SE-0025: Scoped Access Level, next steps


(Thorsten Seitz) #1

I still think that "local" expresses the concept exactly, as it restricts visibility to the local scope, doesn't it?

-Thorsten

···

Am 25.03.2016 um 17:46 schrieb Ross O'Brien via swift-evolution <swift-evolution@swift.org>:

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@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@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@swift.org> wrote:

On Mar 24, 2016, at 16:20 , Erica Sadun via swift-evolution <swift-evolution@swift.org> wrote:

On Mar 24, 2016, at 5:13 PM, Brent Royal-Gordon <brent@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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