Fix unhelpful type error

[bbrk24]

Issue Link

Fixes #54

Jira issue: THOS-5

Overview of Changes

This PR fixes type resolution errors. Basically, what would happen in a situation like this:

protocol P {}
class C: P {
    init(a: Int, c: String) {}
}

func setup() {
    Factory.register { // [1]
        Service(.transient, P.self) { r in
            C(
                a: r.resolve(),
                b: r.resolve(), // [2]
                c: r.resolve()
            )
        }
    }
}

is that Swift would be unable to figure out the generic type argument to r.resolve() at [2], since the initializer for C doesn't take a b. Because it can't determine the return type, swift would report "type of expression is ambiguous without more context", completely ignoring the fact that it's not meant to be there. Due to the result builder transform, the error would be reported at [1] instead of [2].

Adding an overload that returns Any works around this problem: if it can't figure out how to call resolve<T>() -> T, it tries the other overload, resolve() -> Any. This allows it to complete type-checking and realize that b shouldn't even be there.

Anything you want to highlight?

I marked the overload as @available(*, unavailable). This has two consequences:

1. In a line like var x: Any = Factory.shared.resolve(), this is inferred as resolve<Any>() instead of the new overload.
2. A line with no types at all, such as var x = Factory.shared.resolve(), still emits an error:

However, it has the downside that the new overload doesn't show up in the documentation. Using deprecated instead of unavailable makes it show up in the documentation, but also makes point 1 no longer true, and downgrades point 2 from an error to a warning.

Test Plan

Paste the code snippet above (or any equivalent) into a project that imports Dependiject. You should see the error at [2] instead of [1].

[Ljgleeson]

Might be worth adding a note mentioning that this overload doesn't appear in the documentation just incase someone is confused why it isn't.

[bbrk24]

Sure, that makes sense to me.

[wboyd600]

did this link not work?

[bbrk24]

It used to, but for some reason when I added the overload it didn't anymore, and I had to specify the base type.