bjoernager/rust
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Rollup merge of #94869 - jackh726:gats_extended, r=compiler-errors

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Add the generic_associated_types_extended feature

Right now, this only ignore obligations that reference new placeholders in `poly_project_and_unify_type`. In the future, this might do other things, like allowing object-safe GATs.

**This feature is *incomplete* and quite likely unsound. This is mostly just for testing out potential future APIs using a "relaxed" set of rules until we figure out *proper* rules.**

Also drive by cleanup of adding a `ProjectAndUnifyResult` enum instead of using a `Result<Result<Option>>`.

r? `@nikomatsakis`
This commit is contained in:
Dylan DPC 2022-03-31 00:26:29 +02:00 • committed by GitHub
commit e08ab08a2e
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14 changed files with 261 additions and 33 deletions
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9
compiler/rustc_trait_selection/src/traits/select/mod.rs
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@ -21,6 +21,7 @@ use super::{
use crate::infer::{InferCtxt, InferOk, TypeFreshener};
use crate::traits::error_reporting::InferCtxtExt;
use crate::traits::project::ProjectAndUnifyResult;
use crate::traits::project::ProjectionCacheKeyExt;
use crate::traits::ProjectionCacheKey;
use rustc_data_structures::fx::{FxHashMap, FxHashSet};
@ -525,7 +526,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
let data = bound_predicate.rebind(data);
let project_obligation = obligation.with(data);
match project::poly_project_and_unify_type(self, &project_obligation) {
Ok(Ok(Some(mut subobligations))) => {
ProjectAndUnifyResult::Holds(mut subobligations) => {
'compute_res: {
// If we've previously marked this projection as 'complete', then
// use the final cached result (either `EvaluatedToOk` or
@ -573,9 +574,9 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
res
}
}
Ok(Ok(None)) => Ok(EvaluatedToAmbig),
Ok(Err(project::InProgress)) => Ok(EvaluatedToRecur),
Err(_) => Ok(EvaluatedToErr),
ProjectAndUnifyResult::FailedNormalization => Ok(EvaluatedToAmbig),
ProjectAndUnifyResult::Recursive => Ok(EvaluatedToRecur),
ProjectAndUnifyResult::MismatchedProjectionTypes(_) => Ok(EvaluatedToErr),
}
}