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Generalize projection_must_outlive

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This commit is contained in:
Oli Scherer 2022-05-18 15:40:16 +00:00
parent 4d4cc4fe53
commit c8ecf09a25
1 changed files with 29 additions and 14 deletions
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43
compiler/rustc_infer/src/infer/outlives/obligations.rs
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@ -68,6 +68,7 @@
};
use crate::traits::{ObligationCause, ObligationCauseCode};
use rustc_data_structures::undo_log::UndoLogs;
use rustc_hir::def_id::DefId;
use rustc_hir::def_id::LocalDefId;
use rustc_middle::mir::ConstraintCategory;
use rustc_middle::ty::subst::GenericArgKind;
@ -324,6 +325,29 @@ fn projection_must_outlive(
origin: infer::SubregionOrigin<'tcx>,
region: ty::Region<'tcx>,
projection_ty: ty::ProjectionTy<'tcx>,
) {
self.generic_must_outlive(
origin,
region,
GenericKind::Projection(projection_ty),
projection_ty.item_def_id,
projection_ty.substs,
|ty| match ty.kind() {
ty::Projection(projection_ty) => (projection_ty.item_def_id, projection_ty.substs),
_ => bug!("expected only projection types from env, not {:?}", ty),
},
);
}
#[instrument(level = "debug", skip(self, filter))]
fn generic_must_outlive(
&mut self,
origin: infer::SubregionOrigin<'tcx>,
region: ty::Region<'tcx>,
generic: GenericKind<'tcx>,
def_id: DefId,
substs: SubstsRef<'tcx>,
filter: impl Fn(Ty<'tcx>) -> (DefId, SubstsRef<'tcx>),
) {
// This case is thorny for inference. The fundamental problem is
// that there are many cases where we have choice, and inference
@ -342,13 +366,10 @@ fn projection_must_outlive(
// Compute the bounds we can derive from the trait definition.
// These are guaranteed to apply, no matter the inference
// results.
let trait_bounds: Vec<_> =
self.verify_bound.bounds(projection_ty.item_def_id, projection_ty.substs).collect();
let trait_bounds: Vec<_> = self.verify_bound.bounds(def_id, substs).collect();
debug!(?trait_bounds);
let generic = GenericKind::Projection(projection_ty);
// Compute the bounds we can derive from the environment. This
// is an "approximate" match -- in some cases, these bounds
// may not apply.
@ -367,14 +388,8 @@ fn projection_must_outlive(
// If the declaration is `trait Trait<'b> { type Item: 'b; }`, then `projection_declared_bounds_from_trait`
// will be invoked with `['b => ^1]` and so we will get `^1` returned.
let bound = bound_outlives.skip_binder();
match *bound.0.kind() {
ty::Projection(projection_ty) => self
.verify_bound
.bounds(projection_ty.item_def_id, projection_ty.substs)
.all(|r| r != bound.1),
_ => panic!("expected only projection types from env, not {:?}", bound.0),
}
let (def_id, substs) = filter(bound.0);
self.verify_bound.bounds(def_id, substs).all(|r| r != bound.1)
});
// If declared bounds list is empty, the only applicable rule is
@ -391,11 +406,11 @@ fn projection_must_outlive(
// the problem is to add `T: 'r`, which isn't true. So, if there are no
// inference variables, we use a verify constraint instead of adding
// edges, which winds up enforcing the same condition.
let needs_infer = projection_ty.needs_infer();
let needs_infer = substs.needs_infer();
if approx_env_bounds.is_empty() && trait_bounds.is_empty() && needs_infer {
debug!("no declared bounds");
self.substs_must_outlive(projection_ty.substs, origin, region);
self.substs_must_outlive(substs, origin, region);
return;
}