# Expect a `[0-9a-fA-F]+` token.
	fun expect_hex(buffer: Buffer): Bool do
		if is_hex then
			loop
				buffer.chars.push(last_char.code_point)
				read_char
				if not is_hex then return true
			end
		else
			return fire_unexpected_char(". Expecting an hexadecimal digit")
		end
	end