[pushed] c++: CTAD with alias and nested template [PR105655]
Commit Message
Here, alias_ctad_tweaks expect tsubst_decl of a FUNCTION_DECL to return a
FUNCTION_DECL. A reasonable expectation, but in this case we were replacing
the template args of the class-scope deduction guide with equivalent args,
so looking in the hash table we found the partial instantiation stored when
instantiating A<int>, which is a TEMPLATE_DECL. It's fine for that to be
what is stored, but tsubst_function_decl should never return it.
Tested x86_64-pc-linux-gnu, applying to trunk.
PR c++/105655
gcc/cp/ChangeLog:
* pt.cc (build_template_decl): Add assert.
(tsubst_function_decl): Don't return a template.
gcc/testsuite/ChangeLog:
* g++.dg/cpp2a/class-deduction-alias13.C: New test.
---
gcc/cp/pt.cc | 6 ++++-
.../g++.dg/cpp2a/class-deduction-alias13.C | 24 +++++++++++++++++++
2 files changed, 29 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/cpp2a/class-deduction-alias13.C
base-commit: 850a9ce8bcca59c7efabcdeeca14c5bd905e8363
@@ -5021,6 +5021,8 @@ maybe_update_decl_type (tree orig_type, tree scope)
static tree
build_template_decl (tree decl, tree parms, bool member_template_p)
{
+ gcc_checking_assert (TREE_CODE (decl) != TEMPLATE_DECL);
+
tree tmpl = build_lang_decl (TEMPLATE_DECL, DECL_NAME (decl), NULL_TREE);
SET_DECL_LANGUAGE (tmpl, DECL_LANGUAGE (decl));
DECL_TEMPLATE_PARMS (tmpl) = parms;
@@ -14074,7 +14076,9 @@ tsubst_function_decl (tree t, tree args, tsubst_flags_t complain,
{
hash = hash_tmpl_and_args (gen_tmpl, argvec);
if (tree spec = retrieve_specialization (gen_tmpl, argvec, hash))
- return spec;
+ /* The spec for these args might be a partial instantiation of the
+ template, but here what we want is the FUNCTION_DECL. */
+ return STRIP_TEMPLATE (spec);
}
}
else
new file mode 100644
@@ -0,0 +1,24 @@
+// PR c++/105655
+// { dg-do compile { target c++20 } }
+
+template <class T>
+struct A
+{
+ template <class L, class R>
+ struct B
+ {
+ B(const L & left, const R & right)
+ {}
+ };
+
+ template <class L, class R>
+ B(const L &, const R &) -> B<L, R>;
+};
+
+template <class L, class R>
+using C = A<int>::B<L, R>;
+
+int main()
+{
+ C x{0, 0};
+}