[swift-evolution] Allowing `guard let self = self else { ... }` for weakly captured self in a closure.

Jacob Bandes-Storch jtbandes at gmail.com
Wed Jan 6 14:56:39 CST 2016

Not exactly; backticks are for making an identifier out of something that's
not normally an identifier. Most other reserved words are used in control
flow & other declarations. Rarely do they actually represent
identifiers/values that you can work with.

The docs also say "The backticks are not considered part of the identifier;
`x` and x have the same meaning." Thus `self` and self should have the same
meaning. Assigning to `self` is the same as assigning to self, which
intentionally isn't allowed. Backticks shouldn't allow you to circumvent


On Wed, Jan 6, 2016 at 12:50 PM, Paul Cantrell <paul at innig.net> wrote:

> Ummm … isn’t that _exactly_ what backticks are for? From the docs:
>     To use a reserved word as an identifier, put a backtick (`) before
> and after it.
> On Jan 5, 2016, at 10:42 PM, Greg Parker via swift-evolution <
> swift-evolution at swift.org> wrote:
> I think it is a bug  :-)  That's not what backquotes are for. It ought to
> be either supported without the backquotes or banned regardless of
> backquotes.
> On Jan 5, 2016, at 8:34 PM, Jacob Bandes-Storch <jtbandes at gmail.com>
> wrote:
> Yes, it seems to use the strong shadowing variable. (The compiler doesn't
> complain about "self.foo", and "self?.foo" becomes invalid because self is
> no longer optional.)
> If it weren't so useful, I'd call it a bug.
> On Tue, Jan 5, 2016 at 8:34 PM, Greg Parker <gparker at apple.com> wrote:
>> Does further use of self after that actually use a strong shadowing
>> variable? Or does it go back to the weak reference it already had as if the
>> shadow were not there?
>> On Jan 5, 2016, at 8:26 PM, Jacob Bandes-Storch via swift-evolution <
>> swift-evolution at swift.org> wrote:
>> Wow! I didn't know that worked. It's a bit surprising, and perhaps not
>> intended. I think the proposal is still valid.
>> On Tue, Jan 5, 2016 at 8:21 PM, Christopher Rogers <
>> christorogers at gmail.com> wrote:
>>> You can shadow self with a guard like you wrote it if use the keyword
>>> escaping backquotes like so:
>>> guard let `self` = self else { return }
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