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simplify ast_fragments!#155919

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cyrgani wants to merge 5 commits intorust-lang:mainfrom
cyrgani:ast-fragments
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simplify ast_fragments!#155919
cyrgani wants to merge 5 commits intorust-lang:mainfrom
cyrgani:ast-fragments

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@cyrgani cyrgani commented Apr 28, 2026

The syntax and meaning of this macro are not very intuitive as its just a large dump of function names and has some special cases.
Each commit should be a small improvement that can be evaluated on its own.

@rustbot rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Apr 28, 2026
@rustbot rustbot added the T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. label Apr 28, 2026
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rustbot commented Apr 28, 2026

r? @folkertdev

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cyrgani
cyrgani commented Apr 28, 2026
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Comment thread compiler/rustc_expand/src/expand.rs Outdated
| AstFragment::Params(_)
| AstFragment::FieldDefs(_)
| AstFragment::Variants(_)
| AstFragment::WherePredicates(_) => unreachable!(),
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@cyrgani cyrgani Apr 28, 2026 •
edited by rustbot
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This is a small change in behavior: previously, if the contained SmallVecs were empty, using unreachable_to_string would not panic since there were no elements and it was never called. It now panics in all cases. Is this a problem? (I suppose not)

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Looks like this logic is only used in compiler\rustc_expand\src\stats.rs, and only for fragment in macro positions, so things like variants or where clauses should be safe.

Perhaps it would be better to move this function to stats.rs actually.

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folkertdev commented Apr 28, 2026

r? petrochenkov

@rustbot rustbot assigned petrochenkov and unassigned folkertdev Apr 28, 2026
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petrochenkov commented Apr 28, 2026

r=me after moving the fragment stringification to stats.rs, where its use should be limited to.
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@rustbot rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Apr 28, 2026
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rustbot commented Apr 28, 2026

Reminder, once the PR becomes ready for a review, use @rustbot ready.

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