Change #[lang="foo"]-style items to #[lang("foo")]

[pcwalton]

Only one ("string") literal allowed.

[lilyball]

Is this just to simplify the syntax for attributes? Personally, I like seeing #[crate_id="foo"] because it looks like I'm assigning "foo" to crate_id, and that's what I'm trying to do. #[crate_id("foo")] looks like I'm trying to invoke some functionality named crate_id with the value "foo".

[pcwalton]

It also lets us remove the brackets. #crate_id="foo" looks weird, but #crate_id("foo") doesn't.

[lilyball]

I like the brackets!

Removing the brackets means giving up the potential future use of # as an operator outside of attributes. Has this been considered? The meeting discussion seems to take it as given that removing brackets is a good thing. I also note that 3 months ago I commented about this same issue, and got no response there either.

Also, regarding the one literal restriction, doesn't that cause problems for deriving? #[deriving(Eq, Clone)] is pretty common right now.

[pnkfelix]

@kballard the word "literal" in "one literal restriction" is referring solely to string literals. All existing attribute syntax that doesn't use key="value string" would continue to work, I believe.

[lilyball]

Sorry, misclick.

[brson]

I'd rather use #[lang(foo)] since lang item names can just be identifiers.

[brson]

@kballard The problem with brackets is that we also want to add the bang to inner attributes, which means the syntax for inner attributes is #![foo];, which is a heck of a lot of syntax.

[lilyball]

@brson Why not drop the semicolon in that case? #![foo] seems reasonable.

And I agree that #[lang(foo)] is appropriate for that attribute. But attributes like crate_id, crate_type, license, etc. make more sense using the #[crate_id="foo"] syntax.

[brson]

@kballard @pnkfelix likes the semicolon. This is a discussion for #2569.

[brson]

Maybe we should have a discussion on the mailing list about the complete plan for attributes before going through with this.

Personally, I also like the brackets.

[brson]

If we just leave attribute syntax alone it will prevent a lot of work, at the expensive of people forever wtfing over the semicolon distinction.

[glaebhoerl]

Ever since the idea came up I've been writing attributes as #attr and then having to correct myself to add the brackets.

[pnkfelix]

Accepted for 1.0, P-backcompat-lang.