Files and processes are owners too

An open file, a child process and its pipes, and a handle from a C library carry a cleanup obligation in the same way a Buffer does. The binding that acquires one owns it, passing it by value hands the obligation on, and the release happens once.

Check reports a block that is left without releasing, and it reports a release through a copy that does not own the resource. defer on the line after the acquisition always satisfies both.

fn main() {
  let notes = std.fs.try_open("notes.txt", "w").unwrap()
  defer notes.close()
  notes.write("moon\n")
  println("saved")
}