[project @ 2002-03-08 15:50:53 by simonpj]

[ghc-hetmet.git] / ghc / compiler / typecheck / TcType.lhs

diff --git a/ghc/compiler/typecheck/TcType.lhs b/ghc/compiler/typecheck/TcType.lhs
index b8f0878..5b9d8ae 100644 (file)
--- a/ghc/compiler/typecheck/TcType.lhs
+++ b/ghc/compiler/typecheck/TcType.lhs
@@ -46,6 +46,7 @@ module TcType (
   isDoubleTy, isFloatTy, isIntTy,
   isIntegerTy, isAddrTy, isBoolTy, isUnitTy, isForeignPtrTy, 
   isTauTy, tcIsTyVarTy, tcIsForAllTy,
+  allDistinctTyVars,
 
   ---------------------------------
   -- Misc type manipulators
@@ -74,7 +75,6 @@ module TcType (
   ---------------------------------
   -- Unifier and matcher  
   unifyTysX, unifyTyListsX, unifyExtendTysX,
-  allDistinctTyVars,
   matchTy, matchTys, match,
 
   --------------------------------
@@ -250,7 +250,9 @@ isUserTyVar tv = case mutTyVarDetails tv of
 
 isSkolemTyVar :: TcTyVar -> Bool
 isSkolemTyVar tv = case mutTyVarDetails tv of
-                     SigTv -> True
+                     SigTv  -> True
+                     ClsTv  -> True
+                     InstTv -> True
                      oteher -> False
 
 isHoleTyVar :: TcTyVar -> Bool
@@ -453,6 +455,31 @@ tcSplitDFunTy ty
     (tvs, theta, clas, tys) }}
 \end{code}
 
+(allDistinctTyVars tys tvs) = True 
+       iff 
+all the types tys are type variables, 
+distinct from each other and from tvs.
+
+This is useful when checking that unification hasn't unified signature
+type variables.  For example, if the type sig is
+       f :: forall a b. a -> b -> b
+we want to check that 'a' and 'b' havn't 
+       (a) been unified with a non-tyvar type
+       (b) been unified with each other (all distinct)
+       (c) been unified with a variable free in the environment
+
+\begin{code}
+allDistinctTyVars :: [Type] -> TyVarSet -> Bool
+
+allDistinctTyVars []       acc
+  = True
+allDistinctTyVars (ty:tys) acc 
+  = case tcGetTyVar_maybe ty of
+       Nothing                       -> False  -- (a)
+       Just tv | tv `elemVarSet` acc -> False  -- (b) or (c)
+               | otherwise           -> allDistinctTyVars tys (acc `extendVarSet` tv)
+\end{code}    
+
 
 %************************************************************************
 %*                                                                     *
@@ -886,38 +913,6 @@ boxedMarshalableTyCon tc
 %*                                                                     *
 %************************************************************************
 
-(allDistinctTyVars tys tvs) = True 
-       iff 
-all the types tys are type variables, 
-distinct from each other and from tvs.
-
-This is useful when checking that unification hasn't unified signature
-type variables.  For example, if the type sig is
-       f :: forall a b. a -> b -> b
-we want to check that 'a' and 'b' havn't 
-       (a) been unified with a non-tyvar type
-       (b) been unified with each other (all distinct)
-       (c) been unified with a variable free in the environment
-
-\begin{code}
-allDistinctTyVars :: [Type] -> TyVarSet -> Bool
-
-allDistinctTyVars []       acc
-  = True
-allDistinctTyVars (ty:tys) acc 
-  = case tcGetTyVar_maybe ty of
-       Nothing                       -> False  -- (a)
-       Just tv | tv `elemVarSet` acc -> False  -- (b) or (c)
-               | otherwise           -> allDistinctTyVars tys (acc `extendVarSet` tv)
-\end{code}    
-
-
-%************************************************************************
-%*                                                                     *
-\subsection{Unification with an explicit substitution}
-%*                                                                     *
-%************************************************************************
-
 Unify types with an explicit substitution and no monad.
 Ignore usage annotations.