SE-0375: Opening existential arguments to optional parameters

Hello Swift community,

The review of SE-0375: Opening existential arguments to optional parameters begins now and runs through October 25th, 2022.

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Xiaodi Wu
Review Manager


LGTM, but as I mentioned in the pitch thread I would like to see a commitment to a dedicated diagnostic in the (any T)?-to-T? case. People tend to think of the “happy path” (non-nil argument), and it would probably save a lot of hours of frustration worldwide to just say “this can’t work because what if nil?”.


Looks great!

There’s a typo in the proposal: “ This can change the behavior of overload resulting”. I’m assuming that’s “overload resolution”.

This is an important extension to 5.7's existential opening proposal, and will allow more code that previously relied on existentials to be refactored as generic code instead, since currently one of the main reasons to stick with existentials is if a function takes an optional argument.


+1, obviously.

The language workgroup has decided to accept this proposal. Thanks.

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