Replace Date::day_of_week by Date::weekday

[robertbastian]

#7228

Also replace other usages of "day of week" that are not the numeric day of the week (pretty much all of them).

[sffc]

Depending on how we feel about our policy, this might not be semver compatible because clients can stably refer to an associated type of a scaffold trait. It requires the word "scaffold" but not "unstable" in source

[robertbastian]

/// 🚧 This trait is considered unstable; it may change at any time, in breaking or non-breaking ways,

[sffc]

#6659 (comment)

[robertbastian]

I don't see how a comment discussing the unstable feature is relevant here

[robertbastian]

If anything, that comment says that this trait will live behind the unstable feature, so everything about it is unstable (as the comment currently says).

[sffc]

The trait as it currently lives on main is UnstableSealed in a stable module* with stable methods. This implies that the trait is not implementable, and therefore we can add to it, but it is stably usable in bounds, and methods are stably callable.

* Unless we wish to categorize the module named "scaffold" to imply unstable.

[robertbastian]

I don't see why they wouldn't be unstable. They are used for bounds on unstable constructors. When this was designed, I was under the impression that all of this was unstable, as it is documented as unstable

[sffc]

I had intended them to be stably usable in bounds, unstably implementable, and unstably callable. But the draft policy for how to enforce that came after 2.0, which means we need to decide what to do here.

[robertbastian]

Then the docs are wrong