cfg_select!: parse unused branches
#149925
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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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| impl<'cx, 'sess> MacResult for CfgSelectResult<'cx, 'sess> { | ||
| forward_to_parser_any_macro!(make_expr, Box<Expr>); | ||
| forward_to_parser_any_macro!(make_stmts, SmallVec<[ast::Stmt; 1]>); | ||
| forward_to_parser_any_macro!(make_items, SmallVec<[Box<ast::Item>; 1]>); | ||
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| branches.wildcard.map(|(_, tt, span)| (tt, span)) | ||
| forward_to_parser_any_macro!(make_impl_items, SmallVec<[Box<ast::AssocItem>; 1]>); | ||
| forward_to_parser_any_macro!(make_trait_impl_items, SmallVec<[Box<ast::AssocItem>; 1]>); | ||
| forward_to_parser_any_macro!(make_trait_items, SmallVec<[Box<ast::AssocItem>; 1]>); | ||
| forward_to_parser_any_macro!(make_foreign_items, SmallVec<[Box<ast::ForeignItem>; 1]>); | ||
| } |
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I've started a discussion at #t-lang > where can `cfg_select!` go to decide what we want to support.
expr/stmt/item is the bare minimum I think, but we already had some use of (i believe) impl items in the stdlib test suite, so including the other item flavors seems natural. We can see about e.g. patterns or where-clauses etc.
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r? @chenyukang rustbot has assigned @chenyukang. Use |
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r? jdonszelmann (Reviewed similar PRS recently, don't mind taking a look :) |
| where | ||
| F: Fn(&CfgEntry) -> bool, | ||
| { | ||
| for (index, (cfg, _, _)) in self.reachable.iter().enumerate() { |
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might be nicer to write as an iterator? and since it consumes maybe it can take self by value. Then it'd become something like self.reachable.into_iter().find(predicate).unwrap_or(self.wildcard) with maybe something added to just get the tts and span hehe
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That won't work, at least with the current setup. This function isn't just about finding the match, but also specifically about removing it from the CfgSelectBranches so that it does not get parsed twice (which would duplicate errors).
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Reminder, once the PR becomes ready for a review, use |
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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. Parsing the unused branches was requested by T-lang #149783 (comment).