Ok, I have been thinking all day if I can come up with of a design which would
still provide scoped private (and keep file-based private) without causing the
current confusion. Here is the best I have so far. I warn you it trades one
weirdness for another, but at least the new weirdness is progressively
disclosed, so it should be less problematic:
Swift 4
• Depreciate ‘private’ with a warning that it will be removed in Swift 5
Swift 5
• Remove ‘private’ keyword
• Rename ‘fileprivate’ to ‘local’ with the understanding it now means
local to the containing submodule
• If no submodule is declared, the file is its own anonymous submodule
• A group of files can declare themselves a submodule by each saying
‘module name’ with the same name somewhere in the file (only one declaration is
allowed per file)
• Within the file ‘module { }’ can declare an anonymous module (within
the braces) nested inside the current module
• For fun: Stored properties are allowed to be declared within
extensions in a type’s containing submodule
That ‘module { }' part is the new weirdness, but it should cause less confusion
overall. A few points:
• They could be nested as deep as you like
• It needs to be anonymous so you aren’t tempted to connect it with
other submodules (in other files)
• You could recreate the current behavior of private by wrapping your
type in a module block
• …or you could wrap that block around a type and it’s friend
• …or you could wrap only part of your type (crucial if you want both
private and fileprivate behavior in the same type)
• Internal, public, and open would retain their current meanings
Thoughts on this approach? It isn’t my first choice, but it is much better
than what we have now.
It should let you do everything you do now and then some (but with the extra
complexity tucked away for the most part). I.e. If you don’t know what
submodules are, the system appears structurally the same as Swift 2. You can
learn about submodules without learning about ‘module {}’. In exchange, scoped
private becomes more complex… but you also have finer control over the scope
(it can cover only part of a large type or two friend types).
Thanks,
Jon
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