replace several 'fromJust's with 'expectJust's

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

diff --git a/ghc/compiler/typecheck/TcTyClsDecls.lhs b/ghc/compiler/typecheck/TcTyClsDecls.lhs
index d2f53de..9e0b6cc 100644 (file)
--- a/ghc/compiler/typecheck/TcTyClsDecls.lhs
+++ b/ghc/compiler/typecheck/TcTyClsDecls.lhs
@@ -52,7 +52,8 @@ import Var            ( TyVar, idType, idName )
 import VarSet          ( elemVarSet, mkVarSet )
 import Name            ( Name, getSrcLoc )
 import Outputable
-import Maybe           ( isJust, fromJust )
+import Maybe           ( isJust )
+import Maybes          ( expectJust )
 import Unify           ( tcMatchTys, tcMatchTyX )
 import Util            ( zipLazy, isSingleton, notNull, sortLe )
 import List            ( partition )
@@ -663,7 +664,7 @@ checkFieldCompat fld con1 con2 tvs1 res1 res2 fty1 fty2
        ; checkTc (isJust mb_subst2) (fieldTypeMisMatch fld con1 con2) }
   where
     mb_subst1 = tcMatchTys tvs1 res1 res2
-    mb_subst2 = tcMatchTyX tvs1 (fromJust mb_subst1) fty1 fty2
+    mb_subst2 = tcMatchTyX tvs1 (expectJust "checkFieldCompat" mb_subst1) fty1 fty2
 
 -------------------------------
 checkValidDataCon :: TyCon -> DataCon -> TcM ()