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Update now that proc macros can expand to macro_rules. #694

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Oct 17, 2019
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Update now that proc macros can expand to macro_rules. #694

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13 changes: 6 additions & 7 deletions src/procedural-macros.md
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Expand Up @@ -104,11 +104,11 @@ fn main() {
```

Function-like procedural macros may expand to a [type] or any number of
[items]. They may be invoked in a [type expression], [item] position (except
as a [statement]), including items in [`extern` blocks], inherent and trait
[implementations], and [trait definitions]. They cannot be used in a
[statement], [expression], or [pattern]. These macros cannot expand to syntax
that defines new [`macro_rules`] style macros.
[items], including [`macro_rules`] definitions. They may be invoked in a [type
expression], [item] position (except as a [statement]), including items in
[`extern` blocks], inherent and trait [implementations], and [trait
definitions]. They cannot be used in a [statement], [expression], or
[pattern].

### Derive macros

Expand Down Expand Up @@ -202,8 +202,7 @@ tree following the attribute's name, not including the outer delimiters. If
the attribute is written as a bare attribute name, the attribute
[`TokenStream`] is empty. The second [`TokenStream`] is the rest of the [item]
including other [attributes] on the [item]. The returned [`TokenStream`]
replaces the [item] with an arbitrary number of [items]. These macros cannot
expand to syntax that defines new [`macro_rules`] style macros.
replaces the [item] with an arbitrary number of [items].

For example, this attribute macro takes the input stream and returns it as is,
effectively being the no-op of attributes.
Expand Down