> https://github.com/austinzheng/swift-evolution/blob/az-edit-89/proposals/0089-rename-string-reflection-init.md
I prefer the more conservative and backwards-compatible option of using
`description` and conforming `ValuePreservingStringConvertible` to
`CustomStringConvertible`.
This is for three reasons:
* ValuePreservingStringConvertible really is a refinement of
CustomStringConvertible's semantic; a value-preserving `description` should
always be acceptable as an ordinary `description`.
* You should not call `description` directly anyway; you should call
`String.init(_:)`. That makes the arguably non-descriptive name a lot less
important.
* Changing the name of this property now will not actually make `description`
available for the uses you want to put it to in most code. No amount of
monkeying with the Swift standard library in 2016 can change the fact that the
OpenStep specification took that name in 1994, and we need to interoperate with
that heritage. You might free up the name `description` in value types and
Linux-only code, but only at the cost of interoperability headaches. I don't
think that's worth it.
I also think that, if we're serious about ValuePreservingStringConvertible's
initializer restoring the full state of the instance, then it is a full-width
conversion and doesn't need a label.
So, here's what I suggest:
protocol CustomStringConvertible {
var description: String { get }
}
protocol ValuePreservingStringConvertible: CustomStringConvertible {
init?(_ description: String)
}
extension String {
init<Value: ValuePreservingStringConvertible>(_ value: Value) {
... }
init<Value>(describing value: Value) { ... }
}
Actually, I'd *like* to see `String.init(describing:)` constrained to
CustomStringConvertible, but I've lost that argument before.
("Lossless" instead of "ValuePreserving" is fine too, perhaps even slightly
better.)
--
Brent Royal-Gordon
Architechies
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