| validrefs(str, r ' + refs, ty, st), st ⊆ st0, validref(str, r, st[r -- _type] .type, st) ⊦ validrefs(str, r ' + refs, ty, st0) |
⊦ validrefs(str, refs, ty, st) ∧ st ⊆ st0 ∧ ¬ junkref(str, r, st) ∧ refs ≠ [] ∧ refs .first = r → validrefs(str, refs, ty, st0)
[[CONCRETESIMPRULES : ([CSIMPSEQ : ⊦ (refs + refs0) + refs1 = refs + refs0 + refs1], [CSIMPSEQ : ⊦ (r ' + refs) .first = r], [CSIMPSEQ : ⊦ ¬ refs + refs0 ≠ [] ↔ refs = [] ∧ refs0 = []], [CSIMPSEQ : ⊦ r ' ≠ []], [CSIMPSEQ : ⊦ junkref(str, r, st) → ¬ validref(str, r, ty, st)])], [EXTRATERMS : (str, r ' + refs, ty, st, st0, (r ' + refs) .first)]]