X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypes%2FFunDeps.lhs;h=0bea32fe57b124df03882711e3d6a6e45471b410;hb=ced4c13ea3577e01556a2f76c2cc458c0be6c83c;hp=170304c59f70c424aa5c3e5750028b7923e272a4;hpb=5e5310b3cb4f78e30cc7b90879eb016e97c214cb;p=ghc-hetmet.git

diff --git a/compiler/types/FunDeps.lhs b/compiler/types/FunDeps.lhs
index 170304c..0bea32f 100644
--- a/compiler/types/FunDeps.lhs
+++ b/compiler/types/FunDeps.lhs
@@ -9,8 +9,8 @@ It's better to read it as: "if we know these, then we're going to know these"
 
 \begin{code}
 module FunDeps (
- 	Equation, pprEquation,
-	oclose, grow, improveOne,
+ 	Equation, pprEquation, 
+	oclose, improveFromInstEnv, improveFromAnother,
 	checkInstCoverage, checkFunDeps,
 	pprFundeps
     ) where
@@ -132,44 +132,6 @@ oclose preds fixed_tvs
 	      ]
 \end{code}
 
-Note [Growing the tau-tvs using constraints]
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-(grow preds tvs) is the result of extend the set of tyvars tvs
-		 using all conceivable links from pred
-
-E.g. tvs = {a}, preds = {H [a] b, K (b,Int) c, Eq e}
-Then grow precs tvs = {a,b,c}
-
-All the type variables from an implicit parameter are added, whether or
-not they are mentioned in tvs; see Note [Implicit parameters and ambiguity] 
-in TcSimplify.
-
-See also Note [Ambiguity] in TcSimplify
-
-\begin{code}
-grow :: [PredType] -> TyVarSet -> TyVarSet
-grow preds fixed_tvs 
-  | null preds = fixed_tvs
-  | otherwise  = loop real_fixed_tvs
-  where
-	-- Add the implicit parameters; 
-	-- see Note [Implicit parameters and ambiguity] in TcSimplify
-    real_fixed_tvs = foldr unionVarSet fixed_tvs ip_tvs
- 
-    loop fixed_tvs
-	| new_fixed_tvs `subVarSet` fixed_tvs = fixed_tvs
-	| otherwise		  	      = loop new_fixed_tvs
-	where
-	  new_fixed_tvs = foldl extend fixed_tvs non_ip_tvs
-
-    extend fixed_tvs pred_tvs 
-	| fixed_tvs `intersectsVarSet` pred_tvs = fixed_tvs `unionVarSet` pred_tvs
-	| otherwise			        = fixed_tvs
-
-    (ip_tvs, non_ip_tvs) = partitionWith get_ip preds
-    get_ip (IParam _ ty) = Left (tyVarsOfType ty)
-    get_ip other         = Right (tyVarsOfPred other)
-\end{code}
     
 %************************************************************************
 %*									*
@@ -238,6 +200,21 @@ NOTA BENE:
 \begin{code}
 type Pred_Loc = (PredType, SDoc)	-- SDoc says where the Pred comes from
 
+improveFromInstEnv :: (Class -> [Instance]) 
+                     -> Pred_Loc 
+                     -> [(Equation,Pred_Loc,Pred_Loc)]
+-- Improvement from top-level instances 
+improveFromInstEnv _inst_env pred 
+  = improveOne _inst_env pred []        -- TODO: Refactor to directly use instance_eqnd? 
+
+improveFromAnother :: Pred_Loc 
+                   -> Pred_Loc
+                   -> [(Equation,Pred_Loc,Pred_Loc)] 
+-- Improvement from another local (given or wanted) constraint
+improveFromAnother pred1 pred2 
+  = improveOne (\_ -> []) pred1 [pred2] -- TODO: Refactor to directly use pairwise_eqns?
+
+
 improveOne :: (Class -> [Instance])		-- Gives instances for given class
 	   -> Pred_Loc				-- Do improvement triggered by this
 	   -> [Pred_Loc]			-- Current constraints 
@@ -294,8 +271,9 @@ improveOne inst_env pred@(ClassP cls tys, _) preds
 	, not (instanceCantMatch inst_tcs trimmed_tcs)
 	, eqn <- checkClsFD qtvs fd cls_tvs tys_inst tys
 	, let p_inst = (mkClassPred cls tys_inst, 
-		        ptext (sLit "arising from the instance declaration at")
-			<+> ppr (getSrcLoc ispec))
+		        sep [ ptext (sLit "arising from the dependency") <+> quotes (pprFunDep fd)
+			    , ptext (sLit "in the instance declaration at") 
+			          <+> ppr (getSrcLoc ispec)])
 	]
 
 improveOne _ _ _