| validrefset(str, r, st) = ∅, st[r -- fs '] = refval(r0), fs ' ∈ instfields(st[r -- _type] .type .class), is_obj(str, r, st), validrefs(str, r ' + refs0, st[r -- _type] .type, st) ⊦ junkref(str, r, st), cyclic(str, r, st), has_reffield((r ' + refs0) .last, st), dups(refs0), r ∈ refs0 |
⊦ refsset = refsset0 ↔ (∀ refs. refs ∈ refsset ↔ refs ∈ refsset0)
∀ refs. refs ∈ validrefset(str, r, st) ↔ refs ∈ ∅, st[r -- fs '] = refval(r0), fs ' ∈ instfields(st[r -- _type] .type .class), is_obj(str, r, st), validrefs(str, r ' + refs0, st[r -- _type] .type, st) ⊦ junkref(str, r, st), cyclic(str, r, st), has_reffield((r ' + refs0) .last, st), dups(refs0), r ∈ refs0
[[CONCRETESIMPRULES : ()], [EXTRATERMS : (∅, validrefset(str, r, st))]]