More import tidying and fixing the stage 2 build

[ghc-hetmet.git] / compiler / types / TypeRep.lhs

diff --git a/compiler/types/TypeRep.lhs b/compiler/types/TypeRep.lhs
index cef77a1..04cc11f 100644 (file)
--- a/compiler/types/TypeRep.lhs
+++ b/compiler/types/TypeRep.lhs
@@ -1,4 +1,5 @@
 %
+% (c) The University of Glasgow 2006
 % (c) The GRASP/AQUA Project, Glasgow University, 1998
 %
 \section[TypeRep]{Type - friends' interface}
@@ -37,31 +38,24 @@ module TypeRep (
         isTySuperKind, isCoSuperKind,
        tySuperKindTyCon, coSuperKindTyCon,
         
-        isCoercionKindTyCon,
-
        pprKind, pprParendKind
     ) where
 
 #include "HsVersions.h"
 
 import {-# SOURCE #-} DataCon( DataCon, dataConName )
-import Monad     ( guard )
--- friends:
 
-import Var       ( Var, Id, TyVar, tyVarKind )
-import VarSet     ( TyVarSet )
-import Name      ( Name, NamedThing(..), BuiltInSyntax(..), mkWiredInName )
-import OccName   ( mkOccNameFS, tcName, parenSymOcc )
-import BasicTypes ( IPName, tupleParens )
-import TyCon     ( TyCon, mkFunTyCon, tyConArity, tupleTyConBoxity, isTupleTyCon, isRecursiveTyCon, isNewTyCon, mkVoidPrimTyCon, mkSuperKindTyCon, isSuperKindTyCon, mkCoercionTyCon )
-import Class     ( Class )
+-- friends:
+import Var
+import VarSet
+import Name
+import OccName
+import BasicTypes
+import TyCon
+import Class
 
 -- others
-import PrelNames  ( gHC_PRIM, funTyConKey, tySuperKindTyConKey, 
-                    coSuperKindTyConKey, liftedTypeKindTyConKey,
-                    openTypeKindTyConKey, unliftedTypeKindTyConKey,
-                    ubxTupleKindTyConKey, argTypeKindTyConKey, listTyConKey, 
-                    parrTyConKey, hasKey, eqCoercionKindTyConKey )
+import PrelNames
 import Outputable
 \end{code}
 
@@ -192,8 +186,11 @@ data Type
        TyVar
        Type    
 
-  | PredTy             -- A high level source type 
-       PredType        -- ...can be expanded to a representation type...
+  | PredTy             -- The type of evidence for a type predictate
+       PredType        -- See Note [PredTy], and Note [Equality predicates]
+       -- NB: A PredTy (EqPred _ _) can appear only as the kind
+       --     of a coercion variable; never as the argument or result
+       --     of a FunTy (unlike ClassP, IParam)
 
   | NoteTy             -- A type with a note attached
        TyNote
@@ -208,15 +205,11 @@ type Kind = Type  -- Invariant: a kind is always
 type SuperKind = Type   -- Invariant: a super kind is always 
                         --   TyConApp SuperKindTyCon ...
 
-type Coercion = Type
-
-type CoercionKind = Kind
-
 data TyNote = FTVNote TyVarSet -- The free type variables of the noted expression
 \end{code}
 
 -------------------------------------
-               Source types
+               Note [PredTy]
 
 A type of the form
        PredTy p
@@ -256,6 +249,24 @@ The predicate really does turn into a real extra argument to the
 function.  If the argument has type (PredTy p) then the predicate p is
 represented by evidence (a dictionary, for example, of type (predRepTy p).
 
+Note [Equality predicates]
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+       forall a b. (a :=: S b) => a -> b
+could be represented by
+       ForAllTy a (ForAllTy b (FunTy (PredTy (EqPred a (S b))) ...))
+OR
+       ForAllTy a (ForAllTy b (ForAllTy (c::PredTy (EqPred a (S b))) ...))
+
+The latter is what we do.  (Unlike for class and implicit parameter
+constraints, which do use FunTy.)
+
+Reason:
+       * FunTy is always a *value* function
+       * ForAllTy is discarded at runtime
+
+We often need to make a "wildcard" (c::PredTy..).  We always use the same
+name (wildCoVarName), since it's not mentioned.
+
 
 %************************************************************************
 %*                                                                     *
@@ -313,15 +324,13 @@ funTyCon = mkFunTyCon funTyConName (mkArrowKinds [argTypeKind, openTypeKind] lif
 
 
 tySuperKindTyCon     = mkSuperKindTyCon tySuperKindTyConName
-coSuperKindTyCon = mkSuperKindTyCon coSuperKindTyConName
+coSuperKindTyCon     = mkSuperKindTyCon coSuperKindTyConName
 
 liftedTypeKindTyCon   = mkKindTyCon liftedTypeKindTyConName
 openTypeKindTyCon     = mkKindTyCon openTypeKindTyConName
 unliftedTypeKindTyCon = mkKindTyCon unliftedTypeKindTyConName
 ubxTupleKindTyCon     = mkKindTyCon ubxTupleKindTyConName
 argTypeKindTyCon      = mkKindTyCon argTypeKindTyConName
-eqCoercionKindTyCon = 
-  mkCoercionTyCon eqCoercionKindTyConName 2 (\ _ -> coSuperKind)
 
 mkKindTyCon :: Name -> TyCon
 mkKindTyCon name = mkVoidPrimTyCon name tySuperKind 0
@@ -329,22 +338,17 @@ mkKindTyCon name = mkVoidPrimTyCon name tySuperKind 0
 --------------------------
 -- ... and now their names
 
-tySuperKindTyConName     = mkPrimTyConName FSLIT("BOX") tySuperKindTyConKey tySuperKindTyCon
-coSuperKindTyConName = mkPrimTyConName FSLIT("COERCION") coSuperKindTyConKey coSuperKindTyCon
+tySuperKindTyConName      = mkPrimTyConName FSLIT("BOX") tySuperKindTyConKey tySuperKindTyCon
+coSuperKindTyConName      = mkPrimTyConName FSLIT("COERCION") coSuperKindTyConKey coSuperKindTyCon
 liftedTypeKindTyConName   = mkPrimTyConName FSLIT("*") liftedTypeKindTyConKey liftedTypeKindTyCon
 openTypeKindTyConName     = mkPrimTyConName FSLIT("?") openTypeKindTyConKey openTypeKindTyCon
 unliftedTypeKindTyConName = mkPrimTyConName FSLIT("#") unliftedTypeKindTyConKey unliftedTypeKindTyCon
-ubxTupleKindTyConName     = mkPrimTyConName FSLIT("(##)") ubxTupleKindTyConKey ubxTupleKindTyCon
+ubxTupleKindTyConName     = mkPrimTyConName FSLIT("(#)") ubxTupleKindTyConKey ubxTupleKindTyCon
 argTypeKindTyConName      = mkPrimTyConName FSLIT("??") argTypeKindTyConKey argTypeKindTyCon
 funTyConName              = mkPrimTyConName FSLIT("(->)") funTyConKey funTyCon
 
-eqCoercionKindTyConName   = mkWiredInName gHC_PRIM (mkOccNameFS tcName (FSLIT(":=:"))) 
-                                       eqCoercionKindTyConKey Nothing (ATyCon eqCoercionKindTyCon) 
-                                       BuiltInSyntax
- 
 mkPrimTyConName occ key tycon = mkWiredInName gHC_PRIM (mkOccNameFS tcName occ) 
                                              key 
-                                             Nothing           -- No parent object
                                              (ATyCon tycon)
                                              BuiltInSyntax
        -- All of the super kinds and kinds are defined in Prim and use BuiltInSyntax,
@@ -372,15 +376,15 @@ tySuperKind, coSuperKind :: SuperKind
 tySuperKind = kindTyConType tySuperKindTyCon 
 coSuperKind = kindTyConType coSuperKindTyCon 
 
+isTySuperKind (NoteTy _ ty)    = isTySuperKind ty
 isTySuperKind (TyConApp kc []) = kc `hasKey` tySuperKindTyConKey
 isTySuperKind other            = False
 
+isCoSuperKind :: SuperKind -> Bool
+isCoSuperKind (NoteTy _ ty)    = isCoSuperKind ty
 isCoSuperKind (TyConApp kc []) = kc `hasKey` coSuperKindTyConKey
 isCoSuperKind other            = False
 
-isCoercionKindTyCon kc = kc `hasKey` eqCoercionKindTyConKey
-
-
 -------------------
 -- lastly we need a few functions on Kinds