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Rollup merge of #121520 - matthiaskrgr:cloned, r=jackh726

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delay cloning of iterator items
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Matthias Krüger 2024-02-24 15:35:13 +01:00 committed by GitHub
commit 3b827731d0
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1 changed files with 18 additions and 15 deletions
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33
compiler/rustc_trait_selection/src/traits/coherence.rs
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@ -320,22 +320,25 @@ fn impl_intersection_has_impossible_obligation<'a, 'cx, 'tcx>(
let mut errors = fulfill_cx.select_where_possible(infcx);
errors.pop().map(|err| err.obligation)
} else {
obligations.iter().cloned().find(|obligation| {
// We use `evaluate_root_obligation` to correctly track intercrate
// ambiguity clauses. We cannot use this in the new solver.
let evaluation_result = selcx.evaluate_root_obligation(obligation);
obligations
.iter()
.find(|obligation| {
// We use `evaluate_root_obligation` to correctly track intercrate
// ambiguity clauses. We cannot use this in the new solver.
let evaluation_result = selcx.evaluate_root_obligation(obligation);
match evaluation_result {
Ok(result) => !result.may_apply(),
// If overflow occurs, we need to conservatively treat the goal as possibly holding,
// since there can be instantiations of this goal that don't overflow and result in
// success. This isn't much of a problem in the old solver, since we treat overflow
// fatally (this still can be encountered: <https://github.com/rust-lang/rust/issues/105231>),
// but in the new solver, this is very important for correctness, since overflow
// *must* be treated as ambiguity for completeness.
Err(_overflow) => false,
}
})
match evaluation_result {
Ok(result) => !result.may_apply(),
// If overflow occurs, we need to conservatively treat the goal as possibly holding,
// since there can be instantiations of this goal that don't overflow and result in
// success. This isn't much of a problem in the old solver, since we treat overflow
// fatally (this still can be encountered: <https://github.com/rust-lang/rust/issues/105231>),
// but in the new solver, this is very important for correctness, since overflow
// *must* be treated as ambiguity for completeness.
Err(_overflow) => false,
}
})
.cloned()
}
}