PR c++/72415 - member template with fold-expression constraint

	* pt.c (tsubst_pack_expansion): Pull a single pack expansion out
	of the TREE_VEC.

From-SVN: r239138

gcc/cp/ChangeLog

 2016-08-04  Jason Merrill  <jason@redhat.com>
 
+	PR c++/72415
+	* pt.c (tsubst_pack_expansion): Pull a single pack expansion out
+	of the TREE_VEC.
+
 	* cp-tree.h (TYPE_UNNAMED_P): Rename from TYPE_ANONYMOUS_P.
 	(TYPE_WAS_UNNAMED): Rename from TYPE_WAS_ANONYMOUS.
 	* class.c, decl.c, decl2.c, error.c, lambda.c, mangle.c,

gcc/cp/pt.c

@@ -11160,6 +11160,12 @@ tsubst_pack_expansion (tree t, tree args, tsubst_flags_t complain,
       local_specializations = saved_local_specializations;
     }
   
+  /* If the dependent pack arguments were such that we end up with only a
+     single pack expansion again, there's no need to keep it in a TREE_VEC.  */
+  if (len == 1 && TREE_CODE (result) == TREE_VEC
+      && PACK_EXPANSION_P (TREE_VEC_ELT (result, 0)))
+    return TREE_VEC_ELT (result, 0);
+
   return result;
 }
 

gcc/testsuite/g++.dg/concepts/memfun2.C

+// PR c++/72415
+// { dg-options "-std=c++1z -fconcepts" }
+
+template<int... Indices>
+struct indices {};
+
+template<typename Dummy>
+struct foo_type {
+    template<int... Indices>
+    static void impl(indices<Indices...>)
+        requires (... && (Indices, true));
+
+    static auto caller()
+    { return impl(indices<0, 1, 2> {}); }
+};
+
+int main()
+{
+    // internal compiler error: in satisfy_predicate_constraint, at cp/constraint.cc:2013
+    foo_type<void>::caller();
+}