Fix issue with flag stored value

Storing flag keywords as std::true_type and not bool made some g++ chokes when used in requires clause.

Author: jfalcou

include/raberu/impl/keywords.hpp

@@ -288,7 +288,7 @@ namespace rbr
 
     using tag_type          = ID;
     using keyword_type      = flag_keyword;
-    using stored_value_type = std::true_type;
+    using stored_value_type = bool;
 
     template<typename Type>
     constexpr auto operator=(Type&&) const noexcept { return *this; }
@@ -304,7 +304,7 @@ namespace rbr
       return _::type_or_<flag_keyword,call<Func>>{RBR_FWD(v)};
     }
 
-    constexpr std::true_type operator()(keyword_type const&) const noexcept { return {}; }
+    constexpr auto operator()(keyword_type const&) const noexcept { return true; }
 
     template<typename O0, typename O1, typename... Os>
     constexpr decltype(auto) operator()(O0&&, O1&&, Os&&... ) const

include/raberu/impl/settings.hpp

@@ -69,7 +69,7 @@ namespace rbr
     static constexpr auto contains([[maybe_unused]] Key const& kw) noexcept
     {
       using found = decltype((std::declval<base>())(Key{}));
-      return std::bool_constant<!stdfix::same_as<found, unknown_key> >{};
+      return !stdfix::same_as<found, unknown_key>;
     }
 
     //==============================================================================================

standalone/raberu/raberu.hpp

@@ -333,7 +333,7 @@ namespace rbr
     }
     using tag_type          = ID;
     using keyword_type      = flag_keyword;
-    using stored_value_type = std::true_type;
+    using stored_value_type = bool;
     template<typename Type>
     constexpr auto operator=(Type&&) const noexcept { return *this; }
     template<typename Type>
@@ -345,7 +345,7 @@ namespace rbr
     {
       return _::type_or_<flag_keyword,call<Func>>{RBR_FWD(v)};
     }
-    constexpr std::true_type operator()(keyword_type const&) const noexcept { return {}; }
+    constexpr auto operator()(keyword_type const&) const noexcept { return true; }
     template<typename O0, typename O1, typename... Os>
     constexpr decltype(auto) operator()(O0&&, O1&&, Os&&... ) const
     {
@@ -395,7 +395,7 @@ namespace rbr
     static constexpr auto contains([[maybe_unused]] Key const& kw) noexcept
     {
       using found = decltype((std::declval<base>())(Key{}));
-      return std::bool_constant<!stdfix::same_as<found, unknown_key> >{};
+      return !stdfix::same_as<found, unknown_key>;
     }
     template<concepts::keyword... Keys>
     static constexpr auto contains_any(Keys... ks) noexcept { return (contains(ks) || ...); }

test/unit/fetch.cpp

@@ -51,7 +51,7 @@ TTS_CASE("Check rbr::fetch_t behavior on options")
 
   TTS_TYPE_IS( (rbr::result::fetch_t<coord_   , opt1_t, opt2_t, opt3_t>), std::string     );
   TTS_TYPE_IS( (rbr::result::fetch_t<value_   , opt1_t, opt2_t, opt3_t>), float           );
-  TTS_TYPE_IS( (rbr::result::fetch_t<is_modal_, opt1_t, opt2_t, opt3_t>), std::true_type  );
+  TTS_TYPE_IS( (rbr::result::fetch_t<is_modal_, opt1_t, opt2_t, opt3_t>), bool            );
   TTS_TYPE_IS( (rbr::result::fetch_t<"flop"_kw, opt1_t, opt2_t, opt3_t>), rbr::unknown_key);
 };
 
@@ -64,7 +64,7 @@ TTS_CASE("Check rbr::fetch_t behavior on settings")
 
   TTS_TYPE_IS( (rbr::result::fetch_t<coord_   , opts_t>), std::string     );
   TTS_TYPE_IS( (rbr::result::fetch_t<value_   , opts_t>), float           );
-  TTS_TYPE_IS( (rbr::result::fetch_t<is_modal_, opts_t>), std::true_type  );
+  TTS_TYPE_IS( (rbr::result::fetch_t<is_modal_, opts_t>), bool            );
   TTS_TYPE_IS( (rbr::result::fetch_t<"flop"_kw, opts_t>), rbr::unknown_key);
 };