[swift-evolution] SE-0025: Scoped Access Level, next steps

Ross O'Brien narrativium+swift at gmail.com
Fri Mar 25 11:46:06 CDT 2016

Well, several prominent voices seem to think that 'private' is "intuitively
obvious" when it refers to declaration-level scope, so I didn't argue that
point. I still happen to disagree; I would add 'privatetodeclaration' to
'privatetomodule' and 'privatetofile', which would solve that
conversational point: "These properties are private to the declaration".

Alternatively: 'fileaccessible', 'moduleaccessible',
'declarationaccessible'? (Does that confuse code accessibility with such
things as UIAccessibility?)

That doesn't answer your awkward-to-read-in-code problem. I don't have a
solution to that.

To re-specify the problem, again (perhaps more for my benefit while writing
as yours while reading): the terms we choose have to suggest accessibility,
but a subjective spectrum of adjectives does not give us clarity. The idea
of building into these symbols references to exactly where the scope ends
appears to be popular. There aren't any existing one-word terms which
express these concepts so we're coining new words out of two (or more)
existing words. Which combination of words is least awkward to read, or
most intuitive to type, is still going to be subjective.

On Fri, Mar 25, 2016 at 4:29 PM, Jordan Rose <jordan_rose at apple.com> wrote:

> It doesn't solve the problem for me. "These properties are private." "To
> what?" "Just private" / "To the scope".
> They're also still awkward to read in code. I know we have lots of decl
> modifiers, but I've convinced myself we're not in Java's "public static
> void main" soup situation yet.
> Jordan
> On Mar 25, 2016, at 9:27 , Ross O'Brien <narrativium+swift at gmail.com>
> wrote:
> Well... how about we reverse the terms: call them 'privatetomodule' and
> 'privatetofile'.
> This is 'private(module)' and 'private(file)' but fitting the all
> lower-case style. It puts 'private' first (and when you use the keyword,
> 'private' is the bit you want to start with more than 'module' or 'file').
> It's easier to use in conversation ("these properties are private to the
> file").
> Disadvantage: it adds 'to', so the words are even longer (but no longer
> than the parenthesised form would've taken).
> 'privatetofile extension Foo : BarConvertible { }'
> On Fri, Mar 25, 2016 at 4:15 PM, Jordan Rose via swift-evolution <
> swift-evolution at swift.org> wrote:
>> On Mar 24, 2016, at 16:20 , Erica Sadun via swift-evolution <
>> swift-evolution at swift.org> wrote:
>> On Mar 24, 2016, at 5:13 PM, Brent Royal-Gordon <brent at architechies.com>
>> wrote:
>> I think it does. `module` could mean many things related to how Swift
>> creates and consumes modules.
>> `moduleprivate` combines something about access levels (public/private)
>> and scope (module), is easy to
>> Google, offers few "wrong" interpretations. By using a longer keyword, it
>> is less flexible in meaning and
>> more fixed in purpose.
>> Sure, but is that worth 7 to 9 extra characters at every single use site
>> for something that's actually pretty common? Is it worth the muddled mess
>> of an all-lowercase keyword with no obvious break, or the
>> attention-grabbing of a capital letter or an underscore?
>> `module` and `file` are not going to be obscure corners of the language.
>> Most people will probably learn about them at the same time they learn
>> about `public` and `private`.
>> (Actually, if `module` continues to be the default, you probably won't
>> see it *that* often. You *will* see `file`, but that's the one that can't
>> be as easily confused with a declaration.)
>> Obviousness for new users is great, but you can take it too far. We call
>> the type `Int32`, not
>> `SignedIntegerBetweenNegative2ToThe31stPowerAnd2ToThe31stPowerMinus1`—and
>> if we did, it's not clear the longer name would really be more obvious,
>> because it would be such a pain to read.
>> `moduleprivate` is the default value. I doubt it will get  used much if
>> at all. I don't think `fileprivate` will get used much either
>> but in such cases, I think those seven extra letters are essential and
>> documenting.
>> The two remaining public and private access levels are simple and
>> intuitively obvious.
>> I'm going to say that I remain unhappy with these new names. I don't
>> believe that these won't get used, and I don't want them to feel awkward,
>> discouraged, or penalized when they do. The standard library, for example,
>> has in its style guide that all access control should be explicit, which is
>> a reasonable style to enforce. I also have a small concern that they won't
>> be easy to talk about: "this method is private" "wait, file-private or
>> module-private?" "neither, just private-private".
>> I realize these are all vague concerns, and I don't have something more
>> concrete—or a better alternative. "modulescoped" and "filescoped" would be
>> very literally accurate but (a) would force people to learn what "scoped"
>> means unnecessarily, and (b) aren't less awkward.
>> I agree with the concerns that just saying "file var foo" makes it sound
>> like there's one copy of the variable shared in the entire file, even when
>> applied to an instance property. I think there's a lot of value is making
>> the access control terms adjectives.
>> I honestly still think "public, internal, private, local" is a better
>> taxonomy.. It's true that "internal" and "private" aren't automatically
>> ordered relative to each other (and maybe not even "local"), but they're
>> all adjectives (unlike "module" and "file"), and they're not awkward to
>> read or to use in conversation. But both the core team and the list
>> disagree, mainly because (a) it aligns 'private' more closely with other
>> languages, and (b) if you're not thinking about it, more restrictive is
>> better than less. (Both of which I agree are good ideas.)
>> Jordan
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