Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look
OK for trunk/15?
-- >8 --
Like in r15-6740-g27d620d6769715 for instantiate_template, we also need
to set tf_partial during the alias_ctad_tweaks transformation mainly for
benefit of properly handling extra-args trees.
In this testcase during alias_ctad_tweaks we substitute
ElemTs={Tuple<Us...>}, Ts={Ts...} into the requires-clause, which
tsubst_pack_expansion decides to defer via extra-args, and for the
subsequent add_extra_args to merge the deferred dependent arguments
tf_partial has to have been set earlier.
PR c++/122621
gcc/cp/ChangeLog:
* pt.cc (tsubst_pack_expansion): Use tf_partial instead of
tf_none, except when substituting outer (non-dependent) template
arguments.
gcc/testsuite/ChangeLog:
* g++.dg/cpp2a/class-deduction-alias26.C: New test.
---
gcc/cp/pt.cc | 5 +++--
.../g++.dg/cpp2a/class-deduction-alias26.C | 17 +++++++++++++++++
2 files changed, 20 insertions(+), 2 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp2a/class-deduction-alias26.C
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 1ee8e2fff7df..f30840c83a27 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -31711,7 +31711,7 @@ alias_ctad_tweaks (tree tmpl, tree uguides)
(INNERMOST_TEMPLATE_PARMS (fullatparms)));
}
- tsubst_flags_t complain = tf_none;
+ tsubst_flags_t complain = tf_partial;
tree aguides = NULL_TREE;
tree atparms = INNERMOST_TEMPLATE_PARMS (fullatparms);
unsigned natparms = TREE_VEC_LENGTH (atparms);
@@ -31818,7 +31818,8 @@ alias_ctad_tweaks (tree tmpl, tree uguides)
if (ci)
{
if (tree outer_targs = outer_template_args (f))
- ci = tsubst_constraint_info (ci, outer_targs, complain,
in_decl);
+ ci = tsubst_constraint_info (ci, outer_targs,
+ complain & ~tf_partial, in_decl);
ci = tsubst_constraint_info (ci, targs, complain, in_decl);
}
if (ci == error_mark_node)
diff --git a/gcc/testsuite/g++.dg/cpp2a/class-deduction-alias26.C
b/gcc/testsuite/g++.dg/cpp2a/class-deduction-alias26.C
new file mode 100644
index 000000000000..01fd1a4d5e25
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/class-deduction-alias26.C
@@ -0,0 +1,17 @@
+// PR c++/122621
+// { dg-do compile { target c++20 } }
+
+template <class, class>
+concept constructible_from = true;
+
+template <class... ElemTs>
+struct Tuple {
+ template <class... Ts> requires (... && constructible_from<ElemTs, Ts>)
+ Tuple(Ts &&...) {}
+};
+
+template <class... Us>
+using A = Tuple<Tuple<Us...>>;
+
+using type = decltype(A{0});
+using type = Tuple<Tuple<>>;
--
2.53.0.rc1.65.gea24e2c554
