Tested x86_64-pc-linux-gnu, applying to trunk.
-- 8< --
Generally we expect TPARMS_PRIMARY_TEMPLATE to be set, but sometimes it
isn't for partial instantiations. This ought to be improved, but it's
trivial to work around it in this case.
PR c++/108468
gcc/cp/ChangeLog:
* pt.cc (unify_pack_expansion): Check that TPARMS_PRIMARY_TEMPLATE
is non-null.
gcc/testsuite/ChangeLog:
* g++.dg/cpp1y/var-templ78.C: New test.
---
gcc/cp/pt.cc | 2 ++
gcc/testsuite/g++.dg/cpp1y/var-templ78.C | 12 ++++++++++++
2 files changed, 14 insertions(+)
create mode 100644 gcc/testsuite/g++.dg/cpp1y/var-templ78.C
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 65341c40f97..c53d8e279c6 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -24148,6 +24148,8 @@ unify_pack_expansion (tree tparms, tree targs, tree
packed_parms,
arguments if it is not otherwise deduced. */
if (cxx_dialect >= cxx20
&& TREE_VEC_LENGTH (new_args) < TREE_VEC_LENGTH (old_args)
+ /* FIXME This isn't set properly for partial instantiations. */
+ && TPARMS_PRIMARY_TEMPLATE (tparms)
&& builtin_guide_p (TPARMS_PRIMARY_TEMPLATE (tparms)))
TREE_VEC_LENGTH (old_args) = TREE_VEC_LENGTH (new_args);
if (!comp_template_args (old_args, new_args,
diff --git a/gcc/testsuite/g++.dg/cpp1y/var-templ78.C
b/gcc/testsuite/g++.dg/cpp1y/var-templ78.C
new file mode 100644
index 00000000000..48366c92775
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1y/var-templ78.C
@@ -0,0 +1,12 @@
+// PR c++/108468
+// { dg-do compile { target c++14 } }
+
+template<int> struct C {
+ template<class, class>
+ static constexpr int x = 1;
+};
+
+template<int I> template<class... A>
+int C<I>::x<void(A...), void(A...)> = 2;
+
+int y = C<0>::x<void(int), void()>;
base-commit: 2b204accd07a3185b58b1edc6e9b019472857a5d
--
2.31.1
