Use proper span when generating matches token
#398
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In `struct-opt-derive`, a function is generated with a parameter named `matches`. Since `quote!` is used to generate the function, the `matches` token will be resolved using `Span::call_site`. However, the literal identifier `matches` is also used inside several `quote_spanned!` expressions. Such a `matches` identifier will be resolved using the `Span` passed to `quote_spanned!`, which may not be the same as `Span::call_site`. Currently, this is difficult to observe in practice, due to rust-lang/rust#43081 . However, once PR rust-lang/rust#73084 is merged, proc macros will see properly spanned tokens in more cases, which will cause these incorrect uses of `quote_spanned!` to break. This PR uses `quote! { matches }` to generate a correctly spanned `matches` token, which is then include in the `quote_spanned!` expressions using `#matches`.
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The test failures seem unrelated to this PR. |
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This issue is pretty interesting. I recall I had noticed this problem and been thinking about for a while it but eventually came to conclusion that since What I didn't notice is that the match is located inside a cycle ( @Aaron1011 Could you please factor the |
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Merged in #400 |
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@CreepySkeleton: Thanks! Would it be possible for you to make a new point release? This will prevent rust-lang/rust#73084 from causing regressiosn when it lands? |
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Sure. I'm working on another bugfix ATM and I will either finish in a day or two and make one release for the both (just so we have something meaningful to put in changelog) or give up and make a release all the same. Is that fine or you need it ASAP? |
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@CreepySkeleton: That's fine by me - the Rust PR will be merged in a couple days at the absolute earliest, since it's waiting on a Crater run. |
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Released in |
In
struct-opt-derive, a function is generated with a parameter namedmatches. Sincequote!is used to generate the function, thematchestoken will be resolved usingSpan::call_site.However, the literal identifier
matchesis also used inside severalquote_spanned!expressions. Such amatchesidentifier will beresolved using the
Spanpassed toquote_spanned!, which may not bethe same as
Span::call_site.Currently, this is difficult to observe in practice, due to
rust-lang/rust#43081 . However, once PR rust-lang/rust#73084
is merged, proc macros will see properly spanned tokens in more cases,
which will cause these incorrect uses of
quote_spanned!to break.This PR uses
quote! { matches }to generate a correctly spannedmatchestoken, which is then include in thequote_spanned!expressions using
#matches.