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Add a changelog for SE-128 #4152

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27 changes: 27 additions & 0 deletions CHANGELOG.md
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Expand Up @@ -3,6 +3,33 @@ Note: This is in reverse chronological order, so newer entries are added to the
Swift 3.0
---------

* [SE-128](https://github.com/apple/swift-evolution/blob/master/proposals/0128-unicodescalar-failable-initializer.md)

Some UnicodeScalar initializers (ones that are non-failable) now returns an Optional,
i.e., in case a UnicodeScalar can not be constructed, nil is returned.

```swift
// Old
var string = ""
let codepoint: UInt32 = 55357 // this is invalid
let ucode = UnicodeScalar(codepoint) // Program crashes at this point.
string.append(ucode)
```

After marking the initializer as failable, users can write code like this and the
program will execute fine even if the codepoint isn't valid.

```swift
// New
var string = ""
let codepoint: UInt32 = 55357 // this is invalid
if let ucode = UnicodeScalar(codepoint) {
string.append(ucode)
} else {
// do something else
}
```

* [SE-0095](https://github.com/apple/swift-evolution/blob/master/proposals/0095-any-as-existential.md):
The `protocol<...>` composition construct has been removed. In its
place, an infix type operator `&` has been introduced.
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