no existing dependency or dependent should be offered for completion

[propensive]

Depending on a dependent will create a graph cycle, so we want to avoid this. Depending on an existing dependency is not useful.

[propensive]

We should calculate the dependents efficiently, though. It would be easy to come up with an O(n³) algorithm, I think...

[propensive]

This is half-complete. Existing direct dependencies are now not suggested.