Address comments

4 files changed, 52 insertions, 117 deletions

diff --git a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
index 6d6ad199be3..50cd13a2ccc 100644
--- a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
@@ -535,12 +535,12 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             // x += 1;
             // ```
             !i.contains(span)
-                    // We filter these to avoid incorrect main message on `match-cfg-fake-edges.rs`
-                        && !visitor
-                            .errors
-                            .iter()
-                            .map(|(sp, _)| *sp)
-                            .any(|sp| span < sp && !sp.contains(span))
+            // We filter these to avoid incorrect main message on `match-cfg-fake-edges.rs`
+            && !visitor
+                .errors
+                .iter()
+                .map(|(sp, _)| *sp)
+                .any(|sp| span < sp && !sp.contains(span))
         }) {
             show_assign_sugg = true;
             "isn't initialized"
diff --git a/compiler/rustc_borrowck/src/diagnostics/region_errors.rs b/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
index 631e147ce8c..567a9814fcc 100644
--- a/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
@@ -4,9 +4,9 @@
 
 use rustc_data_structures::fx::FxIndexSet;
 use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed, MultiSpan};
+use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
 use rustc_hir::intravisit::Visitor;
-use rustc_hir::{self as hir, Item, ItemKind, Node};
 use rustc_infer::infer::{
     error_reporting::nice_region_error::{
         self, find_anon_type, find_param_with_region, suggest_adding_lifetime_params,
@@ -291,65 +291,6 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
         outlives_suggestion.add_suggestion(self);
     }
 
-    fn get_impl_ident_and_self_ty_from_trait(
-        &self,
-        def_id: DefId,
-        trait_objects: &FxIndexSet<DefId>,
-    ) -> Option<(Ident, &'tcx hir::Ty<'tcx>)> {
-        let tcx = self.infcx.tcx;
-        match tcx.hir().get_if_local(def_id) {
-            Some(Node::ImplItem(impl_item)) => {
-                match tcx.hir().find_by_def_id(tcx.hir().get_parent_item(impl_item.hir_id()).def_id)
-                {
-                    Some(Node::Item(Item {
-                        kind: ItemKind::Impl(hir::Impl { self_ty, .. }),
-                        ..
-                    })) => Some((impl_item.ident, self_ty)),
-                    _ => None,
-                }
-            }
-            Some(Node::TraitItem(trait_item)) => {
-                let trait_did = tcx.hir().get_parent_item(trait_item.hir_id());
-                match tcx.hir().find_by_def_id(trait_did.def_id) {
-                    Some(Node::Item(Item { kind: ItemKind::Trait(..), .. })) => {
-                        // The method being called is defined in the `trait`, but the `'static`
-                        // obligation comes from the `impl`. Find that `impl` so that we can point
-                        // at it in the suggestion.
-                        let trait_did = trait_did.to_def_id();
-                        match tcx.hir().trait_impls(trait_did).iter().find_map(|&impl_did| {
-                            match tcx.hir().get_if_local(impl_did.to_def_id()) {
-                                Some(Node::Item(Item {
-                                    kind: ItemKind::Impl(hir::Impl { self_ty, .. }),
-                                    ..
-                                })) if trait_objects.iter().all(|did| {
-                                    // FIXME: we should check `self_ty` against the receiver
-                                    // type in the `UnifyReceiver` context, but for now, use
-                                    // this imperfect proxy. This will fail if there are
-                                    // multiple `impl`s for the same trait like
-                                    // `impl Foo for Box<dyn Bar>` and `impl Foo for dyn Bar`.
-                                    // In that case, only the first one will get suggestions.
-                                    let mut traits = vec![];
-                                    let mut hir_v = HirTraitObjectVisitor(&mut traits, *did);
-                                    hir_v.visit_ty(self_ty);
-                                    !traits.is_empty()
-                                }) =>
-                                {
-                                    Some(self_ty)
-                                }
-                                _ => None,
-                            }
-                        }) {
-                            Some(self_ty) => Some((trait_item.ident, self_ty)),
-                            _ => None,
-                        }
-                    }
-                    _ => None,
-                }
-            }
-            _ => None,
-        }
-    }
-
     /// Report an error because the universal region `fr` was required to outlive
     /// `outlived_fr` but it is not known to do so. For example:
     ///
@@ -844,7 +785,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
         visitor.visit_ty(param.param_ty);
 
         let Some((ident, self_ty)) =
-            self.get_impl_ident_and_self_ty_from_trait(instance.def_id(), &visitor.0) else {return};
+            NiceRegionError::get_impl_ident_and_self_ty_from_trait(tcx, instance.def_id(), &visitor.0) else { return; };
 
         self.suggest_constrain_dyn_trait_in_impl(diag, &visitor.0, ident, self_ty);
     }
diff --git a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs
index 58be91bc276..d9cdfa9dd4f 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs
@@ -239,7 +239,7 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
             let mut v = TraitObjectVisitor(FxIndexSet::default());
             v.visit_ty(param.param_ty);
             if let Some((ident, self_ty)) =
-                self.get_impl_ident_and_self_ty_from_trait(item_def_id, &v.0)
+                NiceRegionError::get_impl_ident_and_self_ty_from_trait(tcx, item_def_id, &v.0)
                 && self.suggest_constrain_dyn_trait_in_impl(&mut err, &v.0, ident, self_ty)
             {
                 override_error_code = Some(ident.name);
@@ -390,60 +390,54 @@ pub fn suggest_new_region_bound(
 }
 
 impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
-    fn get_impl_ident_and_self_ty_from_trait(
-        &self,
+    pub fn get_impl_ident_and_self_ty_from_trait(
+        tcx: TyCtxt<'tcx>,
         def_id: DefId,
         trait_objects: &FxIndexSet<DefId>,
     ) -> Option<(Ident, &'tcx hir::Ty<'tcx>)> {
-        let tcx = self.tcx();
-        match tcx.hir().get_if_local(def_id) {
-            Some(Node::ImplItem(impl_item)) => {
-                match tcx.hir().find_by_def_id(tcx.hir().get_parent_item(impl_item.hir_id()).def_id)
+        match tcx.hir().get_if_local(def_id)? {
+            Node::ImplItem(impl_item) => {
+                let impl_did = tcx.hir().get_parent_item(impl_item.hir_id());
+                if let hir::OwnerNode::Item(Item {
+                    kind: ItemKind::Impl(hir::Impl { self_ty, .. }),
+                    ..
+                }) = tcx.hir().owner(impl_did)
                 {
-                    Some(Node::Item(Item {
-                        kind: ItemKind::Impl(hir::Impl { self_ty, .. }),
-                        ..
-                    })) => Some((impl_item.ident, self_ty)),
-                    _ => None,
+                    Some((impl_item.ident, self_ty))
+                } else {
+                    None
                 }
             }
-            Some(Node::TraitItem(trait_item)) => {
-                let trait_did = tcx.hir().get_parent_item(trait_item.hir_id());
-                match tcx.hir().find_by_def_id(trait_did.def_id) {
-                    Some(Node::Item(Item { kind: ItemKind::Trait(..), .. })) => {
-                        // The method being called is defined in the `trait`, but the `'static`
-                        // obligation comes from the `impl`. Find that `impl` so that we can point
-                        // at it in the suggestion.
-                        let trait_did = trait_did.to_def_id();
-                        match tcx.hir().trait_impls(trait_did).iter().find_map(|&impl_did| {
-                            match tcx.hir().get_if_local(impl_did.to_def_id()) {
-                                Some(Node::Item(Item {
-                                    kind: ItemKind::Impl(hir::Impl { self_ty, .. }),
-                                    ..
-                                })) if trait_objects.iter().all(|did| {
-                                    // FIXME: we should check `self_ty` against the receiver
-                                    // type in the `UnifyReceiver` context, but for now, use
-                                    // this imperfect proxy. This will fail if there are
-                                    // multiple `impl`s for the same trait like
-                                    // `impl Foo for Box<dyn Bar>` and `impl Foo for dyn Bar`.
-                                    // In that case, only the first one will get suggestions.
-                                    let mut traits = vec![];
-                                    let mut hir_v = HirTraitObjectVisitor(&mut traits, *did);
-                                    hir_v.visit_ty(self_ty);
-                                    !traits.is_empty()
-                                }) =>
-                                {
-                                    Some(self_ty)
-                                }
-                                _ => None,
-                            }
-                        }) {
-                            Some(self_ty) => Some((trait_item.ident, self_ty)),
-                            _ => None,
-                        }
+            Node::TraitItem(trait_item) => {
+                let trait_id = tcx.hir().get_parent_item(trait_item.hir_id());
+                debug_assert_eq!(tcx.def_kind(trait_id.def_id), hir::def::DefKind::Trait);
+                // The method being called is defined in the `trait`, but the `'static`
+                // obligation comes from the `impl`. Find that `impl` so that we can point
+                // at it in the suggestion.
+                let trait_did = trait_id.to_def_id();
+                tcx.hir().trait_impls(trait_did).iter().find_map(|&impl_did| {
+                    if let Node::Item(Item {
+                        kind: ItemKind::Impl(hir::Impl { self_ty, .. }),
+                        ..
+                    }) = tcx.hir().find_by_def_id(impl_did)?
+                        && trait_objects.iter().all(|did| {
+                            // FIXME: we should check `self_ty` against the receiver
+                            // type in the `UnifyReceiver` context, but for now, use
+                            // this imperfect proxy. This will fail if there are
+                            // multiple `impl`s for the same trait like
+                            // `impl Foo for Box<dyn Bar>` and `impl Foo for dyn Bar`.
+                            // In that case, only the first one will get suggestions.
+                            let mut traits = vec![];
+                            let mut hir_v = HirTraitObjectVisitor(&mut traits, *did);
+                            hir_v.visit_ty(self_ty);
+                            !traits.is_empty()
+                        })
+                    {
+                        Some((trait_item.ident, *self_ty))
+                    } else {
+                        None
                     }
-                    _ => None,
-                }
+                })
             }
             _ => None,
         }
@@ -474,7 +468,7 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
 
         // Get the `Ident` of the method being called and the corresponding `impl` (to point at
         // `Bar` in `impl Foo for dyn Bar {}` and the definition of the method being called).
-        let Some((ident, self_ty)) = self.get_impl_ident_and_self_ty_from_trait(instance.def_id(), &v.0) else {
+        let Some((ident, self_ty)) = NiceRegionError::get_impl_ident_and_self_ty_from_trait(tcx, instance.def_id(), &v.0) else {
             return false;
         };
 
diff --git a/compiler/rustc_lint/src/unused.rs b/compiler/rustc_lint/src/unused.rs
index bf1f150fc3b..525079681ca 100644
--- a/compiler/rustc_lint/src/unused.rs
+++ b/compiler/rustc_lint/src/unused.rs
@@ -276,10 +276,10 @@ impl<'tcx> LateLintPass<'tcx> for UnusedResults {
                     {
                         let def_id = trait_ref.def_id;
                         is_def_must_use(cx, def_id, span)
+                            .map(|inner| MustUsePath::TraitObject(Box::new(inner)))
                     } else {
                         None
                     }
-                    .map(|inner| MustUsePath::TraitObject(Box::new(inner)))
                 }),
                 ty::Tuple(tys) => {
                     let elem_exprs = if let hir::ExprKind::Tup(elem_exprs) = expr.kind {