Why doesn't Int64 automatically conform to CodingKeyRepresentable?

[tomhamming]

I found the answer here:

[Pitch] Allow coding of non-`String`/`Int` keyed `Dictionary` into a `KeyedContainer`

While it's not recommended you conform types you don't own to protocols you don't own, until Int64 adopts CodingKeyRepresentable, you could implement a conformance as follows: // Need a key type which can hold any Int value. struct IntCodingKey: CodingKey { let intValue: Int? let stringValue: String init(intValue: Int) { self.intValue = intValue self.stringValue = String(describing: intValue) } init?(stringValue: String) { guard let intValue = Int(s…

And as to why Int64 wasn't originally supported as a key: it's tricky to read back out.

Dictionarys encoding strategy

There are two answers to your questions here: There are corner cases here around integer coding keys which don't always have good answers. The biggest issue to deal with is conversion between integer sizes: It's always safe to promote an integer type smaller than Int to an Int, so it would be possible to encode those values as CodingKeys. On decode, though, you could get a CodingKey whose integer value does not fit in, say, an Int8. You could consider this to be a type mismatch, potentially,…

Hopefully this question makes that more discoverable by search.