[project @ 2001-11-26 09:20:25 by simonpj]

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

diff --git a/ghc/compiler/types/TypeRep.lhs b/ghc/compiler/types/TypeRep.lhs
index d8cf5cd..8e2002c 100644 (file)
--- a/ghc/compiler/types/TypeRep.lhs
+++ b/ghc/compiler/types/TypeRep.lhs
@@ -5,9 +5,10 @@
 
 \begin{code}
 module TypeRep (
-       Type(..), TyNote(..), SourceType(..),           -- Representation visible to friends
+       Type(..), TyNote(..),           -- Representation visible 
+       SourceType(..), IPName(..),     -- to friends
        
-       Kind, TauType, PredType, ThetaType,             -- Synonyms
+       Kind, PredType, ThetaType,              -- Synonyms
        TyVarSubst,
 
        superKind, superBoxity,                         -- KX and BX respectively
@@ -135,7 +136,6 @@ newtype application as a SourceType; instead as a TyConApp.
 \begin{code}
 type SuperKind = Type
 type Kind      = Type
-type TauType   = Type
 
 type TyVarSubst = TyVarEnv Type
 
@@ -207,11 +207,19 @@ Here the "Eq a" and "?x :: Int -> Int" and "r\l" are all called *predicates*
 Predicates are represented inside GHC by PredType:
 
 \begin{code}
-data SourceType  = ClassP Class [Type]         -- Class predicate
-                | IParam Name  Type            -- Implicit parameter
-                | NType TyCon [Type]           -- A *saturated*, *non-recursive* newtype application
-                                               -- [See notes at top about newtypes]
-
+data SourceType 
+  = ClassP Class [Type]                -- Class predicate
+  | IParam (IPName Name) Type  -- Implicit parameter
+  | NType TyCon [Type]         -- A *saturated*, *non-recursive* newtype application
+                               -- [See notes at top about newtypes]
+
+data IPName name
+  = Dupable   name     -- ?x: you can freely duplicate this implicit parameter
+  | MustSplit name     -- %x: you must use the splitting function to duplicate it
+  deriving( Eq, Ord )  -- Ord is used in the IP name cache finite map
+                       --      (used in HscTypes.OrigIParamCache)
+       -- I sometimes thisnk this type should be in BasicTypes
+               
 type PredType  = SourceType    -- A subtype for predicates
 type ThetaType = [PredType]
 \end{code}
@@ -269,8 +277,8 @@ in two situations:
     type variable, one that may very well later be unified with a type.
     For example, suppose f::a, and we see an application (f x).  Then a
     must be a function type, so we unify a with (b->c).  But what kind
-    are b and c?  They can be lifted or unlifted types, so we give them 
-    kind '?'.
+    are b and c?  They can be lifted or unlifted types, or indeed type schemes,
+    so we give them kind '?'.
 
     When the type checker generalises over a bunch of type variables, it
     makes any that still have kind '?' into kind '*'.  So kind '?' is never