Avoid repeated get_span in quote_spanned - #329
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Every group used in `quote_spanned` would cause a nested `quote_spanned` to be called for the contents of the group. This caused `$crate::__private::get_span($span).__into_span()` to be called every time, causing lots of unnecessary code. By only doing this in the user-facing macro and just reusing the identifier for internal recursion we avoid this extra code. This cuts the expanded lines of code from `tracing-attributes` by almost 300.
dtolnay
approved these changes
Jun 22, 2026
| // Special case rules for two tts, for performance. | ||
| ($span:ident=> # $var:ident) => { | ||
| let mut _s = $crate::__private::TokenStream::new(); | ||
| let _: $crate::__private::Span = $crate::__private::get_span($span).__into_span(); |
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| let _: $crate::__private::Span = $crate::__private::get_span($span).__into_span(); |
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Every group used in
quote_spannedwould cause a nestedquote_spannedto be called for the contents of the group. This caused$crate::__private::get_span($span).__into_span()to be called every time, causing lots of unnecessary code.By only doing this in the user-facing macro and just reusing the identifier for internal recursion we avoid this extra code.
This cuts the expanded lines of code from
tracing-attributesby almost 300.