alias-relate: add fast reject optimization #124852
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Some changes occurred to the core trait solver cc @rust-lang/initiative-trait-system-refactor |
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this unfortunately does not fix the hang in rayon. closing while we're trying other approaches |
| if self.fast_reject_unnameable_rigid_term(param_env, lhs, rhs) | ||
| && self.fast_reject_unnameable_rigid_term(param_env, rhs, lhs) |
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damn 🤔 if only there was a reason why this fast path didn't fix the hang in rayon
this literally never triggers 🙃 it needs to be ||
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if there's |
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☔ The latest upstream changes (presumably #125324) made this pull request unmergeable. Please resolve the merge conflicts. |
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| return false; | ||
| } | ||
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| let mut referenced_placeholders = |
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Why IgnoreAliases::Yes?
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Feels like this fast reject could be quickly side-stepped w/ something like Mirror<!A> alias-relate Mirror<!B>
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Update: It occurred to me last night while I was sleeping that we ignore aliases here b/c e.g. Alias<!A> could normalize to sth not mentioning !A.
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| let mut referenced_placeholders = | ||
| self.collect_placeholders_in_term(rigid_term, IgnoreAliases::Yes); | ||
| for clause in param_env.caller_bounds() { |
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Would be nice to explain in detail what this is searching for. Specifically, we disqualify any of our rigid term's placeholders if they show up in projection goals, since that may assist in normalizing.
e.g. if we have
rigid = W<!A>
alias = Alias<!B>
param-env = [Alias<!B> normalizes-to W<!A>, ...]
then we exclude !A from our rigid placeholder list, right?
I think this may also be worth mentioning that this doesn't really care about how the placeholders show up in the term of the projection predicate, since this is really just a quick heuristic.
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| } | ||
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| if referenced_placeholders.is_empty() { |
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Probably a somewhat redundant note, but maybe just say "empty set is a subset of everything, so no need to compute placeholders of alias"
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| let alias_placeholders = self.collect_placeholders_in_term(alias, IgnoreAliases::No); | ||
| // If the rigid term references a placeholder not mentioned by the alias, |
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| // If the rigid term references a placeholder not mentioned by the alias, | |
| // If the rigid term references a placeholder not mentioned by the alias, and isn't potentially reachable by a projection-predicate, |
or something, to explain the way that the projection predicate search above influences this search
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My only outstanding question was answered by myself. I think the only tweaks I want are more thorough comments bc this code is subtle. r=me afterwards |
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☔ The latest upstream changes (presumably #126614) made this pull request unmergeable. Please resolve the merge conflicts. |
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may be necessary to compile rayon rust-lang/trait-system-refactor-initiative#109
r? @compiler-errors