[project @ 2001-10-29 17:59:37 by simonmar]

Give the template tyvars nice print names, as per a suggestion from
Koen Claessen.

Prelude> :i []
-- [] is a data constructor
[] :: forall a. [a]

-- [] is a type constructor
data [] a = [] | (:) a [a]

diff --git a/ghc/compiler/prelude/TysPrim.lhs b/ghc/compiler/prelude/TysPrim.lhs
index d01b25f..a0770af 100644 (file)
--- a/ghc/compiler/prelude/TysPrim.lhs
+++ b/ghc/compiler/prelude/TysPrim.lhs
@@ -49,16 +49,22 @@ module TysPrim(
 
 #include "HsVersions.h"
 
-import Var             ( TyVar, mkSysTyVar )
-import Name            ( Name )
+import Var             ( TyVar, mkTyVar )
+import Name            ( Name, mkLocalName )
+import OccName         ( mkVarOcc )
 import PrimRep         ( PrimRep(..) )
 import TyCon           ( TyCon, ArgVrcs, mkPrimTyCon, mkLiftedPrimTyCon )
 import Type            ( mkTyConApp, mkTyConTy, mkTyVarTys, mkTyVarTy,
-                         unliftedTypeKind, liftedTypeKind, openTypeKind, mkArrowKinds
+                         unliftedTypeKind, liftedTypeKind, openTypeKind, 
+                         Kind, mkArrowKinds
                        )
+import SrcLoc          ( noSrcLoc )
 import Unique          ( mkAlphaTyVarUnique )
 import PrelNames
+import FastString      ( mkFastString )
 import Outputable
+
+import Char            ( ord, chr )
 \end{code}
 
 %************************************************************************
@@ -104,10 +110,22 @@ primTyCons
 %*                                                                     *
 %************************************************************************
 
+alphaTyVars is a list of type variables for use in templates: 
+       ["a", "b", ..., "z", "t1", "t2", ... ]
+
 \begin{code}
+tyVarList :: Kind -> [TyVar]
+tyVarList kind = [ mkTyVar (mkLocalName (mkAlphaTyVarUnique u) 
+                               (mkVarOcc (mkFastString name))
+                               noSrcLoc) kind
+                | u <- [2..],
+                  let name | c <= 'z'  = [c]
+                           | otherwise = 't':show u
+                           where c = chr (u-2 + ord 'a')
+                ]
+
 alphaTyVars :: [TyVar]
-alphaTyVars = [ mkSysTyVar u liftedTypeKind
-             | u <- map mkAlphaTyVarUnique [2..] ]
+alphaTyVars = tyVarList liftedTypeKind
 
 betaTyVars = tail alphaTyVars
 
@@ -120,12 +138,8 @@ alphaTys = mkTyVarTys alphaTyVars
        -- openAlphaTyVar is prepared to be instantiated
        -- to a lifted or unlifted type variable.  It's used for the 
        -- result type for "error", so that we can have (error Int# "Help")
-openAlphaTyVar :: TyVar
-openAlphaTyVar = mkSysTyVar (mkAlphaTyVarUnique 1) openTypeKind
-
 openAlphaTyVars :: [TyVar]
-openAlphaTyVars = [ mkSysTyVar u openTypeKind
-                 | u <- map mkAlphaTyVarUnique [2..] ]
+openAlphaTyVars@(openAlphaTyVar:_) = tyVarList openTypeKind
 
 openAlphaTy = mkTyVarTy openAlphaTyVar