4 files changed, 15 insertions, 20 deletions
diff --git a/compiler/rustc_ty_utils/src/abi.rs b/compiler/rustc_ty_utils/src/abi.rs
index f0ff50318ab..af2e000e340 100644
--- a/compiler/rustc_ty_utils/src/abi.rs
+++ b/compiler/rustc_ty_utils/src/abi.rs
@@ -642,11 +642,11 @@ fn fn_abi_adjust_for_abi<'tcx>(
                 // The `deduced_param_attrs` list could be empty if this is a type of function
                 // we can't deduce any parameters for, so make sure the argument index is in
                 // bounds.
-                if let Some(deduced_param_attrs) = deduced_param_attrs.get(arg_idx) {
-                    if deduced_param_attrs.read_only {
-                        attrs.regular.insert(ArgAttribute::ReadOnly);
-                        debug!("added deduced read-only attribute");
-                    }
+                if let Some(deduced_param_attrs) = deduced_param_attrs.get(arg_idx)
+                    && deduced_param_attrs.read_only
+                {
+                    attrs.regular.insert(ArgAttribute::ReadOnly);
+                    debug!("added deduced read-only attribute");
                 }
             }
         }
diff --git a/compiler/rustc_ty_utils/src/instance.rs b/compiler/rustc_ty_utils/src/instance.rs
index 166e8f19342..e6c3568620b 100644
--- a/compiler/rustc_ty_utils/src/instance.rs
+++ b/compiler/rustc_ty_utils/src/instance.rs
@@ -21,7 +21,7 @@ fn resolve_instance_raw<'tcx>(
 ) -> Result<Option<Instance<'tcx>>, ErrorGuaranteed> {
     let PseudoCanonicalInput { typing_env, value: (def_id, args) } = key;
 
-    let result = if let Some(trait_def_id) = tcx.trait_of_item(def_id) {
+    let result = if let Some(trait_def_id) = tcx.trait_of_assoc(def_id) {
         debug!(" => associated item, attempting to find impl in typing_env {:#?}", typing_env);
         resolve_associated_item(
             tcx,
diff --git a/compiler/rustc_ty_utils/src/layout.rs b/compiler/rustc_ty_utils/src/layout.rs
index 163e2b30883..79f7e228e2a 100644
--- a/compiler/rustc_ty_utils/src/layout.rs
+++ b/compiler/rustc_ty_utils/src/layout.rs
@@ -603,12 +603,6 @@ fn layout_of_uncached<'tcx>(
                     .flatten()
             };
 
-            let dont_niche_optimize_enum = def.repr().inhibit_enum_layout_opt()
-                || def
-                    .variants()
-                    .iter_enumerated()
-                    .any(|(i, v)| v.discr != ty::VariantDiscr::Relative(i.as_u32()));
-
             let maybe_unsized = def.is_struct()
                 && def.non_enum_variant().tail_opt().is_some_and(|last_field| {
                     let typing_env = ty::TypingEnv::post_analysis(tcx, def.did());
@@ -625,7 +619,6 @@ fn layout_of_uncached<'tcx>(
                     tcx.layout_scalar_valid_range(def.did()),
                     get_discriminant_type,
                     discriminants_iter(),
-                    dont_niche_optimize_enum,
                     !maybe_unsized,
                 )
                 .map_err(|err| map_error(cx, ty, err))?;
@@ -651,7 +644,6 @@ fn layout_of_uncached<'tcx>(
                     tcx.layout_scalar_valid_range(def.did()),
                     get_discriminant_type,
                     discriminants_iter(),
-                    dont_niche_optimize_enum,
                     !maybe_unsized,
                 ) else {
                     bug!("failed to compute unsized layout of {ty:?}");
diff --git a/compiler/rustc_ty_utils/src/ty.rs b/compiler/rustc_ty_utils/src/ty.rs
index f8d793464a9..2e0b16d9227 100644
--- a/compiler/rustc_ty_utils/src/ty.rs
+++ b/compiler/rustc_ty_utils/src/ty.rs
@@ -80,8 +80,11 @@ fn sizedness_constraint_for_ty<'tcx>(
 
 fn defaultness(tcx: TyCtxt<'_>, def_id: LocalDefId) -> hir::Defaultness {
     match tcx.hir_node_by_def_id(def_id) {
-        hir::Node::Item(hir::Item { kind: hir::ItemKind::Impl(impl_), .. }) => impl_.defaultness,
-        hir::Node::ImplItem(hir::ImplItem { defaultness, .. })
+        hir::Node::Item(hir::Item {
+            kind: hir::ItemKind::Impl(hir::Impl { defaultness, of_trait: Some(_), .. }),
+            ..
+        })
+        | hir::Node::ImplItem(hir::ImplItem { defaultness, .. })
         | hir::Node::TraitItem(hir::TraitItem { defaultness, .. }) => *defaultness,
         node => {
             bug!("`defaultness` called on {:?}", node);
@@ -106,10 +109,10 @@ fn adt_sizedness_constraint<'tcx>(
     tcx: TyCtxt<'tcx>,
     (def_id, sizedness): (DefId, SizedTraitKind),
 ) -> Option<ty::EarlyBinder<'tcx, Ty<'tcx>>> {
-    if let Some(def_id) = def_id.as_local() {
-        if let ty::Representability::Infinite(_) = tcx.representability(def_id) {
-            return None;
-        }
+    if let Some(def_id) = def_id.as_local()
+        && let ty::Representability::Infinite(_) = tcx.representability(def_id)
+    {
+        return None;
     }
     let def = tcx.adt_def(def_id);