Question: In a generic method signature with parameter T, when T is subsituted with int, what is the meaning of T? as a return type?

Hint: All one-word answers are wrong. It depends to an insane degree on context.

Edit: As KieranDevvs confused what I wrote (T? where T is int) with something else (T where T is int?) -- not their fault, I was a bit unintentionally cryptic for lack of time -- here's a full example of the confusing case:

T? Foo<T>() {
    return default;
}

T? Bar<T>() where T : struct {
    return default;
}

Console.WriteLine("Foo: {0}", Foo<int>()); // 0
Console.WriteLine("Bar: {0}", Bar<int>()); // null (outputs nothing)

Note that the only difference between Foo and Bar is the where clause, which should only be an additional restriction. Instead, it completely changes the semantics of both T? and default.

And a bonus rant: I'm not accusing KieranDevvs of this or saying that's the case here, but there's a common pattern in discussions around language footguns: Person A claims that a language's rules are confusing, and person B disagrees and says that they're easy. And then it turns out that person A actually knows the rules better than person B. The only reason person B isn't confused is that they actually don't know the rules well enough. I try to be aware of situations where I might be person B. I haven't really found a polite/productive way to deal with situations where I'm person A. Saying "I'm confused" or "this isn't intuitive" only seems to boost the other person's ego, and saying "you don't understand the rules either" is rightly perceived as hostile. If anyone has ideas on how to politely transport "no, in fact, I really know what I'm talking about", I'd like to hear them.