Promise chains aren't fully implemented

new Promise((res) => {
    res(1)
})
.then((data) => {
    console.log(data)
    return new Promise((res) => {res(2)});
})
.then((data) => {
    console.log(data)
    return new Promise((res) => {res(3)});
})
.then((data) => {
    console.log(data)
});

qml: 1
qml: 2
qml: 3

qml: 1
qml: [object Promise]
qml: [object Promise]