function IsPromise(x) {
if (Type(x) !== "Object") {
return false;
}
if (!has_slot(x, "[[PromiseStatus]]")) {
return false;
}
if (get_slot(x, "[[PromiseStatus]]") === undefined) {
return false;
}
return true;
}
let F = function (resolve, reject) {
assert(has_slot(F, "[[Capability]]"));
let promiseCapability = get_slot(F, "[[Capability]]");
if (promiseCapability["[[Resolve]]"] !== undefined) {
throw new TypeError("Re-entrant call to get capabilities executor function");
}
if (promiseCapability["[[Reject]]"] !== undefined) {
throw new TypeError("Re-entrant call to get capabilities executor function");
}
promiseCapability["[[Resolve]]"] = resolve;
promiseCapability["[[Reject]]"] = reject;
return undefined;
};
function Promise(executor) {
let promise = this;
if (Type(promise) !== "Object") {
throw new TypeError("Promise constructor called on non-object");
}
if (!has_slot(promise, "[[PromiseStatus]]")) {
throw new TypeError("Promise constructor called on an object not initialized as a promise.");
}
if (get_slot(promise, "[[PromiseStatus]]") !== undefined) {
throw new TypeError("Promise constructor called on a promise that has already been constructed.");
}
if (!IsCallable(executor)) {
throw new TypeError("Promise constructor called with non-callable executor function");
}
return InitialisePromise(promise, executor);
}