rust/compiler/rustc_trait_selection
Aaron Hill 3291218f47
Improve caching during trait evaluation
Previously, we would 'forget' that we had `'static` regions in some
place during trait evaluation. This lead to us producing
`EvaluatedToOkModuloRegions` when we could have produced
`EvaluatedToOk`, causing us to perform unnecessary work.

This PR preserves `'static` regions when we canonicalize a predicate for
`evaluate_obligation`, and when we 'freshen' a predicate during trait
evaluation. Thie ensures that evaluating a predicate containing
`'static` regions can produce `EvaluatedToOk` (assuming that we
don't end up introducing any region dependencies during evaluation).

Building off of this improved caching, we use
`predicate_must_hold_considering_regions` during fulfillment of
projection predicates to see if we can skip performing additional work.
We already do this for trait predicates, but doing this for projection
predicates lead to mixed performance results without the above caching
improvements.
2021-07-21 17:54:05 -05:00
..
src Improve caching during trait evaluation 2021-07-21 17:54:05 -05:00
Cargo.toml bumped smallvec deps 2021-02-14 18:03:11 +03:00