[Dynamic Casting] Allow casts to "more optional" types #33684
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Generally, casting consistency demands that we be able to extract anything from an existential that can be put into that existential. (Which is why the casting spec requires that casting permit arbitrary injection and projection of optionals.) This particular diagnostic prevented optionals from being projected back out of existentials: let i: Int? let a: Any = i // Inject Int? into Any // Error prevents projecting Int? back out of Any a as? Int? This also broke certain uses of Mirror (weak variables get reflected as optionals stored in Any existentials).
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@swift-ci Please test Linux platform |
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Generally, casting consistency demands that we be able to extract anything from an existential that can be put into that existential. (Which is why the casting spec requires that casting permit arbitrary injection and projection of optionals.)
This particular diagnostic prevented optionals from being projected back out of existentials:
This also broke certain uses of Mirror (weak variables get reflected as
optionals stored in Any existentials).