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Add documentation and make matchers more flexible
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@mystor
mystor committed Nov 5, 2019
1 parent e357682 commit 2d9479a
Showing 1 changed file with 21 additions and 5 deletions.
26 changes: 21 additions & 5 deletions src/macros.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -50,13 +50,30 @@ pub use syn::{parse, parse_str, DeriveInput};
/// decl_derive!([Interesting, attributes(interesting_ignore)] => derive_interesting);
/// # };
/// ```
///
/// ### Decl Attributes & Doc Comments
/// ```
/// # fn main() {}
/// fn derive_interesting(_input: synstructure::Structure) -> proc_macro2::TokenStream {
/// quote::quote! { ... }
/// }
///
/// # const _IGNORE: &'static str = stringify! {
/// decl_derive! {
/// [Interesting] =>
/// #[allow(some_lint)]
/// /// Documentation Comments
/// derive_interesting
/// }
/// # };
/// ```
#[macro_export]
macro_rules! decl_derive {
// XXX: Switch to using this variant everywhere?
([$derives:ident $($derive_t:tt)*] => $(#[$attrs:meta])* $inner:path) => {
([$derives:ident $($derive_t:tt)*] => $(#[$($attrs:tt)*])* $inner:path) => {
#[proc_macro_derive($derives $($derive_t)*)]
#[allow(non_snake_case)]
$(#[$attrs])*
$(#[$($attrs)*])*
pub fn $derives(
i: $crate::macros::TokenStream
) -> $crate::macros::TokenStream {
Expand Down Expand Up @@ -102,12 +119,11 @@ macro_rules! decl_derive {
/// decl_attribute!([interesting] => attribute_interesting);
/// # };
/// ```
/// ```
#[macro_export]
macro_rules! decl_attribute {
([$attribute:ident] => $(#[$attrs:meta])* $inner:path) => {
([$attribute:ident] => $(#[$($attrs:tt)*])* $inner:path) => {
#[proc_macro_attribute]
$(#[$attrs])*
$(#[$($attrs)*])*
pub fn $attribute(
attr: $crate::macros::TokenStream,
i: $crate::macros::TokenStream,
Expand Down

2 comments on commit 2d9479a

@CreepySkeleton
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@mystor Out of curiosity, why did you change #[$attrs:meta] to #[$($attrs:tt)*]? Shouldn't it work with meta?

@mystor
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@mystor mystor commented on 2d9479a Nov 6, 2019

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Ha, well this one is kinda funny.

Attributes can technically take the format of any tokens within a #[...] wrapper, rather than specifically something looking like a "Meta Item", which meant that, for a while, it was more correct to match attributes in the manner I wrote it than using $:meta (see rust-lang/rust#49629 for context). I was originally writing the change this way to try to be compatible with these more general attributes.

However, apparently the definition of a valid custom attribute was restricted more in rust-lang/rust#50120, and the $:meta matcher was upgraded to support this new syntax in rust-lang/rust#63674. This means that the $:meta matcher is still fully compatible, and could be used here. I was not aware of rust-lang/rust#63674 at the time, however, and changed it to try to be safe.

I'll probably not back this change out, as it's harmless, but I probably wouldn't make it again after looking up the bug to explain the reasoning to you :-).

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