c) {
            if (value !== null && value !== void 0) {
                if (typeof value !== "object" && typeof value !== "function") throw new TypeError("Object expected.");
                var dispose, inner;
                if (async) {
                    if (!Symbol.asyncDispose) throw new TypeError("Symbol.asyncDispose is not defined.");
                    dispose = value[Symbol.asyncDispose];
                }
                if (dispose === void 0) {
                    if (!Symbol.dispose) throw new TypeError("Symbol.dispose is not defined.");
                    dispose = value[Symbol.dispose];
                    if (async) inner = dispose;
                }
                if (typeof dispose !== "function") throw new TypeError("Object not disposable.");
                if (inner) dispose = function() { try { inner.call(this); } catch (e) { return Promise.reject(e); } };
                env.stack.push({ value: value, dispose: dispose, async: async });
            }
            else if (async) {
                env.stack.push({ async: true });
            }
            return value;
        };