-- in.cue --
root: {
    a: {
        $id: "valToOut"
        $after: c.$id
    }
    b: {
        $id: "valToOut"
        $after: a.$id
        out: "foo"
    }
    c: {
        $id: "valToOut"
        in: b.out
    }
}
-- out/run/errors --
error: cyclic task dependency:
	task root.a refers to
	task root.c refers to
	task root.b refers to
	task root.a:
    ./testdata/in.cue:2:5
    ./testdata/in.cue:6:5
    ./testdata/in.cue:11:5
-- out/run/t0 --
graph TD
  t0("root.a [Waiting]")
  t0-->t2
  t1("root.b [Waiting]")
  t1-->t0
  t2("root.c [Waiting]")
  t2-->t1