Okay I asked the dev who wrote this:

auto(ROII&)(auto(*)(Str&&)noexcept->void) ->void Is is a reference to a function which takes a function pointer as argument. This function pointer is a pointer because its okay to pass nullptr if you dont need it, but the first function must be passed thats why it is a reference. The second pointer is a pointer to a function wich is noexcept and takes a rvalue reference to a string as paremeter. ROII marks game ready functions.

Jesus xD

Thanks for the help anyway guys

Okay I asked the dev who wrote this:

auto(ROII&)(auto(*)(Str&&)noexcept->void) ->void 

Is a reference to a function which takes a function pointer as argument. This function pointer is a pointer because its okay to pass nullptr if you dont need it, but the first function must be passed thats why it is a reference. The second pointer is a pointer to a function wich is noexcept and takes a rvalue reference to a string as paremeter. ROII marks game ready functions.