Fix/matches span #400
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Fix/matches span #400
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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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I'm merging this without approval because it's just a bugfix and a pretty straightforward one. |
Aaron1011
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Jun 12, 2020
| // | ||
| // Given that this ident is used in several places and | ||
| // that the branches are located inside of a loop, it is possible that | ||
| // this ident will be given _different_ spans in different places, and |
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Note that a plain quote { } or format_ident will always use Span::call_site() for hygiene, so the generated matches token will always be 'the same' from the perspective of the compiler's name resolution. However, this change is still a good idea, since it makes it clear that matches is logically independent of the loop.
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Merge #398