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/auto_trait.rs
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@ -5,6 +5,7 @@ use super::*;
use crate::infer::region_constraints::{Constraint, RegionConstraintData};
use crate::infer::InferCtxt;
use crate::traits::project::ProjectAndUnifyResult;
use rustc_middle::ty::fold::TypeFolder;
use rustc_middle::ty::{Region, RegionVid, Term};
@ -751,7 +752,7 @@ impl<'tcx> AutoTraitFinder<'tcx> {
debug!("Projecting and unifying projection predicate {:?}", predicate);
match project::poly_project_and_unify_type(select, &obligation.with(p)) {
Err(e) => {
ProjectAndUnifyResult::MismatchedProjectionTypes(e) => {
debug!(
"evaluate_nested_obligations: Unable to unify predicate \
'{:?}' '{:?}', bailing out",
@ -759,11 +760,11 @@ impl<'tcx> AutoTraitFinder<'tcx> {
);
return false;
}
Ok(Err(project::InProgress)) => {
ProjectAndUnifyResult::Recursive => {
debug!("evaluate_nested_obligations: recursive projection predicate");
return false;
}
Ok(Ok(Some(v))) => {
ProjectAndUnifyResult::Holds(v) => {
// We only care about sub-obligations
// when we started out trying to unify
// some inference variables. See the comment above
@ -782,7 +783,7 @@ impl<'tcx> AutoTraitFinder<'tcx> {
}
}
}
Ok(Ok(None)) => {
ProjectAndUnifyResult::FailedNormalization => {
// It's ok not to make progress when have no inference variables -
// in that case, we were only performing unification to check if an
// error occurred (which would indicate that it's impossible for our