SE-0258: Property Delegates

[Douglas_Gregor]

@DaveZ

What do you think about allowing people to declare type variables? That would solve some problems here. For example, instead of @UnsafeMutablePointer @Atomic var x = y being problematic (because attributes are unordered), one could write var x : Atomic<UnsafeMutablePointer<_>> = y where _ in a type context means "type variable".

I think this would be a nice improvement to the language that composes well with property delegates. It stands alone for, e.g. something like:

let d: Dictionary<_, Double> = ["one": 1, "pi": 3.14159]   // infer the Key type to be String

@DaveZ

How likely is it that the reference storage types could be implemented (or ever be implementable) as property delegates?

I don't know that we could intercept the reference-counting operations well enough, but it's possible that we could pull some Builtin tricks in the standard library to do this.

Doug