Constructing an `AnchorPair` outside of Anchorage will be impossible about anchorage HOT 4 CLOSED

My guess is that it wasn't marked as public because we didn't see a use case, but yours is definitely intriguing. @jvisenti should make the call, but this seems like a reasonable request to me.

from anchorage.

@rlwimi @ZevEisenberg I believe AnchorPair is essentially an internal type because exposing the initializer publicly could allow for unsafe usage of the API. Consider this function:

func == <T, U>(lhs: AnchorPair<T, U>, rhs: AnchorPair<T, U>) -> ConstraintPair

If you were to construct two AnchorPair<NSLayoutAnchor, NSLayoutAnchor>, you could mix NSLayoutXAxisAnchor and NSLayoutYAxisAnchor however you wanted, which would result in a crash if you attempted to use this operator on mismatched types, i.e. trying to constraint an XAxisAnchor to a YAxisAnchor. The current API forbids this by construction.

That said, the existence of a valid use case may outweigh the pretty minor risk that comes with it. Happy to take a look at a PR if you have something put together already, and see how it could fit in.

from anchorage.

I was just reading through some code that I wrote in a project, and found what I believe is a valid use case:

var safeCenterAnchors: AnchorPair<NSLayoutXAxisAnchor, NSLayoutYAxisAnchor> {
    if #available(iOS 11.0, *) {
        return AnchorPair(first: safeAreaLayoutGuide.centerXAnchor, second: safeAreaLayoutGuide.centerYAnchor)
    }
    else {
        return centerAnchors
    }
}

from anchorage.

Thanks, everyone! Much appreciated.

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