X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypecheck%2FFamInst.lhs;h=5a3a6648f644b4e9c8437f10cf76d2997ce53df5;hb=9d0c8f842e35dde3d570580cf62a32779f66a6de;hp=5f4b2a3f922a38ac76a0c12c0ecd822b89091320;hpb=0f66260b5afc88accb6af6a09b20c3a4de51c39a;p=ghc-hetmet.git

diff --git a/compiler/typecheck/FamInst.lhs b/compiler/typecheck/FamInst.lhs
index 5f4b2a3..5a3a664 100644
--- a/compiler/typecheck/FamInst.lhs
+++ b/compiler/typecheck/FamInst.lhs
@@ -11,7 +11,6 @@ import TcMType
 import TcType
 import TcRnMonad
 import TyCon
-import Type
 import Name
 import Module
 import SrcLoc
@@ -178,38 +177,13 @@ checkForConflicts inst_envs famInst
 		-- (since we do unification).  
 		-- We use tcInstSkolType because we don't want to allocate
 		-- fresh *meta* type variables.  
-       ; let { tycon = famInstTyCon famInst
-	     ; ty    = case tyConFamInst_maybe tycon of
-		         Nothing        -> panic "FamInst.checkForConflicts"
-		         Just (tc, tys) -> tc `mkTyConApp` tys
-             }
-       ; (_, _, tau') <- tcInstSkolType FamInstSkol ty
-
-       ; let (fam, tys') = tcSplitTyConApp tau'
-
-       ; let { matches   = lookupFamInstEnvUnify inst_envs fam tys'
-	     ; conflicts = [ conflictingFamInst
-			   | match@((conflictingFamInst, _), _) <- matches
-			   , conflicting tycon match 
-			   ]
-	     }
+
+       ; skol_tvs <- tcInstSkolTyVars FamInstSkol (tyConTyVars (famInstTyCon famInst))
+       ; let conflicts = lookupFamInstEnvConflicts inst_envs famInst skol_tvs
        ; unless (null conflicts) $
-	   conflictInstErr famInst (head conflicts)
+	   conflictInstErr famInst (fst (head conflicts))
        }
   where
-      -- - In the case of data family instances, any overlap is fundamentally a
-      --   conflict (as these instances imply injective type mappings).
-      -- - In the case of type family instances, overlap is admitted as long as
-      --   the right-hand sides of the overlapping rules coincide under the
-      --   overlap substitution.  We require that they are syntactically equal;
-      --   anything else would be difficult to test for at this stage.
-    conflicting tycon1 ((famInst2, _), subst) 
-      | isAlgTyCon tycon1 = True
-      | otherwise         = not (rhs1 `tcEqType` rhs2)
-      where
-        tycon2 = famInstTyCon famInst2
-        rhs1   = substTy subst $ synTyConType tycon1
-        rhs2   = substTy subst $ synTyConType tycon2
 
 conflictInstErr :: FamInst -> FamInst -> TcRn ()
 conflictInstErr famInst conflictingFamInst