Rollup of 8 pull requests

compiler/rustc_hir_analysis/src/astconv/mod.rs

@@ -1335,7 +1335,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                     ty::Clause::RegionOutlives(_) | ty::Clause::ConstArgHasType(..) => bug!(),
                 },
                 ty::PredicateKind::WellFormed(_)
-                | ty::PredicateKind::AliasEq(..)
+                | ty::PredicateKind::AliasRelate(..)
                 | ty::PredicateKind::ObjectSafe(_)
                 | ty::PredicateKind::ClosureKind(_, _, _)
                 | ty::PredicateKind::Subtype(_)

compiler/rustc_hir_analysis/src/impl_wf_check/min_specialization.rs

@@ -528,7 +528,7 @@ fn trait_predicate_kind<'tcx>(
         | ty::PredicateKind::Clause(ty::Clause::TypeOutlives(_))
         | ty::PredicateKind::Clause(ty::Clause::Projection(_))
         | ty::PredicateKind::Clause(ty::Clause::ConstArgHasType(..))
-        | ty::PredicateKind::AliasEq(..)
+        | ty::PredicateKind::AliasRelate(..)
         | ty::PredicateKind::WellFormed(_)
         | ty::PredicateKind::Subtype(_)
         | ty::PredicateKind::Coerce(_)

compiler/rustc_hir_analysis/src/outlives/explicit.rs

@@ -56,7 +56,7 @@ impl<'tcx> ExplicitPredicatesMap<'tcx> {
                     | ty::PredicateKind::Clause(ty::Clause::Projection(..))
                     | ty::PredicateKind::Clause(ty::Clause::ConstArgHasType(..))
                     | ty::PredicateKind::WellFormed(..)
-                    | ty::PredicateKind::AliasEq(..)
+                    | ty::PredicateKind::AliasRelate(..)
                     | ty::PredicateKind::ObjectSafe(..)
                     | ty::PredicateKind::ClosureKind(..)
                     | ty::PredicateKind::Subtype(..)

compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs

@@ -666,7 +666,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 | ty::PredicateKind::Clause(ty::Clause::TypeOutlives(..))
                 | ty::PredicateKind::WellFormed(..)
                 | ty::PredicateKind::ObjectSafe(..)
-                | ty::PredicateKind::AliasEq(..)
+                | ty::PredicateKind::AliasRelate(..)
                 | ty::PredicateKind::ConstEvaluatable(..)
                 | ty::PredicateKind::ConstEquate(..)
                 // N.B., this predicate is created by breaking down a

compiler/rustc_hir_typeck/src/fn_ctxt/adjust_fulfillment_errors.rs

@@ -4,7 +4,7 @@ use rustc_hir::def::Res;
 use rustc_hir::def_id::DefId;
 use rustc_infer::traits::ObligationCauseCode;
 use rustc_middle::ty::{self, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitor};
-use rustc_span::{self, Span};
+use rustc_span::{self, symbol::kw, Span};
 use rustc_trait_selection::traits;
 
 use std::ops::ControlFlow;
@@ -25,17 +25,28 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         let generics = self.tcx.generics_of(def_id);
         let predicate_substs = match unsubstituted_pred.kind().skip_binder() {
-            ty::PredicateKind::Clause(ty::Clause::Trait(pred)) => pred.trait_ref.substs,
-            ty::PredicateKind::Clause(ty::Clause::Projection(pred)) => pred.projection_ty.substs,
-            _ => ty::List::empty(),
+            ty::PredicateKind::Clause(ty::Clause::Trait(pred)) => pred.trait_ref.substs.to_vec(),
+            ty::PredicateKind::Clause(ty::Clause::Projection(pred)) => {
+                pred.projection_ty.substs.to_vec()
+            }
+            ty::PredicateKind::Clause(ty::Clause::ConstArgHasType(arg, ty)) => {
+                vec![ty.into(), arg.into()]
+            }
+            ty::PredicateKind::ConstEvaluatable(e) => vec![e.into()],
+            _ => return false,
         };
 
-        let find_param_matching = |matches: &dyn Fn(&ty::ParamTy) -> bool| {
-            predicate_substs.types().find_map(|ty| {
-                ty.walk().find_map(|arg| {
+        let find_param_matching = |matches: &dyn Fn(ty::ParamTerm) -> bool| {
+            predicate_substs.iter().find_map(|arg| {
+                arg.walk().find_map(|arg| {
                     if let ty::GenericArgKind::Type(ty) = arg.unpack()
-                        && let ty::Param(param_ty) = ty.kind()
-                        && matches(param_ty)
+                        && let ty::Param(param_ty) = *ty.kind()
+                        && matches(ty::ParamTerm::Ty(param_ty))
+                    {
+                        Some(arg)
+                    } else if let ty::GenericArgKind::Const(ct) = arg.unpack()
+                        && let ty::ConstKind::Param(param_ct) = ct.kind()
+                        && matches(ty::ParamTerm::Const(param_ct))
                     {
                         Some(arg)
                     } else {
@@ -47,21 +58,22 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         // Prefer generics that are local to the fn item, since these are likely
         // to be the cause of the unsatisfied predicate.
-        let mut param_to_point_at = find_param_matching(&|param_ty| {
-            self.tcx.parent(generics.type_param(param_ty, self.tcx).def_id) == def_id
+        let mut param_to_point_at = find_param_matching(&|param_term| {
+            self.tcx.parent(generics.param_at(param_term.index(), self.tcx).def_id) == def_id
         });
         // Fall back to generic that isn't local to the fn item. This will come
         // from a trait or impl, for example.
-        let mut fallback_param_to_point_at = find_param_matching(&|param_ty| {
-            self.tcx.parent(generics.type_param(param_ty, self.tcx).def_id) != def_id
-                && param_ty.name != rustc_span::symbol::kw::SelfUpper
+        let mut fallback_param_to_point_at = find_param_matching(&|param_term| {
+            self.tcx.parent(generics.param_at(param_term.index(), self.tcx).def_id) != def_id
+                && !matches!(param_term, ty::ParamTerm::Ty(ty) if ty.name == kw::SelfUpper)
         });
         // Finally, the `Self` parameter is possibly the reason that the predicate
         // is unsatisfied. This is less likely to be true for methods, because
         // method probe means that we already kinda check that the predicates due
         // to the `Self` type are true.
-        let mut self_param_to_point_at =
-            find_param_matching(&|param_ty| param_ty.name == rustc_span::symbol::kw::SelfUpper);
+        let mut self_param_to_point_at = find_param_matching(
+            &|param_term| matches!(param_term, ty::ParamTerm::Ty(ty) if ty.name == kw::SelfUpper),
+        );
 
         // Finally, for ambiguity-related errors, we actually want to look
         // for a parameter that is the source of the inference type left
@@ -225,14 +237,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             .own_substs(ty::InternalSubsts::identity_for_item(self.tcx, def_id));
         let Some((index, _)) = own_substs
             .iter()
-            .filter(|arg| matches!(arg.unpack(), ty::GenericArgKind::Type(_)))
             .enumerate()
             .find(|(_, arg)| **arg == param_to_point_at) else { return false };
         let Some(arg) = segment
             .args()
             .args
             .iter()
-            .filter(|arg| matches!(arg, hir::GenericArg::Type(_)))
             .nth(index) else { return false; };
         error.obligation.cause.span = arg
             .span()

compiler/rustc_hir_typeck/src/method/probe.rs

@@ -838,7 +838,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                 | ty::PredicateKind::ConstEvaluatable(..)
                 | ty::PredicateKind::ConstEquate(..)
                 | ty::PredicateKind::Ambiguous
-                | ty::PredicateKind::AliasEq(..)
+                | ty::PredicateKind::AliasRelate(..)
                 | ty::PredicateKind::TypeWellFormedFromEnv(..) => None,
             }
         });

compiler/rustc_infer/src/infer/combine.rs

@@ -128,7 +128,7 @@ impl<'tcx> InferCtxt<'tcx> {
             (_, ty::Alias(AliasKind::Projection, _)) | (ty::Alias(AliasKind::Projection, _), _)
                 if self.tcx.trait_solver_next() =>
             {
-                relation.register_type_equate_obligation(a, b);
+                relation.register_type_relate_obligation(a, b);
                 Ok(a)
             }
 
@@ -842,23 +842,25 @@ 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::AliasRelate(a.into(), b.into(), ty::AliasRelationDirection::Equate)
         } else {
             ty::PredicateKind::ConstEquate(a, b)
         })]);
     }
 
-    /// Register an obligation that both types must be equal to each other.
-    ///
-    /// 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(
+    /// Register an obligation that both types must be related to each other according to
+    /// the [`ty::AliasRelationDirection`] given by [`ObligationEmittingRelation::alias_relate_direction`]
+    fn register_type_relate_obligation(&mut self, a: Ty<'tcx>, b: Ty<'tcx>) {
+        self.register_predicates([ty::Binder::dummy(ty::PredicateKind::AliasRelate(
             a.into(),
             b.into(),
+            self.alias_relate_direction(),
         ))]);
     }
+
+    /// Relation direction emitted for `AliasRelate` predicates, corresponding to the direction
+    /// of the relation.
+    fn alias_relate_direction(&self) -> ty::AliasRelationDirection;
 }
 
 fn int_unification_error<'tcx>(

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
+    }
 }

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
+    }
 }

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
+    }
 }

compiler/rustc_infer/src/infer/nll_relate/mod.rs

@@ -711,6 +711,34 @@ where
     fn register_obligations(&mut self, obligations: PredicateObligations<'tcx>) {
         self.delegate.register_obligations(obligations);
     }
+
+    fn alias_relate_direction(&self) -> ty::AliasRelationDirection {
+        unreachable!("manually overridden to handle ty::Variance::Contravariant ambient variance")
+    }
+
+    fn register_type_relate_obligation(&mut self, a: Ty<'tcx>, b: Ty<'tcx>) {
+        self.register_predicates([ty::Binder::dummy(match self.ambient_variance {
+            ty::Variance::Covariant => ty::PredicateKind::AliasRelate(
+                a.into(),
+                b.into(),
+                ty::AliasRelationDirection::Subtype,
+            ),
+            // a :> b is b <: a
+            ty::Variance::Contravariant => ty::PredicateKind::AliasRelate(
+                b.into(),
+                a.into(),
+                ty::AliasRelationDirection::Subtype,
+            ),
+            ty::Variance::Invariant => ty::PredicateKind::AliasRelate(
+                a.into(),
+                b.into(),
+                ty::AliasRelationDirection::Equate,
+            ),
+            // FIXME(deferred_projection_equality): Implement this when we trigger it.
+            // Probably just need to do nothing here.
+            ty::Variance::Bivariant => unreachable!(),
+        })]);
+    }
 }
 
 /// When we encounter a binder like `for<..> fn(..)`, we actually have

compiler/rustc_infer/src/infer/outlives/mod.rs

@@ -22,7 +22,7 @@ pub fn explicit_outlives_bounds<'tcx>(
             ty::PredicateKind::Clause(ty::Clause::Projection(..))
             | ty::PredicateKind::Clause(ty::Clause::Trait(..))
             | ty::PredicateKind::Clause(ty::Clause::ConstArgHasType(..))
-            | ty::PredicateKind::AliasEq(..)
+            | ty::PredicateKind::AliasRelate(..)
             | ty::PredicateKind::Coerce(..)
             | ty::PredicateKind::Subtype(..)
             | ty::PredicateKind::WellFormed(..)

compiler/rustc_infer/src/infer/projection.rs

@@ -26,7 +26,7 @@ impl<'tcx> InferCtxt<'tcx> {
             // completely change the normalization routine with the new solver.
             //
             // The new solver correctly handles projection equality so this hack
-            // is not necessary. if re-enabled it should emit `PredicateKind::AliasEq`
+            // is not necessary. if re-enabled it should emit `PredicateKind::AliasRelate`
             // not `PredicateKind::Clause(Clause::Projection(..))` as in the new solver
             // `Projection` is used as `normalizes-to` which will fail for `<T as Trait>::Assoc eq ?0`.
             return projection_ty.to_ty(self.tcx);

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
+    }
 }

compiler/rustc_infer/src/traits/util.rs

@@ -293,7 +293,7 @@ impl<'tcx> Elaborator<'tcx> {
                 // Nothing to elaborate
             }
             ty::PredicateKind::Ambiguous => {}
-            ty::PredicateKind::AliasEq(..) => {
+            ty::PredicateKind::AliasRelate(..) => {
                 // No
             }
             ty::PredicateKind::Clause(ty::Clause::ConstArgHasType(..)) => {

compiler/rustc_lint/src/builtin.rs

@@ -1601,7 +1601,7 @@ impl<'tcx> LateLintPass<'tcx> for TrivialConstraints {
                     // Ignore projections, as they can only be global
                     // if the trait bound is global
                     Clause(Clause::Projection(..)) |
-                    AliasEq(..) |
+                    AliasRelate(..) |
                     // Ignore bounds that a user can't type
                     WellFormed(..) |
                     ObjectSafe(..) |

compiler/rustc_lint/src/opaque_hidden_inferred_bound.rs

@@ -27,6 +27,8 @@ declare_lint! {
     /// ### Example
     ///
     /// ```rust
+    /// #![feature(type_alias_impl_trait)]
+    ///
     /// trait Duh {}
     ///
     /// impl Duh for i32 {}
@@ -41,7 +43,9 @@ declare_lint! {
     ///     type Assoc = F;
     /// }
     ///
-    /// fn test() -> impl Trait<Assoc = impl Sized> {
+    /// type Tait = impl Sized;
+    ///
+    /// fn test() -> impl Trait<Assoc = Tait> {
     ///     42
     /// }
     /// ```
@@ -54,7 +58,7 @@ declare_lint! {
     ///
     /// Although the hidden type, `i32` does satisfy this bound, we do not
     /// consider the return type to be well-formed with this lint. It can be
-    /// fixed by changing `impl Sized` into `impl Sized + Send`.
+    /// fixed by changing `Tait = impl Sized` into `Tait = impl Sized + Send`.
     pub OPAQUE_HIDDEN_INFERRED_BOUND,
     Warn,
     "detects the use of nested `impl Trait` types in associated type bounds that are not general enough"
@@ -64,7 +68,7 @@ declare_lint_pass!(OpaqueHiddenInferredBound => [OPAQUE_HIDDEN_INFERRED_BOUND]);
 
 impl<'tcx> LateLintPass<'tcx> for OpaqueHiddenInferredBound {
     fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>) {
-        let hir::ItemKind::OpaqueTy(_) = &item.kind else { return; };
+        let hir::ItemKind::OpaqueTy(opaque) = &item.kind else { return; };
         let def_id = item.owner_id.def_id.to_def_id();
         let infcx = &cx.tcx.infer_ctxt().build();
         // For every projection predicate in the opaque type's explicit bounds,
@@ -81,6 +85,17 @@ impl<'tcx> LateLintPass<'tcx> for OpaqueHiddenInferredBound {
             // have opaques in them anyways.
             let Some(proj_term) = proj.term.ty() else { continue };
 
+            // HACK: `impl Trait<Assoc = impl Trait2>` from an RPIT is "ok"...
+            if let ty::Alias(ty::Opaque, opaque_ty) = *proj_term.kind()
+                && cx.tcx.parent(opaque_ty.def_id) == def_id
+                && matches!(
+                    opaque.origin,
+                    hir::OpaqueTyOrigin::FnReturn(_) | hir::OpaqueTyOrigin::AsyncFn(_)
+                )
+            {
+                continue;
+            }
+
             let proj_ty =
                 cx.tcx.mk_projection(proj.projection_ty.def_id, proj.projection_ty.substs);
             // For every instance of the projection type in the bounds,

compiler/rustc_metadata/src/rmeta/decoder.rs

@@ -925,10 +925,6 @@ impl<'a, 'tcx> CrateMetadataRef<'a> {
         tcx.mk_adt_def(did, adt_kind, variants, repr)
     }
 
-    fn get_generics(self, item_id: DefIndex, sess: &Session) -> ty::Generics {
-        self.root.tables.generics_of.get(self, item_id).unwrap().decode((self, sess))
-    }
-
     fn get_visibility(self, id: DefIndex) -> Visibility<DefId> {
         self.root
             .tables

compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs

@@ -545,10 +545,6 @@ impl CStore {
         self.get_crate_data(def.krate).def_kind(def.index)
     }
 
-    pub fn item_generics_num_lifetimes(&self, def_id: DefId, sess: &Session) -> usize {
-        self.get_crate_data(def_id.krate).get_generics(def_id.index, sess).own_counts().lifetimes
-    }
-
     pub fn module_expansion_untracked(&self, def_id: DefId, sess: &Session) -> ExpnId {
         self.get_crate_data(def_id.krate).module_expansion(def_id.index, sess)
     }
@@ -560,14 +556,6 @@ impl CStore {
         self.get_crate_data(cnum).num_def_ids()
     }
 
-    pub fn item_attrs_untracked<'a>(
-        &'a self,
-        def_id: DefId,
-        sess: &'a Session,
-    ) -> impl Iterator<Item = ast::Attribute> + 'a {
-        self.get_crate_data(def_id.krate).get_item_attrs(def_id.index, sess)
-    }
-
     pub fn get_proc_macro_quoted_span_untracked(
         &self,
         cnum: CrateNum,

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::AliasRelate(t1, t2, _) => {
                 self.add_term(t1);
                 self.add_term(t2);
             }