Agreed—I think the parentheses have to go on the outside for this to work. In this sense, `\Person.mother.age` is an expression that returns a keypath type, with the idea that the parser is greedy and tries to take as many dotted names that follow. The parentheses halt that if needed, but the backslash needs to be bound to the type name for the part inside the parentheses to be interpreted as a keypath.
`\(Foo.bar)` looks like it would try to evaluate `Foo.bar` first and then compute the "keypath" of that, which doesn't make sense, whereas `(\Foo.bar)` makes it clear that the keypath expression is being separated from whatever might come after it. On Sat, Apr 8, 2017 at 6:12 PM Ricardo Parada via swift-evolution < [email protected]> wrote: At one point I was leaning towards a trailing backslash. Now I prefer parenthesis. If parentheses are used should the escape character be outside the parenthesis or inside? For example: let x = (\Person.mother.age).valueType let y = (\Person.mother.age.valueType) vs. let x = \(Person.mother.age).valueType let y = \(Person.mother.age.valueType) It is a subtle difference. On Apr 8, 2017, at 5:47 PM, Haravikk via swift-evolution < [email protected]> wrote: On 8 Apr 2017, at 22:18, BJ Homer via swift-evolution < [email protected]> wrote: I love the idea of a leading and trailing backslash. It makes it much easier to read, and handles the "but what if I want to access a property of a KeyPath?" case really well. For example, these two are clearly distinct: let x = \Person.mother.age\.valueType let y = \Person.mother.age.valueType\ I'm not sure why an 'age' object would have a 'valueType' property, but this variant makes it easy to handle. Even in cases where no disambiguation is required, having the trailing backslash makes it much easier to read as I'm scanning through code. -BJ I think I'd prefer brackets for that case; in your first example that reads to me like an escape of the period character, rather than "this is the end of the key path". Brackets would make this consistent with escaping within strings, like so: let x = \(Person.mother.age).valueType let y = \(Person.mother.age.valueType) Which makes sense to me if you consider the backslash in this case being an escape from normal type/variable access. Put another way, normally when you type Person. you're telling Swift "access this type and look for static methods/properties etc.", whereas when you "escape" it you're telling Swift to *not* to do that, resulting in a key-path instead. Maybe it's a stretch, it that makes sense logically to me, plus I think the use of brackets just looks cleaner than another backslash. _______________________________________________ swift-evolution mailing list [email protected] https://lists.swift.org/mailman/listinfo/swift-evolution _______________________________________________ swift-evolution mailing list [email protected] https://lists.swift.org/mailman/listinfo/swift-evolution
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