兼容较低版本gcc

Author: CppCXY

include/CodeFormatServer/LanguageClient.h

@@ -11,12 +11,16 @@
 // 前置声明
 class Service;
 
+#if defined(__GNUC__) && __GNUC__ < 10
+#define ServiceClass typename
+#else
 template <class Derived>
 concept ServiceClass = requires(Derived d)
 {
 	std::is_base_of<Service, Derived>::value;
 	Derived::ServiceIndex;
 };
+#endif
 
 class LanguageClient: public std::enable_shared_from_this<LanguageClient>
 {