Yeet propagate_ambiguity - #162935
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adwinwhite wants to merge 4 commits into
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Yeet propagate_ambiguity#162935adwinwhite wants to merge 4 commits into
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| let constraint = ((smallest_universe + 1)..=largest_universe) | ||
| .map(|u| UniverseIndex::from_usize(u)) | ||
| if !self |
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Can you add a comment explaining why we use ambiguity here
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Reminder, once the PR becomes ready for a review, use |
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☔ The latest upstream changes (presumably #163227) made this pull request unmergeable. Please resolve the merge conflicts by rebasing. |
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Fixes rust-lang/project-assumptions-on-binders#29
When assumptions computation fails, we want to force the goal response to be ambiguous since we can't evaluate placeholder constraints.
We used to do this via
LeafRegionConstraint::Ambiguityand propagates it everywhere.This PR simplifies that by tracking whether we should force ambiguity in a more direct way. We just check whether we have computed assumptions for relevant universes.
This also clarifies the meaning of
LeafRegionConstraint::Ambiguitywhich only represents true ambiguity (forever ambiguity no matter inference progress).This doesn't solve the problem that we're being conservative about forcing ambiguity. Maybe we can have
falses in some universes even if other universes don't have assumptions. We can be smart about this in the future.Unsure part: we can also have ambiguity from non-lifetime placeholder. Unsure what to do with that. Still trying to understand it.
r? @BoxyUwU