Add notes on migrating crates to work with both editions #117
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This looks good to me, though I haven't compiled it either. @dtolnay if you have some time, can you check this out?
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| #[doc(hidden)] | ||
| #[macro_export] | ||
| macro_rules! log { |
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I would rename this macro to private_log! or log_impl! or __log! to make it clear that importing it is not a reasonable fix (because the real log crate does export a public log! macro).
| ```rust,ignore | ||
| #[doc(hidden)] | ||
| #[macro_export] | ||
| macro_rules! my_special_stringify { |
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I don't want to see my_special_... in an actual crate. Could you come up with a naming convention that we can recommend to all uses of this pattern?
| #[macro_export] | ||
| macro_rules! my_special_stringify { | ||
| ($($inner:tt)*) => { | ||
| stringify!($($inner)*) |
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Since the approach described here is intended to be picked up by all sorts of macros, I would write this call with curly braces.
stringify! { $($inner)* }Some macros cannot be forwarded with parentheses: playground. All macros can be forwarded with curly braces.
| #[macro_export] | ||
| macro_rules! warn { | ||
| ($msg:expr) => { | ||
| log!(stringify!($crate::LogLevel::Warn), $msg) |
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Please pick a different standard library macro to build this demo code around. You would never see stringify! called like this on a crate local path. format_args! could work better.
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I've made these changes, and turned on CI for the last example, since it should compile in all situations :) |
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This is ready for review again. |
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| So the code knows to look for any macros used locally. But wait - this won't compile, because we | ||
| use the `format_args!` macro that isn't in our local crate (hence the convoluted example). The | ||
| solution is to add a level of indirection: we crate a macro that wraps `format_args`, but is local |
| @@ -78,3 +80,192 @@ struct Bar; | |||
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| This only works for macros defined in external crates. | |||
| For macros defined locally, `#[macro_use] mod foo;` is still required, as it was in Rust 2015. | |||
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| ### Local helper macros | |||
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It may be useful for authors of crates using foreign helper macros to also have some examples. Those examples may almost look exactly the local examples below so it may be even better to rename this sections helper macros with examples using a mix of both foreign-crate:: and $crate:: alike.
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Would it be possible to merge this PR first, and then address this in a new PR?
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Most definitely. I'm just a passer by that was pointed at this PR for documentation on the new feature. No blockers here
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Ping - I think this will be useful to rust users so we should either merge or tell me what I need to change. |
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I just ran into this problem when using the new |
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I'd merge this long time ago, but I don't have rights in this repo unfortunately. ping @steveklabnik |
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woot |
Some notes on supporting both editions while using implementation macros.
I haven't checked that the code compiles, so I would be grateful for a thorough review!