Fix Trac #3102: pre-matching polytypes

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

diff --git a/compiler/typecheck/TcUnify.lhs b/compiler/typecheck/TcUnify.lhs
index e5e16fc..064f199 100644 (file)
--- a/compiler/typecheck/TcUnify.lhs
+++ b/compiler/typecheck/TcUnify.lhs
@@ -578,9 +578,10 @@ boxy_match tmpl_tvs orig_tmpl_ty boxy_tvs orig_boxy_ty subst
 
     go ty1 ty2          -- C.f. the isSigmaTy case for boxySubMatchType
         | isSigmaTy ty1
-        , (tvs1, _, tau1) <- tcSplitSigmaTy ty1
-        , (tvs2, _, tau2) <- tcSplitSigmaTy ty2
+        , (tvs1, ps1, tau1) <- tcSplitSigmaTy ty1
+        , (tvs2, ps2, tau2) <- tcSplitSigmaTy ty2
         , equalLength tvs1 tvs2
+        , equalLength ps1  ps2
         = boxy_match (tmpl_tvs `delVarSetList` tvs1)    tau1
                      (boxy_tvs `extendVarSetList` tvs2) tau2 subst
 
@@ -1039,8 +1040,8 @@ lists, when all the elts should be of the same type.
 unifyTypeList :: [TcTauType] -> TcM ()
 unifyTypeList []                 = return ()
 unifyTypeList [_]                = return ()
-unifyTypeList (ty1:tys@(ty2:_)) = do { unifyType ty1 ty2
-                                      ; unifyTypeList tys }
+unifyTypeList (ty1:tys@(ty2:_)) = do { _ <- unifyType ty1 ty2
+                                     ; unifyTypeList tys }
 \end{code}
 
 %************************************************************************
@@ -1681,7 +1682,7 @@ zapToMonotype :: BoxySigmaType -> TcM TcTauType
 -- with that type.
 zapToMonotype res_ty
   = do  { res_tau <- newFlexiTyVarTy liftedTypeKind
-        ; boxyUnify res_tau res_ty
+        ; _ <- boxyUnify res_tau res_ty
         ; return res_tau }
 
 unBox :: BoxyType -> TcM TcType