Implicit guarding self in closures

[cal (Cal Stephens)]

When I pitched this a few years ago, the core team decided not to run a review for it and shared this feedback:

@John_McCall

The core team talked about this, and we're reluctant to add features that introduce new sources of control flow unless they significantly improve expressive power. This proposal is a simple sugaring of a very specific pattern, but it would not work in a lot of superficially similar situations, like when the function needs to return anything other than Void. The amount of convenience offered also seems fairly low.

@cal, thank you for your suggestion, it was certainly worth considering. However, at this time, we don't think this proposal is likely to be accepted, and so it's not worth taking through the Evolution process. We can reconsider this if someone makes a strong argument to do so in the future.

These days, especially after SE-0345 (slightly reducing the verbosity of guard let self conditions) and SE-0365 (allowing implicit self for weak self closures), I tend to think that the existing weak guard pattern is brief enough that it doesn't need to be sugared. I don't really think there's a way to further simplify this pattern without obscuring control flow.