fix: revert duplicate template default arguments for GCC <12

Author: fbdtemme

include/bencode/detail/bvalue/basic_bvalue.hpp

@@ -35,12 +35,6 @@ constexpr const auto* get_storage(const basic_bvalue<Policy>* value) noexcept;
 template <typename Policy>
 constexpr auto* get_storage(basic_bvalue<Policy>* value) noexcept;
 
-// forward declarations
-template <typename U, typename Policy, typename T>
-    requires serializable<T>
-inline void assign_to_bvalue(basic_bvalue<Policy>& bvalue, U&& value);
-
-
 template <basic_bvalue_instantiation BV>
 decltype(auto) evaluate(const bpointer& pointer, BV&& bv);
 

include/bencode/detail/bvalue/concepts.hpp

@@ -37,10 +37,17 @@ concept bvalue_alternative_type =
 
 namespace detail {
 
-// forward declaration.
-template <typename U, typename Policy, typename T>
+#if defined(__GNUC__) && __GNUC__ < 12
+    // forward declaration.
+    template <typename U, typename Policy, typename T = std::remove_cvref_t<U>>
+        requires serializable<T>
+    inline void assign_to_bvalue(basic_bvalue<Policy>& bvalue, U&& value);
+#else
+    // forward declaration.
+    template <typename U, typename Policy, typename T>
     requires serializable<T>
-inline void assign_to_bvalue(basic_bvalue<Policy>& bvalue, U&& value);
+    inline void assign_to_bvalue(basic_bvalue<Policy>& bvalue, U&& value);
+#endif
 
 // forward declaration.
 template <serializable T, basic_bvalue_instantiation U>

include/bencode/detail/events/concepts.hpp

@@ -61,10 +61,17 @@ concept event_connecting_is_adl_overloaded =
 } // namespace detail
 
 
-// forward declaration
-template <typename EC, typename U, typename T>
-    requires serializable<T> && event_consumer<EC>
-constexpr void connect(EC& consumer, U&& producer);
+#if defined(__GNUC__) && __GNUC__ < 12
+    // forward declaration
+    template <typename EC, typename U, typename T = std::remove_cvref_t<U>>
+        requires serializable<T> && event_consumer<EC>
+    constexpr void connect(EC& consumer, U&& producer);
+#else
+    // forward declaration
+    template <typename EC, typename U, typename T>
+        requires serializable<T> && event_consumer<EC>
+    constexpr void connect(EC& consumer, U&& producer);
+#endif