/usr/include/asio/impl/ is in libasio-dev 1:1.10.6-3.
This file is owned by root:root, with mode 0o755.
..
/usr/include/asio/impl/buffered_read_stream.hpp
/usr/include/asio/impl/buffered_write_stream.hpp
/usr/include/asio/impl/connect.hpp
/usr/include/asio/impl/error.ipp
/usr/include/asio/impl/error_code.ipp
/usr/include/asio/impl/handler_alloc_hook.ipp
/usr/include/asio/impl/io_service.hpp
/usr/include/asio/impl/io_service.ipp
/usr/include/asio/impl/read.hpp
/usr/include/asio/impl/read_at.hpp
/usr/include/asio/impl/read_until.hpp
/usr/include/asio/impl/serial_port_base.hpp
/usr/include/asio/impl/serial_port_base.ipp
/usr/include/asio/impl/spawn.hpp
/usr/include/asio/impl/src.cpp
/usr/include/asio/impl/src.hpp
/usr/include/asio/impl/use_future.hpp
/usr/include/asio/impl/write.hpp
/usr/include/asio/impl/write_at.hpp