[libcxx-commits] [libcxx] [libc++][test] Move the SFINAE test for return types of `quoted` to `libcxx/test/libcxx/` (PR #157026)
Louis Dionne via libcxx-commits
libcxx-commits at lists.llvm.org
Tue Jan 13 06:32:46 PST 2026
https://github.com/ldionne updated https://github.com/llvm/llvm-project/pull/157026
>From 2fe1e9eb9fabec64c9403aeef9033de008cd6c06 Mon Sep 17 00:00:00 2001
From: "A. Jiang" <de34 at live.cn>
Date: Fri, 5 Sep 2025 14:52:34 +0800
Subject: [PATCH 1/2] [libc++][test] Move the SFINAE test for return types of
`quoted` to `libcxx/test/libcxx/`
[quoted.manip] only specifies that `operator<<`/`operator>>` is
well-formed for operands with suitable types, and leaves it undefined
whether they are SFINAE-friendly.
Although it's worthwhile making them SFINAE-friendly, perhaps the
SFINAE-friendliness should be considered as a libc++-specific choice at
this moment.
Also clang-format the file to make CI happy.
---
.../quoted_traits.compile.pass.cpp | 117 +++++++++---------
1 file changed, 60 insertions(+), 57 deletions(-)
rename libcxx/test/{std => libcxx}/input.output/iostream.format/quoted.manip/quoted_traits.compile.pass.cpp (63%)
diff --git a/libcxx/test/std/input.output/iostream.format/quoted.manip/quoted_traits.compile.pass.cpp b/libcxx/test/libcxx/input.output/iostream.format/quoted.manip/quoted_traits.compile.pass.cpp
similarity index 63%
rename from libcxx/test/std/input.output/iostream.format/quoted.manip/quoted_traits.compile.pass.cpp
rename to libcxx/test/libcxx/input.output/iostream.format/quoted.manip/quoted_traits.compile.pass.cpp
index 35aa54b1772b3..eb126ec1e3ad7 100644
--- a/libcxx/test/std/input.output/iostream.format/quoted.manip/quoted_traits.compile.pass.cpp
+++ b/libcxx/test/libcxx/input.output/iostream.format/quoted.manip/quoted_traits.compile.pass.cpp
@@ -16,6 +16,8 @@
// with the wrong CharTraits. To avoid our having to create working
// ostreams with weird CharTraits, this is a compile-only test.
+// It is unspecified whether these operators are SFINAE-friendly. We choose to make them so.
+
#include <iomanip>
#include <istream>
#include <ostream>
@@ -26,44 +28,47 @@
#include "test_allocator.h"
#include "test_macros.h"
-template<class IS, class Q>
-decltype(std::declval<IS>() >> std::declval<Q>(), std::true_type())
-has_rightshift_impl(int) { return std::true_type(); }
+template <class IS, class Q>
+decltype(std::declval<IS>() >> std::declval<Q>(), std::true_type()) has_rightshift_impl(int) {
+ return std::true_type();
+}
-template<class IS, class Q>
-std::false_type
-has_rightshift_impl(long) { return std::false_type(); }
+template <class IS, class Q>
+std::false_type has_rightshift_impl(long) {
+ return std::false_type();
+}
-template<class IS, class Q>
+template <class IS, class Q>
struct HasRightShift : decltype(has_rightshift_impl<IS, Q>(0)) {};
-template<class OS, class Q>
-decltype(std::declval<OS>() << std::declval<Q>(), std::true_type())
-has_leftshift_impl(int) { return std::true_type(); }
+template <class OS, class Q>
+decltype(std::declval<OS>() << std::declval<Q>(), std::true_type()) has_leftshift_impl(int) {
+ return std::true_type();
+}
-template<class OS, class Q>
-std::false_type
-has_leftshift_impl(long) { return std::false_type(); }
+template <class OS, class Q>
+std::false_type has_leftshift_impl(long) {
+ return std::false_type();
+}
-template<class OS, class Q>
+template <class OS, class Q>
struct HasLeftShift : decltype(has_leftshift_impl<OS, Q>(0)) {};
-template<class CharT>
+template <class CharT>
struct FakeCharTraits : std::char_traits<CharT> {};
-void test_string_literal()
-{
+void test_string_literal() {
using Q = decltype(std::quoted("hello"));
- static_assert( HasLeftShift<std::ostream&, Q>::value, "");
+ static_assert(HasLeftShift<std::ostream&, Q>::value, "");
static_assert(!HasRightShift<std::istream&, Q>::value, "");
- static_assert( HasLeftShift<std::basic_ostream<char, FakeCharTraits<char>>&, Q>::value, "");
+ static_assert(HasLeftShift<std::basic_ostream<char, FakeCharTraits<char>>&, Q>::value, "");
static_assert(!HasRightShift<std::basic_istream<char, FakeCharTraits<char>>&, Q>::value, "");
#ifndef TEST_HAS_NO_WIDE_CHARACTERS
using WQ = decltype(std::quoted(L"hello"));
- static_assert( HasLeftShift<std::wostream&, WQ>::value, "");
+ static_assert(HasLeftShift<std::wostream&, WQ>::value, "");
static_assert(!HasRightShift<std::wistream&, WQ>::value, "");
- static_assert( HasLeftShift<std::basic_ostream<wchar_t, FakeCharTraits<wchar_t>>&, WQ>::value, "");
+ static_assert(HasLeftShift<std::basic_ostream<wchar_t, FakeCharTraits<wchar_t>>&, WQ>::value, "");
static_assert(!HasRightShift<std::basic_istream<wchar_t, FakeCharTraits<wchar_t>>&, WQ>::value, "");
static_assert(!HasLeftShift<std::ostream&, WQ>::value, "");
@@ -71,15 +76,14 @@ void test_string_literal()
#endif // TEST_HAS_NO_WIDE_CHARACTERS
}
-void test_std_string()
-{
- std::string s = "hello";
+void test_std_string() {
+ std::string s = "hello";
const auto& cs = s;
- using Q = decltype(std::quoted(s));
- using CQ = decltype(std::quoted(cs));
- static_assert( HasLeftShift<std::ostream&, Q>::value, "");
- static_assert( HasRightShift<std::istream&, Q>::value, "");
- static_assert( HasLeftShift<std::ostream&, CQ>::value, "");
+ using Q = decltype(std::quoted(s));
+ using CQ = decltype(std::quoted(cs));
+ static_assert(HasLeftShift<std::ostream&, Q>::value, "");
+ static_assert(HasRightShift<std::istream&, Q>::value, "");
+ static_assert(HasLeftShift<std::ostream&, CQ>::value, "");
static_assert(!HasRightShift<std::istream&, CQ>::value, "");
static_assert(!HasLeftShift<std::basic_ostream<char, FakeCharTraits<char>>&, Q>::value, "");
static_assert(!HasRightShift<std::basic_istream<char, FakeCharTraits<char>>&, Q>::value, "");
@@ -87,26 +91,26 @@ void test_std_string()
static_assert(!HasRightShift<std::basic_istream<char, FakeCharTraits<char>>&, CQ>::value, "");
std::basic_string<char, FakeCharTraits<char>, test_allocator<char>> st = "hello";
- const auto& cst = st;
- using QT = decltype(std::quoted(st));
- using CQT = decltype(std::quoted(cst));
+ const auto& cst = st;
+ using QT = decltype(std::quoted(st));
+ using CQT = decltype(std::quoted(cst));
static_assert(!HasLeftShift<std::ostream&, QT>::value, "");
static_assert(!HasRightShift<std::istream&, QT>::value, "");
static_assert(!HasLeftShift<std::ostream&, CQT>::value, "");
static_assert(!HasRightShift<std::istream&, CQT>::value, "");
- static_assert( HasLeftShift<std::basic_ostream<char, FakeCharTraits<char>>&, QT>::value, "");
- static_assert( HasRightShift<std::basic_istream<char, FakeCharTraits<char>>&, QT>::value, "");
- static_assert( HasLeftShift<std::basic_ostream<char, FakeCharTraits<char>>&, CQT>::value, "");
+ static_assert(HasLeftShift<std::basic_ostream<char, FakeCharTraits<char>>&, QT>::value, "");
+ static_assert(HasRightShift<std::basic_istream<char, FakeCharTraits<char>>&, QT>::value, "");
+ static_assert(HasLeftShift<std::basic_ostream<char, FakeCharTraits<char>>&, CQT>::value, "");
static_assert(!HasRightShift<std::basic_istream<char, FakeCharTraits<char>>&, CQT>::value, "");
#ifndef TEST_HAS_NO_WIDE_CHARACTERS
std::wstring ws = L"hello";
const auto& cws = ws;
- using WQ = decltype(std::quoted(ws));
- using CWQ = decltype(std::quoted(cws));
- static_assert( HasLeftShift<std::wostream&, WQ>::value, "");
- static_assert( HasRightShift<std::wistream&, WQ>::value, "");
- static_assert( HasLeftShift<std::wostream&, CWQ>::value, "");
+ using WQ = decltype(std::quoted(ws));
+ using CWQ = decltype(std::quoted(cws));
+ static_assert(HasLeftShift<std::wostream&, WQ>::value, "");
+ static_assert(HasRightShift<std::wistream&, WQ>::value, "");
+ static_assert(HasLeftShift<std::wostream&, CWQ>::value, "");
static_assert(!HasRightShift<std::wistream&, CWQ>::value, "");
static_assert(!HasLeftShift<std::basic_ostream<wchar_t, FakeCharTraits<wchar_t>>&, WQ>::value, "");
static_assert(!HasRightShift<std::basic_istream<wchar_t, FakeCharTraits<wchar_t>>&, WQ>::value, "");
@@ -118,15 +122,14 @@ void test_std_string()
#endif // TEST_HAS_NO_WIDE_CHARACTERS
}
-void test_std_string_view()
-{
+void test_std_string_view() {
std::string_view s = "hello";
- const auto& cs = s;
- using Q = decltype(std::quoted(s));
- using CQ = decltype(std::quoted(cs));
- static_assert( HasLeftShift<std::ostream&, Q>::value, "");
+ const auto& cs = s;
+ using Q = decltype(std::quoted(s));
+ using CQ = decltype(std::quoted(cs));
+ static_assert(HasLeftShift<std::ostream&, Q>::value, "");
static_assert(!HasRightShift<std::istream&, Q>::value, "");
- static_assert( HasLeftShift<std::ostream&, CQ>::value, "");
+ static_assert(HasLeftShift<std::ostream&, CQ>::value, "");
static_assert(!HasRightShift<std::istream&, CQ>::value, "");
static_assert(!HasLeftShift<std::basic_ostream<char, FakeCharTraits<char>>&, Q>::value, "");
static_assert(!HasRightShift<std::basic_istream<char, FakeCharTraits<char>>&, Q>::value, "");
@@ -134,26 +137,26 @@ void test_std_string_view()
static_assert(!HasRightShift<std::basic_istream<char, FakeCharTraits<char>>&, CQ>::value, "");
std::basic_string_view<char, FakeCharTraits<char>> st = "hello";
- const auto& cst = st;
- using QT = decltype(std::quoted(st));
- using CQT = decltype(std::quoted(cst));
+ const auto& cst = st;
+ using QT = decltype(std::quoted(st));
+ using CQT = decltype(std::quoted(cst));
static_assert(!HasLeftShift<std::ostream&, QT>::value, "");
static_assert(!HasRightShift<std::istream&, QT>::value, "");
static_assert(!HasLeftShift<std::ostream&, CQT>::value, "");
static_assert(!HasRightShift<std::istream&, CQT>::value, "");
- static_assert( HasLeftShift<std::basic_ostream<char, FakeCharTraits<char>>&, QT>::value, "");
+ static_assert(HasLeftShift<std::basic_ostream<char, FakeCharTraits<char>>&, QT>::value, "");
static_assert(!HasRightShift<std::basic_istream<char, FakeCharTraits<char>>&, QT>::value, "");
- static_assert( HasLeftShift<std::basic_ostream<char, FakeCharTraits<char>>&, CQT>::value, "");
+ static_assert(HasLeftShift<std::basic_ostream<char, FakeCharTraits<char>>&, CQT>::value, "");
static_assert(!HasRightShift<std::basic_istream<char, FakeCharTraits<char>>&, CQT>::value, "");
#ifndef TEST_HAS_NO_WIDE_CHARACTERS
std::wstring_view ws = L"hello";
- const auto& cws = ws;
- using WQ = decltype(std::quoted(ws));
- using CWQ = decltype(std::quoted(cws));
- static_assert( HasLeftShift<std::wostream&, WQ>::value, "");
+ const auto& cws = ws;
+ using WQ = decltype(std::quoted(ws));
+ using CWQ = decltype(std::quoted(cws));
+ static_assert(HasLeftShift<std::wostream&, WQ>::value, "");
static_assert(!HasRightShift<std::wistream&, WQ>::value, "");
- static_assert( HasLeftShift<std::wostream&, CWQ>::value, "");
+ static_assert(HasLeftShift<std::wostream&, CWQ>::value, "");
static_assert(!HasRightShift<std::wistream&, CWQ>::value, "");
static_assert(!HasLeftShift<std::basic_ostream<wchar_t, FakeCharTraits<wchar_t>>&, WQ>::value, "");
static_assert(!HasRightShift<std::basic_istream<wchar_t, FakeCharTraits<wchar_t>>&, WQ>::value, "");
>From f6386395ed029c70b1d5e59c7f075be45053d322 Mon Sep 17 00:00:00 2001
From: Louis Dionne <ldionne.2 at gmail.com>
Date: Tue, 13 Jan 2026 09:32:37 -0500
Subject: [PATCH 2/2] Update
libcxx/test/libcxx/input.output/iostream.format/quoted.manip/quoted_traits.compile.pass.cpp
---
.../iostream.format/quoted.manip/quoted_traits.compile.pass.cpp | 1 +
1 file changed, 1 insertion(+)
diff --git a/libcxx/test/libcxx/input.output/iostream.format/quoted.manip/quoted_traits.compile.pass.cpp b/libcxx/test/libcxx/input.output/iostream.format/quoted.manip/quoted_traits.compile.pass.cpp
index eb126ec1e3ad7..c16e0017822a9 100644
--- a/libcxx/test/libcxx/input.output/iostream.format/quoted.manip/quoted_traits.compile.pass.cpp
+++ b/libcxx/test/libcxx/input.output/iostream.format/quoted.manip/quoted_traits.compile.pass.cpp
@@ -17,6 +17,7 @@
// ostreams with weird CharTraits, this is a compile-only test.
// It is unspecified whether these operators are SFINAE-friendly. We choose to make them so.
+// See https://wg21.link/LWG4364 for whether this should be considered an extension or not.
#include <iomanip>
#include <istream>
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