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[5.3] [Changelog] Mention SR-7083 in changelog under Swift 5.3 #31457

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[5.3] [Changelog] Mention SR-7083 in changelog under Swift 5.3 #31457

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29 changes: 29 additions & 0 deletions CHANGELOG.md
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Expand Up @@ -27,6 +27,34 @@ CHANGELOG
Swift 5.3
----------

* [SR-7083][]:

Property observers such as `willSet` and `didSet` are now supported on `lazy` properties:

```swift
class C {
lazy var property: Int = 0 {
willSet { print("willSet called!") } // Okay
didSet { print("didSet called!") } // Okay
}
}
```

Note that the initial value of the property will be forced and made available as the `oldValue` for the `didSet` observer, if the property hasn't been accessed yet.

```swift
class C {
lazy var property: Int = 0 {
didSet { print("Old value: ", oldValue) }
}
}

let c = C()
c.property = 1 // Prints 'Old value: 0'
```

This could have side-effects, for example if the lazy property's initializer is doing other work.

* [SE-0268][]:

A `didSet` observer which does not refer to the `oldValue` in its body or does not explicitly request it by placing it in the parameter list (i.e. `didSet(oldValue)`) will no longer trigger a call to the property getter to fetch the `oldValue`.
Expand Down Expand Up @@ -8028,6 +8056,7 @@ Swift 1.0
[SR-5581]: <https://bugs.swift.org/browse/SR-5581>
[SR-5719]: <https://bugs.swift.org/browse/SR-5719>
[SR-6118]: <https://bugs.swift.org/browse/SR-6118>
[SR-7083]: <https://bugs.swift.org/browse/SR-7083>
[SR-7139]: <https://bugs.swift.org/browse/SR-7139>
[SR-7251]: <https://bugs.swift.org/browse/SR-7251>
[SR-7601]: <https://bugs.swift.org/browse/SR-7601>
Expand Down