Why new Promise.all().then() worked?

Question

let iconsLoaded = new Promise((resolve, reject) => {
  new Promise.all(
    Object.keys(icons).map(iconName => {
      const Provider = icons[iconName][2] || defaultIconProvider; // Ionicons
      return Provider.getImageSource(
        iconName.replace(replaceSuffixPattern, ''),
        icons[iconName][0],
        icons[iconName][1]
      )
    })
  ).then(sources => {
    Object.keys(icons)
      .forEach((iconName, idx) => iconsMap[iconName] = sources[idx])

    // Call resolve (and we are done)
    resolve(true);
  })
});

Please help me understand above code about Promise.all()

I know this Promise object has an call() method,but as I know it's a static method, it should not be used as above,eg: new Promise.all(),but it give me no error. Why-why-why...

Here is source code:

the code above has no error

But, my code as following was wrong..give me an error

let p2 = new Promise(function(resolve, reject){
    console.log('p2 body')
  resolve('p2 resolve')
})

let p1 = new Promise(function(resolve, reject){
    console.log('p1 body')
  resolve('p1 resolve')
})

var p = new Promise(function(resolve, reject){
   new Promise.all([p2,p1])
   .then(function(){
    console.log('all(p2, p1) then')
  })
    console.log('p body')
})