Auto merge of #122139 - GuillaumeGomez:rollup-37vtwsc, r=GuillaumeGomez

Rollup of 10 pull requests

Successful merges:

 - #121863 (silence mismatched types errors for implied projections)
 - #122043 (Apply `EarlyBinder` only to `TraitRef` in `ImplTraitHeader`)
 - #122066 (Add proper cfgs for struct HirIdValidator used only with debug-assert)
 - #122104 (Rust is a proper name: rust → Rust)
 - #122110 (Make `x t miri` respect `MIRI_TEMP`)
 - #122114 (Make not finding core a fatal error)
 - #122115 (Cancel parsing ever made during recovery)
 - #122123 (Don't require specifying unrelated assoc types when trait alias is in `dyn` type)
 - #122126 (Fix `tidy --bless` on  ̶X̶e̶n̶i̶x̶ Windows)
 - #122129 (Set `RustcDocs` to only run on host)

r? `@ghost`
`@rustbot` modify labels: rollup

8 files changed, 132 insertions, 89 deletions

diff --git a/compiler/rustc_trait_selection/src/solve/normalizes_to/mod.rs b/compiler/rustc_trait_selection/src/solve/normalizes_to/mod.rs
index 248985715c2..ed839d14dc7 100644
--- a/compiler/rustc_trait_selection/src/solve/normalizes_to/mod.rs
+++ b/compiler/rustc_trait_selection/src/solve/normalizes_to/mod.rs
@@ -166,13 +166,13 @@ impl<'tcx> assembly::GoalKind<'tcx> for NormalizesTo<'tcx> {
         let drcx = DeepRejectCtxt { treat_obligation_params: TreatParams::ForLookup };
         if !drcx.args_may_unify(
             goal.predicate.trait_ref(tcx).args,
-            impl_trait_header.skip_binder().trait_ref.args,
+            impl_trait_header.trait_ref.skip_binder().args,
         ) {
             return Err(NoSolution);
         }
 
         // We have to ignore negative impls when projecting.
-        let impl_polarity = impl_trait_header.skip_binder().polarity;
+        let impl_polarity = impl_trait_header.polarity;
         match impl_polarity {
             ty::ImplPolarity::Negative => return Err(NoSolution),
             ty::ImplPolarity::Reservation => {
@@ -183,7 +183,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for NormalizesTo<'tcx> {
 
         ecx.probe_trait_candidate(CandidateSource::Impl(impl_def_id)).enter(|ecx| {
             let impl_args = ecx.fresh_args_for_item(impl_def_id);
-            let impl_trait_ref = impl_trait_header.instantiate(tcx, impl_args).trait_ref;
+            let impl_trait_ref = impl_trait_header.trait_ref.instantiate(tcx, impl_args);
 
             ecx.eq(goal.param_env, goal_trait_ref, impl_trait_ref)?;
 
diff --git a/compiler/rustc_trait_selection/src/solve/trait_goals.rs b/compiler/rustc_trait_selection/src/solve/trait_goals.rs
index 16febf05b60..281f5cc5685 100644
--- a/compiler/rustc_trait_selection/src/solve/trait_goals.rs
+++ b/compiler/rustc_trait_selection/src/solve/trait_goals.rs
@@ -47,14 +47,14 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
         let drcx = DeepRejectCtxt { treat_obligation_params: TreatParams::ForLookup };
         if !drcx.args_may_unify(
             goal.predicate.trait_ref.args,
-            impl_trait_header.skip_binder().trait_ref.args,
+            impl_trait_header.trait_ref.skip_binder().args,
         ) {
             return Err(NoSolution);
         }
 
         // An upper bound of the certainty of this goal, used to lower the certainty
         // of reservation impl to ambiguous during coherence.
-        let impl_polarity = impl_trait_header.skip_binder().polarity;
+        let impl_polarity = impl_trait_header.polarity;
         let maximal_certainty = match impl_polarity {
             ty::ImplPolarity::Positive | ty::ImplPolarity::Negative => {
                 match impl_polarity == goal.predicate.polarity {
@@ -70,7 +70,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
 
         ecx.probe_trait_candidate(CandidateSource::Impl(impl_def_id)).enter(|ecx| {
             let impl_args = ecx.fresh_args_for_item(impl_def_id);
-            let impl_trait_ref = impl_trait_header.instantiate(tcx, impl_args).trait_ref;
+            let impl_trait_ref = impl_trait_header.trait_ref.instantiate(tcx, impl_args);
 
             ecx.eq(goal.param_env, goal.predicate.trait_ref, impl_trait_ref)?;
             let where_clause_bounds = tcx
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs
index 7a930937255..ac2b738d3b6 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs
@@ -1431,45 +1431,64 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
 
 #[extension(pub(super) trait InferCtxtPrivExt<'tcx>)]
 impl<'tcx> TypeErrCtxt<'_, 'tcx> {
+    fn can_match_trait(
+        &self,
+        goal: ty::TraitPredicate<'tcx>,
+        assumption: ty::PolyTraitPredicate<'tcx>,
+    ) -> bool {
+        if goal.polarity != assumption.polarity() {
+            return false;
+        }
+
+        let trait_goal = goal.trait_ref;
+        let trait_assumption = self.instantiate_binder_with_fresh_vars(
+            DUMMY_SP,
+            infer::BoundRegionConversionTime::HigherRankedType,
+            assumption.to_poly_trait_ref(),
+        );
+
+        self.can_eq(ty::ParamEnv::empty(), trait_goal, trait_assumption)
+    }
+
+    fn can_match_projection(
+        &self,
+        goal: ty::ProjectionPredicate<'tcx>,
+        assumption: ty::PolyProjectionPredicate<'tcx>,
+    ) -> bool {
+        let assumption = self.instantiate_binder_with_fresh_vars(
+            DUMMY_SP,
+            infer::BoundRegionConversionTime::HigherRankedType,
+            assumption,
+        );
+
+        let param_env = ty::ParamEnv::empty();
+        self.can_eq(param_env, goal.projection_ty, assumption.projection_ty)
+            && self.can_eq(param_env, goal.term, assumption.term)
+    }
+
     // returns if `cond` not occurring implies that `error` does not occur - i.e., that
     // `error` occurring implies that `cond` occurs.
+    #[instrument(level = "debug", skip(self), ret)]
     fn error_implies(&self, cond: ty::Predicate<'tcx>, error: ty::Predicate<'tcx>) -> bool {
         if cond == error {
             return true;
         }
 
-        // FIXME: It should be possible to deal with `ForAll` in a cleaner way.
-        let bound_error = error.kind();
-        let (cond, error) = match (cond.kind().skip_binder(), bound_error.skip_binder()) {
-            (
-                ty::PredicateKind::Clause(ty::ClauseKind::Trait(..)),
-                ty::PredicateKind::Clause(ty::ClauseKind::Trait(error)),
-            ) => (cond, bound_error.rebind(error)),
-            _ => {
-                // FIXME: make this work in other cases too.
-                return false;
-            }
-        };
-
-        for pred in elaborate(self.tcx, std::iter::once(cond)) {
-            let bound_predicate = pred.kind();
-            if let ty::PredicateKind::Clause(ty::ClauseKind::Trait(implication)) =
-                bound_predicate.skip_binder()
-            {
-                let error = error.to_poly_trait_ref();
-                let implication = bound_predicate.rebind(implication.trait_ref);
-                // FIXME: I'm just not taking associated types at all here.
-                // Eventually I'll need to implement param-env-aware
-                // `Γ₁ ⊦ φ₁ => Γ₂ ⊦ φ₂` logic.
-                let param_env = ty::ParamEnv::empty();
-                if self.can_sub(param_env, error, implication) {
-                    debug!("error_implies: {:?} -> {:?} -> {:?}", cond, error, implication);
-                    return true;
-                }
-            }
+        if let Some(error) = error.to_opt_poly_trait_pred() {
+            self.enter_forall(error, |error| {
+                elaborate(self.tcx, std::iter::once(cond))
+                    .filter_map(|implied| implied.to_opt_poly_trait_pred())
+                    .any(|implied| self.can_match_trait(error, implied))
+            })
+        } else if let Some(error) = error.to_opt_poly_projection_pred() {
+            self.enter_forall(error, |error| {
+                elaborate(self.tcx, std::iter::once(cond))
+                    .filter_map(|implied| implied.to_opt_poly_projection_pred())
+                    .any(|implied| self.can_match_projection(error, implied))
+            })
+        } else {
+            false
         }
-
-        false
     }
 
     #[instrument(skip(self), level = "debug")]
@@ -1888,13 +1907,13 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
             .tcx
             .all_impls(trait_pred.def_id())
             .filter_map(|def_id| {
-                let imp = self.tcx.impl_trait_header(def_id).unwrap().skip_binder();
+                let imp = self.tcx.impl_trait_header(def_id).unwrap();
                 if imp.polarity == ty::ImplPolarity::Negative
                     || !self.tcx.is_user_visible_dep(def_id.krate)
                 {
                     return None;
                 }
-                let imp = imp.trait_ref;
+                let imp = imp.trait_ref.skip_binder();
 
                 self.fuzzy_match_tys(trait_pred.skip_binder().self_ty(), imp.self_ty(), false).map(
                     |similarity| ImplCandidate { trait_ref: imp, similarity, impl_def_id: def_id },
@@ -2078,12 +2097,11 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                 .all_impls(def_id)
                 // Ignore automatically derived impls and `!Trait` impls.
                 .filter_map(|def_id| self.tcx.impl_trait_header(def_id))
-                .map(ty::EarlyBinder::instantiate_identity)
-                .filter(|header| {
-                    header.polarity != ty::ImplPolarity::Negative
-                        || self.tcx.is_automatically_derived(def_id)
+                .filter_map(|header| {
+                    (header.polarity != ty::ImplPolarity::Negative
+                        || self.tcx.is_automatically_derived(def_id))
+                    .then(|| header.trait_ref.instantiate_identity())
                 })
-                .map(|header| header.trait_ref)
                 .filter(|trait_ref| {
                     let self_ty = trait_ref.self_ty();
                     // Avoid mentioning type parameters.
diff --git a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
index 39f4ceda9f1..66f740b761d 100644
--- a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
@@ -562,7 +562,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                 // and so forth that we need to.
                 let impl_trait_header = self.tcx().impl_trait_header(impl_def_id).unwrap();
                 if !drcx
-                    .args_may_unify(obligation_args, impl_trait_header.skip_binder().trait_ref.args)
+                    .args_may_unify(obligation_args, impl_trait_header.trait_ref.skip_binder().args)
                 {
                     return;
                 }
@@ -577,7 +577,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                 if self.reject_fn_ptr_impls(
                     impl_def_id,
                     obligation,
-                    impl_trait_header.skip_binder().trait_ref.self_ty(),
+                    impl_trait_header.trait_ref.skip_binder().self_ty(),
                 ) {
                     return;
                 }
diff --git a/compiler/rustc_trait_selection/src/traits/select/mod.rs b/compiler/rustc_trait_selection/src/traits/select/mod.rs
index 7dbea0cdb90..a6bd1ba9c3f 100644
--- a/compiler/rustc_trait_selection/src/traits/select/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/mod.rs
@@ -42,7 +42,7 @@ use rustc_middle::ty::_match::MatchAgainstFreshVars;
 use rustc_middle::ty::abstract_const::NotConstEvaluatable;
 use rustc_middle::ty::relate::TypeRelation;
 use rustc_middle::ty::GenericArgsRef;
-use rustc_middle::ty::{self, EarlyBinder, PolyProjectionPredicate, ToPolyTraitRef, ToPredicate};
+use rustc_middle::ty::{self, PolyProjectionPredicate, ToPolyTraitRef, ToPredicate};
 use rustc_middle::ty::{Ty, TyCtxt, TypeFoldable, TypeVisitableExt};
 use rustc_span::symbol::sym;
 use rustc_span::Symbol;
@@ -2441,7 +2441,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
     fn match_impl(
         &mut self,
         impl_def_id: DefId,
-        impl_trait_header: EarlyBinder<ty::ImplTraitHeader<'tcx>>,
+        impl_trait_header: ty::ImplTraitHeader<'tcx>,
         obligation: &PolyTraitObligation<'tcx>,
     ) -> Result<Normalized<'tcx, GenericArgsRef<'tcx>>, ()> {
         let placeholder_obligation =
@@ -2450,8 +2450,8 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
 
         let impl_args = self.infcx.fresh_args_for_item(obligation.cause.span, impl_def_id);
 
-        let impl_trait_header = impl_trait_header.instantiate(self.tcx(), impl_args);
-        if impl_trait_header.references_error() {
+        let trait_ref = impl_trait_header.trait_ref.instantiate(self.tcx(), impl_args);
+        if trait_ref.references_error() {
             return Err(());
         }
 
@@ -2464,7 +2464,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
                     obligation.param_env,
                     obligation.cause.clone(),
                     obligation.recursion_depth + 1,
-                    impl_trait_header.trait_ref,
+                    trait_ref,
                 )
             });
 
diff --git a/compiler/rustc_trait_selection/src/traits/specialize/mod.rs b/compiler/rustc_trait_selection/src/traits/specialize/mod.rs
index f5bc6c3ad2c..27dd8f26489 100644
--- a/compiler/rustc_trait_selection/src/traits/specialize/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/specialize/mod.rs
@@ -169,7 +169,7 @@ pub(super) fn specializes(tcx: TyCtxt<'_>, (impl1_def_id, impl2_def_id): (DefId,
         }
     }
 
-    let impl1_trait_header = tcx.impl_trait_header(impl1_def_id).unwrap().instantiate_identity();
+    let impl1_trait_header = tcx.impl_trait_header(impl1_def_id).unwrap();
 
     // We determine whether there's a subset relationship by:
     //
@@ -198,7 +198,7 @@ pub(super) fn specializes(tcx: TyCtxt<'_>, (impl1_def_id, impl2_def_id): (DefId,
     fulfill_implication(
         &infcx,
         penv,
-        impl1_trait_header.trait_ref,
+        impl1_trait_header.trait_ref.instantiate_identity(),
         impl1_def_id,
         impl2_def_id,
         |_, _| ObligationCause::dummy(),
diff --git a/compiler/rustc_trait_selection/src/traits/util.rs b/compiler/rustc_trait_selection/src/traits/util.rs
index 6e01e0b76aa..3f433a9e919 100644
--- a/compiler/rustc_trait_selection/src/traits/util.rs
+++ b/compiler/rustc_trait_selection/src/traits/util.rs
@@ -127,7 +127,7 @@ impl<'tcx> TraitAliasExpander<'tcx> {
         }
 
         // Get components of trait alias.
-        let predicates = tcx.implied_predicates_of(trait_ref.def_id());
+        let predicates = tcx.super_predicates_of(trait_ref.def_id());
         debug!(?predicates);
 
         let items = predicates.predicates.iter().rev().filter_map(|(pred, span)| {
diff --git a/compiler/rustc_trait_selection/src/traits/wf.rs b/compiler/rustc_trait_selection/src/traits/wf.rs
index 15059bc6613..b09a803e856 100644
--- a/compiler/rustc_trait_selection/src/traits/wf.rs
+++ b/compiler/rustc_trait_selection/src/traits/wf.rs
@@ -223,60 +223,87 @@ enum Elaborate {
     None,
 }
 
+/// Points the cause span of a super predicate at the relevant associated type.
+///
+/// Given a trait impl item:
+///
+/// ```ignore (incomplete)
+/// impl TargetTrait for TargetType {
+///    type Assoc = SomeType;
+/// }
+/// ```
+///
+/// And a super predicate of `TargetTrait` that has any of the following forms:
+///
+/// 1. `<OtherType as OtherTrait>::Assoc == <TargetType as TargetTrait>::Assoc`
+/// 2. `<<TargetType as TargetTrait>::Assoc as OtherTrait>::Assoc == OtherType`
+/// 3. `<TargetType as TargetTrait>::Assoc: OtherTrait`
+///
+/// Replace the span of the cause with the span of the associated item:
+///
+/// ```ignore (incomplete)
+/// impl TargetTrait for TargetType {
+///     type Assoc = SomeType;
+/// //               ^^^^^^^^ this span
+/// }
+/// ```
+///
+/// Note that bounds that can be expressed as associated item bounds are **not**
+/// super predicates. This means that form 2 and 3 from above are only relevant if
+/// the [`GenericArgsRef`] of the projection type are not its identity arguments.
 fn extend_cause_with_original_assoc_item_obligation<'tcx>(
     tcx: TyCtxt<'tcx>,
-    trait_ref: ty::TraitRef<'tcx>,
     item: Option<&hir::Item<'tcx>>,
     cause: &mut traits::ObligationCause<'tcx>,
     pred: ty::Predicate<'tcx>,
 ) {
-    debug!(
-        "extended_cause_with_original_assoc_item_obligation {:?} {:?} {:?} {:?}",
-        trait_ref, item, cause, pred
-    );
+    debug!(?item, ?cause, ?pred, "extended_cause_with_original_assoc_item_obligation");
     let (items, impl_def_id) = match item {
         Some(hir::Item { kind: hir::ItemKind::Impl(impl_), owner_id, .. }) => {
             (impl_.items, *owner_id)
         }
         _ => return,
     };
-    let fix_span =
-        |impl_item_ref: &hir::ImplItemRef| match tcx.hir().impl_item(impl_item_ref.id).kind {
-            hir::ImplItemKind::Const(ty, _) | hir::ImplItemKind::Type(ty) => ty.span,
-            _ => impl_item_ref.span,
-        };
+
+    let ty_to_impl_span = |ty: Ty<'_>| {
+        if let ty::Alias(ty::Projection, projection_ty) = ty.kind()
+            && let Some(&impl_item_id) =
+                tcx.impl_item_implementor_ids(impl_def_id).get(&projection_ty.def_id)
+            && let Some(impl_item) =
+                items.iter().find(|item| item.id.owner_id.to_def_id() == impl_item_id)
+        {
+            Some(tcx.hir().impl_item(impl_item.id).expect_type().span)
+        } else {
+            None
+        }
+    };
 
     // It is fine to skip the binder as we don't care about regions here.
     match pred.kind().skip_binder() {
         ty::PredicateKind::Clause(ty::ClauseKind::Projection(proj)) => {
-            // The obligation comes not from the current `impl` nor the `trait` being implemented,
-            // but rather from a "second order" obligation, where an associated type has a
-            // projection coming from another associated type. See
-            // `tests/ui/associated-types/point-at-type-on-obligation-failure.rs` and
-            // `traits-assoc-type-in-supertrait-bad.rs`.
-            if let Some(ty::Alias(ty::Projection, projection_ty)) =
-                proj.term.ty().map(|ty| ty.kind())
-                && let Some(&impl_item_id) =
-                    tcx.impl_item_implementor_ids(impl_def_id).get(&projection_ty.def_id)
-                && let Some(impl_item_span) = items
-                    .iter()
-                    .find(|item| item.id.owner_id.to_def_id() == impl_item_id)
-                    .map(fix_span)
+            // Form 1: The obligation comes not from the current `impl` nor the `trait` being
+            // implemented, but rather from a "second order" obligation, where an associated
+            // type has a projection coming from another associated type.
+            // See `tests/ui/traits/assoc-type-in-superbad.rs` for an example.
+            if let Some(term_ty) = proj.term.ty()
+                && let Some(impl_item_span) = ty_to_impl_span(term_ty)
             {
                 cause.span = impl_item_span;
             }
+
+            // Form 2: A projection obligation for an associated item failed to be met.
+            // We overwrite the span from above to ensure that a bound like
+            // `Self::Assoc1: Trait<OtherAssoc = Self::Assoc2>` gets the same
+            // span for both obligations that it is lowered to.
+            if let Some(impl_item_span) = ty_to_impl_span(proj.self_ty()) {
+                cause.span = impl_item_span;
+            }
         }
+
         ty::PredicateKind::Clause(ty::ClauseKind::Trait(pred)) => {
-            // An associated item obligation born out of the `trait` failed to be met. An example
-            // can be seen in `ui/associated-types/point-at-type-on-obligation-failure-2.rs`.
+            // Form 3: A trait obligation for an associated item failed to be met.
             debug!("extended_cause_with_original_assoc_item_obligation trait proj {:?}", pred);
-            if let ty::Alias(ty::Projection, ty::AliasTy { def_id, .. }) = *pred.self_ty().kind()
-                && let Some(&impl_item_id) = tcx.impl_item_implementor_ids(impl_def_id).get(&def_id)
-                && let Some(impl_item_span) = items
-                    .iter()
-                    .find(|item| item.id.owner_id.to_def_id() == impl_item_id)
-                    .map(fix_span)
-            {
+            if let Some(impl_item_span) = ty_to_impl_span(pred.self_ty()) {
                 cause.span = impl_item_span;
             }
         }
@@ -355,9 +382,7 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
                     traits::ObligationCauseCode::DerivedObligation,
                 );
             }
-            extend_cause_with_original_assoc_item_obligation(
-                tcx, trait_ref, item, &mut cause, predicate,
-            );
+            extend_cause_with_original_assoc_item_obligation(tcx, item, &mut cause, predicate);
             traits::Obligation::with_depth(tcx, cause, depth, param_env, predicate)
         };