Replace std::enable_if with requires

Introduce some concepts for enum and flags handling, goodbye and
thanks for all the fish std::enable_if.

1 files changed, 3 insertions, 5 deletions

diff --git a/src/string_utils.hh b/src/string_utils.hh
index e0adc181..a11aaa91 100644
--- a/src/string_utils.hh
+++ b/src/string_utils.hh
@@ -136,14 +136,12 @@ decltype(auto) to_string(const StronglyTypedNumber<RealType, ValueType>& val)
 namespace detail
 {
 
-template<typename T> constexpr bool is_string = std::is_convertible<T, StringView>::value;
+template<typename T> requires std::is_convertible_v<T, StringView> 
+StringView format_param(const T& val) { return val; }
 
-template<typename T, class = std::enable_if_t<not is_string<T>>>
+template<typename T> requires (not std::is_convertible_v<T, StringView>) 
 decltype(auto) format_param(const T& val) { return to_string(val); }
 
-template<typename T, class = std::enable_if_t<is_string<T>>>
-StringView format_param(const T& val) { return val; }
-
 }
 
 String format(StringView fmt, ArrayView<const StringView> params);