## a raw file descriptor is not a system handle. this is the property that
## stops hak code naming a descriptor it never opened - including hak's own
## multiplexer, signal and io-thread descriptors, and anything the host
## application that embeds hak holds open.
s := (core.sem-new)
core.sem-signal-on-input s 0 ##ERROR: system handle 0

---

s := (core.sem-new)
core.sem-signal-on-input s 4 ##ERROR: system handle 4

---

## a handle id stops resolving once it is closed, so a stale id cannot reach
## a descriptor that has since been recycled
p := (sys.pipe)
r := (core.basicAt p 0)
sys.close r
sys.read r (core.basicNew ByteArray 4) ##ERROR: system handle 0

---

## a regular file is never accepted by the multiplexer: epoll refuses one
## outright, and poll() would report it permanently ready
f := (sys.open "/etc/passwd" "r")
s := (core.sem-new)
core.sem-signal-on-input s f ##ERROR: not of an acceptable kind

---

## the type gate: a pipe handle is not a process handle
p := (sys.pipe)
sys.pwait (core.basicAt p 0) ##ERROR: not of an acceptable kind

---

## ...and a process handle is not a stream
p := (sys.popen "true" "r")
sys.read (core.basicAt p 0) (core.basicNew ByteArray 4) ##ERROR: not of an acceptable kind

---

## a missing file is reported, not guessed at
sys.open "/nonexistent/definitely-not-here" "r" ##ERROR: open /nonexistent/definitely-not-here

---

## an unknown open mode is rejected
sys.open "/tmp/hak-hnd-5001.tmp" "q" ##ERROR: open mode

---

## an unknown popen mode likewise
sys.popen "true" "z" ##ERROR: popen mode