concept checking

pylene/include/mln/core/rangev3/view/transform.hpp

@@ -162,10 +162,23 @@ namespace mln::ranges
         return {::ranges::view::all(static_cast<Rng&&>(rng)), std::move(fun)};
       }
 
-      // TODO: concept checking
       template <typename Rng1, typename Rng2, typename Fun, CONCEPT_REQUIRES_(Concept2<Rng1, Rng2, Fun>())>
-      transform2_view<::ranges::view::all_t<Rng1>, ::ranges::view::all_t<Rng2>, Fun>
-          operator()(Rng1&& rng1, Rng2&& rng2, Fun fun) const
+#ifdef PYLENE_CONCEPT_TS_ENABLED
+          // clang-format off
+      requires mln::concepts::stl::InputRange<Rng1> &&
+               mln::concepts::stl::InputRange<Rng2> &&
+               mln::concepts::stl::CopyConstructible<Fun> &&
+               mln::concepts::stl::Invocable<Fun&,
+                 ::ranges::range_reference_t<Rng1>,
+                 ::ranges::range_reference_t<Rng2>> &&
+               not mln::concepts::stl::Same<void,
+                 std::invoke_result_t<Fun&,
+                   ::ranges::range_reference_t<Rng1>,
+                   ::ranges::range_reference_t<Rng2>>>
+#endif // PYLENE_CONCEPT_TS_ENABLED
+      transform2_view<::ranges::view::all_t<Rng1>, ::ranges::view::all_t<Rng2>, Fun> operator()(
+          Rng1&& rng1, Rng2&& rng2, Fun fun) const
+      // clang-format on
       {
         return {::ranges::view::all(static_cast<Rng1&&>(rng1)), ::ranges::view::all(static_cast<Rng2&&>(rng2)),
                 std::move(fun)};