Remove duplicate util::key_error exception, don't require the key to be convertible to string

libs/util/include/psemek/util/at.hpp

@@ -2,12 +2,30 @@
 
 #include <psemek/util/exception.hpp>
 #include <psemek/util/to_string.hpp>
+#include <psemek/util/type_name.hpp>
 
 #include <vector>
 
 namespace psemek::util
 {
 
+	namespace detail
+	{
+
+		template <typename Key>
+		std::string key_error_to_string(Key const & key, decltype(util::to_string(key)) *)
+		{
+			return util::to_string("key ", key, " not found of type ", type_name<Key>());
+		}
+
+		template <typename Key>
+		std::string key_error_to_string(Key const &, ...)
+		{
+			return util::to_string("key not found of type ", type_name<Key>());
+		}
+
+	}
+
 	struct key_error_base
 		: exception
 	{
@@ -19,7 +37,7 @@ namespace psemek::util
 		: key_error_base
 	{
 		key_error(Key const & key, boost::stacktrace::stacktrace stacktrace = {})
-			: key_error_base(util::to_string("no such key: ", key), std::move(stacktrace))
+			: key_error_base(detail::key_error_to_string(key), std::move(stacktrace))
 			, key_(key)
 		{}
 

libs/util/include/psemek/util/key_error.hpp

@@ -1,29 +0,0 @@
-#pragma once
-
-#include <psemek/util/to_string.hpp>
-#include <psemek/util/type_name.hpp>
-
-#include <stdexcept>
-
-namespace psemek::util
-{
-
-	template <typename Key>
-	struct key_error
-		: std::out_of_range
-	{
-		key_error(Key const & key)
-			: std::out_of_range(to_string("unknown key ", key, " of type ", type_name<Key>()))
-			, key_(key)
-		{}
-
-		Key const & key() const noexcept
-		{
-			return key_;
-		}
-
-	private:
-		Key key_;
-	};
-
-}

libs/util/include/psemek/util/lru_cache.hpp

@@ -1,7 +1,7 @@
 #pragma once
 
 #include <psemek/util/functional.hpp>
-#include <psemek/util/key_error.hpp>
+#include <psemek/util/at.hpp>
 
 #include <list>
 #include <unordered_map>