From 93e02a01568519344310897e8e9f4ee4f32ff75f Mon Sep 17 00:00:00 2001
From: Felix Morgner <felix.morgner@gmail.com>
Date: Thu, 8 Jun 2023 15:42:41 +0200
Subject: concets: replace is_*_input_streamable*

---
 source/lib/include/newtype/concepts.hpp            | 16 +++++++++++++
 .../newtype/impl/type_traits_extensions.hpp        | 27 ----------------------
 source/lib/include/newtype/newtype.hpp             | 20 +++++++++-------
 3 files changed, 28 insertions(+), 35 deletions(-)

diff --git a/source/lib/include/newtype/concepts.hpp b/source/lib/include/newtype/concepts.hpp
index 6db528c..c053612 100644
--- a/source/lib/include/newtype/concepts.hpp
+++ b/source/lib/include/newtype/concepts.hpp
@@ -4,6 +4,7 @@
 #include <concepts>
 #include <cstddef>
 #include <functional>
+#include <iosfwd>
 
 namespace nt::concepts
 {
@@ -38,6 +39,21 @@ namespace nt::concepts
     } noexcept;
   };
 
+  template<typename SubjectType, typename CharType, typename StreamTraits>
+  concept input_streamable = requires(SubjectType subject) {
+    {
+      std::declval<std::basic_istream<CharType, StreamTraits> &>() >> subject
+    } -> std::same_as<std::basic_istream<CharType, StreamTraits> &>;
+  };
+
+  template<typename SubjectType, typename CharType, typename StreamTraits>
+  concept nothrow_input_streamable = requires(SubjectType subject) {
+    requires input_streamable<SubjectType, CharType, StreamTraits>;
+    {
+      std::declval<std::basic_istream<CharType, StreamTraits> &>() >> subject
+    } noexcept;
+  };
+
   template<typename SubjectType>
   concept hashable = requires(SubjectType subject) {
     {
diff --git a/source/lib/include/newtype/impl/type_traits_extensions.hpp b/source/lib/include/newtype/impl/type_traits_extensions.hpp
index c4b9bee..7db8e66 100644
--- a/source/lib/include/newtype/impl/type_traits_extensions.hpp
+++ b/source/lib/include/newtype/impl/type_traits_extensions.hpp
@@ -155,33 +155,6 @@ namespace nt::impl
     template<typename StreamType, typename T>
     auto constexpr is_nothrow_output_streamable_v = is_nothrow_output_streamable<StreamType, T>::value;
 
-    template<typename StreamType, typename T, typename = void>
-    struct is_input_streamable : std::false_type
-    {
-    };
-
-    template<typename StreamType, typename T>
-    struct is_input_streamable<StreamType, T, std::void_t<decltype(std::declval<StreamType &>() >> std::declval<T &>())>> : std::true_type
-    {
-    };
-
-    template<typename StreamType, typename T>
-    auto constexpr is_input_streamable_v = is_input_streamable<StreamType, T>::value;
-
-    template<typename StreamType, typename T, typename = void>
-    struct is_nothrow_input_streamable : std::false_type
-    {
-    };
-
-    template<typename StreamType, typename T>
-    struct is_nothrow_input_streamable<StreamType, T, std::void_t<decltype(std::declval<StreamType &>() >> std::declval<T &>())>>
-        : std::bool_constant<noexcept(std::declval<StreamType &>() >> std::declval<T &>())>
-    {
-    };
-
-    template<typename StreamType, typename T>
-    auto constexpr is_nothrow_input_streamable_v = is_nothrow_input_streamable<StreamType, T>::value;
-
   }  // namespace iostreamable
 
   inline namespace arithmetic
diff --git a/source/lib/include/newtype/newtype.hpp b/source/lib/include/newtype/newtype.hpp
index 33863ac..acfd2f9 100644
--- a/source/lib/include/newtype/newtype.hpp
+++ b/source/lib/include/newtype/newtype.hpp
@@ -25,11 +25,13 @@ namespace nt
     static_assert(!std::is_reference_v<BaseType>, "The base type must not be a reference type");
     static_assert(!std::is_void_v<std::remove_cv_t<BaseType>>, "The base type must not be possibly cv-qualified void");
 
-    template<typename BaseTypeT, typename TagTypeT, auto DerivationClauseV, typename CharType, typename StreamTraits>
+    template<typename CharType,
+             typename StreamTraits,
+             nt::concepts::input_streamable<CharType, StreamTraits> BaseTypeT,
+             typename TagTypeT,
+             nt::contains<nt::Read> auto DerivationClauseV>
     auto friend operator>>(std::basic_istream<CharType, StreamTraits> &, new_type<BaseTypeT, TagTypeT, DerivationClauseV> &) noexcept(
-        impl::is_nothrow_input_streamable_v<std::basic_istream<CharType, StreamTraits>, BaseTypeT>)
-        -> std::enable_if_t<DerivationClauseV(nt::Read) && impl::is_input_streamable_v<std::basic_istream<CharType, StreamTraits>, BaseTypeT>,
-                            std::basic_istream<CharType, StreamTraits>> &;
+        nt::concepts::nothrow_input_streamable<BaseTypeT, CharType, StreamTraits>) -> std::basic_istream<CharType, StreamTraits> &;
 
     template<typename BaseTypeT, typename TagTypeT, auto DerivationClauseV>
     auto constexpr friend
@@ -342,11 +344,13 @@ namespace nt
     return output << source.decay();
   }
 
-  template<typename BaseType, typename TagType, auto DerivationClause, typename CharType, typename StreamTraits>
+  template<typename CharType,
+           typename StreamTraits,
+           nt::concepts::input_streamable<CharType, StreamTraits> BaseType,
+           typename TagType,
+           nt::contains<nt::Read> auto DerivationClause>
   auto operator>>(std::basic_istream<CharType, StreamTraits> & input, new_type<BaseType, TagType, DerivationClause> & target) noexcept(
-      impl::is_nothrow_input_streamable_v<std::basic_istream<CharType, StreamTraits>, BaseType>)
-      -> std::enable_if_t<DerivationClause(nt::Read) && impl::is_input_streamable_v<std::basic_istream<CharType, StreamTraits>, BaseType>,
-                          std::basic_istream<CharType, StreamTraits>> &
+      nt::concepts::nothrow_input_streamable<BaseType, CharType, StreamTraits>) -> std::basic_istream<CharType, StreamTraits> &
   {
     return input >> target.m_value;
   }
-- 
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