Fix RPITITs in default trait methods (by assuming projection predicates in param-env) #108203
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I like this. Not sure if you had anyone else in mind that you wanted to look at this? r=me if not |
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Feb 19, 2023
…llaumeGomez Rollup of 5 pull requests Successful merges: - rust-lang#107766 (Fix json reexports of different items with same name) - rust-lang#108129 (Correctly handle links starting with whitespace) - rust-lang#108188 (Change src/etc/vscode_settings.json to always treat ./library as the sysroot source) - rust-lang#108203 (Fix RPITITs in default trait methods (by assuming projection predicates in param-env)) - rust-lang#108212 (Download rustfmt regardless of rustc being set in config.toml) Failed merges: r? `@ghost` `@rustbot` modify labels: rollup
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This did the trick for hring, thanks for the fix! |
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…lt-constraint, r=oli-obk Add a test for default trait method with RPITITs This didn't work in rust-lang#107013, but now that rust-lang#108203 has landed, let's make sure we don't regress it. r? types
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…hod-with-nested-rpitits, r=spastorino Account for binders correctly when adding default RPITIT method assumption As of rust-lang#108203, we install extra projection predicates into the param-env of a default trait method when it has return-position `impl Trait` (or is async). The implementation didn't account for the fact that it's walking into and out of binders, so we just need to shift all the debruijn indices accordingly when constructing the projection predicates. Fixes rust-lang#108579 r? types
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Instead of having special projection logic that allows us to turn
ProjectionTy(RPITIT, [Self#0, ...])intoOpaqueTy(RPITIT, [Self#0, ...]), we can instead augment the param-env of default trait method bodies to assume these as projection predicates. This should allow us to only project where we're allowed to!In order to make this work without introducing a bunch of cycle errors, we additionally tweak the
OpaqueTypeExpanderused byParamEnv::with_reveal_all_normalizedto not normalize the right-hand side of projection predicates. This should be fine, because if we use the projection predicate to normalize some other projection type, we'll continue to normalize the opaque that it gets projected to.This also makes it possible to support default trait methods with RPITITs in an associated-type based RPITIT lowering strategy without too much extra effort.
Fixes #107002
Alternative to #108142