static void template_parm_level_and_index (tree, int*, int*);
static int unify_pack_expansion (tree, tree, tree,
tree, unification_kind_t, bool, bool);
+static tree copy_template_args (tree);
static tree tsubst_template_arg (tree, tree, tsubst_flags_t, tree);
static tree tsubst_template_args (tree, tree, tsubst_flags_t, tree);
static tree tsubst_template_parms (tree, tree, tsubst_flags_t);
/* For each argument in each argument pack, substitute into the
pattern. */
result = make_tree_vec (len);
+ tree elem_args = copy_template_args (args);
for (i = 0; i < len; ++i)
{
t = gen_elem_of_pack_expansion_instantiation (pattern, packs,
i,
- args, complain,
+ elem_args, complain,
in_decl);
TREE_VEC_ELT (result, i) = t;
if (t == error_mark_node)
return pack;
}
+/* Return an exact copy of template args T that can be modified
+ independently. */
+
+static tree
+copy_template_args (tree t)
+{
+ if (t == error_mark_node)
+ return t;
+
+ int len = TREE_VEC_LENGTH (t);
+ tree new_vec = make_tree_vec (len);
+
+ for (int i = 0; i < len; ++i)
+ {
+ tree elt = TREE_VEC_ELT (t, i);
+ if (elt && TREE_CODE (elt) == TREE_VEC)
+ elt = copy_template_args (elt);
+ TREE_VEC_ELT (new_vec, i) = elt;
+ }
+
+ NON_DEFAULT_TEMPLATE_ARGS_COUNT (new_vec)
+ = NON_DEFAULT_TEMPLATE_ARGS_COUNT (t);
+
+ return new_vec;
+}
+
/* Substitute ARGS into the vector or list of template arguments T. */
static tree
--- /dev/null
+// PR c++/67164
+// { dg-do compile { target c++11 } }
+
+#include <type_traits>
+
+namespace detail {
+ template <bool ...b>
+ struct fast_and
+ : std::is_same<fast_and<b...>, fast_and<(b, true)...>>
+ { };
+}
+
+template <typename ...Xn>
+struct tuple {
+ tuple() { }
+
+ template <typename ...Yn, typename = typename std::enable_if<
+ detail::fast_and<std::is_constructible<Xn, Yn&&>::value...>::value
+ >::type>
+ tuple(Yn&& ...yn) { }
+
+ template <typename ...Yn, typename = typename std::enable_if<
+ detail::fast_and<std::is_constructible<Xn, Yn const&>::value...>::value
+ >::type>
+ tuple(tuple<Yn...> const& other) { }
+};
+
+tuple<tuple<>> t{};
+tuple<tuple<>> copy = t;