X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcPat.lhs;h=bef5ec742b1f2de5178060ffa764038cc526347b;hb=269210b04b1428ae5270f15024ab9af23c7497fc;hp=82ac5e3596a53c1558c6800ed3f58f2b7b09a5fd;hpb=d95190caa3e09b33bca8544051043954ebd89c73;p=ghc-hetmet.git

diff --git a/compiler/typecheck/TcPat.lhs b/compiler/typecheck/TcPat.lhs
index 82ac5e3..bef5ec7 100644
--- a/compiler/typecheck/TcPat.lhs
+++ b/compiler/typecheck/TcPat.lhs
@@ -365,8 +365,11 @@ tc_pat pstate lpat@(LazyPat pat) pat_ty thing_inside
 	-- getLIE/extendLIEs: see Note [Hopping the LIE in lazy patterns]
 
 	-- Check no existentials
-	; if (null pat_tvs) then return ()
-	  else lazyPatErr lpat pat_tvs
+	; unless (null pat_tvs) $ lazyPatErr lpat pat_tvs
+
+	-- Check there are no unlifted types under the lazy pattern
+	; when (any (isUnLiftedType . idType) $ collectPatBinders pat') $
+               lazyUnliftedPatErr lpat
 
 	-- Check that the pattern has a lifted type
 	; pat_tv <- newBoxyTyVar liftedTypeKind
@@ -1040,6 +1043,12 @@ lazyPatErr _ tvs
     hang (ptext (sLit "A lazy (~) pattern cannot match existential or GADT data constructors"))
        2 (vcat (map pprSkolTvBinding tvs))
 
+lazyUnliftedPatErr :: OutputableBndr name => Pat name -> TcM ()
+lazyUnliftedPatErr pat
+  = failWithTc $
+    hang (ptext (sLit "A lazy (~) pattern cannot contain unlifted types"))
+       2 (ppr pat)
+
 nonRigidMatch :: PatCtxt -> DataCon -> SDoc
 nonRigidMatch ctxt con
   =  hang (ptext (sLit "GADT pattern match in non-rigid context for") <+> quotes (ppr con))