[swift-evolution] 100% bikeshed topic: DictionaryLiteral

[Nevin Brackett-Rozinsky]

On Mon, Jan 8, 2018 at 11:53 PM, Xiaodi Wu via swift-evolution <
swift-evolution at swift.org> wrote:

> Thank you for the clarification. It occurred to me in the shower that this
> might be the case, and that I was entirely mistaken as to what we were
> talking about.
>
> Yes, then, I wholeheartedly agree on this point. Out of curiosity, why are
> there source stability issues to 'typealias DictionaryLiteral<Key, Value> =
> [(Key, Value)]'?


Because at the point of use, “DictionaryLiteral” is instantiated with an
actual dictionary literal, eg. “[a: 1, b: 2, c: 3]”, and that syntax isn’t
available for an array of key-value pairs. As near as I can tell, the
convenience of that spelling is the entire *raison-d’être* for
“DictionaryLiteral” in the first place.

The ulterior question of whether preserving “DictionaryLiteral” is
worthwhile, is apparently out of scope. Personally, I have a hard time
imagining a compelling use-case outside of the standard library, and I
doubt it’s being used “in the wild” (I checked several projects in the
source-compatibility suite and found zero occurrences).

Nevin
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