[gcc r13-2312] libstdc++: Add noexcept-specifier to std::reference_wrapper::operator()

[Jonathan Wakely <redi@gcc.gnu.org>]

https://gcc.gnu.org/g:e47df5eb56c4e7aca0d3e50826e5aaa1887fa446

commit r13-2312-ge47df5eb56c4e7aca0d3e50826e5aaa1887fa446
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Wed Aug 31 13:57:34 2022 +0100

    libstdc++: Add noexcept-specifier to std::reference_wrapper::operator()
    
    This isn't required by the standard, but there's an LWG issue suggesting
    to add it.
    
    Also use __invoke_result instead of result_of, to match the spec in
    recent standards.
    
    libstdc++-v3/ChangeLog:
    
            * include/bits/refwrap.h (reference_wrapper::operator()): Add
            noexcept-specifier and use __invoke_result instead of result_of.
            * testsuite/20_util/reference_wrapper/invoke-noexcept.cc: New test.

Diff:
---
 libstdc++-v3/include/bits/refwrap.h                       |  3 ++-
 .../20_util/reference_wrapper/invoke-noexcept.cc          | 15 +++++++++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/libstdc++-v3/include/bits/refwrap.h b/libstdc++-v3/include/bits/refwrap.h
index 8016f87478e..976902bc7bc 100644
--- a/libstdc++-v3/include/bits/refwrap.h
+++ b/libstdc++-v3/include/bits/refwrap.h
@@ -348,8 +348,9 @@ _GLIBCXX_MEM_FN_TRAITS(&& noexcept, false_type, true_type)
 
       template<typename... _Args>
 	_GLIBCXX20_CONSTEXPR
-	typename result_of<_Tp&(_Args&&...)>::type
+	typename __invoke_result<_Tp&, _Args...>::type
 	operator()(_Args&&... __args) const
+	noexcept(__is_nothrow_invocable<_Tp&, _Args...>::value)
 	{
 #if __cplusplus > 201703L
 	  if constexpr (is_object_v<type>)
diff --git a/libstdc++-v3/testsuite/20_util/reference_wrapper/invoke-noexcept.cc b/libstdc++-v3/testsuite/20_util/reference_wrapper/invoke-noexcept.cc
new file mode 100644
index 00000000000..91b5d097f08
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/reference_wrapper/invoke-noexcept.cc
@@ -0,0 +1,15 @@
+// { dg-do compile { target c++11 } }
+
+// C++11 20.8.3.4 reference_wrapper invocation [refwrap.invoke]
+
+#include <functional>
+
+struct F
+{
+  int operator()() noexcept(true) { return 1; }
+  int operator()() const noexcept(false) { return 2; }
+};
+
+F f;
+static_assert( noexcept(std::ref(f)()) );
+static_assert( ! noexcept(std::cref(f)()) );