cfg_select!: parse unused branches
#149925
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folkertdev
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Dec 12, 2025
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| fn tts_to_mac_result<'cx, 'sess>( | ||
| ecx: &'cx mut ExtCtxt<'sess>, | ||
| site_span: Span, | ||
| tts: TokenStream, | ||
| span: Span, | ||
| ) -> Box<dyn MacResult + 'cx> { | ||
| match ExpandResult::from_tts(ecx, tts, site_span, span, Ident::with_dummy_span(sym::cfg_select)) | ||
| { | ||
| ExpandResult::Ready(x) => x, | ||
| _ => unreachable!("from_tts always returns Ready"), | ||
| } | ||
| } |
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This works around ParserAnyMacro not being exported from rustc_expand. Maybe it should be exported though?
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| } | ||
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| impl<'cx, 'sess> MacResult for CfgSelectResult<'cx, 'sess> { |
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the MacResult trait has more methods, supporting macro expansion in more places (e.g. items within an impl or extern block). I've started a discussion at #t-lang > where can `cfg_select!` go to decide what we want to support, but we'll want at least expr/stmt/item.
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tracking issue: #115585
Emit parse errors that are found in the branches that are not selected, like e.g. how
#[cfg(false) { 1 ++ 2 }still emits a parse error even though the expression is never used by the program.