Why does closure support "unpacking" arguments?

[Jumhyn (Frederick Kellison-Linn)]

The relevant thread is here:

[Core team] Addressing the SE-0110 usability regression in Swift 4

Hello Swift community, Swift 3’s SE-0110 <https://github.com/apple/swift-evolution/blob/master/proposals/0110-distingish-single-tuple-arg.md&gt; eliminated the equivalence between function types that accept a single type and function types that take multiple arguments. However, for various implementation reasons <https://lists.swift.org/pipermail/swift-evolution/Week-of-Mon-20170612/037560.html&gt;, the implementation of SE-0110 (as well as the elimination of tuple “splat” behavior in SE-0029 <h…