Here after dependent substitution of {Ts...} into the alias 'wrap',
since we never partially instantiate a requires-expr, we end up with a
requires-expr whose REQUIRES_EXPR_EXTRA_ARGS contains an
ARGUMENT_PACK_SELECT (which just resolves to the parameter pack Ts).
Then when looking up the resulting dependent specialization of A, we
crash from iterative_hash_template_arg since it deliberately doesn't
handle ARGUMENT_PACK_SELECT.
Like with r12-7102-gdb5f1c17031ad8, it seems the right fix here is to
resolve ARGUMENT_PACK_SELECT arguments before storing them into an
extra args tree (such as REQUIRES_EXPR).
Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
trunk/11? For 11, we'd need to backport r12-7102 as a prereq.
PR c++/103105
PR c++/103706
gcc/cp/ChangeLog:
* pt.cc (build_extra_args): Call preserve_args.
gcc/testsuite/ChangeLog:
* g++.dg/cpp2a/concepts-requires29.C: New test.
* g++.dg/cpp2a/concepts-requires29a.C: New test.
---
gcc/cp/pt.cc | 2 +-
.../g++.dg/cpp2a/concepts-requires29.C | 18 +++++++++++++++
.../g++.dg/cpp2a/concepts-requires29a.C | 23 +++++++++++++++++++
3 files changed, 42 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-requires29.C
create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-requires29a.C
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 78519562953..84712e6fc2f 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -13048,7 +13048,7 @@ build_extra_args (tree pattern, tree args,
tsubst_flags_t complain)
{
/* Make a copy of the extra arguments so that they won't get changed
out from under us. */
- tree extra = copy_template_args (args);
+ tree extra = preserve_args (copy_template_args (args), /*cow_p=*/false);
if (local_specializations)
if (tree locals = extract_local_specs (pattern, complain))
extra = tree_cons (NULL_TREE, extra, locals);
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-requires29.C
b/gcc/testsuite/g++.dg/cpp2a/concepts-requires29.C
new file mode 100644
index 00000000000..5118df978c9
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-requires29.C
@@ -0,0 +1,18 @@
+// PR c++/103105
+// { dg-do compile { target c++20 } }
+
+template<bool> class A;
+
+template<class... Ts>
+using wrap = A<1 != (0 + ... + requires { Ts(); })>;
+
+template<class... Ts> using type = wrap<Ts...>;
+
+using ty0 = type<>;
+using ty0 = A<true>;
+
+using ty1 = type<int>;
+using ty1 = A<false>;
+
+using ty2 = type<int, int>;
+using ty2 = A<true>;
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-requires29a.C
b/gcc/testsuite/g++.dg/cpp2a/concepts-requires29a.C
new file mode 100644
index 00000000000..c41c1e6d039
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-requires29a.C
@@ -0,0 +1,23 @@
+// PR c++/103105
+// { dg-do compile { target c++20 } }
+
+template<class...> struct list;
+template<bool> struct A;
+
+template<class T, class... Ts>
+using wrap = A<1 != (0 + ... + requires { T() = Ts(); })>;
+
+template<class... Ts>
+using type = list<wrap<Ts, Ts...>...>;
+
+using ty0 = type<>;
+using ty0 = list<>;
+
+using ty1 = type<int>;
+using ty1 = list<A<true>>;
+
+using ty2 = type<int, int>;
+using ty2 = list<A<true>, A<true>>;
+
+using ty3 = type<int, int, int>;
+using ty3 = list<A<true>, A<true>, A<true>>;
--
2.36.0.rc0
