Move `has_self` field to `hir::AssocKind::Fn`.

`hir::AssocItem` currently has a boolean `fn_has_self_parameter` field,
which is misplaced, because it's only relevant for associated fns, not
for associated consts or types. This commit moves it (and renames it) to
the `AssocKind::Fn` variant, where it belongs.

This requires introducing a new C-style enum, `AssocTag`, which is like
`AssocKind` but without the fields. This is because `AssocKind` values
are passed to various functions like `find_by_ident_and_kind` to
indicate what kind of associated item should be searched for, and having
to specify `has_self` isn't relevant there.

New methods:
- Predicates `AssocItem::is_fn` and `AssocItem::is_method`.
- `AssocItem::as_tag` which converts `AssocItem::kind` to `AssocTag`.

Removed `find_by_name_and_kinds`, which is unused.

`AssocItem::descr` can now distinguish between methods and associated
functions, which slightly improves some error messages.

60 files changed, 288 insertions, 284 deletions

diff --git a/compiler/rustc_ast_lowering/src/delegation.rs b/compiler/rustc_ast_lowering/src/delegation.rs
index 2296b05f69b..93c627f64c9 100644
--- a/compiler/rustc_ast_lowering/src/delegation.rs
+++ b/compiler/rustc_ast_lowering/src/delegation.rs
@@ -85,7 +85,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     .delegation_fn_sigs
                     .get(&local_def_id)
                     .is_some_and(|sig| sig.has_self),
-                None => self.tcx.associated_item(def_id).fn_has_self_parameter,
+                None => self.tcx.associated_item(def_id).is_method(),
             },
             _ => span_bug!(span, "unexpected DefKind for delegation item"),
         }
diff --git a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
index 8a8ecc3b96e..fe6dff7ff1b 100644
--- a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
@@ -647,7 +647,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                     && tc.polarity() == ty::PredicatePolarity::Positive
                     && supertrait_def_ids(tcx, tc.def_id())
                         .flat_map(|trait_did| tcx.associated_items(trait_did).in_definition_order())
-                        .any(|item| item.fn_has_self_parameter)
+                        .any(|item| item.is_method())
             })
         }) {
             return None;
diff --git a/compiler/rustc_codegen_cranelift/src/main_shim.rs b/compiler/rustc_codegen_cranelift/src/main_shim.rs
index 3b48adb7e91..6eef97c14dd 100644
--- a/compiler/rustc_codegen_cranelift/src/main_shim.rs
+++ b/compiler/rustc_codegen_cranelift/src/main_shim.rs
@@ -1,6 +1,6 @@
 use cranelift_frontend::{FunctionBuilder, FunctionBuilderContext};
 use rustc_hir::LangItem;
-use rustc_middle::ty::{AssocKind, GenericArg};
+use rustc_middle::ty::{AssocTag, GenericArg};
 use rustc_session::config::EntryFnType;
 use rustc_span::{DUMMY_SP, Ident};
 
@@ -107,7 +107,7 @@ pub(crate) fn maybe_create_entry_wrapper(
                     .find_by_ident_and_kind(
                         tcx,
                         Ident::from_str("report"),
-                        AssocKind::Fn,
+                        AssocTag::Fn,
                         termination_trait,
                     )
                     .unwrap();
diff --git a/compiler/rustc_hir_analysis/src/check/check.rs b/compiler/rustc_hir_analysis/src/check/check.rs
index f50746dd18d..c2706a1d401 100644
--- a/compiler/rustc_hir_analysis/src/check/check.rs
+++ b/compiler/rustc_hir_analysis/src/check/check.rs
@@ -443,7 +443,7 @@ fn best_definition_site_of_opaque<'tcx>(
             let impl_def_id = tcx.local_parent(parent);
             for assoc in tcx.associated_items(impl_def_id).in_definition_order() {
                 match assoc.kind {
-                    ty::AssocKind::Const | ty::AssocKind::Fn => {
+                    ty::AssocKind::Const | ty::AssocKind::Fn { .. } => {
                         if let ControlFlow::Break(span) = locator.check(assoc.def_id.expect_local())
                         {
                             return Some(span);
@@ -942,7 +942,7 @@ fn check_impl_items_against_trait<'tcx>(
 
         if res.is_ok() {
             match ty_impl_item.kind {
-                ty::AssocKind::Fn => {
+                ty::AssocKind::Fn { .. } => {
                     compare_impl_item::refine::check_refining_return_position_impl_trait_in_trait(
                         tcx,
                         ty_impl_item,
diff --git a/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs b/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
index 29a9931696f..7dfdf1ae237 100644
--- a/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
+++ b/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
@@ -43,7 +43,7 @@ pub(super) fn compare_impl_item(
     debug!(?impl_trait_ref);
 
     match impl_item.kind {
-        ty::AssocKind::Fn => compare_impl_method(tcx, impl_item, trait_item, impl_trait_ref),
+        ty::AssocKind::Fn { .. } => compare_impl_method(tcx, impl_item, trait_item, impl_trait_ref),
         ty::AssocKind::Type => compare_impl_ty(tcx, impl_item, trait_item, impl_trait_ref),
         ty::AssocKind::Const => compare_impl_const(tcx, impl_item, trait_item, impl_trait_ref),
     }
@@ -1036,7 +1036,7 @@ fn report_trait_method_mismatch<'tcx>(
     );
     match &terr {
         TypeError::ArgumentMutability(0) | TypeError::ArgumentSorts(_, 0)
-            if trait_m.fn_has_self_parameter =>
+            if trait_m.is_method() =>
         {
             let ty = trait_sig.inputs()[0];
             let sugg = get_self_string(ty, |ty| ty == impl_trait_ref.self_ty());
@@ -1255,7 +1255,7 @@ fn compare_self_type<'tcx>(
         get_self_string(self_arg_ty, can_eq_self)
     };
 
-    match (trait_m.fn_has_self_parameter, impl_m.fn_has_self_parameter) {
+    match (trait_m.is_method(), impl_m.is_method()) {
         (false, false) | (true, true) => {}
 
         (false, true) => {
@@ -1363,7 +1363,7 @@ fn compare_number_of_generics<'tcx>(
     let mut err_occurred = None;
     for (kind, trait_count, impl_count) in matchings {
         if impl_count != trait_count {
-            let arg_spans = |kind: ty::AssocKind, generics: &hir::Generics<'_>| {
+            let arg_spans = |item: &ty::AssocItem, generics: &hir::Generics<'_>| {
                 let mut spans = generics
                     .params
                     .iter()
@@ -1373,7 +1373,7 @@ fn compare_number_of_generics<'tcx>(
                         } => {
                             // A fn can have an arbitrary number of extra elided lifetimes for the
                             // same signature.
-                            !matches!(kind, ty::AssocKind::Fn)
+                            !item.is_fn()
                         }
                         _ => true,
                     })
@@ -1386,7 +1386,7 @@ fn compare_number_of_generics<'tcx>(
             };
             let (trait_spans, impl_trait_spans) = if let Some(def_id) = trait_.def_id.as_local() {
                 let trait_item = tcx.hir_expect_trait_item(def_id);
-                let arg_spans: Vec<Span> = arg_spans(trait_.kind, trait_item.generics);
+                let arg_spans: Vec<Span> = arg_spans(&trait_, trait_item.generics);
                 let impl_trait_spans: Vec<Span> = trait_item
                     .generics
                     .params
@@ -1412,7 +1412,7 @@ fn compare_number_of_generics<'tcx>(
                     _ => None,
                 })
                 .collect();
-            let spans = arg_spans(impl_.kind, impl_item.generics);
+            let spans = arg_spans(&impl_, impl_item.generics);
             let span = spans.first().copied();
 
             let mut err = tcx.dcx().struct_span_err(
diff --git a/compiler/rustc_hir_analysis/src/check/mod.rs b/compiler/rustc_hir_analysis/src/check/mod.rs
index 30921b6f055..523db9440a4 100644
--- a/compiler/rustc_hir_analysis/src/check/mod.rs
+++ b/compiler/rustc_hir_analysis/src/check/mod.rs
@@ -407,14 +407,14 @@ fn fn_sig_suggestion<'tcx>(
         .enumerate()
         .map(|(i, ty)| {
             Some(match ty.kind() {
-                ty::Param(_) if assoc.fn_has_self_parameter && i == 0 => "self".to_string(),
+                ty::Param(_) if assoc.is_method() && i == 0 => "self".to_string(),
                 ty::Ref(reg, ref_ty, mutability) if i == 0 => {
                     let reg = format!("{reg} ");
                     let reg = match &reg[..] {
                         "'_ " | " " => "",
                         reg => reg,
                     };
-                    if assoc.fn_has_self_parameter {
+                    if assoc.is_method() {
                         match ref_ty.kind() {
                             ty::Param(param) if param.name == kw::SelfUpper => {
                                 format!("&{}{}self", reg, mutability.prefix_str())
@@ -427,7 +427,7 @@ fn fn_sig_suggestion<'tcx>(
                     }
                 }
                 _ => {
-                    if assoc.fn_has_self_parameter && i == 0 {
+                    if assoc.is_method() && i == 0 {
                         format!("self: {ty}")
                     } else {
                         format!("_: {ty}")
@@ -489,7 +489,7 @@ fn suggestion_signature<'tcx>(
     );
 
     match assoc.kind {
-        ty::AssocKind::Fn => fn_sig_suggestion(
+        ty::AssocKind::Fn { .. } => fn_sig_suggestion(
             tcx,
             tcx.liberate_late_bound_regions(
                 assoc.def_id,
diff --git a/compiler/rustc_hir_analysis/src/check/wfcheck.rs b/compiler/rustc_hir_analysis/src/check/wfcheck.rs
index 6292d03bf6a..af7830fd664 100644
--- a/compiler/rustc_hir_analysis/src/check/wfcheck.rs
+++ b/compiler/rustc_hir_analysis/src/check/wfcheck.rs
@@ -432,7 +432,7 @@ fn check_gat_where_clauses(tcx: TyCtxt<'_>, trait_def_id: LocalDefId) {
 
                 let item_required_bounds = match tcx.associated_item(item_def_id).kind {
                     // In our example, this corresponds to `into_iter` method
-                    ty::AssocKind::Fn => {
+                    ty::AssocKind::Fn { .. } => {
                         // For methods, we check the function signature's return type for any GATs
                         // to constrain. In the `into_iter` case, we see that the return type
                         // `Self::Iter<'a>` is a GAT we want to gather any potential missing bounds from.
@@ -1089,7 +1089,7 @@ fn check_associated_item(
                 );
                 Ok(())
             }
-            ty::AssocKind::Fn => {
+            ty::AssocKind::Fn { .. } => {
                 let sig = tcx.fn_sig(item.def_id).instantiate_identity();
                 let hir_sig = sig_if_method.expect("bad signature for method");
                 check_fn_or_method(
@@ -1716,7 +1716,7 @@ fn check_method_receiver<'tcx>(
 ) -> Result<(), ErrorGuaranteed> {
     let tcx = wfcx.tcx();
 
-    if !method.fn_has_self_parameter {
+    if !method.is_method() {
         return Ok(());
     }
 
diff --git a/compiler/rustc_hir_analysis/src/collect.rs b/compiler/rustc_hir_analysis/src/collect.rs
index deded6904d4..4520fbe352c 100644
--- a/compiler/rustc_hir_analysis/src/collect.rs
+++ b/compiler/rustc_hir_analysis/src/collect.rs
@@ -44,7 +44,7 @@ use rustc_trait_selection::traits::ObligationCtxt;
 use tracing::{debug, instrument};
 
 use crate::errors;
-use crate::hir_ty_lowering::errors::assoc_kind_str;
+use crate::hir_ty_lowering::errors::assoc_tag_str;
 use crate::hir_ty_lowering::{FeedConstTy, HirTyLowerer, RegionInferReason};
 
 pub(crate) mod dump;
@@ -450,7 +450,7 @@ impl<'tcx> HirTyLowerer<'tcx> for ItemCtxt<'tcx> {
         item_def_id: DefId,
         item_segment: &rustc_hir::PathSegment<'tcx>,
         poly_trait_ref: ty::PolyTraitRef<'tcx>,
-        kind: ty::AssocKind,
+        assoc_tag: ty::AssocTag,
     ) -> Result<(DefId, ty::GenericArgsRef<'tcx>), ErrorGuaranteed> {
         if let Some(trait_ref) = poly_trait_ref.no_bound_vars() {
             let item_args = self.lowerer().lower_generic_args_of_assoc_item(
@@ -525,7 +525,7 @@ impl<'tcx> HirTyLowerer<'tcx> for ItemCtxt<'tcx> {
                 inferred_sugg,
                 bound,
                 mpart_sugg,
-                what: assoc_kind_str(kind),
+                what: assoc_tag_str(assoc_tag),
             }))
         }
     }
diff --git a/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs b/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
index 9bcda35ee87..1c477755e5a 100644
--- a/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
+++ b/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
@@ -1811,7 +1811,7 @@ impl<'a, 'tcx> BoundVarContext<'a, 'tcx> {
                         self.tcx,
                         type_def_id,
                         constraint.ident,
-                        ty::AssocKind::Fn,
+                        ty::AssocTag::Fn,
                     ) {
                     bound_vars.extend(
                         self.tcx
@@ -1843,7 +1843,7 @@ impl<'a, 'tcx> BoundVarContext<'a, 'tcx> {
                     self.tcx,
                     type_def_id,
                     constraint.ident,
-                    ty::AssocKind::Type,
+                    ty::AssocTag::Type,
                 )
                 .map(|(bound_vars, _)| bound_vars);
                 self.with(scope, |this| {
@@ -1875,13 +1875,13 @@ impl<'a, 'tcx> BoundVarContext<'a, 'tcx> {
         tcx: TyCtxt<'tcx>,
         def_id: DefId,
         assoc_ident: Ident,
-        assoc_kind: ty::AssocKind,
+        assoc_tag: ty::AssocTag,
     ) -> Option<(Vec<ty::BoundVariableKind>, &'tcx ty::AssocItem)> {
         let trait_defines_associated_item_named = |trait_def_id: DefId| {
             tcx.associated_items(trait_def_id).find_by_ident_and_kind(
                 tcx,
                 assoc_ident,
-                assoc_kind,
+                assoc_tag,
                 trait_def_id,
             )
         };
@@ -1894,8 +1894,8 @@ impl<'a, 'tcx> BoundVarContext<'a, 'tcx> {
             let Some((def_id, bound_vars)) = stack.pop() else {
                 break None;
             };
-            // See issue #83753. If someone writes an associated type on a non-trait, just treat it as
-            // there being no supertrait HRTBs.
+            // See issue #83753. If someone writes an associated type on a non-trait, just treat it
+            // as there being no supertrait HRTBs.
             match tcx.def_kind(def_id) {
                 DefKind::Trait | DefKind::TraitAlias | DefKind::Impl { .. } => {}
                 _ => break None,
@@ -2067,7 +2067,7 @@ impl<'a, 'tcx> BoundVarContext<'a, 'tcx> {
                                     self.tcx,
                                     trait_def_id,
                                     item_segment.ident,
-                                    ty::AssocKind::Fn,
+                                    ty::AssocTag::Fn,
                                 )
                             });
 
@@ -2112,7 +2112,7 @@ impl<'a, 'tcx> BoundVarContext<'a, 'tcx> {
                             self.tcx,
                             trait_def_id,
                             item_segment.ident,
-                            ty::AssocKind::Fn,
+                            ty::AssocTag::Fn,
                         ) else {
                             return;
                         };
diff --git a/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs b/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs
index 772197a53ac..f0663644719 100644
--- a/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs
+++ b/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs
@@ -32,7 +32,9 @@ pub(super) fn find_opaque_ty_constraints_for_impl_trait_in_assoc_type(
     for &assoc_id in tcx.associated_item_def_ids(impl_def_id) {
         let assoc = tcx.associated_item(assoc_id);
         match assoc.kind {
-            ty::AssocKind::Const | ty::AssocKind::Fn => locator.check(assoc_id.expect_local()),
+            ty::AssocKind::Const | ty::AssocKind::Fn { .. } => {
+                locator.check(assoc_id.expect_local())
+            }
             // Associated types don't have bodies, so they can't constrain hidden types
             ty::AssocKind::Type => {}
         }
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs
index 24d05b49861..bf91eb1b8fd 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs
@@ -431,16 +431,16 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
     ) -> Result<(), ErrorGuaranteed> {
         let tcx = self.tcx();
 
-        let assoc_kind = if constraint.gen_args.parenthesized
+        let assoc_tag = if constraint.gen_args.parenthesized
             == hir::GenericArgsParentheses::ReturnTypeNotation
         {
-            ty::AssocKind::Fn
+            ty::AssocTag::Fn
         } else if let hir::AssocItemConstraintKind::Equality { term: hir::Term::Const(_) } =
             constraint.kind
         {
-            ty::AssocKind::Const
+            ty::AssocTag::Const
         } else {
-            ty::AssocKind::Type
+            ty::AssocTag::Type
         };
 
         // Given something like `U: Trait<T = X>`, we want to produce a predicate like
@@ -453,7 +453,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         //     trait SuperTrait<A> { type T; }
         let candidate = if self.probe_trait_that_defines_assoc_item(
             trait_ref.def_id(),
-            assoc_kind,
+            assoc_tag,
             constraint.ident,
         ) {
             // Simple case: The assoc item is defined in the current trait.
@@ -464,7 +464,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             self.probe_single_bound_for_assoc_item(
                 || traits::supertraits(tcx, trait_ref),
                 AssocItemQSelf::Trait(trait_ref.def_id()),
-                assoc_kind,
+                assoc_tag,
                 constraint.ident,
                 path_span,
                 Some(constraint),
@@ -474,7 +474,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         let assoc_item = self
             .probe_assoc_item(
                 constraint.ident,
-                assoc_kind,
+                assoc_tag,
                 hir_ref_id,
                 constraint.span,
                 candidate.def_id(),
@@ -493,7 +493,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             })
             .or_insert(constraint.span);
 
-        let projection_term = if let ty::AssocKind::Fn = assoc_kind {
+        let projection_term = if let ty::AssocTag::Fn = assoc_tag {
             let bound_vars = tcx.late_bound_vars(constraint.hir_id);
             ty::Binder::bind_with_vars(
                 self.lower_return_type_notation_ty(candidate, assoc_item.def_id, path_span)?.into(),
@@ -542,7 +542,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         };
 
         match constraint.kind {
-            hir::AssocItemConstraintKind::Equality { .. } if let ty::AssocKind::Fn = assoc_kind => {
+            hir::AssocItemConstraintKind::Equality { .. } if let ty::AssocTag::Fn = assoc_tag => {
                 return Err(self.dcx().emit_err(crate::errors::ReturnTypeNotationEqualityBound {
                     span: constraint.span,
                 }));
@@ -679,7 +679,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                         trait_def_id,
                         hir_ty.span,
                         item_segment,
-                        ty::AssocKind::Type,
+                        ty::AssocTag::Type,
                     );
                     return Ty::new_error(tcx, guar);
                 };
@@ -771,7 +771,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                         )
                     },
                     AssocItemQSelf::SelfTyAlias,
-                    ty::AssocKind::Fn,
+                    ty::AssocTag::Fn,
                     assoc_ident,
                     span,
                     None,
@@ -783,7 +783,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             ) => self.probe_single_ty_param_bound_for_assoc_item(
                 param_did.expect_local(),
                 qself.span,
-                ty::AssocKind::Fn,
+                ty::AssocTag::Fn,
                 assoc_ident,
                 span,
             )?,
@@ -823,7 +823,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
 
         let trait_def_id = bound.def_id();
         let assoc_ty = self
-            .probe_assoc_item(assoc_ident, ty::AssocKind::Fn, qpath_hir_id, span, trait_def_id)
+            .probe_assoc_item(assoc_ident, ty::AssocTag::Fn, qpath_hir_id, span, trait_def_id)
             .expect("failed to find associated type");
 
         Ok((bound, assoc_ty.def_id))
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs
index 5a0524d33fd..4f8d5471b6f 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs
@@ -116,7 +116,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         &self,
         all_candidates: impl Fn() -> I,
         qself: AssocItemQSelf,
-        assoc_kind: ty::AssocKind,
+        assoc_tag: ty::AssocTag,
         assoc_ident: Ident,
         span: Span,
         constraint: Option<&hir::AssocItemConstraint<'tcx>>,
@@ -134,14 +134,14 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         }) {
             return self.complain_about_assoc_kind_mismatch(
                 assoc_item,
-                assoc_kind,
+                assoc_tag,
                 assoc_ident,
                 span,
                 constraint,
             );
         }
 
-        let assoc_kind_str = assoc_kind_str(assoc_kind);
+        let assoc_kind_str = assoc_tag_str(assoc_tag);
         let qself_str = qself.to_string(tcx);
 
         // The fallback span is needed because `assoc_name` might be an `Fn()`'s `Output` without a
@@ -168,7 +168,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         let all_candidate_names: Vec<_> = all_candidates()
             .flat_map(|r| tcx.associated_items(r.def_id()).in_definition_order())
             .filter_map(|item| {
-                (!item.is_impl_trait_in_trait() && item.kind == assoc_kind).then_some(item.name)
+                (!item.is_impl_trait_in_trait() && item.as_tag() == assoc_tag).then_some(item.name)
             })
             .collect();
 
@@ -200,7 +200,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             .iter()
             .flat_map(|trait_def_id| tcx.associated_items(*trait_def_id).in_definition_order())
             .filter_map(|item| {
-                (!item.is_impl_trait_in_trait() && item.kind == assoc_kind).then_some(item.name)
+                (!item.is_impl_trait_in_trait() && item.as_tag() == assoc_tag).then_some(item.name)
             })
             .collect();
 
@@ -213,7 +213,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 .filter(|trait_def_id| {
                     tcx.associated_items(trait_def_id)
                         .filter_by_name_unhygienic(suggested_name)
-                        .any(|item| item.kind == assoc_kind)
+                        .any(|item| item.as_tag() == assoc_tag)
                 })
                 .collect::<Vec<_>>()[..]
             {
@@ -330,7 +330,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
     fn complain_about_assoc_kind_mismatch(
         &self,
         assoc_item: &ty::AssocItem,
-        assoc_kind: ty::AssocKind,
+        assoc_tag: ty::AssocTag,
         ident: Ident,
         span: Span,
         constraint: Option<&hir::AssocItemConstraint<'tcx>>,
@@ -375,17 +375,17 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 hir::Term::Ty(ty) => ty.span,
                 hir::Term::Const(ct) => ct.span(),
             };
-            (span, Some(ident.span), assoc_item.kind, assoc_kind)
+            (span, Some(ident.span), assoc_item.as_tag(), assoc_tag)
         } else {
-            (ident.span, None, assoc_kind, assoc_item.kind)
+            (ident.span, None, assoc_tag, assoc_item.as_tag())
         };
 
         self.dcx().emit_err(errors::AssocKindMismatch {
             span,
-            expected: assoc_kind_str(expected),
-            got: assoc_kind_str(got),
+            expected: assoc_tag_str(expected),
+            got: assoc_tag_str(got),
             expected_because_label,
-            assoc_kind: assoc_kind_str(assoc_item.kind),
+            assoc_kind: assoc_tag_str(assoc_item.as_tag()),
             def_span: tcx.def_span(assoc_item.def_id),
             bound_on_assoc_const_label,
             wrap_in_braces_sugg,
@@ -398,9 +398,9 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         types: &[String],
         traits: &[String],
         name: Symbol,
-        kind: ty::AssocKind,
+        assoc_tag: ty::AssocTag,
     ) -> ErrorGuaranteed {
-        let kind_str = assoc_kind_str(kind);
+        let kind_str = assoc_tag_str(assoc_tag);
         let mut err =
             struct_span_code_err!(self.dcx(), span, E0223, "ambiguous associated {kind_str}");
         if self
@@ -569,7 +569,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         candidates: Vec<(DefId, (DefId, DefId))>,
         fulfillment_errors: Vec<FulfillmentError<'tcx>>,
         span: Span,
-        kind: ty::AssocKind,
+        assoc_tag: ty::AssocTag,
     ) -> ErrorGuaranteed {
         // FIXME(fmease): This was copied in parts from an old version of `rustc_hir_typeck::method::suggest`.
         // Either
@@ -579,14 +579,14 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
 
         let tcx = self.tcx();
 
-        let kind_str = assoc_kind_str(kind);
+        let assoc_tag_str = assoc_tag_str(assoc_tag);
         let adt_did = self_ty.ty_adt_def().map(|def| def.did());
         let add_def_label = |err: &mut Diag<'_>| {
             if let Some(did) = adt_did {
                 err.span_label(
                     tcx.def_span(did),
                     format!(
-                        "associated {kind_str} `{name}` not found for this {}",
+                        "associated {assoc_tag_str} `{name}` not found for this {}",
                         tcx.def_descr(did)
                     ),
                 );
@@ -615,11 +615,11 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 self.dcx(),
                 name.span,
                 E0220,
-                "associated {kind_str} `{name}` not found for `{self_ty}` in the current scope"
+                "associated {assoc_tag_str} `{name}` not found for `{self_ty}` in the current scope"
             );
             err.span_label(name.span, format!("associated item not found in `{self_ty}`"));
             err.note(format!(
-                "the associated {kind_str} was found for\n{type_candidates}{additional_types}",
+                "the associated {assoc_tag_str} was found for\n{type_candidates}{additional_types}",
             ));
             add_def_label(&mut err);
             return err.emit();
@@ -700,7 +700,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
 
         let mut err = self.dcx().struct_span_err(
             name.span,
-            format!("the associated {kind_str} `{name}` exists for `{self_ty}`, but its trait bounds were not satisfied")
+            format!("the associated {assoc_tag_str} `{name}` exists for `{self_ty}`, but its trait bounds were not satisfied")
         );
         if !bounds.is_empty() {
             err.note(format!(
@@ -710,7 +710,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         }
         err.span_label(
             name.span,
-            format!("associated {kind_str} cannot be referenced on `{self_ty}` due to unsatisfied trait bounds")
+            format!("associated {assoc_tag_str} cannot be referenced on `{self_ty}` due to unsatisfied trait bounds")
         );
 
         for (span, mut bounds) in bound_spans {
@@ -812,7 +812,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                     let assoc_item = tcx.associated_items(trait_def).find_by_ident_and_kind(
                         tcx,
                         ident,
-                        ty::AssocKind::Type,
+                        ty::AssocTag::Type,
                         trait_def,
                     );
 
@@ -1022,12 +1022,13 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                         .map(|simple_ty| tcx.incoherent_impls(simple_ty))
                 })
             && let name = Symbol::intern(&format!("{ident2}_{ident3}"))
-            && let Some(ty::AssocItem { kind: ty::AssocKind::Fn, .. }) = inherent_impls
+            && let Some(item) = inherent_impls
                 .iter()
                 .flat_map(|inherent_impl| {
                     tcx.associated_items(inherent_impl).filter_by_name_unhygienic(name)
                 })
                 .next()
+            && item.is_fn()
         {
             Err(struct_span_code_err!(self.dcx(), span, E0223, "ambiguous associated type")
                 .with_span_suggestion_verbose(
@@ -1629,10 +1630,10 @@ fn generics_args_err_extend<'a>(
     }
 }
 
-pub(crate) fn assoc_kind_str(kind: ty::AssocKind) -> &'static str {
-    match kind {
-        ty::AssocKind::Fn => "function",
-        ty::AssocKind::Const => "constant",
-        ty::AssocKind::Type => "type",
+pub(crate) fn assoc_tag_str(assoc_tag: ty::AssocTag) -> &'static str {
+    match assoc_tag {
+        ty::AssocTag::Fn => "function",
+        ty::AssocTag::Const => "constant",
+        ty::AssocTag::Type => "type",
     }
 }
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
index 83aa0d95620..0fb406d9908 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
@@ -38,8 +38,8 @@ use rustc_middle::middle::stability::AllowUnstable;
 use rustc_middle::mir::interpret::LitToConstInput;
 use rustc_middle::ty::print::PrintPolyTraitRefExt as _;
 use rustc_middle::ty::{
-    self, Const, GenericArgKind, GenericArgsRef, GenericParamDefKind, ParamEnv, Ty, TyCtxt,
-    TypeVisitableExt, TypingMode, Upcast, fold_regions,
+    self, AssocTag, Const, GenericArgKind, GenericArgsRef, GenericParamDefKind, ParamEnv, Ty,
+    TyCtxt, TypeVisitableExt, TypingMode, Upcast, fold_regions,
 };
 use rustc_middle::{bug, span_bug};
 use rustc_session::lint::builtin::AMBIGUOUS_ASSOCIATED_ITEMS;
@@ -51,7 +51,7 @@ use rustc_trait_selection::traits::wf::object_region_bounds;
 use rustc_trait_selection::traits::{self, ObligationCtxt};
 use tracing::{debug, instrument};
 
-use self::errors::assoc_kind_str;
+use self::errors::assoc_tag_str;
 use crate::check::check_abi_fn_ptr;
 use crate::errors::{AmbiguousLifetimeBound, BadReturnTypeNotation, NoVariantNamed};
 use crate::hir_ty_lowering::errors::{GenericsArgsErrExtend, prohibit_assoc_item_constraint};
@@ -168,7 +168,7 @@ pub trait HirTyLowerer<'tcx> {
         item_def_id: DefId,
         item_segment: &hir::PathSegment<'tcx>,
         poly_trait_ref: ty::PolyTraitRef<'tcx>,
-        kind: ty::AssocKind,
+        assoc_tag: ty::AssocTag,
     ) -> Result<(DefId, GenericArgsRef<'tcx>), ErrorGuaranteed>;
 
     fn lower_fn_sig(
@@ -251,10 +251,10 @@ enum LowerAssocMode {
 }
 
 impl LowerAssocMode {
-    fn kind(self) -> ty::AssocKind {
+    fn assoc_tag(self) -> ty::AssocTag {
         match self {
-            LowerAssocMode::Type { .. } => ty::AssocKind::Type,
-            LowerAssocMode::Const => ty::AssocKind::Const,
+            LowerAssocMode::Type { .. } => ty::AssocTag::Type,
+            LowerAssocMode::Const => ty::AssocTag::Const,
         }
     }
 
@@ -268,7 +268,8 @@ impl LowerAssocMode {
     fn permit_variants(self) -> bool {
         match self {
             LowerAssocMode::Type { permit_variants } => permit_variants,
-            // FIXME(mgca): Support paths like `Option::<T>::None` or `Option::<T>::Some` which resolve to const ctors/fn items respectively
+            // FIXME(mgca): Support paths like `Option::<T>::None` or `Option::<T>::Some` which
+            // resolve to const ctors/fn items respectively.
             LowerAssocMode::Const => false,
         }
     }
@@ -932,12 +933,12 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
     fn probe_trait_that_defines_assoc_item(
         &self,
         trait_def_id: DefId,
-        assoc_kind: ty::AssocKind,
+        assoc_tag: AssocTag,
         assoc_ident: Ident,
     ) -> bool {
         self.tcx()
             .associated_items(trait_def_id)
-            .find_by_ident_and_kind(self.tcx(), assoc_ident, assoc_kind, trait_def_id)
+            .find_by_ident_and_kind(self.tcx(), assoc_ident, assoc_tag, trait_def_id)
             .is_some()
     }
 
@@ -975,7 +976,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         &self,
         ty_param_def_id: LocalDefId,
         ty_param_span: Span,
-        kind: ty::AssocKind,
+        assoc_tag: AssocTag,
         assoc_ident: Ident,
         span: Span,
     ) -> Result<ty::PolyTraitRef<'tcx>, ErrorGuaranteed> {
@@ -993,7 +994,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 traits::transitive_bounds_that_define_assoc_item(tcx, trait_refs, assoc_ident)
             },
             AssocItemQSelf::TyParam(ty_param_def_id, ty_param_span),
-            kind,
+            assoc_tag,
             assoc_ident,
             span,
             None,
@@ -1010,7 +1011,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         &self,
         all_candidates: impl Fn() -> I,
         qself: AssocItemQSelf,
-        assoc_kind: ty::AssocKind,
+        assoc_tag: AssocTag,
         assoc_ident: Ident,
         span: Span,
         constraint: Option<&hir::AssocItemConstraint<'tcx>>,
@@ -1021,14 +1022,14 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         let tcx = self.tcx();
 
         let mut matching_candidates = all_candidates().filter(|r| {
-            self.probe_trait_that_defines_assoc_item(r.def_id(), assoc_kind, assoc_ident)
+            self.probe_trait_that_defines_assoc_item(r.def_id(), assoc_tag, assoc_ident)
         });
 
         let Some(bound) = matching_candidates.next() else {
             let reported = self.complain_about_assoc_item_not_found(
                 all_candidates,
                 qself,
-                assoc_kind,
+                assoc_tag,
                 assoc_ident,
                 span,
                 constraint,
@@ -1040,7 +1041,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         if let Some(bound2) = matching_candidates.next() {
             debug!(?bound2);
 
-            let assoc_kind_str = errors::assoc_kind_str(assoc_kind);
+            let assoc_kind_str = errors::assoc_tag_str(assoc_tag);
             let qself_str = qself.to_string(tcx);
             let mut err = self.dcx().create_err(crate::errors::AmbiguousAssocItem {
                 span,
@@ -1059,14 +1060,15 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 },
             );
 
-            // FIXME(#97583): Print associated item bindings properly (i.e., not as equality predicates!).
+            // FIXME(#97583): Print associated item bindings properly (i.e., not as equality
+            // predicates!).
             // FIXME: Turn this into a structured, translateable & more actionable suggestion.
             let mut where_bounds = vec![];
             for bound in [bound, bound2].into_iter().chain(matching_candidates) {
                 let bound_id = bound.def_id();
                 let bound_span = tcx
                     .associated_items(bound_id)
-                    .find_by_ident_and_kind(tcx, assoc_ident, assoc_kind, bound_id)
+                    .find_by_ident_and_kind(tcx, assoc_ident, assoc_tag, bound_id)
                     .and_then(|item| tcx.hir_span_if_local(item.def_id));
 
                 if let Some(bound_span) = bound_span {
@@ -1265,7 +1267,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 qself_ty,
                 hir_ref_id,
                 span,
-                mode.kind(),
+                mode.assoc_tag(),
             )? {
                 return Ok(LoweredAssoc::Term(did, args));
             }
@@ -1296,7 +1298,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                         )
                     },
                     AssocItemQSelf::SelfTyAlias,
-                    mode.kind(),
+                    mode.assoc_tag(),
                     assoc_ident,
                     span,
                     None,
@@ -1308,12 +1310,12 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             ) => self.probe_single_ty_param_bound_for_assoc_item(
                 param_did.expect_local(),
                 qself.span,
-                mode.kind(),
+                mode.assoc_tag(),
                 assoc_ident,
                 span,
             )?,
             _ => {
-                let kind_str = assoc_kind_str(mode.kind());
+                let kind_str = assoc_tag_str(mode.assoc_tag());
                 let reported = if variant_resolution.is_some() {
                     // Variant in type position
                     let msg = format!("expected {kind_str}, found variant `{assoc_ident}`");
@@ -1420,7 +1422,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                         &[qself_ty.to_string()],
                         &traits,
                         assoc_ident.name,
-                        mode.kind(),
+                        mode.assoc_tag(),
                     )
                 };
                 return Err(reported);
@@ -1429,10 +1431,15 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
 
         let trait_did = bound.def_id();
         let assoc_item = self
-            .probe_assoc_item(assoc_ident, mode.kind(), hir_ref_id, span, trait_did)
+            .probe_assoc_item(assoc_ident, mode.assoc_tag(), hir_ref_id, span, trait_did)
             .expect("failed to find associated item");
-        let (def_id, args) =
-            self.lower_assoc_shared(span, assoc_item.def_id, assoc_segment, bound, mode.kind())?;
+        let (def_id, args) = self.lower_assoc_shared(
+            span,
+            assoc_item.def_id,
+            assoc_segment,
+            bound,
+            mode.assoc_tag(),
+        )?;
         let result = LoweredAssoc::Term(def_id, args);
 
         if let Some(variant_def_id) = variant_resolution {
@@ -1469,20 +1476,21 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         self_ty: Ty<'tcx>,
         block: HirId,
         span: Span,
-        kind: ty::AssocKind,
+        assoc_tag: ty::AssocTag,
     ) -> Result<Option<(DefId, GenericArgsRef<'tcx>)>, ErrorGuaranteed> {
         let tcx = self.tcx();
 
         if !tcx.features().inherent_associated_types() {
-            match kind {
-                // Don't attempt to look up inherent associated types when the feature is not enabled.
-                // Theoretically it'd be fine to do so since we feature-gate their definition site.
-                // However, due to current limitations of the implementation (caused by us performing
-                // selection during HIR ty lowering instead of in the trait solver), IATs can lead to cycle
-                // errors (#108491) which mask the feature-gate error, needlessly confusing users
-                // who use IATs by accident (#113265).
-                ty::AssocKind::Type => return Ok(None),
-                ty::AssocKind::Const => {
+            match assoc_tag {
+                // Don't attempt to look up inherent associated types when the feature is not
+                // enabled. Theoretically it'd be fine to do so since we feature-gate their
+                // definition site. However, due to current limitations of the implementation
+                // (caused by us performing selection during HIR ty lowering instead of in the
+                // trait solver), IATs can lead to cycle errors (#108491) which mask the
+                // feature-gate error, needlessly confusing users who use IATs by accident
+                // (#113265).
+                ty::AssocTag::Type => return Ok(None),
+                ty::AssocTag::Const => {
                     // We also gate the mgca codepath for type-level uses of inherent consts
                     // with the inherent_associated_types feature gate since it relies on the
                     // same machinery and has similar rough edges.
@@ -1494,7 +1502,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                     )
                     .emit());
                 }
-                ty::AssocKind::Fn => unreachable!(),
+                ty::AssocTag::Fn => unreachable!(),
             }
         }
 
@@ -1503,7 +1511,8 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             .inherent_impls(adt_did)
             .iter()
             .filter_map(|&impl_| {
-                let (item, scope) = self.probe_assoc_item_unchecked(name, kind, block, impl_)?;
+                let (item, scope) =
+                    self.probe_assoc_item_unchecked(name, assoc_tag, block, impl_)?;
                 Some((impl_, (item.def_id, scope)))
             })
             .collect();
@@ -1542,7 +1551,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             self_ty,
             |self_ty| {
                 self.select_inherent_assoc_candidates(
-                    infcx, name, span, self_ty, param_env, candidates, kind,
+                    infcx, name, span, self_ty, param_env, candidates, assoc_tag,
                 )
             },
         )?;
@@ -1570,7 +1579,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         self_ty: Ty<'tcx>,
         param_env: ParamEnv<'tcx>,
         candidates: Vec<(DefId, (DefId, DefId))>,
-        kind: ty::AssocKind,
+        assoc_tag: ty::AssocTag,
     ) -> Result<(DefId, (DefId, DefId)), ErrorGuaranteed> {
         let tcx = self.tcx();
         let mut fulfillment_errors = Vec::new();
@@ -1621,7 +1630,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 candidates,
                 fulfillment_errors,
                 span,
-                kind,
+                assoc_tag,
             )),
 
             &[applicable_candidate] => Ok(applicable_candidate),
@@ -1640,12 +1649,12 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
     fn probe_assoc_item(
         &self,
         ident: Ident,
-        kind: ty::AssocKind,
+        assoc_tag: ty::AssocTag,
         block: HirId,
         span: Span,
         scope: DefId,
     ) -> Option<ty::AssocItem> {
-        let (item, scope) = self.probe_assoc_item_unchecked(ident, kind, block, scope)?;
+        let (item, scope) = self.probe_assoc_item_unchecked(ident, assoc_tag, block, scope)?;
         self.check_assoc_item(item.def_id, ident, scope, block, span);
         Some(item)
     }
@@ -1657,7 +1666,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
     fn probe_assoc_item_unchecked(
         &self,
         ident: Ident,
-        kind: ty::AssocKind,
+        assoc_tag: ty::AssocTag,
         block: HirId,
         scope: DefId,
     ) -> Option<(ty::AssocItem, /*scope*/ DefId)> {
@@ -1670,7 +1679,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         let item = tcx
             .associated_items(scope)
             .filter_by_name_unhygienic(ident.name)
-            .find(|i| i.kind == kind && i.ident(tcx).normalize_to_macros_2_0() == ident)?;
+            .find(|i| i.as_tag() == assoc_tag && i.ident(tcx).normalize_to_macros_2_0() == ident)?;
 
         Some((*item, def_scope))
     }
@@ -1770,7 +1779,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             item_def_id,
             trait_segment,
             item_segment,
-            ty::AssocKind::Type,
+            ty::AssocTag::Type,
         ) {
             Ok((item_def_id, item_args)) => {
                 Ty::new_projection_from_args(self.tcx(), item_def_id, item_args)
@@ -1795,7 +1804,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             item_def_id,
             trait_segment,
             item_segment,
-            ty::AssocKind::Const,
+            ty::AssocTag::Const,
         ) {
             Ok((item_def_id, item_args)) => {
                 let uv = ty::UnevaluatedConst::new(item_def_id, item_args);
@@ -1813,7 +1822,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         item_def_id: DefId,
         trait_segment: &hir::PathSegment<'tcx>,
         item_segment: &hir::PathSegment<'tcx>,
-        kind: ty::AssocKind,
+        assoc_tag: ty::AssocTag,
     ) -> Result<(DefId, GenericArgsRef<'tcx>), ErrorGuaranteed> {
         let tcx = self.tcx();
 
@@ -1821,7 +1830,12 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         debug!(?trait_def_id);
 
         let Some(self_ty) = opt_self_ty else {
-            return Err(self.error_missing_qpath_self_ty(trait_def_id, span, item_segment, kind));
+            return Err(self.error_missing_qpath_self_ty(
+                trait_def_id,
+                span,
+                item_segment,
+                assoc_tag,
+            ));
         };
         debug!(?self_ty);
 
@@ -1840,7 +1854,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         trait_def_id: DefId,
         span: Span,
         item_segment: &hir::PathSegment<'tcx>,
-        kind: ty::AssocKind,
+        assoc_tag: ty::AssocTag,
     ) -> ErrorGuaranteed {
         let tcx = self.tcx();
         let path_str = tcx.def_path_str(trait_def_id);
@@ -1877,7 +1891,13 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         // FIXME: also look at `tcx.generics_of(self.item_def_id()).params` any that
         // references the trait. Relevant for the first case in
         // `src/test/ui/associated-types/associated-types-in-ambiguous-context.rs`
-        self.report_ambiguous_assoc(span, &type_names, &[path_str], item_segment.ident.name, kind)
+        self.report_ambiguous_assoc(
+            span,
+            &type_names,
+            &[path_str],
+            item_segment.ident.name,
+            assoc_tag,
+        )
     }
 
     pub fn prohibit_generic_args<'a>(
@@ -2862,7 +2882,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         let assoc = tcx.associated_items(trait_ref.def_id).find_by_ident_and_kind(
             tcx,
             *ident,
-            ty::AssocKind::Fn,
+            ty::AssocTag::Fn,
             trait_ref.def_id,
         )?;
 
diff --git a/compiler/rustc_hir_analysis/src/impl_wf_check.rs b/compiler/rustc_hir_analysis/src/impl_wf_check.rs
index c30b39dfe76..1ab36ce1dcb 100644
--- a/compiler/rustc_hir_analysis/src/impl_wf_check.rs
+++ b/compiler/rustc_hir_analysis/src/impl_wf_check.rs
@@ -119,7 +119,7 @@ pub(crate) fn enforce_impl_lifetime_params_are_constrained(
                         vec![]
                     }
                 }
-                ty::AssocKind::Fn | ty::AssocKind::Const => vec![],
+                ty::AssocKind::Fn { .. } | ty::AssocKind::Const => vec![],
             }
         })
         .collect();
diff --git a/compiler/rustc_hir_typeck/src/demand.rs b/compiler/rustc_hir_typeck/src/demand.rs
index fec45995410..d1bc54ed73e 100644
--- a/compiler/rustc_hir_typeck/src/demand.rs
+++ b/compiler/rustc_hir_typeck/src/demand.rs
@@ -1089,14 +1089,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
     /// This function checks whether the method is not static and does not accept other parameters than `self`.
     fn has_only_self_parameter(&self, method: &AssocItem) -> bool {
-        match method.kind {
-            ty::AssocKind::Fn => {
-                method.fn_has_self_parameter
-                    && self.tcx.fn_sig(method.def_id).skip_binder().inputs().skip_binder().len()
-                        == 1
-            }
-            _ => false,
-        }
+        method.is_method()
+            && self.tcx.fn_sig(method.def_id).skip_binder().inputs().skip_binder().len() == 1
     }
 
     /// If the given `HirId` corresponds to a block with a trailing expression, return that expression
diff --git a/compiler/rustc_hir_typeck/src/expr.rs b/compiler/rustc_hir_typeck/src/expr.rs
index de2f039cb1c..56c205b6f87 100644
--- a/compiler/rustc_hir_typeck/src/expr.rs
+++ b/compiler/rustc_hir_typeck/src/expr.rs
@@ -2588,9 +2588,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 .into_iter()
                 .flat_map(|i| self.tcx.associated_items(i).in_definition_order())
                 // Only assoc fn with no receivers.
-                .filter(|item| {
-                    matches!(item.kind, ty::AssocKind::Fn) && !item.fn_has_self_parameter
-                })
+                .filter(|item| item.is_fn() && !item.is_method())
                 .filter_map(|item| {
                     // Only assoc fns that return `Self`
                     let fn_sig = self.tcx.fn_sig(item.def_id).skip_binder();
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
index 81eb8510785..3a0f3a4a5f0 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
@@ -616,7 +616,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 if let Some((DefKind::AssocFn, def_id)) =
                     self.typeck_results.borrow().type_dependent_def(call_expr.hir_id)
                     && let Some(assoc) = tcx.opt_associated_item(def_id)
-                    && assoc.fn_has_self_parameter
+                    && assoc.is_method()
                 {
                     Some(*receiver)
                 } else {
@@ -642,8 +642,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     TraitsInScope,
                     |mut ctxt| ctxt.probe_for_similar_candidate(),
                 )
-                && let ty::AssocKind::Fn = assoc.kind
-                && assoc.fn_has_self_parameter
+                && assoc.is_method()
             {
                 let args = self.infcx.fresh_args_for_item(call_name.span, assoc.def_id);
                 let fn_sig = tcx.fn_sig(assoc.def_id).instantiate(tcx, args);
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs
index e14f1528d2c..74cc8181418 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs
@@ -314,7 +314,7 @@ impl<'tcx> HirTyLowerer<'tcx> for FnCtxt<'_, 'tcx> {
         item_def_id: DefId,
         item_segment: &rustc_hir::PathSegment<'tcx>,
         poly_trait_ref: ty::PolyTraitRef<'tcx>,
-        _kind: ty::AssocKind,
+        _assoc_tag: ty::AssocTag,
     ) -> Result<(DefId, ty::GenericArgsRef<'tcx>), ErrorGuaranteed> {
         let trait_ref = self.instantiate_binder_with_fresh_vars(
             span,
diff --git a/compiler/rustc_hir_typeck/src/method/mod.rs b/compiler/rustc_hir_typeck/src/method/mod.rs
index ddfd27ccf6b..39cb139a199 100644
--- a/compiler/rustc_hir_typeck/src/method/mod.rs
+++ b/compiler/rustc_hir_typeck/src/method/mod.rs
@@ -379,7 +379,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         };
 
         let def_id = method_item.def_id;
-        if method_item.kind != ty::AssocKind::Fn {
+        if !method_item.is_fn() {
             span_bug!(tcx.def_span(def_id), "expected `{m_name}` to be an associated function");
         }
 
diff --git a/compiler/rustc_hir_typeck/src/method/probe.rs b/compiler/rustc_hir_typeck/src/method/probe.rs
index 0a01ec89a32..d5d85c812b2 100644
--- a/compiler/rustc_hir_typeck/src/method/probe.rs
+++ b/compiler/rustc_hir_typeck/src/method/probe.rs
@@ -992,7 +992,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
 
     fn matches_return_type(&self, method: ty::AssocItem, expected: Ty<'tcx>) -> bool {
         match method.kind {
-            ty::AssocKind::Fn => self.probe(|_| {
+            ty::AssocKind::Fn { .. } => self.probe(|_| {
                 let args = self.fresh_args_for_item(self.span, method.def_id);
                 let fty = self.tcx.fn_sig(method.def_id).instantiate(self.tcx, args);
                 let fty = self.instantiate_binder_with_fresh_vars(self.span, infer::FnCall, fty);
@@ -1678,7 +1678,6 @@ impl<'tcx> Pick<'tcx> {
                     kind: _,
                     container: _,
                     trait_item_def_id: _,
-                    fn_has_self_parameter: _,
                     opt_rpitit_info: _,
                 },
             kind: _,
@@ -1712,7 +1711,7 @@ impl<'tcx> Pick<'tcx> {
             ));
 
             match (self.item.kind, self.item.container) {
-                (ty::AssocKind::Fn, _) => {
+                (ty::AssocKind::Fn { .. }, _) => {
                     // FIXME: This should be a `span_suggestion` instead of `help`
                     // However `self.span` only
                     // highlights the method name, so we can't use it. Also consider reusing
@@ -2252,10 +2251,10 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
         // In Path mode (i.e., resolving a value like `T::next`), consider any
         // associated value (i.e., methods, constants) but not types.
         match self.mode {
-            Mode::MethodCall => item.fn_has_self_parameter,
+            Mode::MethodCall => item.is_method(),
             Mode::Path => match item.kind {
                 ty::AssocKind::Type => false,
-                ty::AssocKind::Fn | ty::AssocKind::Const => true,
+                ty::AssocKind::Fn { .. } | ty::AssocKind::Const => true,
             },
         }
         // FIXME -- check for types that deref to `Self`,
@@ -2277,7 +2276,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
         impl_ty: Ty<'tcx>,
         args: GenericArgsRef<'tcx>,
     ) -> (Ty<'tcx>, Option<Ty<'tcx>>) {
-        if item.kind == ty::AssocKind::Fn && self.mode == Mode::MethodCall {
+        if item.is_fn() && self.mode == Mode::MethodCall {
             let sig = self.xform_method_sig(item.def_id, args);
             (sig.inputs()[0], Some(sig.output()))
         } else {
@@ -2328,8 +2327,8 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
     /// Determine if the given associated item type is relevant in the current context.
     fn is_relevant_kind_for_mode(&self, kind: ty::AssocKind) -> bool {
         match (self.mode, kind) {
-            (Mode::MethodCall, ty::AssocKind::Fn) => true,
-            (Mode::Path, ty::AssocKind::Const | ty::AssocKind::Fn) => true,
+            (Mode::MethodCall, ty::AssocKind::Fn { .. }) => true,
+            (Mode::Path, ty::AssocKind::Const | ty::AssocKind::Fn { .. }) => true,
             _ => false,
         }
     }
diff --git a/compiler/rustc_hir_typeck/src/method/suggest.rs b/compiler/rustc_hir_typeck/src/method/suggest.rs
index 68f13d654d6..1b9771636a7 100644
--- a/compiler/rustc_hir_typeck/src/method/suggest.rs
+++ b/compiler/rustc_hir_typeck/src/method/suggest.rs
@@ -713,7 +713,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 && let Some(candidate) = tcx.associated_items(impl_def_id).find_by_ident_and_kind(
                     self.tcx,
                     item_ident,
-                    ty::AssocKind::Type,
+                    ty::AssocTag::Type,
                     impl_def_id,
                 )
                 && let Some(adt_def) = tcx.type_of(candidate.def_id).skip_binder().ty_adt_def()
@@ -1442,7 +1442,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             if let Some(assoc) = self.associated_value(*def_id, item_ident) {
                                 // Check for both mode is the same so we avoid suggesting
                                 // incorrect associated item.
-                                match (mode, assoc.fn_has_self_parameter, source) {
+                                match (mode, assoc.is_method(), source) {
                                     (Mode::MethodCall, true, SelfSource::MethodCall(_)) => {
                                         // We check that the suggest type is actually
                                         // different from the received one
@@ -1834,7 +1834,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             let ty_args = self.infcx.fresh_args_for_item(span, similar_candidate.def_id);
             let fn_sig = tcx.fn_sig(similar_candidate.def_id).instantiate(tcx, ty_args);
             let fn_sig = self.instantiate_binder_with_fresh_vars(span, infer::FnCall, fn_sig);
-            if similar_candidate.fn_has_self_parameter {
+            if similar_candidate.is_method() {
                 if let Some(args) = args
                     && fn_sig.inputs()[1..].len() == args.len()
                 {
@@ -1902,7 +1902,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 {
                     if let Some(candidates) = find_attr!(self.tcx.get_all_attrs(inherent_method.def_id), AttributeKind::Confusables{symbols, ..} => symbols)
                         && candidates.contains(&item_name.name)
-                        && let ty::AssocKind::Fn = inherent_method.kind
+                        && inherent_method.is_fn()
                     {
                         let args =
                             ty::GenericArgs::identity_for_item(self.tcx, inherent_method.def_id)
@@ -2116,8 +2116,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             // Only assoc fn with no receivers and only if
             // they are resolvable
             .filter(|item| {
-                matches!(item.kind, ty::AssocKind::Fn)
-                    && !item.fn_has_self_parameter
+                matches!(item.kind, ty::AssocKind::Fn { has_self: false })
                     && self
                         .probe_for_name(
                             Mode::Path,
@@ -2261,7 +2260,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 };
 
                 let assoc = self.associated_value(assoc_did, item_name)?;
-                if assoc.kind != ty::AssocKind::Fn {
+                if !assoc.is_fn() {
                     return None;
                 }
 
@@ -3208,7 +3207,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     // If this method receives `&self`, then the provided
                     // argument _should_ coerce, so it's valid to suggest
                     // just changing the path.
-                    && pick.item.fn_has_self_parameter
+                    && pick.item.is_method()
                     && let Some(self_ty) =
                         self.tcx.fn_sig(pick.item.def_id).instantiate_identity().inputs().skip_binder().get(0)
                     && self_ty.is_ref()
@@ -3560,7 +3559,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             || (("Pin::new" == *pre)
                                 && ((sym::as_ref == item_name.name) || !unpin))
                             || inputs_len.is_some_and(|inputs_len| {
-                                pick.item.kind == ty::AssocKind::Fn
+                                pick.item.is_fn()
                                     && self
                                         .tcx
                                         .fn_sig(pick.item.def_id)
@@ -3618,7 +3617,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     && pick.autoderefs == 0
                     // Check that the method of the same name that was found on the new `Pin<T>`
                     // receiver has the same number of arguments that appear in the user's code.
-                    && inputs_len.is_some_and(|inputs_len| pick.item.kind == ty::AssocKind::Fn && self.tcx.fn_sig(pick.item.def_id).skip_binder().skip_binder().inputs().len() == inputs_len)
+                    && inputs_len.is_some_and(|inputs_len| pick.item.is_fn() && self.tcx.fn_sig(pick.item.def_id).skip_binder().skip_binder().inputs().len() == inputs_len)
                 {
                     let indent = self
                         .tcx
@@ -3756,7 +3755,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     && self
                         .associated_value(info.def_id, item_name)
                         .filter(|item| {
-                            if let ty::AssocKind::Fn = item.kind {
+                            if item.is_fn() {
                                 let id = item
                                     .def_id
                                     .as_local()
@@ -4279,13 +4278,13 @@ fn print_disambiguation_help<'tcx>(
     item: ty::AssocItem,
 ) -> Option<String> {
     let trait_impl_type = trait_ref.self_ty().peel_refs();
-    let trait_ref = if item.fn_has_self_parameter {
+    let trait_ref = if item.is_method() {
         trait_ref.print_only_trait_name().to_string()
     } else {
         format!("<{} as {}>", trait_ref.args[0], trait_ref.print_only_trait_name())
     };
     Some(
-        if matches!(item.kind, ty::AssocKind::Fn)
+        if item.is_fn()
             && let SelfSource::MethodCall(receiver) = source
             && let Some(args) = args
         {
@@ -4304,7 +4303,7 @@ fn print_disambiguation_help<'tcx>(
             let args = if let Some(first_arg_type) = first_arg_type
                 && (first_arg_type == tcx.types.self_param
                     || first_arg_type == trait_impl_type
-                    || item.fn_has_self_parameter)
+                    || item.is_method())
             {
                 Some(receiver)
             } else {
diff --git a/compiler/rustc_lint/src/context.rs b/compiler/rustc_lint/src/context.rs
index a2d5ffe256d..dd3c514704a 100644
--- a/compiler/rustc_lint/src/context.rs
+++ b/compiler/rustc_lint/src/context.rs
@@ -859,12 +859,7 @@ impl<'tcx> LateContext<'tcx> {
     ) -> Option<Ty<'tcx>> {
         let tcx = self.tcx;
         tcx.associated_items(trait_id)
-            .find_by_ident_and_kind(
-                tcx,
-                Ident::with_dummy_span(name),
-                ty::AssocKind::Type,
-                trait_id,
-            )
+            .find_by_ident_and_kind(tcx, Ident::with_dummy_span(name), ty::AssocTag::Type, trait_id)
             .and_then(|assoc| {
                 let proj = Ty::new_projection(tcx, assoc.def_id, [self_ty]);
                 tcx.try_normalize_erasing_regions(self.typing_env(), proj).ok()
diff --git a/compiler/rustc_metadata/src/rmeta/decoder.rs b/compiler/rustc_metadata/src/rmeta/decoder.rs
index 4cc12ca2e0b..cc3b2a241e4 100644
--- a/compiler/rustc_metadata/src/rmeta/decoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/decoder.rs
@@ -1337,10 +1337,12 @@ impl<'a> CrateMetadataRef<'a> {
         } else {
             self.item_name(id)
         };
-        let (kind, has_self) = match self.def_kind(id) {
-            DefKind::AssocConst => (ty::AssocKind::Const, false),
-            DefKind::AssocFn => (ty::AssocKind::Fn, self.get_fn_has_self_parameter(id, sess)),
-            DefKind::AssocTy => (ty::AssocKind::Type, false),
+        let kind = match self.def_kind(id) {
+            DefKind::AssocConst => ty::AssocKind::Const,
+            DefKind::AssocFn => {
+                ty::AssocKind::Fn { has_self: self.get_fn_has_self_parameter(id, sess) }
+            }
+            DefKind::AssocTy => ty::AssocKind::Type,
             _ => bug!("cannot get associated-item of `{:?}`", self.def_key(id)),
         };
         let container = self.root.tables.assoc_container.get(self, id).unwrap();
@@ -1353,7 +1355,6 @@ impl<'a> CrateMetadataRef<'a> {
             def_id: self.local_def_id(id),
             trait_item_def_id: self.get_trait_item_def_id(id),
             container,
-            fn_has_self_parameter: has_self,
             opt_rpitit_info,
         }
     }
diff --git a/compiler/rustc_metadata/src/rmeta/encoder.rs b/compiler/rustc_metadata/src/rmeta/encoder.rs
index 5c8e2888ec9..cc9da16ffdb 100644
--- a/compiler/rustc_metadata/src/rmeta/encoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/encoder.rs
@@ -1338,7 +1338,7 @@ fn should_encode_const(def_kind: DefKind) -> bool {
 fn should_encode_fn_impl_trait_in_trait<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> bool {
     if let Some(assoc_item) = tcx.opt_associated_item(def_id)
         && assoc_item.container == ty::AssocItemContainer::Trait
-        && assoc_item.kind == ty::AssocKind::Fn
+        && assoc_item.is_fn()
     {
         true
     } else {
diff --git a/compiler/rustc_middle/src/mir/mod.rs b/compiler/rustc_middle/src/mir/mod.rs
index 4dfb362f3a2..db19c858e7c 100644
--- a/compiler/rustc_middle/src/mir/mod.rs
+++ b/compiler/rustc_middle/src/mir/mod.rs
@@ -1636,8 +1636,8 @@ pub fn find_self_call<'tcx>(
         &body[block].terminator
         && let Operand::Constant(box ConstOperand { const_, .. }) = func
         && let ty::FnDef(def_id, fn_args) = *const_.ty().kind()
-        && let Some(ty::AssocItem { fn_has_self_parameter: true, .. }) =
-            tcx.opt_associated_item(def_id)
+        && let Some(item) = tcx.opt_associated_item(def_id)
+        && item.is_method()
         && let [Spanned { node: Operand::Move(self_place) | Operand::Copy(self_place), .. }, ..] =
             **args
     {
diff --git a/compiler/rustc_middle/src/ty/adjustment.rs b/compiler/rustc_middle/src/ty/adjustment.rs
index f8ab555305f..3425da48559 100644
--- a/compiler/rustc_middle/src/ty/adjustment.rs
+++ b/compiler/rustc_middle/src/ty/adjustment.rs
@@ -5,7 +5,7 @@ use rustc_hir::lang_items::LangItem;
 use rustc_macros::{HashStable, TyDecodable, TyEncodable, TypeFoldable, TypeVisitable};
 use rustc_span::Span;
 
-use crate::ty::{self, Ty, TyCtxt};
+use crate::ty::{Ty, TyCtxt};
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable)]
 pub enum PointerCoercion {
@@ -133,7 +133,7 @@ impl OverloadedDeref {
         };
         tcx.associated_items(trait_def_id)
             .in_definition_order()
-            .find(|m| m.kind == ty::AssocKind::Fn)
+            .find(|item| item.is_fn())
             .unwrap()
             .def_id
     }
diff --git a/compiler/rustc_middle/src/ty/assoc.rs b/compiler/rustc_middle/src/ty/assoc.rs
index bbaf735fbdb..3c1e5ed9e11 100644
--- a/compiler/rustc_middle/src/ty/assoc.rs
+++ b/compiler/rustc_middle/src/ty/assoc.rs
@@ -26,10 +26,6 @@ pub struct AssocItem {
     /// the associated item on the trait that this implements.
     pub trait_item_def_id: Option<DefId>,
 
-    /// Whether this is a method with an explicit self
-    /// as its first parameter, allowing method calls.
-    pub fn_has_self_parameter: bool,
-
     /// `Some` if the associated item (an associated type) comes from the
     /// return-position `impl Trait` in trait desugaring. The `ImplTraitInTraitData`
     /// provides additional information about its source.
@@ -78,7 +74,7 @@ impl AssocItem {
 
     pub fn signature(&self, tcx: TyCtxt<'_>) -> String {
         match self.kind {
-            ty::AssocKind::Fn => {
+            ty::AssocKind::Fn { .. } => {
                 // We skip the binder here because the binder would deanonymize all
                 // late-bound regions, and we don't want method signatures to show up
                 // `as for<'r> fn(&'r MyType)`. Pretty-printing handles late-bound
@@ -99,12 +95,28 @@ impl AssocItem {
     pub fn descr(&self) -> &'static str {
         match self.kind {
             ty::AssocKind::Const => "associated const",
-            ty::AssocKind::Fn if self.fn_has_self_parameter => "method",
-            ty::AssocKind::Fn => "associated function",
+            ty::AssocKind::Fn { has_self: true } => "method",
+            ty::AssocKind::Fn { has_self: false } => "associated function",
             ty::AssocKind::Type => "associated type",
         }
     }
 
+    pub fn is_fn(&self) -> bool {
+        matches!(self.kind, ty::AssocKind::Fn { .. })
+    }
+
+    pub fn is_method(&self) -> bool {
+        matches!(self.kind, ty::AssocKind::Fn { has_self: true })
+    }
+
+    pub fn as_tag(&self) -> AssocTag {
+        match self.kind {
+            AssocKind::Const => AssocTag::Const,
+            AssocKind::Fn { .. } => AssocTag::Fn,
+            AssocKind::Type => AssocTag::Type,
+        }
+    }
+
     pub fn is_impl_trait_in_trait(&self) -> bool {
         self.opt_rpitit_info.is_some()
     }
@@ -131,7 +143,7 @@ impl AssocItem {
 #[derive(Copy, Clone, PartialEq, Debug, HashStable, Eq, Hash, Encodable, Decodable)]
 pub enum AssocKind {
     Const,
-    Fn,
+    Fn { has_self: bool },
     Type,
 }
 
@@ -139,14 +151,14 @@ impl AssocKind {
     pub fn namespace(&self) -> Namespace {
         match *self {
             ty::AssocKind::Type => Namespace::TypeNS,
-            ty::AssocKind::Const | ty::AssocKind::Fn => Namespace::ValueNS,
+            ty::AssocKind::Const | ty::AssocKind::Fn { .. } => Namespace::ValueNS,
         }
     }
 
     pub fn as_def_kind(&self) -> DefKind {
         match self {
             AssocKind::Const => DefKind::AssocConst,
-            AssocKind::Fn => DefKind::AssocFn,
+            AssocKind::Fn { .. } => DefKind::AssocFn,
             AssocKind::Type => DefKind::AssocTy,
         }
     }
@@ -155,15 +167,22 @@ impl AssocKind {
 impl std::fmt::Display for AssocKind {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         match self {
-            // FIXME: fails to distinguish between "associated function" and
-            // "method" because `has_self` isn't known here.
-            AssocKind::Fn => write!(f, "method"),
+            AssocKind::Fn { has_self: true } => write!(f, "method"),
+            AssocKind::Fn { has_self: false } => write!(f, "associated function"),
             AssocKind::Const => write!(f, "associated const"),
             AssocKind::Type => write!(f, "associated type"),
         }
     }
 }
 
+// Like `AssocKind`, but just the tag, no fields. Used in various kinds of matching.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum AssocTag {
+    Const,
+    Fn,
+    Type,
+}
+
 /// A list of `ty::AssocItem`s in definition order that allows for efficient lookup by name.
 ///
 /// When doing lookup by name, we try to postpone hygienic comparison for as long as possible since
@@ -207,27 +226,14 @@ impl AssocItems {
         &self,
         tcx: TyCtxt<'_>,
         ident: Ident,
-        kind: AssocKind,
+        assoc_tag: AssocTag,
         parent_def_id: DefId,
     ) -> Option<&ty::AssocItem> {
         self.filter_by_name_unhygienic(ident.name)
-            .filter(|item| item.kind == kind)
+            .filter(|item| item.as_tag() == assoc_tag)
             .find(|item| tcx.hygienic_eq(ident, item.ident(tcx), parent_def_id))
     }
 
-    /// Returns the associated item with the given identifier and any of `AssocKind`, if one
-    /// exists. The identifier is matched hygienically.
-    pub fn find_by_ident_and_kinds(
-        &self,
-        tcx: TyCtxt<'_>,
-        ident: Ident,
-        // Sorted in order of what kinds to look at
-        kinds: &[AssocKind],
-        parent_def_id: DefId,
-    ) -> Option<&ty::AssocItem> {
-        kinds.iter().find_map(|kind| self.find_by_ident_and_kind(tcx, ident, *kind, parent_def_id))
-    }
-
     /// Returns the associated item with the given identifier in the given `Namespace`, if one
     /// exists. The identifier is matched hygienically.
     pub fn find_by_ident_and_namespace(
diff --git a/compiler/rustc_middle/src/ty/instance.rs b/compiler/rustc_middle/src/ty/instance.rs
index 07f2a602f2b..faad0a82acb 100644
--- a/compiler/rustc_middle/src/ty/instance.rs
+++ b/compiler/rustc_middle/src/ty/instance.rs
@@ -746,7 +746,7 @@ impl<'tcx> Instance<'tcx> {
         let call_once = tcx
             .associated_items(fn_once)
             .in_definition_order()
-            .find(|it| it.kind == ty::AssocKind::Fn)
+            .find(|it| it.is_fn())
             .unwrap()
             .def_id;
         let track_caller =
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index a2b3acac3f2..30c889c39d9 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -1464,7 +1464,7 @@ impl<'tcx> TyCtxt<'tcx> {
     pub fn provided_trait_methods(self, id: DefId) -> impl 'tcx + Iterator<Item = &'tcx AssocItem> {
         self.associated_items(id)
             .in_definition_order()
-            .filter(move |item| item.kind == AssocKind::Fn && item.defaultness(self).has_value())
+            .filter(move |item| item.is_fn() && item.defaultness(self).has_value())
     }
 
     pub fn repr_options_of_def(self, did: LocalDefId) -> ReprOptions {
diff --git a/compiler/rustc_middle/src/ty/util.rs b/compiler/rustc_middle/src/ty/util.rs
index 857b462b9eb..dfc11de283d 100644
--- a/compiler/rustc_middle/src/ty/util.rs
+++ b/compiler/rustc_middle/src/ty/util.rs
@@ -819,7 +819,7 @@ impl<'tcx> TyCtxt<'tcx> {
     /// Get an English description for the item's kind.
     pub fn def_kind_descr(self, def_kind: DefKind, def_id: DefId) -> &'static str {
         match def_kind {
-            DefKind::AssocFn if self.associated_item(def_id).fn_has_self_parameter => "method",
+            DefKind::AssocFn if self.associated_item(def_id).is_method() => "method",
             DefKind::Closure if let Some(coroutine_kind) = self.coroutine_kind(def_id) => {
                 match coroutine_kind {
                     hir::CoroutineKind::Desugared(
@@ -873,7 +873,7 @@ impl<'tcx> TyCtxt<'tcx> {
     /// Gets an English article for the [`TyCtxt::def_kind_descr`].
     pub fn def_kind_descr_article(self, def_kind: DefKind, def_id: DefId) -> &'static str {
         match def_kind {
-            DefKind::AssocFn if self.associated_item(def_id).fn_has_self_parameter => "a",
+            DefKind::AssocFn if self.associated_item(def_id).is_method() => "a",
             DefKind::Closure if let Some(coroutine_kind) = self.coroutine_kind(def_id) => {
                 match coroutine_kind {
                     hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::Async, ..) => "an",
diff --git a/compiler/rustc_mir_build/src/builder/matches/test.rs b/compiler/rustc_mir_build/src/builder/matches/test.rs
index d1f9d4c34fe..16da6092998 100644
--- a/compiler/rustc_mir_build/src/builder/matches/test.rs
+++ b/compiler/rustc_mir_build/src/builder/matches/test.rs
@@ -715,7 +715,7 @@ fn trait_method<'tcx>(
     let item = tcx
         .associated_items(trait_def_id)
         .filter_by_name_unhygienic(method_name)
-        .find(|item| item.kind == ty::AssocKind::Fn)
+        .find(|item| item.is_fn())
         .expect("trait method not found");
 
     let method_ty = Ty::new_fn_def(tcx, item.def_id, args);
diff --git a/compiler/rustc_mir_transform/src/shim.rs b/compiler/rustc_mir_transform/src/shim.rs
index c9771467e49..c13ffae3649 100644
--- a/compiler/rustc_mir_transform/src/shim.rs
+++ b/compiler/rustc_mir_transform/src/shim.rs
@@ -66,7 +66,7 @@ fn make_shim<'tcx>(tcx: TyCtxt<'tcx>, instance: ty::InstanceKind<'tcx>) -> Body<
             let call_mut = tcx
                 .associated_items(fn_mut)
                 .in_definition_order()
-                .find(|it| it.kind == ty::AssocKind::Fn)
+                .find(|it| it.is_fn())
                 .unwrap()
                 .def_id;
 
diff --git a/compiler/rustc_monomorphize/src/mono_checks/move_check.rs b/compiler/rustc_monomorphize/src/mono_checks/move_check.rs
index 55d52d5075d..7251ef478c6 100644
--- a/compiler/rustc_monomorphize/src/mono_checks/move_check.rs
+++ b/compiler/rustc_monomorphize/src/mono_checks/move_check.rs
@@ -3,7 +3,7 @@ use rustc_data_structures::fx::FxIndexSet;
 use rustc_hir::def_id::DefId;
 use rustc_middle::mir::visit::Visitor as MirVisitor;
 use rustc_middle::mir::{self, Location, traversal};
-use rustc_middle::ty::{self, AssocKind, Instance, Ty, TyCtxt, TypeFoldable};
+use rustc_middle::ty::{self, AssocTag, Instance, Ty, TyCtxt, TypeFoldable};
 use rustc_session::Limit;
 use rustc_session::lint::builtin::LARGE_ASSIGNMENTS;
 use rustc_span::source_map::Spanned;
@@ -194,7 +194,7 @@ fn assoc_fn_of_type<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId, fn_ident: Ident) ->
         if let Some(new) = tcx.associated_items(impl_def_id).find_by_ident_and_kind(
             tcx,
             fn_ident,
-            AssocKind::Fn,
+            AssocTag::Fn,
             def_id,
         ) {
             return Some(new.def_id);
diff --git a/compiler/rustc_resolve/src/late/diagnostics.rs b/compiler/rustc_resolve/src/late/diagnostics.rs
index c2761bd2717..ae81021e0be 100644
--- a/compiler/rustc_resolve/src/late/diagnostics.rs
+++ b/compiler/rustc_resolve/src/late/diagnostics.rs
@@ -1994,7 +1994,7 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
             .iter()
             .flat_map(|i| self.r.tcx.associated_items(i).in_definition_order())
             // Only assoc fn with no receivers.
-            .filter(|item| matches!(item.kind, ty::AssocKind::Fn) && !item.fn_has_self_parameter)
+            .filter(|item| item.is_fn() && !item.is_method())
             .filter_map(|item| {
                 // Only assoc fns that return `Self`
                 let fn_sig = self.r.tcx.fn_sig(item.def_id).skip_binder();
diff --git a/compiler/rustc_sanitizers/src/cfi/typeid/itanium_cxx_abi/transform.rs b/compiler/rustc_sanitizers/src/cfi/typeid/itanium_cxx_abi/transform.rs
index 129a32c6edd..718b9a4fa3b 100644
--- a/compiler/rustc_sanitizers/src/cfi/typeid/itanium_cxx_abi/transform.rs
+++ b/compiler/rustc_sanitizers/src/cfi/typeid/itanium_cxx_abi/transform.rs
@@ -446,7 +446,7 @@ pub(crate) fn transform_instance<'tcx>(
             let call = tcx
                 .associated_items(trait_id)
                 .in_definition_order()
-                .find(|it| it.kind == ty::AssocKind::Fn)
+                .find(|it| it.is_fn())
                 .expect("No call-family function on closure-like Fn trait?")
                 .def_id;
 
diff --git a/compiler/rustc_smir/src/rustc_smir/convert/ty.rs b/compiler/rustc_smir/src/rustc_smir/convert/ty.rs
index 28fc68d5e49..94f3be9fef7 100644
--- a/compiler/rustc_smir/src/rustc_smir/convert/ty.rs
+++ b/compiler/rustc_smir/src/rustc_smir/convert/ty.rs
@@ -896,9 +896,9 @@ impl<'tcx> Stable<'tcx> for ty::AssocKind {
 
     fn stable(&self, _tables: &mut Tables<'_>) -> Self::T {
         use stable_mir::ty::AssocKind;
-        match self {
+        match *self {
             ty::AssocKind::Const => AssocKind::Const,
-            ty::AssocKind::Fn => AssocKind::Fn,
+            ty::AssocKind::Fn { has_self } => AssocKind::Fn { has_self },
             ty::AssocKind::Type => AssocKind::Type,
         }
     }
@@ -926,7 +926,6 @@ impl<'tcx> Stable<'tcx> for ty::AssocItem {
             kind: self.kind.stable(tables),
             container: self.container.stable(tables),
             trait_item_def_id: self.trait_item_def_id.map(|did| tables.assoc_def(did)),
-            fn_has_self_parameter: self.fn_has_self_parameter,
             opt_rpitit_info: self.opt_rpitit_info.map(|rpitit| rpitit.stable(tables)),
         }
     }
diff --git a/compiler/rustc_smir/src/stable_mir/mir/pretty.rs b/compiler/rustc_smir/src/stable_mir/mir/pretty.rs
index 439ebe978e5..60d9e122940 100644
--- a/compiler/rustc_smir/src/stable_mir/mir/pretty.rs
+++ b/compiler/rustc_smir/src/stable_mir/mir/pretty.rs
@@ -22,7 +22,8 @@ impl Display for Ty {
 impl Display for AssocKind {
     fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
         match self {
-            AssocKind::Fn => write!(f, "method"),
+            AssocKind::Fn { has_self: true } => write!(f, "method"),
+            AssocKind::Fn { has_self: false } => write!(f, "associated function"),
             AssocKind::Const => write!(f, "associated const"),
             AssocKind::Type => write!(f, "associated type"),
         }
diff --git a/compiler/rustc_smir/src/stable_mir/ty.rs b/compiler/rustc_smir/src/stable_mir/ty.rs
index 3fcbbb0e138..63ce756162a 100644
--- a/compiler/rustc_smir/src/stable_mir/ty.rs
+++ b/compiler/rustc_smir/src/stable_mir/ty.rs
@@ -1586,10 +1586,6 @@ pub struct AssocItem {
     /// the associated item on the trait that this implements.
     pub trait_item_def_id: Option<AssocDef>,
 
-    /// Whether this is a method with an explicit self
-    /// as its first parameter, allowing method calls.
-    pub fn_has_self_parameter: bool,
-
     /// `Some` if the associated item (an associated type) comes from the
     /// return-position `impl Trait` in trait desugaring. The `ImplTraitInTraitData`
     /// provides additional information about its source.
@@ -1599,7 +1595,7 @@ pub struct AssocItem {
 #[derive(Clone, Debug, Eq, PartialEq, Serialize)]
 pub enum AssocKind {
     Const,
-    Fn,
+    Fn { has_self: bool },
     Type,
 }
 
diff --git a/compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs b/compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
index 40f8af1f691..cbadb46c17d 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
@@ -2334,7 +2334,7 @@ impl<'tcx> ObligationCause<'tcx> {
         subdiags: Vec<TypeErrorAdditionalDiags>,
     ) -> ObligationCauseFailureCode {
         match self.code() {
-            ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Fn, .. } => {
+            ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Fn { .. }, .. } => {
                 ObligationCauseFailureCode::MethodCompat { span, subdiags }
             }
             ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Type, .. } => {
@@ -2398,7 +2398,7 @@ impl<'tcx> ObligationCause<'tcx> {
 
     fn as_requirement_str(&self) -> &'static str {
         match self.code() {
-            ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Fn, .. } => {
+            ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Fn { .. }, .. } => {
                 "method type is compatible with trait"
             }
             ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Type, .. } => {
@@ -2422,7 +2422,9 @@ pub struct ObligationCauseAsDiagArg<'tcx>(pub ObligationCause<'tcx>);
 impl IntoDiagArg for ObligationCauseAsDiagArg<'_> {
     fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> rustc_errors::DiagArgValue {
         let kind = match self.0.code() {
-            ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Fn, .. } => "method_compat",
+            ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Fn { .. }, .. } => {
+                "method_compat"
+            }
             ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Type, .. } => "type_compat",
             ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Const, .. } => {
                 "const_compat"
diff --git a/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/trait_impl_difference.rs b/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/trait_impl_difference.rs
index 74205922851..b66bd2c6ab7 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/trait_impl_difference.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/trait_impl_difference.rs
@@ -98,7 +98,7 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
         let assoc_item = self.tcx().associated_item(trait_item_def_id);
         let mut visitor = TypeParamSpanVisitor { tcx: self.tcx(), types: vec![] };
         match assoc_item.kind {
-            ty::AssocKind::Fn => {
+            ty::AssocKind::Fn { .. } => {
                 if let Some(hir_id) =
                     assoc_item.def_id.as_local().map(|id| self.tcx().local_def_id_to_hir_id(id))
                 {
diff --git a/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/util.rs b/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/util.rs
index fd2d2fa7210..4a71ab4e06a 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/util.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/util.rs
@@ -158,6 +158,6 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
             && self
                 .tcx()
                 .opt_associated_item(scope_def_id.to_def_id())
-                .is_some_and(|i| i.fn_has_self_parameter)
+                .is_some_and(|i| i.is_method())
     }
 }
diff --git a/compiler/rustc_trait_selection/src/error_reporting/infer/note_and_explain.rs b/compiler/rustc_trait_selection/src/error_reporting/infer/note_and_explain.rs
index 5583deda99a..02f21b5465c 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/infer/note_and_explain.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/infer/note_and_explain.rs
@@ -782,7 +782,7 @@ fn foo(&self) -> Self::T { String::new() }
         let methods: Vec<(Span, String)> = items
             .in_definition_order()
             .filter(|item| {
-                ty::AssocKind::Fn == item.kind
+                item.is_fn()
                     && Some(item.name) != current_method_ident
                     && !tcx.is_doc_hidden(item.def_id)
             })
diff --git a/compiler/rustc_trait_selection/src/error_reporting/traits/ambiguity.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/ambiguity.rs
index 59c93db9c8f..e3e1583a48f 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/traits/ambiguity.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/traits/ambiguity.rs
@@ -349,7 +349,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                     {
                         let (verb, noun) = match self.tcx.associated_item(item_id).kind {
                             ty::AssocKind::Const => ("refer to the", "constant"),
-                            ty::AssocKind::Fn => ("call", "function"),
+                            ty::AssocKind::Fn { .. } => ("call", "function"),
                             // This is already covered by E0223, but this following single match
                             // arm doesn't hurt here.
                             ty::AssocKind::Type => ("refer to the", "type"),
diff --git a/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
index b963e4a2c7c..38aac8e70b5 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
@@ -5411,7 +5411,7 @@ fn point_at_assoc_type_restriction<G: EmissionGuarantee>(
                 tcx.associated_items(data.impl_or_alias_def_id).find_by_ident_and_kind(
                     tcx,
                     Ident::with_dummy_span(name),
-                    ty::AssocKind::Type,
+                    ty::AssocTag::Type,
                     data.impl_or_alias_def_id,
                 )
             {
diff --git a/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs b/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs
index bf9fcb0915a..76892db9ef7 100644
--- a/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs
+++ b/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs
@@ -301,7 +301,7 @@ pub fn dyn_compatibility_violations_for_assoc_item(
         ty::AssocKind::Const => {
             vec![DynCompatibilityViolation::AssocConst(item.name, item.ident(tcx).span)]
         }
-        ty::AssocKind::Fn => virtual_call_violations_for_method(tcx, trait_def_id, item)
+        ty::AssocKind::Fn { .. } => virtual_call_violations_for_method(tcx, trait_def_id, item)
             .into_iter()
             .map(|v| {
                 let node = tcx.hir_get_if_local(item.def_id);
@@ -344,7 +344,7 @@ fn virtual_call_violations_for_method<'tcx>(
     let sig = tcx.fn_sig(method.def_id).instantiate_identity();
 
     // The method's first parameter must be named `self`
-    if !method.fn_has_self_parameter {
+    if !method.is_method() {
         let sugg = if let Some(hir::Node::TraitItem(hir::TraitItem {
             generics,
             kind: hir::TraitItemKind::Fn(sig, _),
diff --git a/compiler/rustc_trait_selection/src/traits/vtable.rs b/compiler/rustc_trait_selection/src/traits/vtable.rs
index 165174c0bcc..3565c11249a 100644
--- a/compiler/rustc_trait_selection/src/traits/vtable.rs
+++ b/compiler/rustc_trait_selection/src/traits/vtable.rs
@@ -197,10 +197,8 @@ fn own_existential_vtable_entries_iter(
     tcx: TyCtxt<'_>,
     trait_def_id: DefId,
 ) -> impl Iterator<Item = DefId> {
-    let trait_methods = tcx
-        .associated_items(trait_def_id)
-        .in_definition_order()
-        .filter(|item| item.kind == ty::AssocKind::Fn);
+    let trait_methods =
+        tcx.associated_items(trait_def_id).in_definition_order().filter(|item| item.is_fn());
 
     // Now list each method's DefId (for within its trait).
     let own_entries = trait_methods.filter_map(move |&trait_method| {
diff --git a/compiler/rustc_ty_utils/src/assoc.rs b/compiler/rustc_ty_utils/src/assoc.rs
index 9520d948f51..79de071b687 100644
--- a/compiler/rustc_ty_utils/src/assoc.rs
+++ b/compiler/rustc_ty_utils/src/assoc.rs
@@ -129,10 +129,10 @@ fn associated_item(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::AssocItem {
 
 fn associated_item_from_trait_item_ref(trait_item_ref: &hir::TraitItemRef) -> ty::AssocItem {
     let owner_id = trait_item_ref.id.owner_id;
-    let (kind, has_self) = match trait_item_ref.kind {
-        hir::AssocItemKind::Const => (ty::AssocKind::Const, false),
-        hir::AssocItemKind::Fn { has_self } => (ty::AssocKind::Fn, has_self),
-        hir::AssocItemKind::Type => (ty::AssocKind::Type, false),
+    let kind = match trait_item_ref.kind {
+        hir::AssocItemKind::Const => ty::AssocKind::Const,
+        hir::AssocItemKind::Fn { has_self } => ty::AssocKind::Fn { has_self },
+        hir::AssocItemKind::Type => ty::AssocKind::Type,
     };
 
     ty::AssocItem {
@@ -141,17 +141,16 @@ fn associated_item_from_trait_item_ref(trait_item_ref: &hir::TraitItemRef) -> ty
         def_id: owner_id.to_def_id(),
         trait_item_def_id: Some(owner_id.to_def_id()),
         container: ty::AssocItemContainer::Trait,
-        fn_has_self_parameter: has_self,
         opt_rpitit_info: None,
     }
 }
 
 fn associated_item_from_impl_item_ref(impl_item_ref: &hir::ImplItemRef) -> ty::AssocItem {
     let def_id = impl_item_ref.id.owner_id;
-    let (kind, has_self) = match impl_item_ref.kind {
-        hir::AssocItemKind::Const => (ty::AssocKind::Const, false),
-        hir::AssocItemKind::Fn { has_self } => (ty::AssocKind::Fn, has_self),
-        hir::AssocItemKind::Type => (ty::AssocKind::Type, false),
+    let kind = match impl_item_ref.kind {
+        hir::AssocItemKind::Const => ty::AssocKind::Const,
+        hir::AssocItemKind::Fn { has_self } => ty::AssocKind::Fn { has_self },
+        hir::AssocItemKind::Type => ty::AssocKind::Type,
     };
 
     ty::AssocItem {
@@ -160,7 +159,6 @@ fn associated_item_from_impl_item_ref(impl_item_ref: &hir::ImplItemRef) -> ty::A
         def_id: def_id.to_def_id(),
         trait_item_def_id: impl_item_ref.trait_item_def_id,
         container: ty::AssocItemContainer::Impl,
-        fn_has_self_parameter: has_self,
         opt_rpitit_info: None,
     }
 }
@@ -269,7 +267,6 @@ fn associated_type_for_impl_trait_in_trait(
         def_id,
         trait_item_def_id: None,
         container: ty::AssocItemContainer::Trait,
-        fn_has_self_parameter: false,
         opt_rpitit_info: Some(ImplTraitInTraitData::Trait {
             fn_def_id: fn_def_id.to_def_id(),
             opaque_def_id: opaque_ty_def_id.to_def_id(),
@@ -322,7 +319,6 @@ fn associated_type_for_impl_trait_in_impl(
         def_id,
         trait_item_def_id: Some(trait_assoc_def_id),
         container: ty::AssocItemContainer::Impl,
-        fn_has_self_parameter: false,
         opt_rpitit_info: Some(ImplTraitInTraitData::Impl { fn_def_id: impl_fn_def_id.to_def_id() }),
     });
 
diff --git a/src/librustdoc/clean/inline.rs b/src/librustdoc/clean/inline.rs
index 3a2b6974681..2f6870e3c36 100644
--- a/src/librustdoc/clean/inline.rs
+++ b/src/librustdoc/clean/inline.rs
@@ -490,17 +490,17 @@ pub(crate) fn build_impl(
                         return true;
                     }
                     if let Some(associated_trait) = associated_trait {
-                        let assoc_kind = match item.kind {
-                            hir::ImplItemKind::Const(..) => ty::AssocKind::Const,
-                            hir::ImplItemKind::Fn(..) => ty::AssocKind::Fn,
-                            hir::ImplItemKind::Type(..) => ty::AssocKind::Type,
+                        let assoc_tag = match item.kind {
+                            hir::ImplItemKind::Const(..) => ty::AssocTag::Const,
+                            hir::ImplItemKind::Fn(..) => ty::AssocTag::Fn,
+                            hir::ImplItemKind::Type(..) => ty::AssocTag::Type,
                         };
                         let trait_item = tcx
                             .associated_items(associated_trait.def_id)
                             .find_by_ident_and_kind(
                                 tcx,
                                 item.ident,
-                                assoc_kind,
+                                assoc_tag,
                                 associated_trait.def_id,
                             )
                             .unwrap(); // SAFETY: For all impl items there exists trait item that has the same name.
@@ -527,7 +527,7 @@ pub(crate) fn build_impl(
                             .find_by_ident_and_kind(
                                 tcx,
                                 item.ident(tcx),
-                                item.kind,
+                                item.as_tag(),
                                 associated_trait.def_id,
                             )
                             .unwrap(); // corresponding associated item has to exist
diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index 45a915719e9..7cfd204aa13 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -1374,10 +1374,10 @@ pub(crate) fn clean_middle_assoc_item(assoc_item: &ty::AssocItem, cx: &mut DocCo
                 }
             }
         }
-        ty::AssocKind::Fn => {
+        ty::AssocKind::Fn { has_self } => {
             let mut item = inline::build_function(cx, assoc_item.def_id);
 
-            if assoc_item.fn_has_self_parameter {
+            if has_self {
                 let self_ty = match assoc_item.container {
                     ty::AssocItemContainer::Impl => {
                         tcx.type_of(assoc_item.container_id(tcx)).instantiate_identity()
diff --git a/src/tools/clippy/clippy_lints/src/bool_assert_comparison.rs b/src/tools/clippy/clippy_lints/src/bool_assert_comparison.rs
index ad18c7039ee..4a876b85416 100644
--- a/src/tools/clippy/clippy_lints/src/bool_assert_comparison.rs
+++ b/src/tools/clippy/clippy_lints/src/bool_assert_comparison.rs
@@ -56,7 +56,7 @@ fn is_impl_not_trait_with_bool_out<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -
             cx.tcx.associated_items(trait_id).find_by_ident_and_kind(
                 cx.tcx,
                 Ident::from_str("Output"),
-                ty::AssocKind::Type,
+                ty::AssocTag::Type,
                 trait_id,
             )
         })
diff --git a/src/tools/clippy/clippy_lints/src/len_zero.rs b/src/tools/clippy/clippy_lints/src/len_zero.rs
index b01929747d6..77085d52a32 100644
--- a/src/tools/clippy/clippy_lints/src/len_zero.rs
+++ b/src/tools/clippy/clippy_lints/src/len_zero.rs
@@ -13,7 +13,7 @@ use rustc_hir::{
     QPath, TraitItemRef, TyKind,
 };
 use rustc_lint::{LateContext, LateLintPass};
-use rustc_middle::ty::{self, AssocKind, FnSig, Ty};
+use rustc_middle::ty::{self, FnSig, Ty};
 use rustc_session::declare_lint_pass;
 use rustc_span::source_map::Spanned;
 use rustc_span::symbol::sym;
@@ -288,8 +288,7 @@ fn check_trait_items(cx: &LateContext<'_>, visited_trait: &Item<'_>, ident: Iden
             .items()
             .flat_map(|&i| cx.tcx.associated_items(i).filter_by_name_unhygienic(is_empty))
             .any(|i| {
-                i.kind == AssocKind::Fn
-                    && i.fn_has_self_parameter
+                i.is_method()
                     && cx.tcx.fn_sig(i.def_id).skip_binder().inputs().skip_binder().len() == 1
             });
 
@@ -466,7 +465,7 @@ fn check_for_is_empty(
         .inherent_impls(impl_ty)
         .iter()
         .flat_map(|&id| cx.tcx.associated_items(id).filter_by_name_unhygienic(is_empty))
-        .find(|item| item.kind == AssocKind::Fn);
+        .find(|item| item.is_fn());
 
     let (msg, is_empty_span, self_kind) = match is_empty {
         None => (
@@ -486,7 +485,7 @@ fn check_for_is_empty(
             None,
         ),
         Some(is_empty)
-            if !(is_empty.fn_has_self_parameter
+            if !(is_empty.is_method()
                 && check_is_empty_sig(
                     cx,
                     cx.tcx.fn_sig(is_empty.def_id).instantiate_identity().skip_binder(),
@@ -608,7 +607,7 @@ fn is_empty_array(expr: &Expr<'_>) -> bool {
 fn has_is_empty(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
     /// Gets an `AssocItem` and return true if it matches `is_empty(self)`.
     fn is_is_empty(cx: &LateContext<'_>, item: &ty::AssocItem) -> bool {
-        if item.kind == AssocKind::Fn {
+        if item.is_fn() {
             let sig = cx.tcx.fn_sig(item.def_id).skip_binder();
             let ty = sig.skip_binder();
             ty.inputs().len() == 1
diff --git a/src/tools/clippy/clippy_lints/src/methods/needless_collect.rs b/src/tools/clippy/clippy_lints/src/methods/needless_collect.rs
index 239ee6c729f..e4a29b6560e 100644
--- a/src/tools/clippy/clippy_lints/src/methods/needless_collect.rs
+++ b/src/tools/clippy/clippy_lints/src/methods/needless_collect.rs
@@ -17,7 +17,7 @@ use rustc_hir::{
 };
 use rustc_lint::LateContext;
 use rustc_middle::hir::nested_filter;
-use rustc_middle::ty::{self, AssocKind, ClauseKind, EarlyBinder, GenericArg, GenericArgKind, Ty};
+use rustc_middle::ty::{self, AssocTag, ClauseKind, EarlyBinder, GenericArg, GenericArgKind, Ty};
 use rustc_span::symbol::Ident;
 use rustc_span::{Span, sym};
 
@@ -241,7 +241,7 @@ fn is_contains_sig(cx: &LateContext<'_>, call_id: HirId, iter_expr: &Expr<'_>) -
         && let Some(iter_item) = cx.tcx.associated_items(iter_trait).find_by_ident_and_kind(
             cx.tcx,
             Ident::with_dummy_span(sym::Item),
-            AssocKind::Type,
+            AssocTag::Type,
             iter_trait,
         )
         && let args = cx.tcx.mk_args(&[GenericArg::from(typeck.expr_ty_adjusted(iter_expr))])
diff --git a/src/tools/clippy/clippy_lints/src/methods/or_fun_call.rs b/src/tools/clippy/clippy_lints/src/methods/or_fun_call.rs
index c03420a5143..6eeeea5d77c 100644
--- a/src/tools/clippy/clippy_lints/src/methods/or_fun_call.rs
+++ b/src/tools/clippy/clippy_lints/src/methods/or_fun_call.rs
@@ -78,7 +78,7 @@ pub(super) fn check<'tcx>(
                 .iter()
                 .flat_map(|impl_id| cx.tcx.associated_items(impl_id).filter_by_name_unhygienic(sugg))
                 .find_map(|assoc| {
-                    if assoc.fn_has_self_parameter
+                    if assoc.is_method()
                         && cx.tcx.fn_sig(assoc.def_id).skip_binder().inputs().skip_binder().len() == 1
                     {
                         Some(assoc.def_id)
diff --git a/src/tools/clippy/clippy_lints/src/needless_borrows_for_generic_args.rs b/src/tools/clippy/clippy_lints/src/needless_borrows_for_generic_args.rs
index f686cc912dd..e579dd5947d 100644
--- a/src/tools/clippy/clippy_lints/src/needless_borrows_for_generic_args.rs
+++ b/src/tools/clippy/clippy_lints/src/needless_borrows_for_generic_args.rs
@@ -299,7 +299,7 @@ fn has_ref_mut_self_method(cx: &LateContext<'_>, trait_def_id: DefId) -> bool {
         .associated_items(trait_def_id)
         .in_definition_order()
         .any(|assoc_item| {
-            if assoc_item.fn_has_self_parameter {
+            if assoc_item.is_method() {
                 let self_ty = cx
                     .tcx
                     .fn_sig(assoc_item.def_id)
diff --git a/src/tools/clippy/clippy_lints/src/same_name_method.rs b/src/tools/clippy/clippy_lints/src/same_name_method.rs
index 552135b15fd..ae677e110af 100644
--- a/src/tools/clippy/clippy_lints/src/same_name_method.rs
+++ b/src/tools/clippy/clippy_lints/src/same_name_method.rs
@@ -3,7 +3,6 @@ use rustc_data_structures::fx::FxHashMap;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::{HirId, Impl, ItemKind, Node, Path, QPath, TraitRef, TyKind};
 use rustc_lint::{LateContext, LateLintPass};
-use rustc_middle::ty::AssocKind;
 use rustc_session::declare_lint_pass;
 use rustc_span::Span;
 use rustc_span::symbol::Symbol;
@@ -85,7 +84,7 @@ impl<'tcx> LateLintPass<'tcx> for SameNameMethod {
                             cx.tcx
                                 .associated_items(did)
                                 .in_definition_order()
-                                .filter(|assoc_item| matches!(assoc_item.kind, AssocKind::Fn))
+                                .filter(|assoc_item| assoc_item.is_fn())
                                 .map(|assoc_item| assoc_item.name)
                                 .collect()
                         } else {
diff --git a/src/tools/clippy/clippy_lints/src/unconditional_recursion.rs b/src/tools/clippy/clippy_lints/src/unconditional_recursion.rs
index 51c7d6fce31..2104eb302ab 100644
--- a/src/tools/clippy/clippy_lints/src/unconditional_recursion.rs
+++ b/src/tools/clippy/clippy_lints/src/unconditional_recursion.rs
@@ -10,7 +10,7 @@ use rustc_hir::{Body, Expr, ExprKind, FnDecl, HirId, Item, ItemKind, Node, QPath
 use rustc_hir_analysis::lower_ty;
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::hir::nested_filter;
-use rustc_middle::ty::{self, AssocKind, Ty, TyCtxt};
+use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_session::impl_lint_pass;
 use rustc_span::symbol::{Ident, kw};
 use rustc_span::{Span, sym};
@@ -322,7 +322,7 @@ impl UnconditionalRecursion {
                             .in_definition_order()
                             // We're not interested in foreign implementations of the `Default` trait.
                             .find(|item| {
-                                item.kind == AssocKind::Fn && item.def_id.is_local() && item.name == kw::Default
+                                item.is_fn() && item.def_id.is_local() && item.name == kw::Default
                             })
                         && let Some(body_node) = cx.tcx.hir_get_if_local(assoc_item.def_id)
                         && let Some(body_id) = body_node.body_id()
diff --git a/src/tools/clippy/clippy_lints/src/unused_self.rs b/src/tools/clippy/clippy_lints/src/unused_self.rs
index 582aa6e6001..d0067b1a65e 100644
--- a/src/tools/clippy/clippy_lints/src/unused_self.rs
+++ b/src/tools/clippy/clippy_lints/src/unused_self.rs
@@ -74,7 +74,7 @@ impl<'tcx> LateLintPass<'tcx> for UnusedSelf {
             .is_some()
         };
         if let ItemKind::Impl(Impl { of_trait: None, .. }) = parent_item.kind
-            && assoc_item.fn_has_self_parameter
+            && assoc_item.is_method()
             && let ImplItemKind::Fn(.., body_id) = &impl_item.kind
             && (!cx.effective_visibilities.is_exported(impl_item.owner_id.def_id) || !self.avoid_breaking_exported_api)
             && let body = cx.tcx.hir_body(*body_id)
diff --git a/src/tools/clippy/clippy_utils/src/ty/mod.rs b/src/tools/clippy/clippy_utils/src/ty/mod.rs
index 3779e2f3062..d33e59342a5 100644
--- a/src/tools/clippy/clippy_utils/src/ty/mod.rs
+++ b/src/tools/clippy/clippy_utils/src/ty/mod.rs
@@ -19,7 +19,7 @@ use rustc_middle::mir::interpret::Scalar;
 use rustc_middle::traits::EvaluationResult;
 use rustc_middle::ty::layout::ValidityRequirement;
 use rustc_middle::ty::{
-    self, AdtDef, AliasTy, AssocItem, AssocKind, Binder, BoundRegion, FnSig, GenericArg, GenericArgKind,
+    self, AdtDef, AliasTy, AssocItem, AssocTag, Binder, BoundRegion, FnSig, GenericArg, GenericArgKind,
     GenericArgsRef, GenericParamDefKind, IntTy, ParamEnv, Region, RegionKind, TraitRef, Ty, TyCtxt, TypeSuperVisitable,
     TypeVisitable, TypeVisitableExt, TypeVisitor, UintTy, Upcast, VariantDef, VariantDiscr,
 };
@@ -1112,7 +1112,7 @@ pub fn make_projection<'tcx>(
         let Some(assoc_item) = tcx.associated_items(container_id).find_by_ident_and_kind(
             tcx,
             Ident::with_dummy_span(assoc_ty),
-            AssocKind::Type,
+            AssocTag::Type,
             container_id,
         ) else {
             debug_assert!(false, "type `{assoc_ty}` not found in `{container_id:?}`");
@@ -1345,7 +1345,7 @@ pub fn get_adt_inherent_method<'a>(cx: &'a LateContext<'_>, ty: Ty<'_>, method_n
                 .associated_items(did)
                 .filter_by_name_unhygienic(method_name)
                 .next()
-                .filter(|item| item.kind == AssocKind::Fn)
+                .filter(|item| item.as_tag() == AssocTag::Fn)
         })
     } else {
         None
diff --git a/tests/ui/generic-associated-types/impl_bounds.stderr b/tests/ui/generic-associated-types/impl_bounds.stderr
index 231c0dd89c5..7847bbd813c 100644
--- a/tests/ui/generic-associated-types/impl_bounds.stderr
+++ b/tests/ui/generic-associated-types/impl_bounds.stderr
@@ -57,14 +57,14 @@ note: required for `Fooy<T>` to implement `Copy`
    |
 LL | #[derive(Copy, Clone)]
    |          ^^^^ unsatisfied trait bound introduced in this `derive` macro
-note: the requirement `Fooy<T>: Copy` appears on the `impl`'s method `d` but not on the corresponding trait's method
+note: the requirement `Fooy<T>: Copy` appears on the `impl`'s associated function `d` but not on the corresponding trait's associated function
   --> $DIR/impl_bounds.rs:7:8
    |
 LL | trait Foo {
    |       --- in this trait
 ...
 LL |     fn d() where Self: Clone;
-   |        ^ this trait's method doesn't have the requirement `Fooy<T>: Copy`
+   |        ^ this trait's associated function doesn't have the requirement `Fooy<T>: Copy`
 help: consider restricting type parameter `T` with trait `Copy`
    |
 LL | impl<T: std::marker::Copy> Foo for Fooy<T> {
diff --git a/tests/ui/traits/next-solver/normalize/normalize-param-env-2.stderr b/tests/ui/traits/next-solver/normalize/normalize-param-env-2.stderr
index 74a0a90885d..d179c805962 100644
--- a/tests/ui/traits/next-solver/normalize/normalize-param-env-2.stderr
+++ b/tests/ui/traits/next-solver/normalize/normalize-param-env-2.stderr
@@ -4,14 +4,14 @@ error[E0275]: overflow evaluating the requirement `<() as A<T>>::Assoc: A<T>`
 LL |         Self::Assoc: A<T>,
    |                      ^^^^
    |
-note: the requirement `<() as A<T>>::Assoc: A<T>` appears on the `impl`'s method `f` but not on the corresponding trait's method
+note: the requirement `<() as A<T>>::Assoc: A<T>` appears on the `impl`'s associated function `f` but not on the corresponding trait's associated function
   --> $DIR/normalize-param-env-2.rs:12:8
    |
 LL | trait A<T> {
    |       - in this trait
 ...
 LL |     fn f()
-   |        ^ this trait's method doesn't have the requirement `<() as A<T>>::Assoc: A<T>`
+   |        ^ this trait's associated function doesn't have the requirement `<() as A<T>>::Assoc: A<T>`
 
 error[E0275]: overflow evaluating the requirement `<() as A<T>>::Assoc: A<T>`
   --> $DIR/normalize-param-env-2.rs:24:22