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Helper attributes in attribute macros #716

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Helper attributes in attribute macros #716

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5 changes: 5 additions & 0 deletions src/procedural-macros.md
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Expand Up @@ -273,6 +273,11 @@ fn invoke4() {}
// out: item: "fn invoke4() {}"
```

#### Attribute macro helper attributes
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I do not understand this addition; until we have something like rust-lang/rust#65823 there is no such thing in the language definition as "attribute macro helper attributes". (N.B. the reference is not a user guide -- it is an incomplete definition of the language).

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Thanks for pointing me to that issue, its basically the same reason for my edit: new comers might be confused how to get the same behaviour like the helper attributes in a full fledged proc macro attribute, not realising that it is the macro's job to actually strip those out (or what ever else for that matter) - I get that it is weird to put something in the docs that looks like a user-guide thing but clearly I am not the only person stumbling over this...

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@extrawurst I think adding this sort of documentation would be appropriate for e.g. a book on procedural macros or some other sort of tutorial (cc @dtolnay for possible locations). But people stumbling over things is not a good reason to add help notes to the reference, which is not teaching material.

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fair enough


Unlike for [Derive macros] helper attributes do not have to be marked explicitly.
Since attribute macros can completely discard the input token stream filtering out custom `helper` attributes is entirely the job of the attribute macro.
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Suggested change
Since attribute macros can completely discard the input token stream filtering out custom `helper` attributes is entirely the job of the attribute macro.
Since attribute macros can completely discard the input token stream filtering
out custom `helper` attributes is entirely the job of the attribute macro.


[Attribute macros]: #attribute-macros
[Cargo's build scripts]: ../cargo/reference/build-scripts.html
[Derive macros]: #derive-macros
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