diff --git a/compiler/rustc_infer/src/infer/combine.rs b/compiler/rustc_infer/src/infer/combine.rs
index 4503af03ca3..c82438f05e1 100644
--- a/compiler/rustc_infer/src/infer/combine.rs
+++ b/compiler/rustc_infer/src/infer/combine.rs
@@ -842,7 +842,7 @@ pub trait ObligationEmittingRelation<'tcx>: TypeRelation<'tcx> {
let (a, b) = if self.a_is_expected() { (a, b) } else { (b, a) };
self.register_predicates([ty::Binder::dummy(if self.tcx().trait_solver_next() {
- ty::PredicateKind::AliasEq(a.into(), b.into())
+ ty::PredicateKind::AliasEq(a.into(), b.into(), ty::AliasRelationDirection::Equate)
} else {
ty::PredicateKind::ConstEquate(a, b)
})]);
@@ -852,13 +852,15 @@ pub trait ObligationEmittingRelation<'tcx>: TypeRelation<'tcx> {
///
/// If they aren't equal then the relation doesn't hold.
fn register_type_equate_obligation(&mut self, a: Ty<'tcx>, b: Ty<'tcx>) {
- let (a, b) = if self.a_is_expected() { (a, b) } else { (b, a) };
-
self.register_predicates([ty::Binder::dummy(ty::PredicateKind::AliasEq(
a.into(),
b.into(),
+ self.alias_relate_direction(),
))]);
}
+
+ /// Relation direction emitted for `AliasEq` predicates
+ fn alias_relate_direction(&self) -> ty::AliasRelationDirection;
}
fn int_unification_error<'tcx>(
diff --git a/compiler/rustc_infer/src/infer/equate.rs b/compiler/rustc_infer/src/infer/equate.rs
index c92a74b6241..38002357cde 100644
--- a/compiler/rustc_infer/src/infer/equate.rs
+++ b/compiler/rustc_infer/src/infer/equate.rs
@@ -210,4 +210,8 @@ impl<'tcx> ObligationEmittingRelation<'tcx> for Equate<'_, '_, 'tcx> {
fn register_obligations(&mut self, obligations: PredicateObligations<'tcx>) {
self.fields.register_obligations(obligations);
}
+
+ fn alias_relate_direction(&self) -> ty::AliasRelationDirection {
+ ty::AliasRelationDirection::Equate
+ }
}
diff --git a/compiler/rustc_infer/src/infer/glb.rs b/compiler/rustc_infer/src/infer/glb.rs
index 5c12351226a..6395c4d4b20 100644
--- a/compiler/rustc_infer/src/infer/glb.rs
+++ b/compiler/rustc_infer/src/infer/glb.rs
@@ -155,4 +155,9 @@ impl<'tcx> ObligationEmittingRelation<'tcx> for Glb<'_, '_, 'tcx> {
fn register_obligations(&mut self, obligations: PredicateObligations<'tcx>) {
self.fields.register_obligations(obligations);
}
+
+ fn alias_relate_direction(&self) -> ty::AliasRelationDirection {
+ // FIXME(deferred_projection_equality): This isn't right, I think?
+ ty::AliasRelationDirection::Equate
+ }
}
diff --git a/compiler/rustc_infer/src/infer/lub.rs b/compiler/rustc_infer/src/infer/lub.rs
index dbef42db8f1..98cbd4c561c 100644
--- a/compiler/rustc_infer/src/infer/lub.rs
+++ b/compiler/rustc_infer/src/infer/lub.rs
@@ -155,4 +155,9 @@ impl<'tcx> ObligationEmittingRelation<'tcx> for Lub<'_, '_, 'tcx> {
fn register_obligations(&mut self, obligations: PredicateObligations<'tcx>) {
self.fields.register_obligations(obligations)
}
+
+ fn alias_relate_direction(&self) -> ty::AliasRelationDirection {
+ // FIXME(deferred_projection_equality): This isn't right, I think?
+ ty::AliasRelationDirection::Equate
+ }
}
diff --git a/compiler/rustc_infer/src/infer/nll_relate/mod.rs b/compiler/rustc_infer/src/infer/nll_relate/mod.rs
index 573cd91a2a2..216d2965da7 100644
--- a/compiler/rustc_infer/src/infer/nll_relate/mod.rs
+++ b/compiler/rustc_infer/src/infer/nll_relate/mod.rs
@@ -777,6 +777,16 @@ where
fn register_obligations(&mut self, obligations: PredicateObligations<'tcx>) {
self.delegate.register_obligations(obligations);
}
+
+ fn alias_relate_direction(&self) -> ty::AliasRelationDirection {
+ match self.ambient_variance {
+ ty::Variance::Covariant => ty::AliasRelationDirection::Subtype,
+ ty::Variance::Contravariant => ty::AliasRelationDirection::Supertype,
+ ty::Variance::Invariant => ty::AliasRelationDirection::Equate,
+ // FIXME(deferred_projection_equality): Implement this when we trigger it
+ ty::Variance::Bivariant => unreachable!(),
+ }
+ }
}
/// When we encounter a binder like `for<..> fn(..)`, we actually have
diff --git a/compiler/rustc_infer/src/infer/sub.rs b/compiler/rustc_infer/src/infer/sub.rs
index 230cadb1184..fc73ca7606d 100644
--- a/compiler/rustc_infer/src/infer/sub.rs
+++ b/compiler/rustc_infer/src/infer/sub.rs
@@ -236,4 +236,8 @@ impl<'tcx> ObligationEmittingRelation<'tcx> for Sub<'_, '_, 'tcx> {
fn register_obligations(&mut self, obligations: PredicateObligations<'tcx>) {
self.fields.register_obligations(obligations);
}
+
+ fn alias_relate_direction(&self) -> ty::AliasRelationDirection {
+ ty::AliasRelationDirection::Subtype
+ }
}
diff --git a/compiler/rustc_middle/src/ty/flags.rs b/compiler/rustc_middle/src/ty/flags.rs
index 91241ff404f..1ae47fddccc 100644
--- a/compiler/rustc_middle/src/ty/flags.rs
+++ b/compiler/rustc_middle/src/ty/flags.rs
@@ -288,7 +288,7 @@ impl FlagComputation {
self.add_ty(ty);
}
ty::PredicateKind::Ambiguous => {}
- ty::PredicateKind::AliasEq(t1, t2) => {
+ ty::PredicateKind::AliasEq(t1, t2, _) => {
self.add_term(t1);
self.add_term(t2);
}
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index d383a413208..d1e268f49c4 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -640,7 +640,25 @@ pub enum PredicateKind<'tcx> {
/// This predicate requires two terms to be equal to eachother.
///
/// Only used for new solver
- AliasEq(Term<'tcx>, Term<'tcx>),
+ AliasEq(Term<'tcx>, Term<'tcx>, AliasRelationDirection),
+}
+
+#[derive(Clone, Copy, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]
+#[derive(HashStable, Debug)]
+pub enum AliasRelationDirection {
+ Equate,
+ Subtype,
+ Supertype,
+}
+
+impl AliasRelationDirection {
+ pub fn invert(self) -> Self {
+ match self {
+ AliasRelationDirection::Equate => AliasRelationDirection::Equate,
+ AliasRelationDirection::Subtype => AliasRelationDirection::Supertype,
+ AliasRelationDirection::Supertype => AliasRelationDirection::Subtype,
+ }
+ }
}
/// The crate outlives map is computed during typeck and contains the
@@ -976,11 +994,11 @@ impl<'tcx> Term<'tcx> {
}
}
- /// This function returns `None` for `AliasKind::Opaque`.
+ /// This function returns the inner `AliasTy` if this term is a projection.
///
/// FIXME: rename `AliasTy` to `AliasTerm` and make sure we correctly
/// deal with constants.
- pub fn to_alias_term_no_opaque(&self, tcx: TyCtxt<'tcx>) -> Option<AliasTy<'tcx>> {
+ pub fn to_projection_term(&self, tcx: TyCtxt<'tcx>) -> Option<AliasTy<'tcx>> {
match self.unpack() {
TermKind::Ty(ty) => match ty.kind() {
ty::Alias(kind, alias_ty) => match kind {
diff --git a/compiler/rustc_middle/src/ty/print/pretty.rs b/compiler/rustc_middle/src/ty/print/pretty.rs
index fffdbfc9660..e96856231ce 100644
--- a/compiler/rustc_middle/src/ty/print/pretty.rs
+++ b/compiler/rustc_middle/src/ty/print/pretty.rs
@@ -2847,7 +2847,8 @@ define_print_and_forward_display! {
p!("the type `", print(ty), "` is found in the environment")
}
ty::PredicateKind::Ambiguous => p!("ambiguous"),
- ty::PredicateKind::AliasEq(t1, t2) => p!(print(t1), " == ", print(t2)),
+ // TODO
+ ty::PredicateKind::AliasEq(t1, t2, _) => p!(print(t1), " == ", print(t2)),
}
}
diff --git a/compiler/rustc_middle/src/ty/structural_impls.rs b/compiler/rustc_middle/src/ty/structural_impls.rs
index ef643531bb2..92a2b4b18dd 100644
--- a/compiler/rustc_middle/src/ty/structural_impls.rs
+++ b/compiler/rustc_middle/src/ty/structural_impls.rs
@@ -177,7 +177,8 @@ impl<'tcx> fmt::Debug for ty::PredicateKind<'tcx> {
write!(f, "TypeWellFormedFromEnv({:?})", ty)
}
ty::PredicateKind::Ambiguous => write!(f, "Ambiguous"),
- ty::PredicateKind::AliasEq(t1, t2) => write!(f, "AliasEq({t1:?}, {t2:?})"),
+ // TODO
+ ty::PredicateKind::AliasEq(t1, t2, _) => write!(f, "AliasEq({t1:?}, {t2:?})"),
}
}
}
@@ -250,6 +251,7 @@ TrivialTypeTraversalAndLiftImpls! {
crate::ty::AssocItem,
crate::ty::AssocKind,
crate::ty::AliasKind,
+ crate::ty::AliasRelationDirection,
crate::ty::Placeholder<crate::ty::BoundRegionKind>,
crate::ty::Placeholder<crate::ty::BoundTyKind>,
crate::ty::ClosureKind,
diff --git a/compiler/rustc_privacy/src/lib.rs b/compiler/rustc_privacy/src/lib.rs
index d884ebd9acc..fda9ef008d7 100644
--- a/compiler/rustc_privacy/src/lib.rs
+++ b/compiler/rustc_privacy/src/lib.rs
@@ -180,7 +180,7 @@ where
| ty::PredicateKind::ConstEquate(_, _)
| ty::PredicateKind::TypeWellFormedFromEnv(_)
| ty::PredicateKind::Ambiguous
- | ty::PredicateKind::AliasEq(_, _) => bug!("unexpected predicate: {:?}", predicate),
+ | ty::PredicateKind::AliasEq(..) => bug!("unexpected predicate: {:?}", predicate),
}
}
diff --git a/compiler/rustc_trait_selection/src/solve/eval_ctxt.rs b/compiler/rustc_trait_selection/src/solve/eval_ctxt.rs
index 95412922357..106a989b22f 100644
--- a/compiler/rustc_trait_selection/src/solve/eval_ctxt.rs
+++ b/compiler/rustc_trait_selection/src/solve/eval_ctxt.rs
@@ -223,8 +223,8 @@ impl<'a, 'tcx> EvalCtxt<'a, 'tcx> {
ty::PredicateKind::TypeWellFormedFromEnv(..) => {
bug!("TypeWellFormedFromEnv is only used for Chalk")
}
- ty::PredicateKind::AliasEq(lhs, rhs) => {
- self.compute_alias_eq_goal(Goal { param_env, predicate: (lhs, rhs) })
+ ty::PredicateKind::AliasEq(lhs, rhs, direction) => {
+ self.compute_alias_eq_goal(Goal { param_env, predicate: (lhs, rhs, direction) })
}
}
} else {
diff --git a/compiler/rustc_trait_selection/src/solve/fulfill.rs b/compiler/rustc_trait_selection/src/solve/fulfill.rs
index 38120b9760f..a9c9e5761a8 100644
--- a/compiler/rustc_trait_selection/src/solve/fulfill.rs
+++ b/compiler/rustc_trait_selection/src/solve/fulfill.rs
@@ -73,7 +73,7 @@ impl<'tcx> TraitEngine<'tcx> for FulfillmentCtxt<'tcx> {
MismatchedProjectionTypes { err: TypeError::Mismatch },
)
}
- ty::PredicateKind::AliasEq(_, _) => {
+ ty::PredicateKind::AliasEq(_, _, _) => {
FulfillmentErrorCode::CodeProjectionError(
MismatchedProjectionTypes { err: TypeError::Mismatch },
)
diff --git a/compiler/rustc_trait_selection/src/solve/mod.rs b/compiler/rustc_trait_selection/src/solve/mod.rs
index 606c2eaa510..48ef089a7b2 100644
--- a/compiler/rustc_trait_selection/src/solve/mod.rs
+++ b/compiler/rustc_trait_selection/src/solve/mod.rs
@@ -158,13 +158,35 @@ impl<'a, 'tcx> EvalCtxt<'a, 'tcx> {
#[instrument(level = "debug", skip(self), ret)]
fn compute_alias_eq_goal(
&mut self,
- goal: Goal<'tcx, (ty::Term<'tcx>, ty::Term<'tcx>)>,
+ goal: Goal<'tcx, (ty::Term<'tcx>, ty::Term<'tcx>, ty::AliasRelationDirection)>,
) -> QueryResult<'tcx> {
let tcx = self.tcx();
- let evaluate_normalizes_to = |ecx: &mut EvalCtxt<'_, 'tcx>, alias, other| {
+ let evaluate_normalizes_to = |ecx: &mut EvalCtxt<'_, 'tcx>, alias, other, direction| {
debug!("evaluate_normalizes_to(alias={:?}, other={:?})", alias, other);
- let r = ecx.probe(|ecx| {
+ let result = ecx.probe(|ecx| {
+ let other = match direction {
+ // This is purely an optimization.
+ ty::AliasRelationDirection::Equate => other,
+
+ ty::AliasRelationDirection::Subtype | ty::AliasRelationDirection::Supertype => {
+ let fresh = ecx.next_term_infer_of_kind(other);
+ let (sub, sup) = if direction == ty::AliasRelationDirection::Subtype {
+ (fresh, other)
+ } else {
+ (other, fresh)
+ };
+ ecx.add_goals(
+ ecx.infcx
+ .at(&ObligationCause::dummy(), goal.param_env)
+ .sub(DefineOpaqueTypes::No, sub, sup)?
+ .into_obligations()
+ .into_iter()
+ .map(|o| o.into()),
+ );
+ fresh
+ }
+ };
ecx.add_goal(goal.with(
tcx,
ty::Binder::dummy(ty::ProjectionPredicate {
@@ -174,37 +196,64 @@ impl<'a, 'tcx> EvalCtxt<'a, 'tcx> {
));
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
});
- debug!("evaluate_normalizes_to(..) -> {:?}", r);
- r
+ debug!("evaluate_normalizes_to({alias}, {other}, {direction:?}) -> {result:?}");
+ result
};
- if goal.predicate.0.is_infer() || goal.predicate.1.is_infer() {
+ let (lhs, rhs, direction) = goal.predicate;
+
+ if lhs.is_infer() || rhs.is_infer() {
bug!(
"`AliasEq` goal with an infer var on lhs or rhs which should have been instantiated"
);
}
- match (
- goal.predicate.0.to_alias_term_no_opaque(tcx),
- goal.predicate.1.to_alias_term_no_opaque(tcx),
- ) {
+ match (lhs.to_projection_term(tcx), rhs.to_projection_term(tcx)) {
(None, None) => bug!("`AliasEq` goal without an alias on either lhs or rhs"),
- (Some(alias), None) => evaluate_normalizes_to(self, alias, goal.predicate.1),
- (None, Some(alias)) => evaluate_normalizes_to(self, alias, goal.predicate.0),
+
+ // RHS is not a projection, only way this is true is if LHS normalizes-to RHS
+ (Some(alias_lhs), None) => evaluate_normalizes_to(self, alias_lhs, rhs, direction),
+
+ // LHS is not a projection, only way this is true is if RHS normalizes-to LHS
+ (None, Some(alias_rhs)) => {
+ evaluate_normalizes_to(self, alias_rhs, lhs, direction.invert())
+ }
+
(Some(alias_lhs), Some(alias_rhs)) => {
debug!("compute_alias_eq_goal: both sides are aliases");
- let mut candidates = Vec::with_capacity(3);
+ let candidates = vec![
+ // LHS normalizes-to RHS
+ evaluate_normalizes_to(self, alias_lhs, rhs, direction),
+ // RHS normalizes-to RHS
+ evaluate_normalizes_to(self, alias_rhs, lhs, direction.invert()),
+ // Relate via substs
+ self.probe(|ecx| {
+ debug!("compute_alias_eq_goal: alias defids are equal, equating substs");
- // Evaluate all 3 potential candidates for the alias' being equal
- candidates.push(evaluate_normalizes_to(self, alias_lhs, goal.predicate.1));
- candidates.push(evaluate_normalizes_to(self, alias_rhs, goal.predicate.0));
- candidates.push(self.probe(|ecx| {
- debug!("compute_alias_eq_goal: alias defids are equal, equating substs");
- ecx.eq(goal.param_env, alias_lhs, alias_rhs)?;
- ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
- }));
+ ecx.add_goals(
+ match direction {
+ ty::AliasRelationDirection::Equate => ecx
+ .infcx
+ .at(&ObligationCause::dummy(), goal.param_env)
+ .eq(DefineOpaqueTypes::No, alias_lhs, alias_rhs),
+ ty::AliasRelationDirection::Subtype => ecx
+ .infcx
+ .at(&ObligationCause::dummy(), goal.param_env)
+ .sub(DefineOpaqueTypes::No, alias_lhs, alias_rhs),
+ ty::AliasRelationDirection::Supertype => ecx
+ .infcx
+ .at(&ObligationCause::dummy(), goal.param_env)
+ .sup(DefineOpaqueTypes::No, alias_lhs, alias_rhs),
+ }?
+ .into_obligations()
+ .into_iter()
+ .map(|o| o.into()),
+ );
+ ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
+ }),
+ ];
debug!(?candidates);
self.try_merge_responses(candidates.into_iter())
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/method_chain.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/method_chain.rs
index 1174efdbfa8..13607b9079a 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/method_chain.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/method_chain.rs
@@ -92,6 +92,11 @@ impl<'a, 'tcx> TypeRelation<'tcx> for CollectAllMismatches<'a, 'tcx> {
}
impl<'tcx> ObligationEmittingRelation<'tcx> for CollectAllMismatches<'_, 'tcx> {
+ fn alias_relate_direction(&self) -> ty::AliasRelationDirection {
+ // FIXME(deferred_projection_equality): We really should get rid of this relation.
+ ty::AliasRelationDirection::Equate
+ }
+
fn register_obligations(&mut self, _obligations: PredicateObligations<'tcx>) {
// FIXME(deferred_projection_equality)
}
diff --git a/tests/ui/traits/new-solver/alias-sub.rs b/tests/ui/traits/new-solver/alias-sub.rs
new file mode 100644
index 00000000000..30c1981a92e
--- /dev/null
+++ b/tests/ui/traits/new-solver/alias-sub.rs
@@ -0,0 +1,34 @@
+// compile-flags: -Ztrait-solver=next
+// check-pass
+
+trait Trait {
+ type Assoc: Sized;
+}
+
+impl Trait for &'static str {
+ type Assoc = &'static str;
+}
+
+// Wrapper is just here to get around stupid `Sized` obligations in mir typeck
+struct Wrapper<T: ?Sized>(std::marker::PhantomData<T>);
+fn mk<T: Trait>(x: T) -> Wrapper<<T as Trait>::Assoc> { todo!() }
+
+
+trait IsStaticStr {}
+impl IsStaticStr for (&'static str,) {}
+fn define<T: IsStaticStr>(_: T) {}
+
+fn foo<'a, T: Trait>() {
+ let y = Default::default();
+
+ // `<?0 as Trait>::Assoc <: &'a str`
+ // In the old solver, this would *equate* the LHS and RHS.
+ let _: Wrapper<&'a str> = mk(y);
+
+ // ... then later on, we constrain `?0 = &'static str`
+ // but that should not mean that `'a = 'static`, because
+ // we should use *sub* above.
+ define((y,));
+}
+
+fn main() {}