From 10e0da40bcc582aa8149e25cb379bcd2c379961a Mon Sep 17 00:00:00 2001
From: Steffen Schuemann <s.schuemann@pobox.com>
Date: Tue, 17 Nov 2020 07:57:25 +0100
Subject: [PATCH] refs #79, constexpr on non-assigning bitmask operations

---
 include/ghc/filesystem.hpp | 8 ++++----
 test/filesystem_test.cpp   | 6 ++++++
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/include/ghc/filesystem.hpp b/include/ghc/filesystem.hpp
index 12bd8cc..2aca83f 100644
--- a/include/ghc/filesystem.hpp
+++ b/include/ghc/filesystem.hpp
@@ -1352,28 +1352,28 @@ using EnableBitmask = typename std::enable_if<std::is_same<Enum, perms>::value |
 }  // namespace detail
 
 template <typename Enum>
-detail::EnableBitmask<Enum> operator&(Enum X, Enum Y)
+constexpr detail::EnableBitmask<Enum> operator&(Enum X, Enum Y)
 {
     using underlying = typename std::underlying_type<Enum>::type;
     return static_cast<Enum>(static_cast<underlying>(X) & static_cast<underlying>(Y));
 }
 
 template <typename Enum>
-detail::EnableBitmask<Enum> operator|(Enum X, Enum Y)
+constexpr detail::EnableBitmask<Enum> operator|(Enum X, Enum Y)
 {
     using underlying = typename std::underlying_type<Enum>::type;
     return static_cast<Enum>(static_cast<underlying>(X) | static_cast<underlying>(Y));
 }
 
 template <typename Enum>
-detail::EnableBitmask<Enum> operator^(Enum X, Enum Y)
+constexpr detail::EnableBitmask<Enum> operator^(Enum X, Enum Y)
 {
     using underlying = typename std::underlying_type<Enum>::type;
     return static_cast<Enum>(static_cast<underlying>(X) ^ static_cast<underlying>(Y));
 }
 
 template <typename Enum>
-detail::EnableBitmask<Enum> operator~(Enum X)
+constexpr detail::EnableBitmask<Enum> operator~(Enum X)
 {
     using underlying = typename std::underlying_type<Enum>::type;
     return static_cast<Enum>(~static_cast<underlying>(X));
diff --git a/test/filesystem_test.cpp b/test/filesystem_test.cpp
index e9fe2d8..c3df41a 100644
--- a/test/filesystem_test.cpp
+++ b/test/filesystem_test.cpp
@@ -1145,8 +1145,14 @@ TEST_CASE("30.10.9 class filesystem_error", "[filesystem][filesystem_error][fs.c
     CHECK(fse.path2() == "some/other");
 }
 
+constexpr fs::perms constExprOwnerAll()
+{
+    return fs::perms::owner_read | fs::perms::owner_write | fs::perms::owner_exec;
+}
+
 TEST_CASE("30.10.10.4 enum class perms", "[filesystem][enum][fs.enum]")
 {
+    static_assert(constExprOwnerAll() == fs::perms::owner_all, "constexpr didn't result in owner_all");
     CHECK((fs::perms::owner_read | fs::perms::owner_write | fs::perms::owner_exec) == fs::perms::owner_all);
     CHECK((fs::perms::group_read | fs::perms::group_write | fs::perms::group_exec) == fs::perms::group_all);
     CHECK((fs::perms::others_read | fs::perms::others_write | fs::perms::others_exec) == fs::perms::others_all);