Allow to extract code containing `return` statement if it's at the end of a function

TypeScript Version: nightly (2.6.0-dev.20170904)

Code

export function f() {
    if (1) {
        return 1;
    }
    
    ...do stuff...
}

export function g() {
    ...do stuff...

    if (1) {
        return 1;
    }
}

Expected behavior:

Able to extract the if statement out of g.
Not able to extract from f because that would change the control flow.

Actual behavior:

Not able to extract in either case. (But somehow it works in #18091?)

[amcasey]

I'm not sure I understand. Are you taking advantage of the fact that the range of the if in g implicitly contains the implicit return at the end of g? If so, I would say that is more of a suggestion than a bug, insofar as we don't guarantee that every meaningfully extractable range will offer the refactoring.

I think is should be as simple as saying that any selection inside a function that is not followed by anything else should be extractable. No matter where (or if) returns appear in it, it is equivalent to say return newFunction(); and move whatever control flow exists inside of newFunction instead.

[amcasey]

From our offline suggestion, I understand this to be a suggestion that we create an exception to our "no extracting conditional returns" in the case where the extracted range is at the end of the method (easy: syntactically; harder: via control flow).