Discuss unambiguous function call syntax #45
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And shrink the undocumented list
src/expressions.md
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| <T as SizeOf>::size_of() | ||
| ``` | ||
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| Refer to [RFC 132] for further details, motivations, and subtleties of syntax. |
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Is this temporary? RFC 1636 seems to say that RFCs aren't supposed to be stable documentation.
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Hm, I want to keep the link to the RFC. I need more explanation before the link, though. As that RFC says, the reference should be good enough for normal users to learn how to use a feature without referring to the RFC. Thanks for pointing that RFC out; I'd forgotten about it!
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Note to self: Needs more and better examples |
src/expressions.md
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| * Auto-`deref` is undesirable; for example, distinguishing between methods on a | ||
| smart pointer itself and the pointer's referent. | ||
| * Methods which take no arguments and return properties of a type, like | ||
| `SizeOf::size_of()` |
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I took the example from the RFC. It became out-of-date, apparently! I'll correct it.
src/expressions.md
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| * Auto-`deref` is undesirable; for example, distinguishing between methods on a | ||
| smart pointer itself and the pointer's referent | ||
| * Methods which take no arguments, like `default()`, and return properties of a | ||
| type, like `size_of()` |
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How could default() result in an ambiguity?
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fn main() {
let a = Default::default();
println!("{:?}", a);
}You can (must) use a type annotation or UFCS, right?
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This seems alright to me, seems like it could be a little more detailed with some of the specifics of the syntax, but I still feel comfortable landing it in its current state. Any else have thoughts? @steveklabnik @GuillaumeGomez @QuietMisdreavus |
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Feel the same: could be more detailed. |
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It might be worth mentioning the |
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@GuillaumeGomez @QuietMisdreavus @frewsxcv I'd love to add more examples and detail, but I'm afraid the RFC itself seems somewhat out-of-date ( If y'all have any examples I could include, I'd appreciate it! I'll see what I can come up with tonight. |
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I was just wanting another sentence or two describing the full form, and mentioning that either Edit: Unless there's more to UFCS than |
src/expressions.md
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| Function calls may sometimes result in ambiguities about receiver or referent. | ||
| See [UFCS](#unambiguous-function-call-syntax) for how to resolve this. | ||
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| ### Unambiguous Function Call Syntax (UFCS) |
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So, it's been the opinion of the language team for a long time that "UFCS" is a terrible name and shouldn't be used. It's also not exactly a separate feature, it's that the usual way of calling trait methods is sugar for this syntax. As such, I'm not sure the framing of this PR is right, though there is no way for you to have known that, of course.
I am tempted to merge it as such, and then, we'll end up doing another pass later that cleans this up. This is okay with me, but I don't know how you feel about it.
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oh that's helpful. with that in mind, maybe I can have a sub-section here instead of the new section I created? I can describe roughly what you said: "UFCS" confuses the issue, and the RFC didn't add a separate feature. It merely generalized some syntax and turned the then-current syntax into sugar for the fully-qualified function-call syntax. FQFC.
iono @steveklabnik, I'll push some updates, and you can tell me what you think.
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@steveklabnik let me know what you think of the description now |
src/expressions.md
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| @@ -220,6 +220,9 @@ exact `self`-type of the left-hand-side is known, or dynamically dispatching if | |||
| the left-hand-side expression is an indirect [trait | |||
| object](types.html#trait-objects). | |||
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| [UFCS](#unambiguous-function-call-syntax) allows method invocation using | |||
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this link is still wrong, no?
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oh yeah. bigly. thx for heads up
…On Mon, May 22, 2017, 09:36 Steve Klabnik ***@***.***> wrote:
***@***.**** commented on this pull request.
looks good to me; i think a link might be broken though?
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In src/expressions.md
<#45 (comment)>
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> @@ -220,6 +220,9 @@ exact `self`-type of the left-hand-side is known, or dynamically dispatching if
the left-hand-side expression is an indirect [trait
object](types.html#trait-objects).
+[UFCS](#unambiguous-function-call-syntax) allows method invocation using
this link is still wrong, no?
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<#45 (review)>,
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@steveklabnik @QuietMisdreavus ok, fixed that last link (and rewrote the sentence around it). |
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Great, thanks! |
And shrink the undocumented list
CC #9