It’s not just a syntactic thing we’re talking about here.  The grammar permits 
all kinds of wonky combinations of things that will parse as “TSPL Swift", but 
will fail in Sema.  In that sense, no, this feature is not documented there.

~Robert Widmann

> On Jun 15, 2017, at 12:08 PM, Kyle Murray via swift-evolution 
> <swift-evolution@swift.org> wrote:
> 
> Yes, in the sense that the grammar 
> <https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/Patterns.html#//apple_ref/doc/uid/TP40014097-CH36-ID423>
>  has a production that permits the tuple element name. But there aren't any 
> examples that use labels within patterns.
> 
> 
> GRAMMAR OF A TUPLE PATTERN
> 
>  <>tuple-pattern → (­tuple-pattern-element-list 
> <https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/Patterns.html#//apple_ref/swift/grammar/tuple-pattern-element-list>­opt­)­
>  <>tuple-pattern-element-list → tuple-pattern-element 
> <https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/Patterns.html#//apple_ref/swift/grammar/tuple-pattern-element>­
>    | tuple-pattern-element 
> <https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/Patterns.html#//apple_ref/swift/grammar/tuple-pattern-element>­,­tuple-pattern-element-list
>  
> <https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/Patterns.html#//apple_ref/swift/grammar/tuple-pattern-element-list>­
>  <>tuple-pattern-element → pattern 
> <https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/Patterns.html#//apple_ref/swift/grammar/pattern>­
>    |  identifier 
> <https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/LexicalStructure.html#//apple_ref/swift/grammar/identifier>­:­pattern
>  
> <https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/Patterns.html#//apple_ref/swift/grammar/pattern>­
>  <>
> 
> -Kyle
> 
>> On Jun 15, 2017, at 10:34 AM, Chris Lattner via swift-evolution 
>> <swift-evolution@swift.org <mailto:swift-evolution@swift.org>> wrote:
>> 
>> Is this capability even documented in TSPL?
> 
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