[Pitch] Type Wrappers

[xedin (Pavel Yaskevich)]

@mpangburn

Is the following example well-formed, limiting @OnlyAppliesToHashable to types which conform to Hashable?

S in your example represents $Storage not the wrapped type and there is no synthesis of Hashable, Equatable etc. yet as I mentioned in my previous comment.

@mpangburn

3. Like (2), but for protocols: is an inheritance constraint implied?

Applying type wrapper to a protocol does two things:

• Injects associatedtype $Storage and var $_storage: OnlyAppliesToHashable<Self.$Storage>
• Allows it infer @OnlyAppliesToHashable from conformance to NotExplicitlyHashable

@mpangburn

Can subscript(storageKeyPath:) specify a constraint on the key path value type? If so, does it imply that a wrapped type can only have stored mutable properties that meet this constraint?

Yes, there are no limitations to subscript besides that it has to have storageKeyPath that accepts a key path.