20128, "lydia-duncan", "SysBasic module: What should we do with 'fd_t'?", "2022-06-30T21:16:34Z"
fd_t is a c_int representation of a file descriptor. The name itself has origins in C, though seems like it is not necessarily present in every implementation.
There's also an openfd in the IO module (will link to issue about that when I make it) that takes an fd_t as an argument.
It seemed like the general lean was towards hiding this in the implementation, though I was a little concerned that implementing a version of openfd that continues to use it as an argument would be more of a pain for users to write on their own (though that depends on if we want to keep openfd with a c_int argument)