Type inference fails with complex generic tuples #4136

I've been trying to come up with a smarter type def for Angular's $q.all (https://docs.angularjs.org/api/ng/service/$q#all) which takes an array of promises and spits out a promise with an array of results as the value.

For reference, the current DefinitelyTyped implementation is:

    all(promises: IPromise<any>[]): IPromise<any[]>;

I'm attempting to rewrite it with tuples, like so:

    all<T1, T2, T3>([t1, t2, t3]: [IPromise<T1>, IPromise<T2>, IPromise<T3>]): IPromise<[T1, T2, T3]>;
    all<T1, T2>([t1, t2]: [IPromise<T1>, IPromise<T2>]): IPromise<[T1, T2]>;
    all<T1>([t1]: [IPromise<T1>]): IPromise<[T1]>;

Usage:

    // Fails type inference, causes error
    var a = $q.all([$q.when<string>(), $q.when<number>()]);

    // Explicit types work fine
    var b = $q.all<string, number>([$q.when<string>(), $q.when<number>()]);

    // Same generic type works fine
    var c = $q.all([$q.when<string>(), $q.when<string>()]);

Full example on Typescript playground: http://goo.gl/UOKBp7

Attempting to use this with multiple different implicit generic types (example a) causes this error:

The type argument for type parameter 'T1' cannot be inferred from the usage. Consider specifying the type arguments explicitly. The argument candidate 'string' is not a valid type argument because it is not a supertype of candidate 'number'.

As far as I can tell, the Typescript compiler should (ideally) be able to infer this fine. The error seems wrong: 'number' shouldn't be a candidate for T1 at all.