atom in disjunction visible in answer set although it is not visible in grounding (and should not be true)

[peschue]

In the attached minimal.lp there is a fact
sequence (0,"Volkstheater").
and a rule with the disjunctive head
sequence(I,L) | nsequence (I,L)

There is no other rule defining sequence/2 or nsequence/2.

Therefore nsequence(0,"Volkstheater") can never become true.

However if I run minimal.lp with clingo 5.2.0 or with clingo 01dffb (quite recent master branch hash) then some answer sets contain this atom. If I pipe gringo output into clasp directly this also happens.

If I use gringo --text on minimal.lp then the rule with nsequence(0,"Volkstheater") in the head is not even shown, it seems to be optimized away (which is correct, because it is satisfied by the fact).

minimal.zip

[rkaminsk]

Will be fixed in next release.

[peschue]

Thank you, it is solved!