Wrong type with Promise chaining

[tkrotoff]

With 2.1.4 (edit: first reported with [email protected]):

declare function createHello(): Promise<Hello>;

interface Hello {
  world(): Promise<any>;
}

createHello()
  .then(hello => hello.world())
  .then(message => {
    console.log(message); // BUG: message is of type Hello instead of any
  });

On TypeScript playground, no problem (edit: this is not true anymore, was working with 2.0.10, not with 2.1.4): https://www.typescriptlang.org/play/index.html#src=declare%20function%20createHello()%3A%20Promise%3CHello%3E%3B%0D%0A%0D%0Ainterface%20Hello%20%7B%0D%0A%20%20world()%3A%20Promise%3Cany%3E%3B%0D%0A%7D%0D%0A%0D%0AcreateHello()%0D%0A%20%20.then(hello%20%3D%3E%20hello.world())%0D%0A%20%20.then(message%20%3D%3E%20%7B%0D%0A%20%20%20%20console.log(message)%3B%20%2F%2F%20message%20is%20of%20type%20any%20%3D%3E%20works%0D%0A%20%20%7D)%3B%0D%0A

(for the little story, the bug was found here: DefinitelyTyped/DefinitelyTyped#12808 (comment))

[brandedoutcast]

@tkrotoff I'm not sure if it's an issue or a feature but the recent changes to then callback might be breaking code & the alternative I see is to use the generic version of then<TResult>.

createHello()
  .then<any>(hello => hello.world())
  .then(message => {
    console.log(message); // Now message is of type any
});

Breaking changes

[jwbay]

Duplicate of #10977 I think

[tkrotoff]

TypeScript 2.2 Promise implementation is still broken, example:

interface Toto {}

const promise = new Promise<Toto>((resolve, reject) => {
  resolve('toto');
});

promise
  .then(value => { // value is of type Toto => OK
    console.log('then1 value=', value);
    return 'titi';
  })
  .then(value => { // value is of type Toto => KO, should be 'titi' or string
    console.log('then2 value=', value);
    return 2;
  })
  .then(value => { // value is of type Toto => KO, should be 2 or number
    console.log('then3 value=', value);
  });

Verification by executing the code inside Chrome DevTools:

then1 value= toto
then2 value= titi
then3 value= 2

Solution for now:

promise
  .then<string>(value => {
    console.log('then1 value=', value);
    return 'titi';
  })
  .then<number>(value => {
    console.log('then2 value=', value);
    return 2;
  })
  .then(value => {
    console.log('then3 value=', value);
  });

[jwbay]

The fix is in version 2.3, not 2.2.