Generic methods are not properly inferred when used as a value

[david-driscoll]

I think I have noticed a problem with Generic Methods, not properly inferring their types, when they are used as a value, instead of as a method. I'm not sure if it's a known issue or not.

It's easy enough to work around by using a function, but I'd prefer to just hand in the method, since it's already a method that can be called.

This case is in Rx, but I've seen other examples of it too.

var observableOfAny = Observable.from(items)
    .flatMap(Observable.from); // using as a variable doesn't work

var observableOfString = Observable.from(items)
    .flatMap(x => Observable.from(x)); // Using a delegate works

var fromString: (arr: string[]) => Observable<string> = Observable.from;
var observableOfString = Observable.from(items)
    .flatMap(fromString); // Properly casting the method works

I've got an example, again using rx interfaces (so maybe something is wrong with them? it's possible). playground example

[mhegazy]

This is a duplicate of #3410. also see #5616 (comment).

[mhegazy]

tracked by #5616