Function undefinedIdentifiers

src/compute-engine/assume.ts:1167–1169

(expr: Expression)

  }

  // 6. Inert/unknown set: store a membership fact (design §4.1 — this used
  //    to throw "Invalid domain")
  if (isNumber(setExpr) || isString(setExpr)) return 'not-a-predicate';
  const fact = ce.function('Element', [ce.symbol(symbol), setExpr]);
  if (!fact.isValid) return 'not-a-predicate';
  ce.context.assumptions.set(fact, true);