SE-0255 has removed a small but important inconsistency in the language: single-expression functions that return a value can now remove the return keyword and Swift will understand it implicitly.
In previous versions of Swift, single-line closures that returned a value you could omit the return keyword because the only line of code that was there must be the one that returned a value. So, these two pieces of code were identical:
let doubled1 = [1, 2, 3].map { $0 * 2 }
let doubled2 = [1, 2, 3].map { return $0 * 2 }In Swift 5.1, this behavior has now been extended to functions as well: if they contain a single expression – effectively a single piece of code that evaluates to a value – then you can leave off the return keyword, like this:
func double(_ number: Int) -> Int {
number * 2
}That will probably cause some people to do a double take at first, but I’m sure it will become second nature over time.
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Other changes in Swift 5.1…
- Improvements to synthesized memberwise initializers
- Universal Self
- Opaque return types
- Static and class subscripts
- Warnings for ambiguous none cases
- Matching optional enums against non-optionals
- Ordered collection diffing
- Creating uninitialized arrays
Download all Swift 5.1 changes as a playground Link to Swift 5.1 changes
