Fix upcxx problem with a template argument list is expected after a name prefixed by the template keyword

var/spack/repos/builtin/packages/upcxx/fix_template_argument_list_error.patch

@@ -0,0 +1,26 @@
+diff --git a/src/future/future1.hpp b/src/future/future1.hpp
+index c2fd535a..e0fb187b 100644
+--- a/src/future/future1.hpp
++++ b/src/future/future1.hpp
+@@ -410,7 +410,7 @@ namespace upcxx {
+
+       UPCXXI_PROGRESS_UNTIL(impl_.ready(), detail::future_wait_upcxx_progress_user{});
+
+-      return std::move(*this).template result_tuple();
++      return std::move(*this).result_tuple();
+     }
+
+     template<int i=-1>
+diff --git a/src/rpc.hpp b/src/rpc.hpp
+index 4b644fa9..55feb545 100644
+--- a/src/rpc.hpp
++++ b/src/rpc.hpp
+@@ -301,7 +301,7 @@ namespace upcxx {
+
+       template<typename ...Arg>
+       void operator()(Arg &&...arg) const {
+-        backend::template send_awaken_lpc(
++        backend::send_awaken_lpc(
+           initiator,
+           remote_lpc, std::tuple<Arg&&...>(std::forward<Arg>(arg)...)
+         );

var/spack/repos/builtin/packages/upcxx/package.py

@@ -105,6 +105,7 @@ class Upcxx(Package, CudaPackage, ROCmPackage):
     depends_on("gmake", type="build")
 
     patch("fix_configure_ldflags.patch", when="@2021.9.0:master")
+    patch("fix_template_argument_list_error.patch", when="@2023.9.0:master")
 
     variant("mpi", default=False, description="Enables MPI-based spawners and mpi-conduit")