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Walk un-shifted nested impl Trait in trait when setting up default trait method assumptions

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This commit is contained in:
Michael Goulet 2023-03-16 23:27:09 +00:00
parent da7c50c089
commit 9f80c75703
2 changed files with 32 additions and 16 deletions
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42
compiler/rustc_ty_utils/src/ty.rs
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@ -7,7 +7,10 @@ use rustc_middle::ty::{
TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitor,
};
use rustc_session::config::TraitSolver;
use rustc_span::def_id::{DefId, CRATE_DEF_ID};
use rustc_span::{
def_id::{DefId, CRATE_DEF_ID},
DUMMY_SP,
};
use rustc_trait_selection::traits;
fn sized_constraint_for_ty<'tcx>(
@ -275,16 +278,22 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for ImplTraitInTraitFinder<'_, 'tcx> {
}
fn visit_ty(&mut self, ty: Ty<'tcx>) -> std::ops::ControlFlow<Self::BreakTy> {
if let ty::Alias(ty::Projection, alias_ty) = *ty.kind()
&& self.tcx.is_impl_trait_in_trait(alias_ty.def_id)
&& self.tcx.impl_trait_in_trait_parent_fn(alias_ty.def_id) == self.fn_def_id
&& self.seen.insert(alias_ty.def_id)
if let ty::Alias(ty::Projection, unshifted_alias_ty) = *ty.kind()
&& self.tcx.is_impl_trait_in_trait(unshifted_alias_ty.def_id)
&& self.tcx.impl_trait_in_trait_parent_fn(unshifted_alias_ty.def_id) == self.fn_def_id
&& self.seen.insert(unshifted_alias_ty.def_id)
{
// We have entered some binders as we've walked into the
// bounds of the RPITIT. Shift these binders back out when
// constructing the top-level projection predicate.
let alias_ty = self.tcx.fold_regions(alias_ty, |re, _| {
let shifted_alias_ty = self.tcx.fold_regions(unshifted_alias_ty, |re, depth| {
if let ty::ReLateBound(index, bv) = re.kind() {
if depth != ty::INNERMOST {
return self.tcx.mk_re_error_with_message(
DUMMY_SP,
"we shouldn't walk non-predicate binders with `impl Trait`...",
);
}
self.tcx.mk_re_late_bound(index.shifted_out_to_binder(self.depth), bv)
} else {
re
@ -295,26 +304,27 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for ImplTraitInTraitFinder<'_, 'tcx> {
// the `type_of` of the trait's associated item. If we're using the old lowering
// strategy, then just reinterpret the associated type like an opaque :^)
let default_ty = if self.tcx.lower_impl_trait_in_trait_to_assoc_ty() {
self
.tcx
.type_of(alias_ty.def_id)
.subst(self.tcx, alias_ty.substs)
self.tcx.type_of(shifted_alias_ty.def_id).subst(self.tcx, shifted_alias_ty.substs)
} else {
self.tcx.mk_alias(ty::Opaque, alias_ty)
self.tcx.mk_alias(ty::Opaque, shifted_alias_ty)
};
self.predicates.push(
ty::Binder::bind_with_vars(
ty::ProjectionPredicate {
projection_ty: alias_ty,
term: default_ty.into(),
},
ty::ProjectionPredicate { projection_ty: shifted_alias_ty, term: default_ty.into() },
self.bound_vars,
)
.to_predicate(self.tcx),
);
for bound in self.tcx.item_bounds(alias_ty.def_id).subst_iter(self.tcx, alias_ty.substs)
// We walk the *un-shifted* alias ty, because we're tracking the de bruijn
// binder depth, and if we were to walk `shifted_alias_ty` instead, we'd
// have to reset `self.depth` back to `ty::INNERMOST` or something. It's
// easier to just do this.
for bound in self
.tcx
.item_bounds(unshifted_alias_ty.def_id)
.subst_iter(self.tcx, unshifted_alias_ty.substs)
{
bound.visit_with(self);
}