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delay cloning of iterator items

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This commit is contained in:
Matthias Krüger 2024-02-23 19:07:42 +01:00
parent b6a23b8537
commit 62cb9d1a97
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); let mut errors = fulfill_cx.select_where_possible(infcx);
errors.pop().map(|err| err.obligation) errors.pop().map(|err| err.obligation)
} else { } else {
obligations.iter().cloned().find(|obligation| { obligations
// We use `evaluate_root_obligation` to correctly track intercrate .iter()
// ambiguity clauses. We cannot use this in the new solver. .find(|obligation| {
let evaluation_result = selcx.evaluate_root_obligation(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 { match evaluation_result {
Ok(result) => !result.may_apply(), Ok(result) => !result.may_apply(),
// If overflow occurs, we need to conservatively treat the goal as possibly holding, // 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 // 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 // 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>), // 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 // but in the new solver, this is very important for correctness, since overflow
// *must* be treated as ambiguity for completeness. // *must* be treated as ambiguity for completeness.
Err(_overflow) => false, Err(_overflow) => false,
} }
}) })
.cloned()
} }
} }