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Promise of type { } ignored when nested #13008

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@NoelAbrahams

Description

@NoelAbrahams

TypeScript Version: 2.1.4

Code

function getDate(): Promise<Date> {
    return Promise.resolve(new Date());
}

function getFoo(): Promise<{}> {
    return Promise.resolve({});
}

function doFoo() : Promise<number> {

    // Error: Type 'Promise<Date>' is not assignable to type 'Promise<number>'.
    return (
        getDate()
            .then(() => {

                return (
                    getFoo()
                        .then(() => {

                            return 10;
                        })
                );
            })
    );
}

Expected behavior:

No compilation error

Actual behavior:

Compiler error: Type 'Promise<Date>' is not assignable to type 'Promise<number>'.

Futher Notes
Changing getFoo to return any other value, e.g. function getFoo(): Promise<void> fixes the compilation error.

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