[swift-evolution] [Pitch] Removing the empty initialiser requirement from RangeReplaceableCollection

[Tim Vermeulen]

This is a follow up from this swift-users thread: https://lists.swift.org/pipermail/swift-users/Week-of-Mon-20160704/002489.html

As it stands, RangeReplaceableCollection requires an implementation for init(), which is used in the default implementations of (as far as I can tell) init(_:), init(repeating:count:) and removeAll(keepingCapacity:). The latter of these methods should be implementable with removeSubrange(_:) instead.

I would like to propose to *remove* all three initialisers from this protocol, because it makes it impossible for some collections to conform to it that need extra data for its initialisation, but are otherwise perfectly capable of having arbitrary subranges replaced by elements from another collection. Those three initialisers could either move to a new protocol or simply not be part of any protocol.

On a similar note, I’d like to have all initialisers of SetAlgebra removed as well, but that might need its own review.