Function invokeLambda

tutorials/external/catch.hpp:7293–7299

    template<typename ArgType, typename L>
    inline auto invokeLambda( L const &lambda, std::string const &arg ) -> ParserResult {
        ArgType temp{};
        auto result = convertInto( arg, temp );
        return !result
           ? result
           : LambdaInvoker<typename UnaryLambdaTraits<L>::ReturnType>::invoke( lambda, temp );
    }

    template<typename L>
    struct BoundLambda : BoundValueRefBase {