`IsAcyclicDigraph` producing errors when digraph is not outputted first

[joe-dw]

The following function generates a digraph which is claimed to not be acyclic if it has not been printed to terminal.

StarDigraphReverse := function(n)
  return Digraph (Concatenation ([[2 .. n]], List([1 .. n-1], i -> [] ) ) );
end;

The issue is shown below

gap> IsAcyclicDigraph(StarDigraphReverse(3));
false
gap> StarDigraphReverse(3);
<immutable digraph with 3 vertices, 2 edges>
gap> IsAcyclicDigraph(last);
true

The issue appears to occur for all values of n at least 2.

[reiniscirpons]

We tracked it down at the meeting, it seems the issue is the range constructor. Essentially culprit is the FuncIS_ACYCLIC_DIGRAPH function assuming that the underlying lists are all plain lists, and ranges are not like this.

Minimal failing example:

gap> IsAcyclicDigraph(Digraph([[2 .. 4], [], [], []]));
false

Should be fixed by #901 .

[reiniscirpons]

Resolved by #901