PR c++/84368 - wrong error with local variable in variadic lambda.

	* pt.c (tsubst_pack_expansion): Fix handling of non-packs in
	local_specializations.

From-SVN: r257699

gcc/cp/ChangeLog

+2018-02-15  Jason Merrill  <jason@redhat.com>
+
+	PR c++/84368 - wrong error with local variable in variadic lambda.
+	* pt.c (tsubst_pack_expansion): Fix handling of non-packs in
+	local_specializations.
+
 2018-02-15  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	PR c++/84330

gcc/cp/pt.c

@@ -11521,8 +11521,9 @@ tsubst_pack_expansion (tree t, tree args, tsubst_flags_t complain,
 	     context.  */
 	  tree gen = TREE_PURPOSE (elt);
 	  tree inst = TREE_VALUE (elt);
-	  if (DECL_PACK_P (inst))
-	    inst = retrieve_local_specialization (inst);
+	  if (DECL_P (inst))
+	    if (tree local = retrieve_local_specialization (inst))
+	      inst = local;
 	  /* else inst is already a full instantiation of the pack.  */
 	  register_local_specialization (inst, gen);
 	}

gcc/testsuite/g++.dg/cpp1y/lambda-generic-variadic14.C

+// PR c++/84368
+// { dg-do compile { target c++14 } }
+
+template < typename ... T >
+void sink(T ...){}
+
+template < typename ... T >
+void foo(T ... v){
+    [](auto ... v){
+        auto bar = [](auto, auto){ return 0; };
+        sink(bar(v, T{}) ...);
+    }(v ...);
+}
+
+int main(){
+    foo(0);
+}