Use is_global in candidate_should_be_dropped_in_favor_of#90375
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bors merged 3 commits intorust-lang:masterfrom Oct 30, 2021
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Use is_global in candidate_should_be_dropped_in_favor_of#90375bors merged 3 commits intorust-lang:masterfrom
is_global in candidate_should_be_dropped_in_favor_of#90375bors merged 3 commits intorust-lang:masterfrom
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This manifistated in rust-lang#90195 with compiler being unable to keep one candidate for a trait impl, if where is a global impl and more than one trait bound in the where clause. Before rust-lang#87280 `candidate_should_be_dropped_in_favor_of` was using `TypeFoldable::is_global()` that was enough to discard the two `ParamCandidate`s. But rust-lang#87280 changed it to use `TypeFoldable::is_known_global()` instead, which is pessimistic, so now the compiler drops the global impl instead (because `is_known_global` is not sure) and then can't decide between the two `ParamCandidate`s. Switching it to use `is_global` again solves the issue. Fixes rust-lang#90195.
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#90266 does fix that issue in a more general way, but the underlying issue with Your PR is correct and probably just generally a good idea, so |
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…laumeGomez Rollup of 5 pull requests Successful merges: - rust-lang#90156 (Remove underlines from non-top docblocks.) - rust-lang#90183 (Show all Deref implementations recursively) - rust-lang#90202 (Improve and test cross-crate hygiene) - rust-lang#90375 (Use `is_global` in `candidate_should_be_dropped_in_favor_of`) - rust-lang#90399 (Skipping verbose diagnostic suggestions when calling .as_ref() on type not implementing AsRef) Failed merges: r? `@ghost` `@rustbot` modify labels: rollup
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This manifistated in #90195 with compiler being unable to keep
one candidate for a trait impl, if where is a global impl and more
than one trait bound in the where clause.
Before #87280
candidate_should_be_dropped_in_favor_ofwas usingTypeFoldable::is_global()that was enough to discard the twoParamCandidates. But #87280 changed it to useTypeFoldable::is_known_global()instead, which is pessimistic, sonow the compiler drops the global impl instead (because
is_known_globalis not sure) and then can't decide between thetwo
ParamCandidates.Switching it to use
is_globalagain solves the issue.Fixes #90195.