From 02c9b9ccffc66ec68ad4c2a0786c00984563d863 Mon Sep 17 00:00:00 2001
From: Jonathan Wakely <jwakely@redhat.com>
Date: Wed, 17 Apr 2019 14:13:30 +0100
Subject: [PATCH] Add constexpr to std::optional::value_or(U&&)&&

In C++1z drafts up to N4606 the constexpr keyword was missing from the
detailed description of this function, despite being shown in the class
synopsis.  That was fixed editorially for N4618, but our implementation
was not corrected to match.

	* include/std/optional (optional::value_or(U&&) &&): Add missing
	constexpr specifier.
	* testsuite/20_util/optional/constexpr/observers/4.cc: Check value_or
	for disengaged optionals and rvalue optionals.
	* testsuite/20_util/optional/observers/4.cc: Likewise.

From-SVN: r270409
---
 libstdc++-v3/ChangeLog                        |  8 ++++
 libstdc++-v3/include/std/optional             |  2 +-
 .../20_util/optional/constexpr/observers/4.cc | 38 +++++++++++++++++--
 .../testsuite/20_util/optional/observers/4.cc | 34 ++++++++++++++++-
 4 files changed, 77 insertions(+), 5 deletions(-)

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 55d2538b76e..9ab8bb9154a 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,11 @@
+2019-04-17  Jonathan Wakely  <jwakely@redhat.com>
+
+	* include/std/optional (optional::value_or(U&&) &&): Add missing
+	constexpr specifier.
+	* testsuite/20_util/optional/constexpr/observers/4.cc: Check value_or
+	for disengaged optionals and rvalue optionals.
+	* testsuite/20_util/optional/observers/4.cc: Likewise.
+
 2019-04-12  Thomas Rodgers  <trodgers@redhat.com>
 	
 	* include/pstl/algorithm_impl.h: Uglify identfiers.
diff --git a/libstdc++-v3/include/std/optional b/libstdc++-v3/include/std/optional
index d243930fed4..503d859bee6 100644
--- a/libstdc++-v3/include/std/optional
+++ b/libstdc++-v3/include/std/optional
@@ -959,7 +959,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	}
 
       template<typename _Up>
-	_Tp
+	constexpr _Tp
 	value_or(_Up&& __u) &&
 	{
 	  static_assert(is_move_constructible_v<_Tp>);
diff --git a/libstdc++-v3/testsuite/20_util/optional/constexpr/observers/4.cc b/libstdc++-v3/testsuite/20_util/optional/constexpr/observers/4.cc
index 1f7f0e8b6a2..a085f53f8fa 100644
--- a/libstdc++-v3/testsuite/20_util/optional/constexpr/observers/4.cc
+++ b/libstdc++-v3/testsuite/20_util/optional/constexpr/observers/4.cc
@@ -25,10 +25,42 @@ struct value_type
   int i;
 };
 
-int main()
+void test01()
 {
   constexpr std::optional<value_type> o { value_type { 51 } };
   constexpr value_type fallback { 3 };
-  static_assert( o.value_or(fallback).i == 51, "" );
-  static_assert( o.value_or(fallback).i == (*o).i, "" );
+  static_assert( o.value_or(fallback).i == 51 );
+  static_assert( o.value_or(fallback).i == (*o).i );
+}
+
+void test02()
+{
+  constexpr std::optional<value_type> o;
+  constexpr value_type fallback { 3 };
+  static_assert( o.value_or(fallback).i == 3 );
+}
+
+template<typename T>
+  constexpr std::optional<value_type>
+  make_rvalue(T t)
+  { return std::optional<value_type>{t}; }
+
+void test03()
+{
+  constexpr value_type fallback { 3 };
+  static_assert( make_rvalue(value_type{51}).value_or(fallback).i == 51 );
+}
+
+void test04()
+{
+  constexpr value_type fallback { 3 };
+  static_assert( make_rvalue(std::nullopt).value_or(fallback).i == 3 );
+}
+
+int main()
+{
+  test01();
+  test02();
+  test03();
+  test04();
 }
diff --git a/libstdc++-v3/testsuite/20_util/optional/observers/4.cc b/libstdc++-v3/testsuite/20_util/optional/observers/4.cc
index c24e4e6856e..5d608cdeaf7 100644
--- a/libstdc++-v3/testsuite/20_util/optional/observers/4.cc
+++ b/libstdc++-v3/testsuite/20_util/optional/observers/4.cc
@@ -26,10 +26,42 @@ struct value_type
   int i;
 };
 
-int main()
+void test01()
 {
   std::optional<value_type> o { value_type { 51 } };
   value_type fallback { 3 };
   VERIFY( o.value_or(fallback).i == 51 );
   VERIFY( o.value_or(fallback).i == (*o).i );
 }
+
+void test02()
+{
+  std::optional<value_type> o;
+  value_type fallback { 3 };
+  VERIFY( o.value_or(fallback).i == 3 );
+}
+
+void test03()
+{
+  std::optional<value_type> o { value_type { 51 } };
+  value_type fallback { 3 };
+  VERIFY( std::move(o).value_or(fallback).i == 51 );
+  VERIFY( o.has_value() );
+  VERIFY( std::move(o).value_or(fallback).i == (*o).i );
+}
+
+void test04()
+{
+  std::optional<value_type> o;
+  value_type fallback { 3 };
+  VERIFY( std::move(o).value_or(fallback).i == 3 );
+  VERIFY( !o.has_value() );
+}
+
+int main()
+{
+  test01();
+  test02();
+  test03();
+  test04();
+}
-- 
2.30.2