Move `opt_rpitit_info` field to `hir::AssocKind::Type`.

From `hir::AssocItem`.

28 files changed, 103 insertions, 91 deletions

diff --git a/compiler/rustc_hir_analysis/src/check/check.rs b/compiler/rustc_hir_analysis/src/check/check.rs
index c2706a1d401..12c36e0f4c2 100644
--- a/compiler/rustc_hir_analysis/src/check/check.rs
+++ b/compiler/rustc_hir_analysis/src/check/check.rs
@@ -449,7 +449,7 @@ fn best_definition_site_of_opaque<'tcx>(
                             return Some(span);
                         }
                     }
-                    ty::AssocKind::Type => {}
+                    ty::AssocKind::Type { .. } => {}
                 }
             }
 
@@ -740,7 +740,7 @@ pub(crate) fn check_item_type(tcx: TyCtxt<'_>, def_id: LocalDefId) {
 
             for &assoc_item in assoc_items.in_definition_order() {
                 match assoc_item.kind {
-                    ty::AssocKind::Type if assoc_item.defaultness(tcx).has_value() => {
+                    ty::AssocKind::Type { .. } if assoc_item.defaultness(tcx).has_value() => {
                         let trait_args = GenericArgs::identity_for_item(tcx, def_id);
                         let _: Result<_, rustc_errors::ErrorGuaranteed> = check_type_bounds(
                             tcx,
@@ -953,7 +953,7 @@ fn check_impl_items_against_trait<'tcx>(
                     );
                 }
                 ty::AssocKind::Const => {}
-                ty::AssocKind::Type => {}
+                ty::AssocKind::Type { .. } => {}
             }
         }
 
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 7dfdf1ae237..d208aa71971 100644
--- a/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
+++ b/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
@@ -44,7 +44,7 @@ pub(super) fn compare_impl_item(
 
     match impl_item.kind {
         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::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),
     }
 }
@@ -1703,7 +1703,7 @@ fn compare_generic_param_kinds<'tcx>(
     trait_item: ty::AssocItem,
     delay: bool,
 ) -> Result<(), ErrorGuaranteed> {
-    assert_eq!(impl_item.kind, trait_item.kind);
+    assert_eq!(impl_item.as_tag(), trait_item.as_tag());
 
     let ty_const_params_of = |def_id| {
         tcx.generics_of(def_id).own_params.iter().filter(|param| {
@@ -2235,16 +2235,19 @@ fn param_env_with_gat_bounds<'tcx>(
     // of the RPITITs associated with the same body. This is because checking
     // the item bounds of RPITITs often involves nested RPITITs having to prove
     // bounds about themselves.
-    let impl_tys_to_install = match impl_ty.opt_rpitit_info {
-        None => vec![impl_ty],
-        Some(
-            ty::ImplTraitInTraitData::Impl { fn_def_id }
-            | ty::ImplTraitInTraitData::Trait { fn_def_id, .. },
-        ) => tcx
+    let impl_tys_to_install = match impl_ty.kind {
+        ty::AssocKind::Type {
+            opt_rpitit_info:
+                Some(
+                    ty::ImplTraitInTraitData::Impl { fn_def_id }
+                    | ty::ImplTraitInTraitData::Trait { fn_def_id, .. },
+                ),
+        } => tcx
             .associated_types_for_impl_traits_in_associated_fn(fn_def_id)
             .iter()
             .map(|def_id| tcx.associated_item(*def_id))
             .collect(),
+        _ => vec![impl_ty],
     };
 
     for impl_ty in impl_tys_to_install {
diff --git a/compiler/rustc_hir_analysis/src/check/mod.rs b/compiler/rustc_hir_analysis/src/check/mod.rs
index 523db9440a4..ec934b1f620 100644
--- a/compiler/rustc_hir_analysis/src/check/mod.rs
+++ b/compiler/rustc_hir_analysis/src/check/mod.rs
@@ -499,7 +499,7 @@ fn suggestion_signature<'tcx>(
             tcx.predicates_of(assoc.def_id).instantiate_own(tcx, args),
             assoc,
         ),
-        ty::AssocKind::Type => {
+        ty::AssocKind::Type { .. } => {
             let (generics, where_clauses) = bounds_from_generic_predicates(
                 tcx,
                 tcx.predicates_of(assoc.def_id).instantiate_own(tcx, args),
diff --git a/compiler/rustc_hir_analysis/src/check/wfcheck.rs b/compiler/rustc_hir_analysis/src/check/wfcheck.rs
index af7830fd664..c6c370c4a84 100644
--- a/compiler/rustc_hir_analysis/src/check/wfcheck.rs
+++ b/compiler/rustc_hir_analysis/src/check/wfcheck.rs
@@ -408,7 +408,7 @@ fn check_gat_where_clauses(tcx: TyCtxt<'_>, trait_def_id: LocalDefId) {
             let gat_def_id = gat_item.def_id.expect_local();
             let gat_item = tcx.associated_item(gat_def_id);
             // If this item is not an assoc ty, or has no args, then it's not a GAT
-            if gat_item.kind != ty::AssocKind::Type {
+            if !gat_item.is_type() {
                 continue;
             }
             let gat_generics = tcx.generics_of(gat_def_id);
@@ -453,7 +453,7 @@ fn check_gat_where_clauses(tcx: TyCtxt<'_>, trait_def_id: LocalDefId) {
                         )
                     }
                     // In our example, this corresponds to the `Iter` and `Item` associated types
-                    ty::AssocKind::Type => {
+                    ty::AssocKind::Type { .. } => {
                         // If our associated item is a GAT with missing bounds, add them to
                         // the param-env here. This allows this GAT to propagate missing bounds
                         // to other GATs.
@@ -1101,7 +1101,7 @@ fn check_associated_item(
                 );
                 check_method_receiver(wfcx, hir_sig, item, self_ty)
             }
-            ty::AssocKind::Type => {
+            ty::AssocKind::Type { .. } => {
                 if let ty::AssocItemContainer::Trait = item.container {
                     check_associated_type_bounds(wfcx, item, span)
                 }
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 f0663644719..653adc6b3ba 100644
--- a/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs
+++ b/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs
@@ -36,7 +36,7 @@ pub(super) fn find_opaque_ty_constraints_for_impl_trait_in_assoc_type(
                 locator.check(assoc_id.expect_local())
             }
             // Associated types don't have bodies, so they can't constrain hidden types
-            ty::AssocKind::Type => {}
+            ty::AssocKind::Type { .. } => {}
         }
     }
 
diff --git a/compiler/rustc_hir_analysis/src/errors/wrong_number_of_generic_args.rs b/compiler/rustc_hir_analysis/src/errors/wrong_number_of_generic_args.rs
index 610b293a114..70d60bfcf2d 100644
--- a/compiler/rustc_hir_analysis/src/errors/wrong_number_of_generic_args.rs
+++ b/compiler/rustc_hir_analysis/src/errors/wrong_number_of_generic_args.rs
@@ -4,7 +4,7 @@ use GenericArgsInfo::*;
 use rustc_errors::codes::*;
 use rustc_errors::{Applicability, Diag, Diagnostic, EmissionGuarantee, MultiSpan, pluralize};
 use rustc_hir as hir;
-use rustc_middle::ty::{self as ty, AssocItems, AssocKind, TyCtxt};
+use rustc_middle::ty::{self as ty, AssocItems, TyCtxt};
 use rustc_span::def_id::DefId;
 use tracing::debug;
 
@@ -486,7 +486,7 @@ impl<'a, 'tcx> WrongNumberOfGenericArgs<'a, 'tcx> {
             let items: &AssocItems = self.tcx.associated_items(self.def_id);
             items
                 .in_definition_order()
-                .filter(|item| item.kind == AssocKind::Type)
+                .filter(|item| item.is_type())
                 .filter(|item| {
                     !self
                         .gen_args
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs
index e64cd8ec302..2e39beed8ae 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs
@@ -201,7 +201,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                             tcx.associated_items(pred.trait_ref.def_id)
                                 .in_definition_order()
                                 // We only care about associated types.
-                                .filter(|item| item.kind == ty::AssocKind::Type)
+                                .filter(|item| item.is_type())
                                 // No RPITITs -- they're not dyn-compatible for now.
                                 .filter(|item| !item.is_impl_trait_in_trait())
                                 // If the associated type has a `where Self: Sized` bound,
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 0fb406d9908..0394dd20e28 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
@@ -1733,7 +1733,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                         .any(|i| {
                             i.kind.namespace() == Namespace::TypeNS
                                 && i.ident(tcx).normalize_to_macros_2_0() == assoc_ident
-                                && matches!(i.kind, ty::AssocKind::Type)
+                                && i.is_type()
                         })
                     // Consider only accessible traits
                     && tcx.visibility(*trait_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 1ab36ce1dcb..127ca846b9f 100644
--- a/compiler/rustc_hir_analysis/src/impl_wf_check.rs
+++ b/compiler/rustc_hir_analysis/src/impl_wf_check.rs
@@ -112,7 +112,7 @@ pub(crate) fn enforce_impl_lifetime_params_are_constrained(
         .flat_map(|def_id| {
             let item = tcx.associated_item(def_id);
             match item.kind {
-                ty::AssocKind::Type => {
+                ty::AssocKind::Type { .. } => {
                     if item.defaultness(tcx).has_value() {
                         cgp::parameters_for(tcx, tcx.type_of(def_id).instantiate_identity(), true)
                     } else {
diff --git a/compiler/rustc_hir_typeck/src/method/probe.rs b/compiler/rustc_hir_typeck/src/method/probe.rs
index d5d85c812b2..07cb8c2a5bb 100644
--- a/compiler/rustc_hir_typeck/src/method/probe.rs
+++ b/compiler/rustc_hir_typeck/src/method/probe.rs
@@ -1671,15 +1671,7 @@ impl<'tcx> Pick<'tcx> {
     /// Do not use for type checking.
     pub(crate) fn differs_from(&self, other: &Self) -> bool {
         let Self {
-            item:
-                AssocItem {
-                    def_id,
-                    name: _,
-                    kind: _,
-                    container: _,
-                    trait_item_def_id: _,
-                    opt_rpitit_info: _,
-                },
+            item: AssocItem { def_id, name: _, kind: _, container: _, trait_item_def_id: _ },
             kind: _,
             import_ids: _,
             autoderefs: _,
@@ -2253,7 +2245,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
         match self.mode {
             Mode::MethodCall => item.is_method(),
             Mode::Path => match item.kind {
-                ty::AssocKind::Type => false,
+                ty::AssocKind::Type { .. } => false,
                 ty::AssocKind::Fn { .. } | ty::AssocKind::Const => true,
             },
         }
diff --git a/compiler/rustc_metadata/src/rmeta/decoder.rs b/compiler/rustc_metadata/src/rmeta/decoder.rs
index cc3b2a241e4..3cbe09280f6 100644
--- a/compiler/rustc_metadata/src/rmeta/decoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/decoder.rs
@@ -1342,12 +1342,17 @@ impl<'a> CrateMetadataRef<'a> {
             DefKind::AssocFn => {
                 ty::AssocKind::Fn { has_self: self.get_fn_has_self_parameter(id, sess) }
             }
-            DefKind::AssocTy => ty::AssocKind::Type,
+            DefKind::AssocTy => ty::AssocKind::Type {
+                opt_rpitit_info: self
+                    .root
+                    .tables
+                    .opt_rpitit_info
+                    .get(self, id)
+                    .map(|d| d.decode(self)),
+            },
             _ => bug!("cannot get associated-item of `{:?}`", self.def_key(id)),
         };
         let container = self.root.tables.assoc_container.get(self, id).unwrap();
-        let opt_rpitit_info =
-            self.root.tables.opt_rpitit_info.get(self, id).map(|d| d.decode(self));
 
         ty::AssocItem {
             name,
@@ -1355,7 +1360,6 @@ impl<'a> CrateMetadataRef<'a> {
             def_id: self.local_def_id(id),
             trait_item_def_id: self.get_trait_item_def_id(id),
             container,
-            opt_rpitit_info,
         }
     }
 
diff --git a/compiler/rustc_metadata/src/rmeta/encoder.rs b/compiler/rustc_metadata/src/rmeta/encoder.rs
index cc9da16ffdb..b900100c3c0 100644
--- a/compiler/rustc_metadata/src/rmeta/encoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/encoder.rs
@@ -1691,7 +1691,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
 
         match item.container {
             AssocItemContainer::Trait => {
-                if let ty::AssocKind::Type = item.kind {
+                if item.is_type() {
                     self.encode_explicit_item_bounds(def_id);
                     self.encode_explicit_item_self_bounds(def_id);
                     if tcx.is_conditionally_const(def_id) {
@@ -1706,7 +1706,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
                 }
             }
         }
-        if let Some(rpitit_info) = item.opt_rpitit_info {
+        if let ty::AssocKind::Type { opt_rpitit_info: Some(rpitit_info) } = item.kind {
             record!(self.tables.opt_rpitit_info[def_id] <- rpitit_info);
             if matches!(rpitit_info, ty::ImplTraitInTraitData::Trait { .. }) {
                 record_array!(
diff --git a/compiler/rustc_middle/src/ty/assoc.rs b/compiler/rustc_middle/src/ty/assoc.rs
index 3c1e5ed9e11..eac8f04f84f 100644
--- a/compiler/rustc_middle/src/ty/assoc.rs
+++ b/compiler/rustc_middle/src/ty/assoc.rs
@@ -25,11 +25,6 @@ pub struct AssocItem {
     /// If this is an item in an impl of a trait then this is the `DefId` of
     /// the associated item on the trait that this implements.
     pub trait_item_def_id: Option<DefId>,
-
-    /// `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.
-    pub opt_rpitit_info: Option<ty::ImplTraitInTraitData>,
 }
 
 impl AssocItem {
@@ -81,7 +76,7 @@ impl AssocItem {
                 // regions just fine, showing `fn(&MyType)`.
                 tcx.fn_sig(self.def_id).instantiate_identity().skip_binder().to_string()
             }
-            ty::AssocKind::Type => format!("type {};", self.name),
+            ty::AssocKind::Type { .. } => format!("type {};", self.name),
             ty::AssocKind::Const => {
                 format!(
                     "const {}: {:?};",
@@ -97,10 +92,14 @@ impl AssocItem {
             ty::AssocKind::Const => "associated const",
             ty::AssocKind::Fn { has_self: true } => "method",
             ty::AssocKind::Fn { has_self: false } => "associated function",
-            ty::AssocKind::Type => "associated type",
+            ty::AssocKind::Type { .. } => "associated type",
         }
     }
 
+    pub fn is_type(&self) -> bool {
+        matches!(self.kind, ty::AssocKind::Type { .. })
+    }
+
     pub fn is_fn(&self) -> bool {
         matches!(self.kind, ty::AssocKind::Fn { .. })
     }
@@ -113,12 +112,12 @@ impl AssocItem {
         match self.kind {
             AssocKind::Const => AssocTag::Const,
             AssocKind::Fn { .. } => AssocTag::Fn,
-            AssocKind::Type => AssocTag::Type,
+            AssocKind::Type { .. } => AssocTag::Type,
         }
     }
 
     pub fn is_impl_trait_in_trait(&self) -> bool {
-        self.opt_rpitit_info.is_some()
+        matches!(self.kind, AssocKind::Type { opt_rpitit_info: Some(_) })
     }
 
     /// Returns true if:
@@ -143,14 +142,21 @@ impl AssocItem {
 #[derive(Copy, Clone, PartialEq, Debug, HashStable, Eq, Hash, Encodable, Decodable)]
 pub enum AssocKind {
     Const,
-    Fn { has_self: bool },
-    Type,
+    Fn {
+        has_self: bool,
+    },
+    Type {
+        /// `Some` if the associated type comes from an RPITIT. The
+        /// `ImplTraitInTraitData` provides additional information about its
+        /// source.
+        opt_rpitit_info: Option<ty::ImplTraitInTraitData>,
+    },
 }
 
 impl AssocKind {
     pub fn namespace(&self) -> Namespace {
         match *self {
-            ty::AssocKind::Type => Namespace::TypeNS,
+            ty::AssocKind::Type { .. } => Namespace::TypeNS,
             ty::AssocKind::Const | ty::AssocKind::Fn { .. } => Namespace::ValueNS,
         }
     }
@@ -159,7 +165,7 @@ impl AssocKind {
         match self {
             AssocKind::Const => DefKind::AssocConst,
             AssocKind::Fn { .. } => DefKind::AssocFn,
-            AssocKind::Type => DefKind::AssocTy,
+            AssocKind::Type { .. } => DefKind::AssocTy,
         }
     }
 }
@@ -170,7 +176,7 @@ impl std::fmt::Display for AssocKind {
             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"),
+            AssocKind::Type { .. } => write!(f, "associated type"),
         }
     }
 }
diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
index abf6cbbcd87..fb25b8e130b 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -464,7 +464,7 @@ impl<'tcx> Interner for TyCtxt<'tcx> {
     fn associated_type_def_ids(self, def_id: DefId) -> impl IntoIterator<Item = DefId> {
         self.associated_items(def_id)
             .in_definition_order()
-            .filter(|assoc_item| matches!(assoc_item.kind, ty::AssocKind::Type))
+            .filter(|assoc_item| assoc_item.is_type())
             .map(|assoc_item| assoc_item.def_id)
     }
 
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index 30c889c39d9..395d2ec4814 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -1610,8 +1610,10 @@ impl<'tcx> TyCtxt<'tcx> {
     /// return-position `impl Trait` from a trait, then provide the source info
     /// about where that RPITIT came from.
     pub fn opt_rpitit_info(self, def_id: DefId) -> Option<ImplTraitInTraitData> {
-        if let DefKind::AssocTy = self.def_kind(def_id) {
-            self.associated_item(def_id).opt_rpitit_info
+        if let DefKind::AssocTy = self.def_kind(def_id)
+            && let AssocKind::Type { opt_rpitit_info } = self.associated_item(def_id).kind
+        {
+            opt_rpitit_info
         } else {
             None
         }
diff --git a/compiler/rustc_middle/src/ty/sty.rs b/compiler/rustc_middle/src/ty/sty.rs
index 27ee363f1c1..bb178fe4253 100644
--- a/compiler/rustc_middle/src/ty/sty.rs
+++ b/compiler/rustc_middle/src/ty/sty.rs
@@ -734,7 +734,7 @@ impl<'tcx> Ty<'tcx> {
                     .map(|principal| {
                         tcx.associated_items(principal.def_id())
                             .in_definition_order()
-                            .filter(|item| item.kind == ty::AssocKind::Type)
+                            .filter(|item| item.is_type())
                             .filter(|item| !item.is_impl_trait_in_trait())
                             .filter(|item| !tcx.generics_require_sized_self(item.def_id))
                             .count()
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 718b9a4fa3b..d2917478e4e 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
@@ -240,7 +240,7 @@ fn trait_object_ty<'tcx>(tcx: TyCtxt<'tcx>, poly_trait_ref: ty::PolyTraitRef<'tc
         .flat_map(|super_poly_trait_ref| {
             tcx.associated_items(super_poly_trait_ref.def_id())
                 .in_definition_order()
-                .filter(|item| item.kind == ty::AssocKind::Type)
+                .filter(|item| item.is_type())
                 .filter(|item| !tcx.generics_require_sized_self(item.def_id))
                 .map(move |assoc_ty| {
                     super_poly_trait_ref.map_bound(|super_trait_ref| {
diff --git a/compiler/rustc_smir/src/rustc_smir/convert/ty.rs b/compiler/rustc_smir/src/rustc_smir/convert/ty.rs
index 94f3be9fef7..55f698b8f21 100644
--- a/compiler/rustc_smir/src/rustc_smir/convert/ty.rs
+++ b/compiler/rustc_smir/src/rustc_smir/convert/ty.rs
@@ -894,12 +894,14 @@ impl<'tcx> Stable<'tcx> for rustc_session::cstore::ForeignModule {
 impl<'tcx> Stable<'tcx> for ty::AssocKind {
     type T = stable_mir::ty::AssocKind;
 
-    fn stable(&self, _tables: &mut Tables<'_>) -> Self::T {
+    fn stable(&self, tables: &mut Tables<'_>) -> Self::T {
         use stable_mir::ty::AssocKind;
         match *self {
             ty::AssocKind::Const => AssocKind::Const,
             ty::AssocKind::Fn { has_self } => AssocKind::Fn { has_self },
-            ty::AssocKind::Type => AssocKind::Type,
+            ty::AssocKind::Type { opt_rpitit_info } => AssocKind::Type {
+                opt_rpitit_info: opt_rpitit_info.map(|rpitit| rpitit.stable(tables)),
+            },
         }
     }
 }
@@ -926,7 +928,6 @@ 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)),
-            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 60d9e122940..9fa97763907 100644
--- a/compiler/rustc_smir/src/stable_mir/mir/pretty.rs
+++ b/compiler/rustc_smir/src/stable_mir/mir/pretty.rs
@@ -25,7 +25,7 @@ impl Display for AssocKind {
             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"),
+            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 63ce756162a..6eac0885d76 100644
--- a/compiler/rustc_smir/src/stable_mir/ty.rs
+++ b/compiler/rustc_smir/src/stable_mir/ty.rs
@@ -1585,18 +1585,20 @@ pub struct AssocItem {
     /// If this is an item in an impl of a trait then this is the `DefId` of
     /// the associated item on the trait that this implements.
     pub trait_item_def_id: Option<AssocDef>,
-
-    /// `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.
-    pub opt_rpitit_info: Option<ImplTraitInTraitData>,
 }
 
 #[derive(Clone, Debug, Eq, PartialEq, Serialize)]
 pub enum AssocKind {
     Const,
-    Fn { has_self: bool },
-    Type,
+    Fn {
+        has_self: bool,
+    },
+    Type {
+        /// `Some` if the associated type comes from an RPITIT. The
+        /// `ImplTraitInTraitData` provides additional information about its
+        /// source.
+        opt_rpitit_info: Option<ImplTraitInTraitData>,
+    },
 }
 
 #[derive(Clone, Debug, Eq, PartialEq, Serialize)]
@@ -1613,6 +1615,6 @@ pub enum ImplTraitInTraitData {
 
 impl AssocItem {
     pub fn is_impl_trait_in_trait(&self) -> bool {
-        self.opt_rpitit_info.is_some()
+        matches!(self.kind, AssocKind::Type { opt_rpitit_info: Some(_) })
     }
 }
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 cbadb46c17d..1c71fe028d4 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
@@ -2337,7 +2337,7 @@ impl<'tcx> ObligationCause<'tcx> {
             ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Fn { .. }, .. } => {
                 ObligationCauseFailureCode::MethodCompat { span, subdiags }
             }
-            ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Type, .. } => {
+            ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Type { .. }, .. } => {
                 ObligationCauseFailureCode::TypeCompat { span, subdiags }
             }
             ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Const, .. } => {
@@ -2401,7 +2401,7 @@ impl<'tcx> ObligationCause<'tcx> {
             ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Fn { .. }, .. } => {
                 "method type is compatible with trait"
             }
-            ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Type, .. } => {
+            ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Type { .. }, .. } => {
                 "associated type is compatible with trait"
             }
             ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Const, .. } => {
@@ -2425,7 +2425,9 @@ impl IntoDiagArg for ObligationCauseAsDiagArg<'_> {
             ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Fn { .. }, .. } => {
                 "method_compat"
             }
-            ObligationCauseCode::CompareImplItem { kind: ty::AssocKind::Type, .. } => "type_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/traits/ambiguity.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/ambiguity.rs
index e3e1583a48f..c4b0ca9cf8f 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/traits/ambiguity.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/traits/ambiguity.rs
@@ -352,7 +352,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                             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"),
+                            ty::AssocKind::Type { .. } => ("refer to the", "type"),
                         };
 
                         // Replace the more general E0283 with a more specific error
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 38aac8e70b5..084942cd8af 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
@@ -2112,7 +2112,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
         trait_ref: DefId,
     ) {
         if let Some(assoc_item) = self.tcx.opt_associated_item(item_def_id) {
-            if let ty::AssocKind::Const | ty::AssocKind::Type = assoc_item.kind {
+            if let ty::AssocKind::Const | ty::AssocKind::Type { .. } = assoc_item.kind {
                 err.note(format!(
                     "{}s cannot be accessed directly on a `trait`, they can only be \
                         accessed through a specific `impl`",
diff --git a/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs b/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs
index 76892db9ef7..1ef16f34702 100644
--- a/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs
+++ b/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs
@@ -188,7 +188,7 @@ fn bounds_reference_self(tcx: TyCtxt<'_>, trait_def_id: DefId) -> SmallVec<[Span
     tcx.associated_items(trait_def_id)
         .in_definition_order()
         // We're only looking at associated type bounds
-        .filter(|item| item.kind == ty::AssocKind::Type)
+        .filter(|item| item.is_type())
         // Ignore GATs with `Self: Sized`
         .filter(|item| !tcx.generics_require_sized_self(item.def_id))
         .flat_map(|item| tcx.explicit_item_bounds(item.def_id).iter_identity_copied())
@@ -320,7 +320,7 @@ pub fn dyn_compatibility_violations_for_assoc_item(
             })
             .collect(),
         // Associated types can only be dyn-compatible if they have `Self: Sized` bounds.
-        ty::AssocKind::Type => {
+        ty::AssocKind::Type { .. } => {
             if !tcx.generics_of(item.def_id).is_own_empty() && !item.is_impl_trait_in_trait() {
                 vec![DynCompatibilityViolation::GAT(item.name, item.ident(tcx).span)]
             } else {
diff --git a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
index 69e7b2a43ff..d71d1e9ae0f 100644
--- a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
@@ -594,9 +594,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             // Associated types that require `Self: Sized` do not show up in the built-in
             // implementation of `Trait for dyn Trait`, and can be dropped here.
             .filter(|item| !tcx.generics_require_sized_self(item.def_id))
-            .filter_map(
-                |item| if item.kind == ty::AssocKind::Type { Some(item.def_id) } else { None },
-            )
+            .filter_map(|item| if item.is_type() { Some(item.def_id) } else { None })
             .collect();
 
         for assoc_type in assoc_types {
diff --git a/compiler/rustc_ty_utils/src/assoc.rs b/compiler/rustc_ty_utils/src/assoc.rs
index 79de071b687..2275fbb9792 100644
--- a/compiler/rustc_ty_utils/src/assoc.rs
+++ b/compiler/rustc_ty_utils/src/assoc.rs
@@ -132,7 +132,7 @@ fn associated_item_from_trait_item_ref(trait_item_ref: &hir::TraitItemRef) -> ty
     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,
+        hir::AssocItemKind::Type => ty::AssocKind::Type { opt_rpitit_info: None },
     };
 
     ty::AssocItem {
@@ -141,7 +141,6 @@ 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,
-        opt_rpitit_info: None,
     }
 }
 
@@ -150,7 +149,7 @@ fn associated_item_from_impl_item_ref(impl_item_ref: &hir::ImplItemRef) -> ty::A
     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,
+        hir::AssocItemKind::Type => ty::AssocKind::Type { opt_rpitit_info: None },
     };
 
     ty::AssocItem {
@@ -159,7 +158,6 @@ 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,
-        opt_rpitit_info: None,
     }
 }
 
@@ -263,14 +261,15 @@ fn associated_type_for_impl_trait_in_trait(
 
     trait_assoc_ty.associated_item(ty::AssocItem {
         name: kw::Empty,
-        kind: ty::AssocKind::Type,
+        kind: ty::AssocKind::Type {
+            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(),
+            }),
+        },
         def_id,
         trait_item_def_id: None,
         container: ty::AssocItemContainer::Trait,
-        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(),
-        }),
     });
 
     // Copy visility of the containing function.
@@ -315,11 +314,14 @@ fn associated_type_for_impl_trait_in_impl(
 
     impl_assoc_ty.associated_item(ty::AssocItem {
         name: kw::Empty,
-        kind: ty::AssocKind::Type,
+        kind: ty::AssocKind::Type {
+            opt_rpitit_info: Some(ImplTraitInTraitData::Impl {
+                fn_def_id: impl_fn_def_id.to_def_id(),
+            }),
+        },
         def_id,
         trait_item_def_id: Some(trait_assoc_def_id),
         container: ty::AssocItemContainer::Impl,
-        opt_rpitit_info: Some(ImplTraitInTraitData::Impl { fn_def_id: impl_fn_def_id.to_def_id() }),
     });
 
     // Copy visility of the containing function.
diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index 7cfd204aa13..74dbc7d0600 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -1412,7 +1412,7 @@ pub(crate) fn clean_middle_assoc_item(assoc_item: &ty::AssocItem, cx: &mut DocCo
                 RequiredMethodItem(item)
             }
         }
-        ty::AssocKind::Type => {
+        ty::AssocKind::Type { .. } => {
             let my_name = assoc_item.name;
 
             fn param_eq_arg(param: &GenericParamDef, arg: &GenericArg) -> bool {
diff --git a/src/tools/clippy/clippy_lints/src/implied_bounds_in_impls.rs b/src/tools/clippy/clippy_lints/src/implied_bounds_in_impls.rs
index d02d9b2102b..430f2411183 100644
--- a/src/tools/clippy/clippy_lints/src/implied_bounds_in_impls.rs
+++ b/src/tools/clippy/clippy_lints/src/implied_bounds_in_impls.rs
@@ -315,7 +315,7 @@ fn check<'tcx>(cx: &LateContext<'tcx>, bounds: GenericBounds<'tcx>) {
                 assocs
                     .filter_by_name_unhygienic(constraint.ident.name)
                     .next()
-                    .is_some_and(|assoc| assoc.kind == ty::AssocKind::Type)
+                    .is_some_and(|assoc| assoc.is_type())
                 })
         {
             emit_lint(cx, poly_trait, bounds, index, implied_constraints, bound);