rn_errs_bag, rn_warns_bag) 
-	   <- initRn (mkThisModule mod_name) us 
+	   <- initRn pcs 
+		     (mkThisModule mod_name) 
 		     (mkSearchPath opt_HiMap) loc
 		     (rename this_mod) ;
 
diff --git a/ghc/compiler/rename/RnMonad.lhs b/ghc/compiler/rename/RnMonad.lhs
index c6f6c1e6c6..f266b24aa1 100644
--- a/ghc/compiler/rename/RnMonad.lhs
+++ b/ghc/compiler/rename/RnMonad.lhs
@@ -103,24 +103,27 @@ type RnMS r  = RnM SDown r		-- Renaming source
 type RnMG r  = RnM ()    r		-- Getting global names etc
 
 	-- Common part
-data RnDown = RnDown {
-		  rn_mod     :: Module,
-		  rn_loc     :: SrcLoc,
-		  rn_ns      :: IORef RnNameSupply,
-		  rn_errs    :: IORef (Bag WarnMsg, Bag ErrMsg),
-	  	  rn_ifaces  :: IORef Ifaces,
-		  rn_hi_maps :: (SearchPath,	-- For error messages
-				 ModuleHiMap,	-- for .hi files
-				 ModuleHiMap)	-- for .hi-boot files
-		}
+data RnDown
+  = RnDown {
+	rn_mod     :: Module,			-- This module
+	rn_loc     :: SrcLoc,			-- Current locn
+
+	rn_finder  :: Finder,
+	rn_flags   :: DynFlags,
+	rn_gst     :: GlobalSymbolTable,	-- Both home modules and packages,
+						-- at the moment we started compiling 
+						-- this module
+
+	rn_errs    :: IORef (Bag WarnMsg, Bag ErrMsg),
+	rn_ns      :: IORef NameSupply,
+	rn_ifaces  :: IORef Ifaces,
+    }
 
 	-- For renaming source code
 data SDown = SDown {
 		  rn_mode :: RnMode,
 
-		  rn_genv :: GlobalRdrEnv,
-		    	--   Global envt; the fixity component gets extended
-		    	--   with local fixity decls
+		  rn_genv :: GlobalRdrEnv,    	-- Global envt
 
 		  rn_lenv :: LocalRdrEnv,	-- Local name envt
 			--   Does *not* include global name envt; may shadow it
@@ -162,46 +165,15 @@ lookupFixity env name
   = case lookupNameEnv env name of 
 	Just (FixitySig _ fix _) -> fix
 	Nothing		  	 -> defaultFixity
-
---------------------------------
-type DeprecationEnv = NameEnv DeprecTxt
 \end{code}
 
 \begin{code}
---------------------------------
-type RnNameSupply
- = ( UniqSupply
-
-   , FiniteMap (ModuleName, OccName) Name
-	-- Ensures that one (module,occname) pair gets one unique
-   , FiniteMap OccName Name
-	-- Ensures that one implicit parameter name gets one unique
-   )
-
-
---------------------------------
-type Avails	  = [AvailInfo]
-
 type ExportAvails = (FiniteMap ModuleName Avails,
 	-- Used to figure out "module M" export specifiers
 	-- Includes avails only from *unqualified* imports
 	-- (see 1.4 Report Section 5.1.1)
 
 		     AvailEnv)	-- Used to figure out all other export specifiers.
-			
-
-data GenAvailInfo name	= Avail name	 -- An ordinary identifier
-			| AvailTC name 	 -- The name of the type or class
-				  [name] -- The available pieces of type/class.
-					 -- NB: If the type or class is itself
-					 -- to be in scope, it must be in this list.
-					 -- Thus, typically: AvailTC Eq [Eq, ==, /=]
-			deriving( Eq )
-			-- Equality used when deciding if the interface has changed
-
-type AvailEnv	  = NameEnv AvailInfo	-- Maps a Name to the AvailInfo that contains it
-type AvailInfo    = GenAvailInfo Name
-type RdrAvailInfo = GenAvailInfo OccName
 \end{code}
 
 %===================================================
@@ -264,7 +236,16 @@ data ParsedIface
 type RdrNamePragma = ()				-- Fudge for now
 -------------------
 
+%************************************************************************
+%*									*
+\subsection{The renamer state}
+%*									*
+%************************************************************************
+
+\begin{code}
 data Ifaces = Ifaces {
+
+	-- PERSISTENT FIELDS
 		iImpModInfo :: ImportedModuleInfo,
 				-- Modules this one depends on: that is, the union 
 				-- of the modules its *direct* imports depend on.
@@ -272,26 +253,8 @@ data Ifaces = Ifaces {
 				-- dependencies (direct or not) of the imported module.
 
 		iDecls :: DeclsMap,	-- A single, global map of Names to decls
-
-		iDeferred :: NameSet,	-- data (not newtype) TyCons that have been slurped, 
-					-- but none of their constructors have.
-					-- If this is still the case right at the end
 					-- we can get away with importing them abstractly
 
-		iFixes :: FixityEnv,	
-				-- A single, global map of Names to fixities
-				-- See comments with RnIfaces.lookupFixity
-
-		iSlurp :: NameSet,
-		-- All the names (whether "big" or "small", whether wired-in or not,
-		-- whether locally defined or not) that have been slurped in so far.
-
-		iVSlurp :: [(Name,Version)],
-		-- All the (a) non-wired-in (b) "big" (c) non-locally-defined 
-		-- names that have been slurped in so far, with their versions.
-		-- This is used to generate the "usage" information for this module.
-		-- Subset of the previous field.
-
 		iInsts :: IfaceInsts,
 		-- The as-yet un-slurped instance decls; this bag is depleted when we
 		-- slurp an instance decl so that we don't slurp the same one twice.
@@ -301,13 +264,31 @@ data Ifaces = Ifaces {
 		iRules :: IfaceRules,
 		-- Similar to instance decls, only for rules
 
-		iDeprecs :: DeprecationEnv
-	}
+	-- SEMI-EPHEMERAL FIELDS
+		-- iFixes and iDeprecs are accumulated here while one module
+		-- is compiled, but are transferred to the package symbol table
+		-- at the end.  We don't add them to the table as we encounter them
+		-- because doing so would require us to have a mutable symbol table
+		-- which is yukky.
+
+		iFixes :: FixityEnv,		-- A single, global map of Names to fixities
+						-- See comments with RnIfaces.lookupFixity
+		iDeprecs :: DeprecationEnv,
 
-type IfaceInsts = Bag GatedDecl
-type IfaceRules = Bag GatedDecl
 
-type GatedDecl = (NameSet, (Module, RdrNameHsDecl))
+	-- EPHEMERAL FIELDS
+	-- These fields persist during the compilation of a single module only
+
+		iSlurp :: NameSet,
+		-- All the names (whether "big" or "small", whether wired-in or not,
+		-- whether locally defined or not) that have been slurped in so far.
+
+		iVSlurp :: [(Name,Version)],
+		-- All the (a) non-wired-in (b) "big" (c) non-locally-defined 
+		-- names that have been slurped in so far, with their versions.
+		-- This is used to generate the "usage" information for this module.
+		-- Subset of the previous field.
+	}
 
 type ImportedModuleInfo 
      = FiniteMap ModuleName (WhetherHasOrphans, IsBootInterface, 
@@ -332,11 +313,6 @@ type ImportedModuleInfo
 		-- A.hi or A.hi-boot when importing A.f.
 		-- Basically, we look for A.hi if A is in the map, and A.hi-boot
 		-- otherwise
-
-type DeclsMap = NameEnv (Version, AvailInfo, Bool, (Module, RdrNameHsDecl))
-		-- A DeclsMap contains a binding for each Name in the declaration
-		-- including the constructors of a type decl etc.
-		-- The Bool is True just for the 'main' Name.
 \end{code}
 
 
@@ -347,21 +323,29 @@ type DeclsMap = NameEnv (Version, AvailInfo, Bool, (Module, RdrNameHsDecl))
 %************************************************************************
 
 \begin{code}
-initRn :: Module -> UniqSupply -> SearchPath -> SrcLoc
+initRn :: DynFlags -> Finder -> GlobalSymbolTable
+       -> PersistentRenamerState
+       -> Module -> SrcLoc
        -> RnMG r
        -> IO (r, Bag ErrMsg, Bag WarnMsg)
 
-initRn mod us dirs loc do_rn = do
+initRn flags finder gst prs mod loc do_rn = do
   himaps    <- mkModuleHiMaps dirs
-  names_var <- newIORef (us, builtins, emptyFM)
+  names_var <- newIORef (prsNS pcs)
   errs_var  <- newIORef (emptyBag,emptyBag)
-  iface_var <- newIORef emptyIfaces 
+  iface_var <- newIORef (initIfaces prs)
   let
-        rn_down = RnDown { rn_loc = loc, rn_ns = names_var, 
-			   rn_errs = errs_var, 
-			   rn_hi_maps = himaps, 
+        rn_down = RnDown { rn_mod = mod,
+			   rn_loc = loc, 
+
+			   rn_finder = finder,
+			   rn_flags  = flags,
+			   rn_gst    = gst,
+				
+			   rn_ns     = names_var, 
+			   rn_errs   = errs_var, 
 		  	   rn_ifaces = iface_var,
-			   rn_mod = mod }
+		  }
 
 	-- do the business
   res <- do_rn rn_down ()
@@ -372,6 +356,25 @@ initRn mod us dirs loc do_rn = do
   return (res, errs, warns)
 
 
+initIfaces :: PersistentRenamerState -> Ifaces
+initIfaces prs
+  = Ifaces { iDecls = prsDecls prs,
+	     iInsts = prsInsts prs,
+	     iRules = prsRules rules,
+
+	     iFixes   = emptyNameEnv,
+	     iDeprecs = emptyNameEnv,
+
+	     iImpModInfo = emptyFM,
+	     iDeferred   = emptyNameSet,
+	     iSlurp      = unitNameSet (mkUnboundName dummyRdrVarName),
+			-- Pretend that the dummy unbound name has already been
+			-- slurped.  This is what's returned for an out-of-scope name,
+			-- and we don't want thereby to try to suck it in!
+	     iVSlurp = []
+      }
+
+
 initRnMS :: GlobalRdrEnv -> FixityEnv -> RnMode -> RnMS r -> RnM d r
 initRnMS rn_env fixity_env mode thing_inside rn_down g_down
   = let
@@ -385,21 +388,6 @@ initIfaceRnMS mod thing_inside
   = initRnMS emptyRdrEnv emptyNameEnv InterfaceMode $
     setModuleRn mod thing_inside
 
-emptyIfaces :: Ifaces
-emptyIfaces = Ifaces { iImpModInfo = emptyFM,
-		       iDecls = emptyNameEnv,
-		       iDeferred = emptyNameSet,
-		       iFixes = emptyNameEnv,
-		       iSlurp = unitNameSet (mkUnboundName dummyRdrVarName),
-			-- Pretend that the dummy unbound name has already been
-			-- slurped.  This is what's returned for an out-of-scope name,
-			-- and we don't want thereby to try to suck it in!
-		       iVSlurp = [],
-		       iInsts = emptyBag,
-		       iRules = emptyBag,
-		       iDeprecs = emptyNameEnv
-	      }
-
 builtins :: FiniteMap (ModuleName,OccName) Name
 builtins = listToFM wired_in `plusFM` listToFM known_key
 	 where
@@ -415,12 +403,12 @@ that is, not as part of the main renamer.
 Sole examples: derived definitions,
 which are only generated in the type checker.
 
-The @RnNameSupply@ includes a @UniqueSupply@, so if you call it more than
+The @NameSupply@ includes a @UniqueSupply@, so if you call it more than
 once you must either split it, or install a fresh unique supply.
 
 \begin{code}
 renameSourceCode :: Module
-		 -> RnNameSupply
+		 -> NameSupply
 	         -> RnMS r
 	         -> r
 
@@ -604,11 +592,11 @@ getSrcLocRn down l_down
 %=====================
 
 \begin{code}
-getNameSupplyRn :: RnM d RnNameSupply
+getNameSupplyRn :: RnM d NameSupply
 getNameSupplyRn rn_down l_down
   = readIORef (rn_ns rn_down)
 
-setNameSupplyRn :: RnNameSupply -> RnM d ()
+setNameSupplyRn :: NameSupply -> RnM d ()
 setNameSupplyRn names' (RnDown {rn_ns = names_var}) l_down
   = writeIORef names_var names'
 
diff --git a/ghc/compiler/typecheck/TcEnv.lhs b/ghc/compiler/typecheck/TcEnv.lhs
index bde67bacf5..b1fd6398b8 100644
--- a/ghc/compiler/typecheck/TcEnv.lhs
+++ b/ghc/compiler/typecheck/TcEnv.lhs
@@ -145,27 +145,37 @@ Data type declarations
 ~~~~~~~~~~~~~~~~~~~~~
 
 \begin{code}
-data TcEnv = TcEnv
-                  UsageEnv
-		  TypeEnv
-		  ValueEnv 
-		  InstEnv
-		  (TcTyVarSet,		-- The in-scope TyVars
-		   TcRef TcTyVarSet)	-- Free type variables of the value env
-					-- ...why mutable? see notes with tcGetGlobalTyVars
-					-- Includes the in-scope tyvars
+data TcEnv
+  = TcEnv {
+	tcGST  	 :: GlobalSymbolTable,	-- The symbol table at the moment we began this compilation
+
+	tcGEnv	 :: NameEnv TyThing	-- The global type environment we've accumulated while
+					-- compiling this module:
+					--	types and classes (both imported and local)
+					-- 	imported Ids
+					-- (Ids defined in this module are in the local envt)
+		-- When type checking is over we'll augment the
+		-- global symbol table with everything in tcGEnv
+		
+	tcInst 	 :: InstEnv,		-- All instances (both imported and in this module)
+
+	tcLEnv 	 :: NameEnv TcTyThing,	-- The local type environment: Ids and TyVars
+					-- defined in this module
+
+	tcTyVars :: FreeTyVars		-- Type variables free in tcLST
+    }
 
-type UsageEnv   = NameEnv UVar
-type TypeEnv	= NameEnv TyThing
-type ValueEnv	= NameEnv Id	
+
+type InScopeTyVars = (TcTyVarSet,	-- The in-scope TyVars
+		      TcRef TcTyVarSet)	-- Free type variables of the value env
+					-- ...why mutable? see notes with tcGetGlobalTyVars
 
 valueEnvIds :: ValueEnv -> [Id]
 valueEnvIds ve = nameEnvElts ve
 
-data TyThing = ATyVar TyVar
-	     | ATyCon TyCon
-	     | AClass Class
-	     | AThing TcKind	-- Used temporarily, during kind checking
+data TcTyThing = ATyVar TyVar
+	       | ATcId  TcId
+	       | AThing TcKind	-- Used temporarily, during kind checking
 -- For example, when checking (forall a. T a Int):
 --	1. We first bind (a -> AThink kv), where kv is a kind variable. 
 --	2. Then we kind-check the (T a Int) part.