> On Apr 3, 2017, at 9:25 PM, Ben Rimmington via swift-evolution
> <swift-evolution@swift.org> wrote:
>
>
>> On 3 Apr 2017, at 17:55, Tony Allevato wrote:
>>
>> I just checked with -O and without and was surprised to find that `let x =
>> "abc" + "def" + "ghi"` wasn't collapsed into a single string literal
>> "abcdefghi" in the generated assembly code. Maybe it's more difficult than
>> it is in some other languages because of operator overloads and different
>> kinds of text literals (strings, extended grapheme clusters, Unicode
>> scalars)?
>
> Is this a regression since Swift 2.0 added the optimization?
I'd say it's a regression since 3.0 since I remember testing the optimizer even
being able to put together this during compile time:
struct URLString {
let urlString: String
init(host: String, path: String, query: String) {
self.urlString = "http://"; + host + path + "?" + query
}
}
URLString(host: "apple.com <http://apple.com/>", path: "/mac", query:
"target=imac")
This produced a single string literal - I confirmed this using MachOView on the
final binary...
>
> * Concatenation of Swift string literals, including across multiple
> lines, is
> now a guaranteed compile-time optimization, even at `-Onone`.
> **(19125926)**
>
> <https://github.com/apple/swift/blame/97db3931f2c5a21ea87ad6e71cdecbec325bff91/CHANGELOG.md#L1329-L1330>
>
> -- Ben
>
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