function_output_iterator does not support specialization

[livicitu]

I have a vector of std::byte and I want to call boost::unhex for this vector by creating a custom output iterator with my own unary function to convert unsiged char to std::byte. Note that std::byte is not an integral type so I cannot pass it directly to boost::unhex It is possible to create a function_output_iterator where we can specify the value_type (ex, function_output_iterator<unsigned char>)? The alternative I have is to create a vector of unsigned char then copy it into a vector of std::byte but this is what I want to avoid.

This is what I tried:

	const std::string hexString = "0A";
	auto outputVector = std::vector<std::byte>{};
	auto unary_func = [&](const unsigned char& c) { outputVector .push_back(std::byte{c}); };
	auto func_out_iterator = boost::make_function_output_iterator(unary_func);
	boost::algorithm::unhex(hexString, func_out_iterator );

and I got:

 error C2893: Failed to specialize function template 'boost::enable_if<boost::is_integral<hex_iterator_traits<OutputIterator>::value_type>,OutputIterator>::type boost::algorithm::detail::decode_one(InputIterator &,InputIterator,OutputIterator,EndPred)'