Rollup of 10 pull requests

compiler/rustc_hir_analysis/src/astconv/mod.rs

@@ -1612,10 +1612,11 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                         .any(|impl_def_id| {
                             let impl_header = tcx.impl_trait_header(impl_def_id);
                             impl_header.is_some_and(|header| {
-                                let header = header.instantiate(
+                                let trait_ref = header.trait_ref.instantiate(
                                     tcx,
                                     infcx.fresh_args_for_item(DUMMY_SP, impl_def_id),
                                 );
+
                                 let value = tcx.fold_regions(qself_ty, |_, _| tcx.lifetimes.re_erased);
                                 // FIXME: Don't bother dealing with non-lifetime binders here...
                                 if value.has_escaping_bound_vars() {
@@ -1624,7 +1625,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                                 infcx
                                     .can_eq(
                                         ty::ParamEnv::empty(),
-                                        header.trait_ref.self_ty(),
+                                        trait_ref.self_ty(),
                                         value,
                                     ) && header.polarity != ty::ImplPolarity::Negative
                             })
@@ -1677,9 +1678,9 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                     .filter(|header| {
                         // Consider only accessible traits
                         tcx.visibility(trait_def_id).is_accessible_from(self.item_def_id(), tcx)
-                            && header.skip_binder().polarity != ty::ImplPolarity::Negative
+                            && header.polarity != ty::ImplPolarity::Negative
                     })
-                    .map(|header| header.instantiate_identity().trait_ref.self_ty())
+                    .map(|header| header.trait_ref.instantiate_identity().self_ty())
                     // We don't care about blanket impls.
                     .filter(|self_ty| !self_ty.has_non_region_param())
                     .map(|self_ty| tcx.erase_regions(self_ty).to_string())

compiler/rustc_hir_analysis/src/astconv/object_safety.rs

@@ -45,10 +45,9 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                 dummy_self,
                 &mut bounds,
                 false,
-                // FIXME: This should be `true`, but we don't really handle
-                // associated type bounds or type aliases in objects in a way
-                // that makes this meaningful, I think.
-                OnlySelfBounds(false),
+                // True so we don't populate `bounds` with associated type bounds, even
+                // though they're disallowed from object types.
+                OnlySelfBounds(true),
             ) {
                 potential_assoc_types.extend(cur_potential_assoc_types);
             }
@@ -83,9 +82,8 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         let expanded_traits =
             traits::expand_trait_aliases(tcx, trait_bounds.iter().map(|&(a, b)| (a, b)));
 
-        let (mut auto_traits, regular_traits): (Vec<_>, Vec<_>) = expanded_traits
-            .filter(|i| i.trait_ref().self_ty().skip_binder() == dummy_self)
-            .partition(|i| tcx.trait_is_auto(i.trait_ref().def_id()));
+        let (mut auto_traits, regular_traits): (Vec<_>, Vec<_>) =
+            expanded_traits.partition(|i| tcx.trait_is_auto(i.trait_ref().def_id()));
         if regular_traits.len() > 1 {
             let first_trait = &regular_traits[0];
             let additional_trait = &regular_traits[1];
@@ -158,7 +156,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
 
         for (base_trait_ref, span) in regular_traits_refs_spans {
             let base_pred: ty::Predicate<'tcx> = base_trait_ref.to_predicate(tcx);
-            for pred in traits::elaborate(tcx, [base_pred]) {
+            for pred in traits::elaborate(tcx, [base_pred]).filter_only_self() {
                 debug!("conv_object_ty_poly_trait_ref: observing object predicate `{:?}`", pred);
 
                 let bound_predicate = pred.kind();
@@ -312,45 +310,39 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
             })
         });
 
-        let existential_projections = projection_bounds
-            .iter()
-            // We filter out traits that don't have `Self` as their self type above,
-            // we need to do the same for projections.
-            .filter(|(bound, _)| bound.skip_binder().self_ty() == dummy_self)
-            .map(|(bound, _)| {
-                bound.map_bound(|mut b| {
-                    assert_eq!(b.projection_ty.self_ty(), dummy_self);
+        let existential_projections = projection_bounds.iter().map(|(bound, _)| {
+            bound.map_bound(|mut b| {
+                assert_eq!(b.projection_ty.self_ty(), dummy_self);
 
-                    // Like for trait refs, verify that `dummy_self` did not leak inside default type
-                    // parameters.
-                    let references_self = b.projection_ty.args.iter().skip(1).any(|arg| {
-                        if arg.walk().any(|arg| arg == dummy_self.into()) {
-                            return true;
-                        }
-                        false
-                    });
-                    if references_self {
-                        let guar = tcx.dcx().span_delayed_bug(
-                            span,
-                            "trait object projection bounds reference `Self`",
-                        );
-                        let args: Vec<_> = b
-                            .projection_ty
-                            .args
-                            .iter()
-                            .map(|arg| {
-                                if arg.walk().any(|arg| arg == dummy_self.into()) {
-                                    return Ty::new_error(tcx, guar).into();
-                                }
-                                arg
-                            })
-                            .collect();
-                        b.projection_ty.args = tcx.mk_args(&args);
+                // Like for trait refs, verify that `dummy_self` did not leak inside default type
+                // parameters.
+                let references_self = b.projection_ty.args.iter().skip(1).any(|arg| {
+                    if arg.walk().any(|arg| arg == dummy_self.into()) {
+                        return true;
                     }
+                    false
+                });
+                if references_self {
+                    let guar = tcx
+                        .dcx()
+                        .span_delayed_bug(span, "trait object projection bounds reference `Self`");
+                    let args: Vec<_> = b
+                        .projection_ty
+                        .args
+                        .iter()
+                        .map(|arg| {
+                            if arg.walk().any(|arg| arg == dummy_self.into()) {
+                                return Ty::new_error(tcx, guar).into();
+                            }
+                            arg
+                        })
+                        .collect();
+                    b.projection_ty.args = tcx.mk_args(&args);
+                }
 
-                    ty::ExistentialProjection::erase_self_ty(tcx, b)
-                })
-            });
+                ty::ExistentialProjection::erase_self_ty(tcx, b)
+            })
+        });
 
         let regular_trait_predicates = existential_trait_refs
             .map(|trait_ref| trait_ref.map_bound(ty::ExistentialPredicate::Trait));

compiler/rustc_hir_analysis/src/check/check.rs

@@ -530,11 +530,7 @@ pub(crate) fn check_item_type(tcx: TyCtxt<'_>, def_id: LocalDefId) {
         }
         DefKind::Impl { of_trait } => {
             if of_trait && let Some(impl_trait_header) = tcx.impl_trait_header(def_id) {
-                check_impl_items_against_trait(
-                    tcx,
-                    def_id,
-                    impl_trait_header.instantiate_identity(),
-                );
+                check_impl_items_against_trait(tcx, def_id, impl_trait_header);
                 check_on_unimplemented(tcx, def_id);
             }
         }
@@ -725,10 +721,11 @@ fn check_impl_items_against_trait<'tcx>(
     impl_id: LocalDefId,
     impl_trait_header: ty::ImplTraitHeader<'tcx>,
 ) {
+    let trait_ref = impl_trait_header.trait_ref.instantiate_identity();
     // If the trait reference itself is erroneous (so the compilation is going
     // to fail), skip checking the items here -- the `impl_item` table in `tcx`
     // isn't populated for such impls.
-    if impl_trait_header.references_error() {
+    if trait_ref.references_error() {
         return;
     }
 
@@ -752,7 +749,7 @@ fn check_impl_items_against_trait<'tcx>(
         }
     }
 
-    let trait_def = tcx.trait_def(impl_trait_header.trait_ref.def_id);
+    let trait_def = tcx.trait_def(trait_ref.def_id);
 
     for &impl_item in impl_item_refs {
         let ty_impl_item = tcx.associated_item(impl_item);
@@ -771,10 +768,10 @@ fn check_impl_items_against_trait<'tcx>(
                 ));
             }
             ty::AssocKind::Fn => {
-                compare_impl_method(tcx, ty_impl_item, ty_trait_item, impl_trait_header.trait_ref);
+                compare_impl_method(tcx, ty_impl_item, ty_trait_item, trait_ref);
             }
             ty::AssocKind::Type => {
-                compare_impl_ty(tcx, ty_impl_item, ty_trait_item, impl_trait_header.trait_ref);
+                compare_impl_ty(tcx, ty_impl_item, ty_trait_item, trait_ref);
             }
         }
 
@@ -794,7 +791,7 @@ fn check_impl_items_against_trait<'tcx>(
         let mut must_implement_one_of: Option<&[Ident]> =
             trait_def.must_implement_one_of.as_deref();
 
-        for &trait_item_id in tcx.associated_item_def_ids(impl_trait_header.trait_ref.def_id) {
+        for &trait_item_id in tcx.associated_item_def_ids(trait_ref.def_id) {
             let leaf_def = ancestors.leaf_def(tcx, trait_item_id);
 
             let is_implemented = leaf_def
@@ -872,7 +869,7 @@ fn check_impl_items_against_trait<'tcx>(
 
         if let Some(missing_items) = must_implement_one_of {
             let attr_span = tcx
-                .get_attr(impl_trait_header.trait_ref.def_id, sym::rustc_must_implement_one_of)
+                .get_attr(trait_ref.def_id, sym::rustc_must_implement_one_of)
                 .map(|attr| attr.span);
 
             missing_items_must_implement_one_of_err(

compiler/rustc_hir_analysis/src/check/wfcheck.rs

@@ -247,7 +247,7 @@ fn check_item<'tcx>(tcx: TyCtxt<'tcx>, item: &'tcx hir::Item<'tcx>) -> Result<()
         hir::ItemKind::Impl(impl_) => {
             let header = tcx.impl_trait_header(def_id);
             let is_auto = header
-                .is_some_and(|header| tcx.trait_is_auto(header.skip_binder().trait_ref.def_id));
+                .is_some_and(|header| tcx.trait_is_auto(header.trait_ref.skip_binder().def_id));
 
             crate::impl_wf_check::check_impl_wf(tcx, def_id)?;
             let mut res = Ok(());
@@ -261,7 +261,7 @@ fn check_item<'tcx>(tcx: TyCtxt<'tcx>, item: &'tcx hir::Item<'tcx>) -> Result<()
                     .emit());
             }
             // We match on both `ty::ImplPolarity` and `ast::ImplPolarity` just to get the `!` span.
-            match header.map(|h| h.skip_binder().polarity) {
+            match header.map(|h| h.polarity) {
                 // `None` means this is an inherent impl
                 Some(ty::ImplPolarity::Positive) | None => {
                     res = res.and(check_impl(tcx, item, impl_.self_ty, &impl_.of_trait));
@@ -298,31 +298,31 @@ fn check_item<'tcx>(tcx: TyCtxt<'tcx>, item: &'tcx hir::Item<'tcx>) -> Result<()
         hir::ItemKind::Const(ty, ..) => {
             check_item_type(tcx, def_id, ty.span, UnsizedHandling::Forbid)
         }
-        hir::ItemKind::Struct(_, ast_generics) => {
+        hir::ItemKind::Struct(_, hir_generics) => {
             let res = check_type_defn(tcx, item, false);
-            check_variances_for_type_defn(tcx, item, ast_generics);
+            check_variances_for_type_defn(tcx, item, hir_generics);
             res
         }
-        hir::ItemKind::Union(_, ast_generics) => {
+        hir::ItemKind::Union(_, hir_generics) => {
             let res = check_type_defn(tcx, item, true);
-            check_variances_for_type_defn(tcx, item, ast_generics);
+            check_variances_for_type_defn(tcx, item, hir_generics);
             res
         }
-        hir::ItemKind::Enum(_, ast_generics) => {
+        hir::ItemKind::Enum(_, hir_generics) => {
             let res = check_type_defn(tcx, item, true);
-            check_variances_for_type_defn(tcx, item, ast_generics);
+            check_variances_for_type_defn(tcx, item, hir_generics);
             res
         }
         hir::ItemKind::Trait(..) => check_trait(tcx, item),
         hir::ItemKind::TraitAlias(..) => check_trait(tcx, item),
         // `ForeignItem`s are handled separately.
         hir::ItemKind::ForeignMod { .. } => Ok(()),
-        hir::ItemKind::TyAlias(hir_ty, ast_generics) => {
+        hir::ItemKind::TyAlias(hir_ty, hir_generics) => {
             if tcx.type_alias_is_lazy(item.owner_id) {
                 // Bounds of lazy type aliases and of eager ones that contain opaque types are respected.
                 // E.g: `type X = impl Trait;`, `type X = (impl Trait, Y);`.
                 let res = check_item_type(tcx, def_id, hir_ty.span, UnsizedHandling::Allow);
-                check_variances_for_type_defn(tcx, item, ast_generics);
+                check_variances_for_type_defn(tcx, item, hir_generics);
                 res
             } else {
                 Ok(())
@@ -1277,25 +1277,26 @@ fn check_item_type(
     })
 }
 
-#[instrument(level = "debug", skip(tcx, ast_self_ty, ast_trait_ref))]
+#[instrument(level = "debug", skip(tcx, hir_self_ty, hir_trait_ref))]
 fn check_impl<'tcx>(
     tcx: TyCtxt<'tcx>,
     item: &'tcx hir::Item<'tcx>,
-    ast_self_ty: &hir::Ty<'_>,
-    ast_trait_ref: &Option<hir::TraitRef<'_>>,
+    hir_self_ty: &hir::Ty<'_>,
+    hir_trait_ref: &Option<hir::TraitRef<'_>>,
 ) -> Result<(), ErrorGuaranteed> {
     enter_wf_checking_ctxt(tcx, item.span, item.owner_id.def_id, |wfcx| {
-        match ast_trait_ref {
-            Some(ast_trait_ref) => {
+        match hir_trait_ref {
+            Some(hir_trait_ref) => {
                 // `#[rustc_reservation_impl]` impls are not real impls and
                 // therefore don't need to be WF (the trait's `Self: Trait` predicate
                 // won't hold).
                 let trait_ref = tcx.impl_trait_ref(item.owner_id).unwrap().instantiate_identity();
                 // Avoid bogus "type annotations needed `Foo: Bar`" errors on `impl Bar for Foo` in case
                 // other `Foo` impls are incoherent.
                 tcx.ensure().coherent_trait(trait_ref.def_id)?;
+                let trait_span = hir_trait_ref.path.span;
                 let trait_ref = wfcx.normalize(
-                    ast_trait_ref.path.span,
+                    trait_span,
                     Some(WellFormedLoc::Ty(item.hir_id().expect_owner().def_id)),
                     trait_ref,
                 );
@@ -1306,14 +1307,23 @@ fn check_impl<'tcx>(
                     wfcx.param_env,
                     wfcx.body_def_id,
                     trait_pred,
-                    ast_trait_ref.path.span,
+                    trait_span,
                     item,
                 );
                 for obligation in &mut obligations {
+                    if obligation.cause.span != trait_span {
+                        // We already have a better span.
+                        continue;
+                    }
                     if let Some(pred) = obligation.predicate.to_opt_poly_trait_pred()
-                        && pred.self_ty().skip_binder() == trait_ref.self_ty()
+                        && pred.skip_binder().self_ty() == trait_ref.self_ty()
+                    {
+                        obligation.cause.span = hir_self_ty.span;
+                    }
+                    if let Some(pred) = obligation.predicate.to_opt_poly_projection_pred()
+                        && pred.skip_binder().self_ty() == trait_ref.self_ty()
                     {
-                        obligation.cause.span = ast_self_ty.span;
+                        obligation.cause.span = hir_self_ty.span;
                     }
                 }
                 debug!(?obligations);
@@ -1327,7 +1337,7 @@ fn check_impl<'tcx>(
                     self_ty,
                 );
                 wfcx.register_wf_obligation(
-                    ast_self_ty.span,
+                    hir_self_ty.span,
                     Some(WellFormedLoc::Ty(item.hir_id().expect_owner().def_id)),
                     self_ty.into(),
                 );

compiler/rustc_hir_analysis/src/coherence/builtin.rs

@@ -25,7 +25,7 @@ use rustc_trait_selection::traits::ObligationCtxt;
 use rustc_trait_selection::traits::{self, ObligationCause};
 use std::collections::BTreeMap;
 
-pub fn check_trait<'tcx>(
+pub(super) fn check_trait<'tcx>(
     tcx: TyCtxt<'tcx>,
     trait_def_id: DefId,
     impl_def_id: LocalDefId,
@@ -66,10 +66,9 @@ impl<'tcx> Checker<'tcx> {
 
 fn visit_implementation_of_drop(checker: &Checker<'_>) -> Result<(), ErrorGuaranteed> {
     let tcx = checker.tcx;
-    let header = checker.impl_header;
     let impl_did = checker.impl_def_id;
     // Destructors only work on local ADT types.
-    match header.trait_ref.self_ty().kind() {
+    match checker.impl_header.trait_ref.instantiate_identity().self_ty().kind() {
         ty::Adt(def, _) if def.did().is_local() => return Ok(()),
         ty::Error(_) => return Ok(()),
         _ => {}
@@ -86,7 +85,7 @@ fn visit_implementation_of_copy(checker: &Checker<'_>) -> Result<(), ErrorGuaran
     let impl_did = checker.impl_def_id;
     debug!("visit_implementation_of_copy: impl_did={:?}", impl_did);
 
-    let self_type = impl_header.trait_ref.self_ty();
+    let self_type = impl_header.trait_ref.instantiate_identity().self_ty();
     debug!("visit_implementation_of_copy: self_type={:?} (bound)", self_type);
 
     let param_env = tcx.param_env(impl_did);
@@ -120,7 +119,7 @@ fn visit_implementation_of_const_param_ty(checker: &Checker<'_>) -> Result<(), E
     let tcx = checker.tcx;
     let header = checker.impl_header;
     let impl_did = checker.impl_def_id;
-    let self_type = header.trait_ref.self_ty();
+    let self_type = header.trait_ref.instantiate_identity().self_ty();
     assert!(!self_type.has_escaping_bound_vars());
 
     let param_env = tcx.param_env(impl_did);
@@ -157,9 +156,8 @@ fn visit_implementation_of_coerce_unsized(checker: &Checker<'_>) -> Result<(), E
 
 fn visit_implementation_of_dispatch_from_dyn(checker: &Checker<'_>) -> Result<(), ErrorGuaranteed> {
     let tcx = checker.tcx;
-    let header = checker.impl_header;
     let impl_did = checker.impl_def_id;
-    let trait_ref = header.trait_ref;
+    let trait_ref = checker.impl_header.trait_ref.instantiate_identity();
     debug!("visit_implementation_of_dispatch_from_dyn: impl_did={:?}", impl_did);
 
     let span = tcx.def_span(impl_did);