Remove DefId from AssocItemContainer.

40 files changed, 190 insertions, 220 deletions

diff --git a/compiler/rustc_const_eval/src/util/call_kind.rs b/compiler/rustc_const_eval/src/util/call_kind.rs
index a7a480dd1d7..af9d83f0609 100644
--- a/compiler/rustc_const_eval/src/util/call_kind.rs
+++ b/compiler/rustc_const_eval/src/util/call_kind.rs
@@ -66,9 +66,12 @@ pub fn call_kind<'tcx>(
     from_hir_call: bool,
     self_arg: Option<Ident>,
 ) -> CallKind<'tcx> {
-    let parent = tcx.opt_associated_item(method_did).and_then(|assoc| match assoc.container {
-        AssocItemContainer::ImplContainer(impl_did) => tcx.trait_id_of_impl(impl_did),
-        AssocItemContainer::TraitContainer(trait_did) => Some(trait_did),
+    let parent = tcx.opt_associated_item(method_did).and_then(|assoc| {
+        let container_id = assoc.container_id(tcx);
+        match assoc.container {
+            AssocItemContainer::ImplContainer => tcx.trait_id_of_impl(container_id),
+            AssocItemContainer::TraitContainer => Some(container_id),
+        }
     });
 
     let fn_call = parent
diff --git a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs
index 246d27be71c..9886c572a8a 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs
@@ -76,10 +76,11 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
                             "...is used and required to live as long as `'static` here \
                              because of an implicit lifetime bound on the {}",
                             match ctxt.assoc_item.container {
-                                AssocItemContainer::TraitContainer(id) =>
-                                    format!("`impl` of `{}`", tcx.def_path_str(id)),
-                                AssocItemContainer::ImplContainer(_) =>
-                                    "inherent `impl`".to_string(),
+                                AssocItemContainer::TraitContainer => {
+                                    let id = ctxt.assoc_item.container_id(tcx);
+                                    format!("`impl` of `{}`", tcx.def_path_str(id))
+                                }
+                                AssocItemContainer::ImplContainer => "inherent `impl`".to_string(),
                             },
                         ),
                     );
diff --git a/compiler/rustc_lint/src/nonstandard_style.rs b/compiler/rustc_lint/src/nonstandard_style.rs
index 33ac2ed02aa..8d04d68bf1c 100644
--- a/compiler/rustc_lint/src/nonstandard_style.rs
+++ b/compiler/rustc_lint/src/nonstandard_style.rs
@@ -22,8 +22,8 @@ pub fn method_context(cx: &LateContext<'_>, id: hir::HirId) -> MethodLateContext
     let def_id = cx.tcx.hir().local_def_id(id);
     let item = cx.tcx.associated_item(def_id);
     match item.container {
-        ty::TraitContainer(..) => MethodLateContext::TraitAutoImpl,
-        ty::ImplContainer(cid) => match cx.tcx.impl_trait_ref(cid) {
+        ty::TraitContainer => MethodLateContext::TraitAutoImpl,
+        ty::ImplContainer => match cx.tcx.impl_trait_ref(item.container_id(cx.tcx)) {
             Some(_) => MethodLateContext::TraitImpl,
             None => MethodLateContext::PlainImpl,
         },
diff --git a/compiler/rustc_metadata/src/rmeta/decoder.rs b/compiler/rustc_metadata/src/rmeta/decoder.rs
index 40f8da43c66..d8d2ac32c2f 100644
--- a/compiler/rustc_metadata/src/rmeta/decoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/decoder.rs
@@ -1114,7 +1114,7 @@ impl<'a, 'tcx> CrateMetadataRef<'a> {
 
     fn get_fn_has_self_parameter(self, id: DefIndex) -> bool {
         match self.kind(id) {
-            EntryKind::AssocFn(data) => data.decode(self).has_self,
+            EntryKind::AssocFn { has_self, .. } => has_self,
             _ => false,
         }
     }
@@ -1134,18 +1134,13 @@ impl<'a, 'tcx> CrateMetadataRef<'a> {
     }
 
     fn get_associated_item(self, id: DefIndex) -> ty::AssocItem {
-        let def_key = self.def_key(id);
-        let parent = self.local_def_id(def_key.parent.unwrap());
         let name = self.item_name(id);
 
         let (kind, container, has_self) = match self.kind(id) {
             EntryKind::AssocConst(container) => (ty::AssocKind::Const, container, false),
-            EntryKind::AssocFn(data) => {
-                let data = data.decode(self);
-                (ty::AssocKind::Fn, data.container, data.has_self)
-            }
+            EntryKind::AssocFn { container, has_self } => (ty::AssocKind::Fn, container, has_self),
             EntryKind::AssocType(container) => (ty::AssocKind::Type, container, false),
-            _ => bug!("cannot get associated-item of `{:?}`", def_key),
+            _ => bug!("cannot get associated-item of `{:?}`", id),
         };
 
         ty::AssocItem {
@@ -1153,7 +1148,7 @@ impl<'a, 'tcx> CrateMetadataRef<'a> {
             kind,
             def_id: self.local_def_id(id),
             trait_item_def_id: self.get_trait_item_def_id(id),
-            container: container.with_def_id(parent),
+            container,
             fn_has_self_parameter: has_self,
         }
     }
diff --git a/compiler/rustc_metadata/src/rmeta/encoder.rs b/compiler/rustc_metadata/src/rmeta/encoder.rs
index 1fbd6f3795f..33278367ce3 100644
--- a/compiler/rustc_metadata/src/rmeta/encoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/encoder.rs
@@ -1222,7 +1222,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
                     |s| s.print_trait_item(ast_item),
                 );
 
-                record!(self.tables.kind[def_id] <- EntryKind::AssocConst(AssocContainer::Trait));
+                record!(self.tables.kind[def_id] <- EntryKind::AssocConst(ty::AssocItemContainer::TraitContainer));
                 record!(self.tables.mir_const_qualif[def_id] <- mir::ConstQualifs::default());
                 record!(self.tables.rendered_const[def_id] <- rendered);
             }
@@ -1238,14 +1238,14 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
                 };
                 self.tables.asyncness.set(def_id.index, m_sig.header.asyncness);
                 self.tables.constness.set(def_id.index, hir::Constness::NotConst);
-                record!(self.tables.kind[def_id] <- EntryKind::AssocFn(self.lazy(AssocFnData {
-                    container:AssocContainer::Trait,
+                record!(self.tables.kind[def_id] <- EntryKind::AssocFn {
+                    container: ty::AssocItemContainer::TraitContainer,
                     has_self: trait_item.fn_has_self_parameter,
-                })));
+                });
             }
             ty::AssocKind::Type => {
                 self.encode_explicit_item_bounds(def_id);
-                record!(self.tables.kind[def_id] <- EntryKind::AssocType(AssocContainer::Trait));
+                record!(self.tables.kind[def_id] <- EntryKind::AssocType(ty::AssocItemContainer::TraitContainer));
             }
         }
         match trait_item.kind {
@@ -1277,7 +1277,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
                     let qualifs = self.tcx.at(ast_item.span).mir_const_qualif(def_id);
                     let const_data = self.encode_rendered_const_for_body(body_id);
 
-                    record!(self.tables.kind[def_id] <- EntryKind::AssocConst(AssocContainer::Impl));
+                    record!(self.tables.kind[def_id] <- EntryKind::AssocConst(ty::AssocItemContainer::ImplContainer));
                     record!(self.tables.mir_const_qualif[def_id] <- qualifs);
                     record!(self.tables.rendered_const[def_id] <- const_data);
                 } else {
@@ -1295,13 +1295,13 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
                     hir::Constness::NotConst
                 };
                 self.tables.constness.set(def_id.index, constness);
-                record!(self.tables.kind[def_id] <- EntryKind::AssocFn(self.lazy(AssocFnData {
-                    container:AssocContainer::Impl,
+                record!(self.tables.kind[def_id] <- EntryKind::AssocFn {
+                    container: ty::AssocItemContainer::ImplContainer,
                     has_self: impl_item.fn_has_self_parameter,
-                })));
+                });
             }
             ty::AssocKind::Type => {
-                record!(self.tables.kind[def_id] <- EntryKind::AssocType(AssocContainer::Impl));
+                record!(self.tables.kind[def_id] <- EntryKind::AssocType(ty::AssocItemContainer::ImplContainer));
             }
         }
         self.encode_item_type(def_id);
diff --git a/compiler/rustc_metadata/src/rmeta/mod.rs b/compiler/rustc_metadata/src/rmeta/mod.rs
index d93d6323475..66bdecc30db 100644
--- a/compiler/rustc_metadata/src/rmeta/mod.rs
+++ b/compiler/rustc_metadata/src/rmeta/mod.rs
@@ -419,9 +419,9 @@ enum EntryKind {
     Generator,
     Trait,
     Impl,
-    AssocFn(LazyValue<AssocFnData>),
-    AssocType(AssocContainer),
-    AssocConst(AssocContainer),
+    AssocFn { container: ty::AssocItemContainer, has_self: bool },
+    AssocType(ty::AssocItemContainer),
+    AssocConst(ty::AssocItemContainer),
     TraitAlias,
 }
 
@@ -434,30 +434,6 @@ struct VariantData {
     is_non_exhaustive: bool,
 }
 
-/// Describes whether the container of an associated item
-/// is a trait or an impl and whether, in a trait, it has
-/// a default, or an in impl, whether it's marked "default".
-#[derive(Copy, Clone, TyEncodable, TyDecodable)]
-enum AssocContainer {
-    Trait,
-    Impl,
-}
-
-impl AssocContainer {
-    fn with_def_id(&self, def_id: DefId) -> ty::AssocItemContainer {
-        match *self {
-            AssocContainer::Trait => ty::TraitContainer(def_id),
-            AssocContainer::Impl => ty::ImplContainer(def_id),
-        }
-    }
-}
-
-#[derive(MetadataEncodable, MetadataDecodable)]
-struct AssocFnData {
-    container: AssocContainer,
-    has_self: bool,
-}
-
 #[derive(TyEncodable, TyDecodable)]
 struct GeneratorData<'tcx> {
     layout: mir::GeneratorLayout<'tcx>,
@@ -475,7 +451,6 @@ pub fn provide(providers: &mut Providers) {
 
 trivially_parameterized_over_tcx! {
     VariantData,
-    AssocFnData,
     EntryKind,
     RawDefId,
     TraitImpls,
diff --git a/compiler/rustc_middle/src/ty/assoc.rs b/compiler/rustc_middle/src/ty/assoc.rs
index e18737c0d7c..c97156ac17f 100644
--- a/compiler/rustc_middle/src/ty/assoc.rs
+++ b/compiler/rustc_middle/src/ty/assoc.rs
@@ -1,6 +1,6 @@
 pub use self::AssocItemContainer::*;
 
-use crate::ty;
+use crate::ty::{self, DefIdTree};
 use rustc_data_structures::sorted_map::SortedIndexMultiMap;
 use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Namespace};
@@ -11,33 +11,8 @@ use super::{TyCtxt, Visibility};
 
 #[derive(Clone, Copy, PartialEq, Eq, Debug, HashStable, Hash, Encodable, Decodable)]
 pub enum AssocItemContainer {
-    TraitContainer(DefId),
-    ImplContainer(DefId),
-}
-
-impl AssocItemContainer {
-    pub fn impl_def_id(&self) -> Option<DefId> {
-        match *self {
-            ImplContainer(id) => Some(id),
-            _ => None,
-        }
-    }
-
-    /// Asserts that this is the `DefId` of an associated item declared
-    /// in a trait, and returns the trait `DefId`.
-    pub fn assert_trait(&self) -> DefId {
-        match *self {
-            TraitContainer(id) => id,
-            _ => bug!("associated item has wrong container type: {:?}", self),
-        }
-    }
-
-    pub fn id(&self) -> DefId {
-        match *self {
-            TraitContainer(id) => id,
-            ImplContainer(id) => id,
-        }
-    }
+    TraitContainer,
+    ImplContainer,
 }
 
 /// Information about an associated item
@@ -71,6 +46,27 @@ impl AssocItem {
         tcx.visibility(self.def_id)
     }
 
+    #[inline]
+    pub fn container_id(&self, tcx: TyCtxt<'_>) -> DefId {
+        tcx.parent(self.def_id)
+    }
+
+    #[inline]
+    pub fn trait_container(&self, tcx: TyCtxt<'_>) -> Option<DefId> {
+        match self.container {
+            AssocItemContainer::ImplContainer => None,
+            AssocItemContainer::TraitContainer => Some(tcx.parent(self.def_id)),
+        }
+    }
+
+    #[inline]
+    pub fn impl_container(&self, tcx: TyCtxt<'_>) -> Option<DefId> {
+        match self.container {
+            AssocItemContainer::ImplContainer => Some(tcx.parent(self.def_id)),
+            AssocItemContainer::TraitContainer => None,
+        }
+    }
+
     pub fn signature(&self, tcx: TyCtxt<'_>) -> String {
         match self.kind {
             ty::AssocKind::Fn => {
diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
index 541763e294f..0a0f45ce1a0 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -1668,8 +1668,7 @@ impl<'tcx> TyCtxt<'tcx> {
 
     // Checks if the bound region is in Impl Item.
     pub fn is_bound_region_in_impl_item(self, suitable_region_binding_scope: LocalDefId) -> bool {
-        let container_id =
-            self.associated_item(suitable_region_binding_scope.to_def_id()).container.id();
+        let container_id = self.parent(suitable_region_binding_scope.to_def_id());
         if self.impl_trait_ref(container_id).is_some() {
             // For now, we do not try to target impls of traits. This is
             // because this message is going to suggest that the user
diff --git a/compiler/rustc_middle/src/ty/error.rs b/compiler/rustc_middle/src/ty/error.rs
index 6fbe4ee8f7d..4b0bc3c1114 100644
--- a/compiler/rustc_middle/src/ty/error.rs
+++ b/compiler/rustc_middle/src/ty/error.rs
@@ -673,7 +673,7 @@ impl<T> Trait<T> for X {
             // the associated type or calling a method that returns the associated type".
             let point_at_assoc_fn = self.point_at_methods_that_satisfy_associated_type(
                 diag,
-                assoc.container.id(),
+                assoc.container_id(self),
                 current_method_ident,
                 proj_ty.item_def_id,
                 values.expected,
diff --git a/compiler/rustc_middle/src/ty/instance.rs b/compiler/rustc_middle/src/ty/instance.rs
index 33a46f809b0..53218225d53 100644
--- a/compiler/rustc_middle/src/ty/instance.rs
+++ b/compiler/rustc_middle/src/ty/instance.rs
@@ -460,7 +460,7 @@ impl<'tcx> Instance<'tcx> {
                             && !matches!(
                                 tcx.opt_associated_item(def.did),
                                 Some(ty::AssocItem {
-                                    container: ty::AssocItemContainer::TraitContainer(_),
+                                    container: ty::AssocItemContainer::TraitContainer,
                                     ..
                                 })
                             )
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index 96ce1fef77e..77c6c532f41 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -2194,10 +2194,7 @@ impl<'tcx> TyCtxt<'tcx> {
     /// If the given `DefId` describes a method belonging to an impl, returns the
     /// `DefId` of the impl that the method belongs to; otherwise, returns `None`.
     pub fn impl_of_method(self, def_id: DefId) -> Option<DefId> {
-        self.opt_associated_item(def_id).and_then(|trait_item| match trait_item.container {
-            TraitContainer(_) => None,
-            ImplContainer(def_id) => Some(def_id),
-        })
+        self.opt_associated_item(def_id).and_then(|trait_item| trait_item.impl_container(self))
     }
 
     /// If the given `DefId` belongs to a trait that was automatically derived, returns `true`.
diff --git a/compiler/rustc_middle/src/ty/sty.rs b/compiler/rustc_middle/src/ty/sty.rs
index 411d5c55829..fb0a4b4e8f4 100644
--- a/compiler/rustc_middle/src/ty/sty.rs
+++ b/compiler/rustc_middle/src/ty/sty.rs
@@ -1179,13 +1179,14 @@ pub struct ProjectionTy<'tcx> {
     /// The `DefId` of the `TraitItem` for the associated type `N`.
     ///
     /// Note that this is not the `DefId` of the `TraitRef` containing this
-    /// associated type, which is in `tcx.associated_item(item_def_id).container`.
+    /// associated type, which is in `tcx.associated_item(item_def_id).container`,
+    /// aka. `tcx.parent(item_def_id).unwrap()`.
     pub item_def_id: DefId,
 }
 
 impl<'tcx> ProjectionTy<'tcx> {
     pub fn trait_def_id(&self, tcx: TyCtxt<'tcx>) -> DefId {
-        tcx.associated_item(self.item_def_id).container.id()
+        tcx.parent(self.item_def_id)
     }
 
     /// Extracts the underlying trait reference and own substs from this projection.
@@ -1195,7 +1196,7 @@ impl<'tcx> ProjectionTy<'tcx> {
         &self,
         tcx: TyCtxt<'tcx>,
     ) -> (ty::TraitRef<'tcx>, &'tcx [ty::GenericArg<'tcx>]) {
-        let def_id = tcx.associated_item(self.item_def_id).container.id();
+        let def_id = tcx.parent(self.item_def_id);
         let trait_generics = tcx.generics_of(def_id);
         (
             ty::TraitRef { def_id, substs: self.substs.truncate_to(tcx, trait_generics) },
@@ -1433,7 +1434,7 @@ impl<'tcx> ExistentialProjection<'tcx> {
     /// then this function would return an `exists T. T: Iterator` existential trait
     /// reference.
     pub fn trait_ref(&self, tcx: TyCtxt<'tcx>) -> ty::ExistentialTraitRef<'tcx> {
-        let def_id = tcx.associated_item(self.item_def_id).container.id();
+        let def_id = tcx.parent(self.item_def_id);
         let subst_count = tcx.generics_of(def_id).count() - 1;
         let substs = tcx.intern_substs(&self.substs[..subst_count]);
         ty::ExistentialTraitRef { def_id, substs }
diff --git a/compiler/rustc_middle/src/ty/util.rs b/compiler/rustc_middle/src/ty/util.rs
index 4d2f69b23fa..4b5bf80c071 100644
--- a/compiler/rustc_middle/src/ty/util.rs
+++ b/compiler/rustc_middle/src/ty/util.rs
@@ -402,7 +402,7 @@ impl<'tcx> TyCtxt<'tcx> {
             Some(dtor) => dtor.did,
         };
 
-        let impl_def_id = self.associated_item(dtor).container.id();
+        let impl_def_id = self.parent(dtor);
         let impl_generics = self.generics_of(impl_def_id);
 
         // We have a destructor - all the parameters that are not
diff --git a/compiler/rustc_mir_build/src/lints.rs b/compiler/rustc_mir_build/src/lints.rs
index bc6241b3810..3a32fa310d4 100644
--- a/compiler/rustc_mir_build/src/lints.rs
+++ b/compiler/rustc_mir_build/src/lints.rs
@@ -4,7 +4,7 @@ use rustc_data_structures::graph::iterate::{
 use rustc_hir::def::DefKind;
 use rustc_middle::mir::{BasicBlock, BasicBlocks, Body, Operand, TerminatorKind};
 use rustc_middle::ty::subst::{GenericArg, InternalSubsts};
-use rustc_middle::ty::{self, AssocItem, AssocItemContainer, Instance, TyCtxt};
+use rustc_middle::ty::{self, Instance, TyCtxt};
 use rustc_session::lint::builtin::UNCONDITIONAL_RECURSION;
 use rustc_span::Span;
 use std::ops::ControlFlow;
@@ -14,11 +14,9 @@ pub(crate) fn check<'tcx>(tcx: TyCtxt<'tcx>, body: &Body<'tcx>) {
 
     if let DefKind::Fn | DefKind::AssocFn = tcx.def_kind(def_id) {
         // If this is trait/impl method, extract the trait's substs.
-        let trait_substs = match tcx.opt_associated_item(def_id.to_def_id()) {
-            Some(AssocItem {
-                container: AssocItemContainer::TraitContainer(trait_def_id), ..
-            }) => {
-                let trait_substs_count = tcx.generics_of(*trait_def_id).count();
+        let trait_substs = match tcx.trait_of_item(def_id) {
+            Some(trait_def_id) => {
+                let trait_substs_count = tcx.generics_of(trait_def_id).count();
                 &InternalSubsts::identity_for_item(tcx, def_id.to_def_id())[..trait_substs_count]
             }
             _ => &[],
diff --git a/compiler/rustc_privacy/src/lib.rs b/compiler/rustc_privacy/src/lib.rs
index ee9f10930c4..7d4ee832974 100644
--- a/compiler/rustc_privacy/src/lib.rs
+++ b/compiler/rustc_privacy/src/lib.rs
@@ -212,7 +212,7 @@ where
                 // `impl Pub<Priv> { pub fn my_method() {} }` is considered a private type,
                 // so we need to visit the self type additionally.
                 if let Some(assoc_item) = tcx.opt_associated_item(def_id) {
-                    if let ty::ImplContainer(impl_def_id) = assoc_item.container {
+                    if let Some(impl_def_id) = assoc_item.impl_container(tcx) {
                         tcx.type_of(impl_def_id).visit_with(self)?;
                     }
                 }
diff --git a/compiler/rustc_save_analysis/src/lib.rs b/compiler/rustc_save_analysis/src/lib.rs
index a8e392d692c..a1a2040bbca 100644
--- a/compiler/rustc_save_analysis/src/lib.rs
+++ b/compiler/rustc_save_analysis/src/lib.rs
@@ -564,8 +564,8 @@ impl<'tcx> SaveContext<'tcx> {
                     return None;
                 };
                 let (def_id, decl_id) = match self.tcx.associated_item(method_id).container {
-                    ty::ImplContainer(_) => (Some(method_id), None),
-                    ty::TraitContainer(_) => (None, Some(method_id)),
+                    ty::ImplContainer => (Some(method_id), None),
+                    ty::TraitContainer => (None, Some(method_id)),
                 };
                 let sub_span = seg.ident.span;
                 filter!(self.span_utils, sub_span);
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
index c3abb515b03..219413121d8 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
@@ -2714,7 +2714,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                 if let Some(ident) = self
                     .tcx
                     .opt_associated_item(trait_item_def_id)
-                    .and_then(|i| self.tcx.opt_item_ident(i.container.id()))
+                    .and_then(|i| self.tcx.opt_item_ident(i.container_id(self.tcx)))
                 {
                     assoc_span.push_span_label(ident.span, "in this trait");
                 }
diff --git a/compiler/rustc_trait_selection/src/traits/object_safety.rs b/compiler/rustc_trait_selection/src/traits/object_safety.rs
index 2921ce0ffef..612f5130908 100644
--- a/compiler/rustc_trait_selection/src/traits/object_safety.rs
+++ b/compiler/rustc_trait_selection/src/traits/object_safety.rs
@@ -690,7 +690,7 @@ fn receiver_is_dispatchable<'tcx>(
         // U: Trait<Arg1, ..., ArgN>
         let trait_predicate = {
             let substs =
-                InternalSubsts::for_item(tcx, method.container.assert_trait(), |param, _| {
+                InternalSubsts::for_item(tcx, method.trait_container(tcx).unwrap(), |param, _| {
                     if param.index == 0 {
                         unsized_self_ty.into()
                     } else {
diff --git a/compiler/rustc_trait_selection/src/traits/util.rs b/compiler/rustc_trait_selection/src/traits/util.rs
index e9bbc25d026..b9259196c48 100644
--- a/compiler/rustc_trait_selection/src/traits/util.rs
+++ b/compiler/rustc_trait_selection/src/traits/util.rs
@@ -359,7 +359,7 @@ pub fn generator_trait_ref_and_outputs<'tcx>(
 
 pub fn impl_item_is_final(tcx: TyCtxt<'_>, assoc_item: &ty::AssocItem) -> bool {
     assoc_item.defaultness(tcx).is_final()
-        && tcx.impl_defaultness(assoc_item.container.id()).is_final()
+        && tcx.impl_defaultness(assoc_item.container_id(tcx)).is_final()
 }
 
 pub enum TupleArgumentsFlag {
diff --git a/compiler/rustc_traits/src/chalk/db.rs b/compiler/rustc_traits/src/chalk/db.rs
index 497819ce5c5..14a60ace441 100644
--- a/compiler/rustc_traits/src/chalk/db.rs
+++ b/compiler/rustc_traits/src/chalk/db.rs
@@ -8,9 +8,7 @@
 
 use rustc_middle::traits::ChalkRustInterner as RustInterner;
 use rustc_middle::ty::subst::{InternalSubsts, Subst, SubstsRef};
-use rustc_middle::ty::{
-    self, AssocItemContainer, AssocKind, EarlyBinder, Ty, TyCtxt, TypeFoldable, TypeSuperFoldable,
-};
+use rustc_middle::ty::{self, AssocKind, EarlyBinder, Ty, TyCtxt, TypeFoldable, TypeSuperFoldable};
 
 use rustc_ast::ast;
 use rustc_attr as attr;
@@ -74,7 +72,7 @@ impl<'tcx> chalk_solve::RustIrDatabase<RustInterner<'tcx>> for RustIrDatabase<'t
     ) -> Arc<chalk_solve::rust_ir::AssociatedTyDatum<RustInterner<'tcx>>> {
         let def_id = assoc_type_id.0;
         let assoc_item = self.interner.tcx.associated_item(def_id);
-        let AssocItemContainer::TraitContainer(trait_def_id) = assoc_item.container else {
+        let Some(trait_def_id) = assoc_item.trait_container(self.interner.tcx) else {
             unimplemented!("Not possible??");
         };
         match assoc_item.kind {
@@ -455,7 +453,7 @@ impl<'tcx> chalk_solve::RustIrDatabase<RustInterner<'tcx>> for RustIrDatabase<'t
     ) -> Arc<chalk_solve::rust_ir::AssociatedTyValue<RustInterner<'tcx>>> {
         let def_id = associated_ty_id.0;
         let assoc_item = self.interner.tcx.associated_item(def_id);
-        let impl_id = assoc_item.container.id();
+        let impl_id = assoc_item.container_id(self.interner.tcx);
         match assoc_item.kind {
             AssocKind::Type => {}
             _ => unimplemented!("Not possible??"),
diff --git a/compiler/rustc_ty_utils/src/assoc.rs b/compiler/rustc_ty_utils/src/assoc.rs
index 64574ade2bb..db4f53aace4 100644
--- a/compiler/rustc_ty_utils/src/assoc.rs
+++ b/compiler/rustc_ty_utils/src/assoc.rs
@@ -1,6 +1,6 @@
 use rustc_data_structures::fx::FxHashMap;
 use rustc_hir as hir;
-use rustc_hir::def_id::{DefId, LocalDefId};
+use rustc_hir::def_id::DefId;
 use rustc_middle::ty::{self, TyCtxt};
 
 pub fn provide(providers: &mut ty::query::Providers) {
@@ -44,10 +44,7 @@ fn impl_item_implementor_ids(tcx: TyCtxt<'_>, impl_id: DefId) -> FxHashMap<DefId
 /// returns the `DefId` of the trait that the trait item belongs to;
 /// otherwise, returns `None`.
 fn trait_of_item(tcx: TyCtxt<'_>, def_id: DefId) -> Option<DefId> {
-    tcx.opt_associated_item(def_id).and_then(|associated_item| match associated_item.container {
-        ty::TraitContainer(def_id) => Some(def_id),
-        ty::ImplContainer(_) => None,
-    })
+    tcx.opt_associated_item(def_id).and_then(|associated_item| associated_item.trait_container(tcx))
 }
 
 fn associated_item(tcx: TyCtxt<'_>, def_id: DefId) -> ty::AssocItem {
@@ -59,7 +56,7 @@ fn associated_item(tcx: TyCtxt<'_>, def_id: DefId) -> ty::AssocItem {
             if let Some(impl_item_ref) =
                 impl_.items.iter().find(|i| i.id.def_id.to_def_id() == def_id)
             {
-                let assoc_item = associated_item_from_impl_item_ref(parent_def_id, impl_item_ref);
+                let assoc_item = associated_item_from_impl_item_ref(impl_item_ref);
                 debug_assert_eq!(assoc_item.def_id, def_id);
                 return assoc_item;
             }
@@ -69,7 +66,7 @@ fn associated_item(tcx: TyCtxt<'_>, def_id: DefId) -> ty::AssocItem {
             if let Some(trait_item_ref) =
                 trait_item_refs.iter().find(|i| i.id.def_id.to_def_id() == def_id)
             {
-                let assoc_item = associated_item_from_trait_item_ref(parent_def_id, trait_item_ref);
+                let assoc_item = associated_item_from_trait_item_ref(trait_item_ref);
                 debug_assert_eq!(assoc_item.def_id, def_id);
                 return assoc_item;
             }
@@ -85,10 +82,7 @@ fn associated_item(tcx: TyCtxt<'_>, def_id: DefId) -> ty::AssocItem {
     )
 }
 
-fn associated_item_from_trait_item_ref(
-    parent_def_id: LocalDefId,
-    trait_item_ref: &hir::TraitItemRef,
-) -> ty::AssocItem {
+fn associated_item_from_trait_item_ref(trait_item_ref: &hir::TraitItemRef) -> ty::AssocItem {
     let def_id = trait_item_ref.id.def_id;
     let (kind, has_self) = match trait_item_ref.kind {
         hir::AssocItemKind::Const => (ty::AssocKind::Const, false),
@@ -101,15 +95,12 @@ fn associated_item_from_trait_item_ref(
         kind,
         def_id: def_id.to_def_id(),
         trait_item_def_id: Some(def_id.to_def_id()),
-        container: ty::TraitContainer(parent_def_id.to_def_id()),
+        container: ty::TraitContainer,
         fn_has_self_parameter: has_self,
     }
 }
 
-fn associated_item_from_impl_item_ref(
-    parent_def_id: LocalDefId,
-    impl_item_ref: &hir::ImplItemRef,
-) -> ty::AssocItem {
+fn associated_item_from_impl_item_ref(impl_item_ref: &hir::ImplItemRef) -> ty::AssocItem {
     let def_id = impl_item_ref.id.def_id;
     let (kind, has_self) = match impl_item_ref.kind {
         hir::AssocItemKind::Const => (ty::AssocKind::Const, false),
@@ -122,7 +113,7 @@ fn associated_item_from_impl_item_ref(
         kind,
         def_id: def_id.to_def_id(),
         trait_item_def_id: impl_item_ref.trait_item_def_id,
-        container: ty::ImplContainer(parent_def_id.to_def_id()),
+        container: ty::ImplContainer,
         fn_has_self_parameter: has_self,
     }
 }
diff --git a/compiler/rustc_typeck/src/astconv/errors.rs b/compiler/rustc_typeck/src/astconv/errors.rs
index 99a8101dc96..ff39bf36129 100644
--- a/compiler/rustc_typeck/src/astconv/errors.rs
+++ b/compiler/rustc_typeck/src/astconv/errors.rs
@@ -255,7 +255,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                 trait_bound_spans.push(*span);
             }
             for assoc_item in items {
-                let trait_def_id = assoc_item.container.id();
+                let trait_def_id = assoc_item.container_id(tcx);
                 names.push(format!(
                     "`{}` (from trait `{}`)",
                     assoc_item.name,
@@ -321,7 +321,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
             let mut dupes = false;
             for item in assoc_items {
                 let prefix = if names[&item.name] > 1 {
-                    let trait_def_id = item.container.id();
+                    let trait_def_id = item.container_id(tcx);
                     dupes = true;
                     format!("{}::", tcx.def_path_str(trait_def_id))
                 } else {
@@ -376,7 +376,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                 let mut label = vec![];
                 for item in assoc_items {
                     let postfix = if names[&item.name] > 1 {
-                        let trait_def_id = item.container.id();
+                        let trait_def_id = item.container_id(tcx);
                         format!(" (from trait `{}`)", tcx.def_path_str(trait_def_id))
                     } else {
                         String::new()
diff --git a/compiler/rustc_typeck/src/astconv/mod.rs b/compiler/rustc_typeck/src/astconv/mod.rs
index 5026715804f..8a5c7fee697 100644
--- a/compiler/rustc_typeck/src/astconv/mod.rs
+++ b/compiler/rustc_typeck/src/astconv/mod.rs
@@ -1160,7 +1160,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                         span: binding.span,
                         prev_span: *prev_span,
                         item_name: binding.item_name,
-                        def_path: tcx.def_path_str(assoc_item.container.id()),
+                        def_path: tcx.def_path_str(assoc_item.container_id(tcx)),
                     });
                 })
                 .or_insert(binding.span);
diff --git a/compiler/rustc_typeck/src/check/compare_method.rs b/compiler/rustc_typeck/src/check/compare_method.rs
index e3ac23686b6..666498403c4 100644
--- a/compiler/rustc_typeck/src/check/compare_method.rs
+++ b/compiler/rustc_typeck/src/check/compare_method.rs
@@ -165,7 +165,7 @@ fn compare_predicate_entailment<'tcx>(
 
     // Create mapping from trait to placeholder.
     let trait_to_placeholder_substs =
-        impl_to_placeholder_substs.rebase_onto(tcx, impl_m.container.id(), trait_to_impl_substs);
+        impl_to_placeholder_substs.rebase_onto(tcx, impl_m.container_id(tcx), trait_to_impl_substs);
     debug!("compare_impl_method: trait_to_placeholder_substs={:?}", trait_to_placeholder_substs);
 
     let impl_m_generics = tcx.generics_of(impl_m.def_id);
@@ -511,8 +511,8 @@ fn compare_self_type<'tcx>(
 
     let self_string = |method: &ty::AssocItem| {
         let untransformed_self_ty = match method.container {
-            ty::ImplContainer(_) => impl_trait_ref.self_ty(),
-            ty::TraitContainer(_) => tcx.types.self_param,
+            ty::ImplContainer => impl_trait_ref.self_ty(),
+            ty::TraitContainer => tcx.types.self_param,
         };
         let self_arg_ty = tcx.fn_sig(method.def_id).input(0);
         let param_env = ty::ParamEnv::reveal_all();
@@ -1194,7 +1194,7 @@ fn compare_type_predicate_entailment<'tcx>(
 ) -> Result<(), ErrorGuaranteed> {
     let impl_substs = InternalSubsts::identity_for_item(tcx, impl_ty.def_id);
     let trait_to_impl_substs =
-        impl_substs.rebase_onto(tcx, impl_ty.container.id(), impl_trait_ref.substs);
+        impl_substs.rebase_onto(tcx, impl_ty.container_id(tcx), impl_trait_ref.substs);
 
     let impl_ty_generics = tcx.generics_of(impl_ty.def_id);
     let trait_ty_generics = tcx.generics_of(trait_ty.def_id);
@@ -1390,9 +1390,9 @@ pub fn check_type_bounds<'tcx>(
     });
     let bound_vars = tcx.mk_bound_variable_kinds(bound_vars.into_iter());
     let impl_ty_substs = tcx.intern_substs(&substs);
+    let container_id = impl_ty.container_id(tcx);
 
-    let rebased_substs =
-        impl_ty_substs.rebase_onto(tcx, impl_ty.container.id(), impl_trait_ref.substs);
+    let rebased_substs = impl_ty_substs.rebase_onto(tcx, container_id, impl_trait_ref.substs);
     let impl_ty_value = tcx.type_of(impl_ty.def_id);
 
     let param_env = tcx.param_env(impl_ty.def_id);
@@ -1441,8 +1441,7 @@ pub fn check_type_bounds<'tcx>(
     debug!(?normalize_param_env);
 
     let impl_ty_substs = InternalSubsts::identity_for_item(tcx, impl_ty.def_id);
-    let rebased_substs =
-        impl_ty_substs.rebase_onto(tcx, impl_ty.container.id(), impl_trait_ref.substs);
+    let rebased_substs = impl_ty_substs.rebase_onto(tcx, container_id, impl_trait_ref.substs);
 
     tcx.infer_ctxt().enter(move |infcx| {
         let ocx = ObligationCtxt::new(&infcx);
@@ -1505,10 +1504,13 @@ pub fn check_type_bounds<'tcx>(
         // Finally, resolve all regions. This catches wily misuses of
         // lifetime parameters.
         let implied_bounds = match impl_ty.container {
-            ty::TraitContainer(_) => FxHashSet::default(),
-            ty::ImplContainer(def_id) => {
-                wfcheck::impl_implied_bounds(tcx, param_env, def_id.expect_local(), impl_ty_span)
-            }
+            ty::TraitContainer => FxHashSet::default(),
+            ty::ImplContainer => wfcheck::impl_implied_bounds(
+                tcx,
+                param_env,
+                container_id.expect_local(),
+                impl_ty_span,
+            ),
         };
         let mut outlives_environment = OutlivesEnvironment::new(param_env);
         outlives_environment.add_implied_bounds(&infcx, implied_bounds, impl_ty_hir_id);
diff --git a/compiler/rustc_typeck/src/check/demand.rs b/compiler/rustc_typeck/src/check/demand.rs
index f0110645551..4de48dc5ba1 100644
--- a/compiler/rustc_typeck/src/check/demand.rs
+++ b/compiler/rustc_typeck/src/check/demand.rs
@@ -775,7 +775,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             self.typeck_results.borrow().type_dependent_def_id(expr.hir_id).map(
                                 |did| {
                                     let ai = self.tcx.associated_item(did);
-                                    ai.container == ty::TraitContainer(clone_trait)
+                                    ai.trait_container(self.tcx) == Some(clone_trait)
                                 },
                             ),
                             segment.ident.name,
diff --git a/compiler/rustc_typeck/src/check/fn_ctxt/_impl.rs b/compiler/rustc_typeck/src/check/fn_ctxt/_impl.rs
index 22087219667..3a809334511 100644
--- a/compiler/rustc_typeck/src/check/fn_ctxt/_impl.rs
+++ b/compiler/rustc_typeck/src/check/fn_ctxt/_impl.rs
@@ -1090,13 +1090,15 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 is_alias_variant_ctor = true;
             }
             Res::Def(DefKind::AssocFn | DefKind::AssocConst, def_id) => {
-                let container = tcx.associated_item(def_id).container;
-                debug!(?def_id, ?container);
+                let assoc_item = tcx.associated_item(def_id);
+                let container = assoc_item.container;
+                let container_id = assoc_item.container_id(tcx);
+                debug!(?def_id, ?container, ?container_id);
                 match container {
-                    ty::TraitContainer(trait_did) => {
-                        callee::check_legal_trait_for_method_call(tcx, span, None, span, trait_did)
+                    ty::TraitContainer => {
+                        callee::check_legal_trait_for_method_call(tcx, span, None, span, container_id)
                     }
-                    ty::ImplContainer(impl_def_id) => {
+                    ty::ImplContainer => {
                         if segments.len() == 1 {
                             // `<T>::assoc` will end up here, and so
                             // can `T::assoc`. It this came from an
@@ -1104,7 +1106,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             // `T` for posterity (see `UserSelfTy` for
                             // details).
                             let self_ty = self_ty.expect("UFCS sugared assoc missing Self");
-                            user_self_ty = Some(UserSelfTy { impl_def_id, self_ty });
+                            user_self_ty = Some(UserSelfTy { impl_def_id: container_id, self_ty });
                         }
                     }
                 }
diff --git a/compiler/rustc_typeck/src/check/fn_ctxt/suggestions.rs b/compiler/rustc_typeck/src/check/fn_ctxt/suggestions.rs
index 097fff6418e..57771e0969b 100644
--- a/compiler/rustc_typeck/src/check/fn_ctxt/suggestions.rs
+++ b/compiler/rustc_typeck/src/check/fn_ctxt/suggestions.rs
@@ -839,8 +839,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             && results.type_dependent_def_id(expr.hir_id).map_or(
                 false,
                 |did| {
-                    self.tcx.associated_item(did).container
-                        == ty::AssocItemContainer::TraitContainer(clone_trait_did)
+                    let assoc_item = self.tcx.associated_item(did);
+                    assoc_item.container == ty::AssocItemContainer::TraitContainer
+                        && assoc_item.container_id(self.tcx) == clone_trait_did
                 },
             )
             // If that clone call hasn't already dereferenced the self type (i.e. don't give this
diff --git a/compiler/rustc_typeck/src/check/method/confirm.rs b/compiler/rustc_typeck/src/check/method/confirm.rs
index b14f3d6de4e..2c89b63ae84 100644
--- a/compiler/rustc_typeck/src/check/method/confirm.rs
+++ b/compiler/rustc_typeck/src/check/method/confirm.rs
@@ -238,7 +238,7 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
     ) -> SubstsRef<'tcx> {
         match pick.kind {
             probe::InherentImplPick => {
-                let impl_def_id = pick.item.container.id();
+                let impl_def_id = pick.item.container_id(self.tcx);
                 assert!(
                     self.tcx.impl_trait_ref(impl_def_id).is_none(),
                     "impl {:?} is not an inherent impl",
@@ -248,7 +248,7 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
             }
 
             probe::ObjectPick => {
-                let trait_def_id = pick.item.container.id();
+                let trait_def_id = pick.item.container_id(self.tcx);
                 self.extract_existential_trait_ref(self_ty, |this, object_ty, principal| {
                     // The object data has no entry for the Self
                     // Type. For the purposes of this method call, we
@@ -273,7 +273,7 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
             }
 
             probe::TraitPick => {
-                let trait_def_id = pick.item.container.id();
+                let trait_def_id = pick.item.container_id(self.tcx);
 
                 // Make a trait reference `$0 : Trait<$1...$n>`
                 // consisting entirely of type variables. Later on in
@@ -540,15 +540,14 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
 
     fn enforce_illegal_method_limitations(&self, pick: &probe::Pick<'_>) {
         // Disallow calls to the method `drop` defined in the `Drop` trait.
-        match pick.item.container {
-            ty::TraitContainer(trait_def_id) => callee::check_legal_trait_for_method_call(
+        if let Some(trait_def_id) = pick.item.trait_container(self.tcx) {
+            callee::check_legal_trait_for_method_call(
                 self.tcx,
                 self.span,
                 Some(self.self_expr.span),
                 self.call_expr.span,
                 trait_def_id,
-            ),
-            ty::ImplContainer(..) => {}
+            )
         }
     }
 
diff --git a/compiler/rustc_typeck/src/check/method/mod.rs b/compiler/rustc_typeck/src/check/method/mod.rs
index c09f63f1e8f..0e678c41f8b 100644
--- a/compiler/rustc_typeck/src/check/method/mod.rs
+++ b/compiler/rustc_typeck/src/check/method/mod.rs
@@ -231,7 +231,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 ProbeScope::AllTraits,
             ) {
                 // If we find a different result the caller probably forgot to import a trait.
-                Ok(ref new_pick) if *new_pick != pick => vec![new_pick.item.container.id()],
+                Ok(ref new_pick) if *new_pick != pick => vec![new_pick.item.container_id(self.tcx)],
                 Err(Ambiguity(ref sources)) => sources
                     .iter()
                     .filter_map(|source| {
diff --git a/compiler/rustc_typeck/src/check/method/prelude2021.rs b/compiler/rustc_typeck/src/check/method/prelude2021.rs
index a2f1f5692c7..7c68d930405 100644
--- a/compiler/rustc_typeck/src/check/method/prelude2021.rs
+++ b/compiler/rustc_typeck/src/check/method/prelude2021.rs
@@ -148,7 +148,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     let trait_name = self.trait_path_or_bare_name(
                         span,
                         call_expr.hir_id,
-                        pick.item.container.id(),
+                        pick.item.container_id(self.tcx),
                     );
 
                     let mut lint = lint.build(&format!(
@@ -261,8 +261,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         self.tcx.struct_span_lint_hir(RUST_2021_PRELUDE_COLLISIONS, expr_id, span, |lint| {
             // "type" refers to either a type or, more likely, a trait from which
             // the associated function or method is from.
-            let trait_path = self.trait_path_or_bare_name(span, expr_id, pick.item.container.id());
-            let trait_generics = self.tcx.generics_of(pick.item.container.id());
+            let container_id = pick.item.container_id(self.tcx);
+            let trait_path = self.trait_path_or_bare_name(span, expr_id, container_id);
+            let trait_generics = self.tcx.generics_of(container_id);
 
             let trait_name =
                 if trait_generics.params.len() <= trait_generics.has_self as usize {
diff --git a/compiler/rustc_typeck/src/check/method/probe.rs b/compiler/rustc_typeck/src/check/method/probe.rs
index 3771920d6b5..efe15fec7cb 100644
--- a/compiler/rustc_typeck/src/check/method/probe.rs
+++ b/compiler/rustc_typeck/src/check/method/probe.rs
@@ -592,8 +592,10 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
     fn push_candidate(&mut self, candidate: Candidate<'tcx>, is_inherent: bool) {
         let is_accessible = if let Some(name) = self.method_name {
             let item = candidate.item;
-            let def_scope =
-                self.tcx.adjust_ident_and_get_scope(name, item.container.id(), self.body_id).1;
+            let def_scope = self
+                .tcx
+                .adjust_ident_and_get_scope(name, item.container_id(self.tcx), self.body_id)
+                .1;
             item.visibility(self.tcx).is_accessible_from(def_scope, self.tcx)
         } else {
             true
@@ -1025,7 +1027,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
         self.assemble_extension_candidates_for_all_traits();
 
         let out_of_scope_traits = match self.pick_core() {
-            Some(Ok(p)) => vec![p.item.container.id()],
+            Some(Ok(p)) => vec![p.item.container_id(self.tcx)],
             //Some(Ok(p)) => p.iter().map(|p| p.item.container().id()).collect(),
             Some(Err(MethodError::Ambiguity(v))) => v
                 .into_iter()
@@ -1387,7 +1389,8 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                             self.tcx.def_path_str(stable_pick.item.def_id),
                         ));
                     }
-                    (ty::AssocKind::Const, ty::AssocItemContainer::TraitContainer(def_id)) => {
+                    (ty::AssocKind::Const, ty::AssocItemContainer::TraitContainer) => {
+                        let def_id = stable_pick.item.container_id(self.tcx);
                         diag.span_suggestion(
                             self.span,
                             "use the fully qualified path to the associated const",
@@ -1429,9 +1432,11 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
 
     fn candidate_source(&self, candidate: &Candidate<'tcx>, self_ty: Ty<'tcx>) -> CandidateSource {
         match candidate.kind {
-            InherentImplCandidate(..) => CandidateSource::Impl(candidate.item.container.id()),
+            InherentImplCandidate(..) => {
+                CandidateSource::Impl(candidate.item.container_id(self.tcx))
+            }
             ObjectCandidate | WhereClauseCandidate(_) => {
-                CandidateSource::Trait(candidate.item.container.id())
+                CandidateSource::Trait(candidate.item.container_id(self.tcx))
             }
             TraitCandidate(trait_ref) => self.probe(|_| {
                 let _ = self
@@ -1444,7 +1449,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                         // to that impl.
                         CandidateSource::Impl(impl_data.impl_def_id)
                     }
-                    _ => CandidateSource::Trait(candidate.item.container.id()),
+                    _ => CandidateSource::Trait(candidate.item.container_id(self.tcx)),
                 }
             }),
         }
@@ -1502,7 +1507,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                     debug!("xform_ret_ty after normalization: {:?}", xform_ret_ty);
 
                     // Check whether the impl imposes obligations we have to worry about.
-                    let impl_def_id = probe.item.container.id();
+                    let impl_def_id = probe.item.container_id(self.tcx);
                     let impl_bounds = self.tcx.predicates_of(impl_def_id);
                     let impl_bounds = impl_bounds.instantiate(self.tcx, substs);
                     let traits::Normalized { value: impl_bounds, obligations: norm_obligations } =
@@ -1653,12 +1658,12 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
         probes: &[(&Candidate<'tcx>, ProbeResult)],
     ) -> Option<Pick<'tcx>> {
         // Do all probes correspond to the same trait?
-        let container = probes[0].0.item.container;
-        if let ty::ImplContainer(_) = container {
-            return None;
-        }
-        if probes[1..].iter().any(|&(p, _)| p.item.container != container) {
-            return None;
+        let container = probes[0].0.item.trait_container(self.tcx)?;
+        for (p, _) in &probes[1..] {
+            let p_container = p.item.trait_container(self.tcx)?;
+            if p_container != container {
+                return None;
+            }
         }
 
         // FIXME: check the return type here somehow.
diff --git a/compiler/rustc_typeck/src/check/method/suggest.rs b/compiler/rustc_typeck/src/check/method/suggest.rs
index e0253ee04c4..c92b93cbc22 100644
--- a/compiler/rustc_typeck/src/check/method/suggest.rs
+++ b/compiler/rustc_typeck/src/check/method/suggest.rs
@@ -1789,7 +1789,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         // We point at the method, but we just skip the rest of the check for arbitrary
                         // self types and rely on the suggestion to `use` the trait from
                         // `suggest_valid_traits`.
-                        let did = Some(pick.item.container.id());
+                        let did = Some(pick.item.container_id(self.tcx));
                         let skip = skippable.contains(&did);
                         if pick.autoderefs == 0 && !skip {
                             err.span_label(
@@ -1825,7 +1825,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         )
                     {
                         debug!("try_alt_rcvr: pick candidate {:?}", pick);
-                        let did = Some(pick.item.container.id());
+                        let did = Some(pick.item.container_id(self.tcx));
                         // We don't want to suggest a container type when the missing
                         // method is `.clone()` or `.deref()` otherwise we'd suggest
                         // `Arc::new(foo).clone()`, which is far from what the user wants.
diff --git a/compiler/rustc_typeck/src/check/wfcheck.rs b/compiler/rustc_typeck/src/check/wfcheck.rs
index 543e005c634..95f32711225 100644
--- a/compiler/rustc_typeck/src/check/wfcheck.rs
+++ b/compiler/rustc_typeck/src/check/wfcheck.rs
@@ -977,11 +977,14 @@ fn check_associated_item(
         let item = tcx.associated_item(item_id);
 
         let (mut implied_bounds, self_ty) = match item.container {
-            ty::TraitContainer(_) => (FxHashSet::default(), tcx.types.self_param),
-            ty::ImplContainer(def_id) => (
-                impl_implied_bounds(tcx, wfcx.param_env, def_id.expect_local(), span),
-                tcx.type_of(def_id),
-            ),
+            ty::TraitContainer => (FxHashSet::default(), tcx.types.self_param),
+            ty::ImplContainer => {
+                let def_id = item.container_id(tcx);
+                (
+                    impl_implied_bounds(tcx, wfcx.param_env, def_id.expect_local(), span),
+                    tcx.type_of(def_id),
+                )
+            }
         };
 
         match item.kind {
@@ -1004,7 +1007,7 @@ fn check_associated_item(
                 check_method_receiver(wfcx, hir_sig, item, self_ty);
             }
             ty::AssocKind::Type => {
-                if let ty::AssocItemContainer::TraitContainer(_) = item.container {
+                if let ty::AssocItemContainer::TraitContainer = item.container {
                     check_associated_type_bounds(wfcx, item, span)
                 }
                 if item.defaultness(tcx).has_value() {
diff --git a/compiler/rustc_typeck/src/collect.rs b/compiler/rustc_typeck/src/collect.rs
index 91c90d1fa52..99996e80c9c 100644
--- a/compiler/rustc_typeck/src/collect.rs
+++ b/compiler/rustc_typeck/src/collect.rs
@@ -2433,7 +2433,7 @@ fn explicit_predicates_of<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> ty::Generic
             //   supertrait).
             if let ty::Projection(projection) = ty.kind() {
                 projection.substs == trait_identity_substs
-                    && tcx.associated_item(projection.item_def_id).container.id() == def_id
+                    && tcx.associated_item(projection.item_def_id).container_id(tcx) == def_id
             } else {
                 false
             }
@@ -3264,7 +3264,7 @@ fn asm_target_features<'tcx>(tcx: TyCtxt<'tcx>, did: DefId) -> &'tcx FxHashSet<S
 /// applied to the method prototype.
 fn should_inherit_track_caller(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
     if let Some(impl_item) = tcx.opt_associated_item(def_id)
-        && let ty::AssocItemContainer::ImplContainer(_) = impl_item.container
+        && let ty::AssocItemContainer::ImplContainer = impl_item.container
         && let Some(trait_item) = impl_item.trait_item_def_id
     {
         return tcx
diff --git a/compiler/rustc_typeck/src/collect/item_bounds.rs b/compiler/rustc_typeck/src/collect/item_bounds.rs
index 8801d0260bf..0d2b75d3328 100644
--- a/compiler/rustc_typeck/src/collect/item_bounds.rs
+++ b/compiler/rustc_typeck/src/collect/item_bounds.rs
@@ -3,7 +3,7 @@ use crate::astconv::AstConv;
 use rustc_hir as hir;
 use rustc_infer::traits::util;
 use rustc_middle::ty::subst::InternalSubsts;
-use rustc_middle::ty::{self, TyCtxt};
+use rustc_middle::ty::{self, DefIdTree, TyCtxt};
 use rustc_span::def_id::DefId;
 use rustc_span::Span;
 
@@ -30,7 +30,7 @@ fn associated_type_bounds<'tcx>(
     // Associated types are implicitly sized unless a `?Sized` bound is found
     <dyn AstConv<'_>>::add_implicitly_sized(&icx, &mut bounds, ast_bounds, None, span);
 
-    let trait_def_id = tcx.associated_item(assoc_item_def_id).container.id();
+    let trait_def_id = tcx.parent(assoc_item_def_id);
     let trait_predicates = tcx.trait_explicit_predicates_and_bounds(trait_def_id.expect_local());
 
     let bounds_from_parent = trait_predicates.predicates.iter().copied().filter(|(pred, _)| {
diff --git a/compiler/rustc_typeck/src/outlives/implicit_infer.rs b/compiler/rustc_typeck/src/outlives/implicit_infer.rs
index 257a9520eeb..3b779280eda 100644
--- a/compiler/rustc_typeck/src/outlives/implicit_infer.rs
+++ b/compiler/rustc_typeck/src/outlives/implicit_infer.rs
@@ -2,7 +2,7 @@ use rustc_data_structures::fx::FxHashMap;
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::DefId;
 use rustc_middle::ty::subst::{GenericArg, GenericArgKind, Subst};
-use rustc_middle::ty::{self, Ty, TyCtxt};
+use rustc_middle::ty::{self, DefIdTree, Ty, TyCtxt};
 use rustc_span::Span;
 
 use super::explicit::ExplicitPredicatesMap;
@@ -202,7 +202,7 @@ fn insert_required_predicates_to_be_wf<'tcx>(
                 debug!("Projection");
                 check_explicit_predicates(
                     tcx,
-                    tcx.associated_item(obj.item_def_id).container.id(),
+                    tcx.parent(obj.item_def_id),
                     obj.substs,
                     required_predicates,
                     explicit_map,
diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index c9778b3e5a0..b6791bfab4a 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -1139,8 +1139,8 @@ impl<'tcx> Clean<'tcx, Item> for ty::AssocItem {
                 let ty = clean_middle_ty(tcx.type_of(self.def_id), cx, Some(self.def_id));
 
                 let provided = match self.container {
-                    ty::ImplContainer(_) => true,
-                    ty::TraitContainer(_) => tcx.impl_defaultness(self.def_id).has_value(),
+                    ty::ImplContainer => true,
+                    ty::TraitContainer => tcx.impl_defaultness(self.def_id).has_value(),
                 };
                 if provided {
                     AssocConstItem(ty, ConstantKind::Extern { def_id: self.def_id })
@@ -1159,8 +1159,8 @@ impl<'tcx> Clean<'tcx, Item> for ty::AssocItem {
 
                 if self.fn_has_self_parameter {
                     let self_ty = match self.container {
-                        ty::ImplContainer(def_id) => tcx.type_of(def_id),
-                        ty::TraitContainer(_) => tcx.types.self_param,
+                        ty::ImplContainer => tcx.type_of(self.container_id(tcx)),
+                        ty::TraitContainer => tcx.types.self_param,
                     };
                     let self_arg_ty = sig.input(0).skip_binder();
                     if self_arg_ty == self_ty {
@@ -1178,13 +1178,13 @@ impl<'tcx> Clean<'tcx, Item> for ty::AssocItem {
                 }
 
                 let provided = match self.container {
-                    ty::ImplContainer(_) => true,
-                    ty::TraitContainer(_) => self.defaultness(tcx).has_value(),
+                    ty::ImplContainer => true,
+                    ty::TraitContainer => self.defaultness(tcx).has_value(),
                 };
                 if provided {
                     let defaultness = match self.container {
-                        ty::ImplContainer(_) => Some(self.defaultness(tcx)),
-                        ty::TraitContainer(_) => None,
+                        ty::ImplContainer => Some(self.defaultness(tcx)),
+                        ty::TraitContainer => None,
                     };
                     MethodItem(Box::new(Function { generics, decl }), defaultness)
                 } else {
@@ -1215,7 +1215,7 @@ impl<'tcx> Clean<'tcx, Item> for ty::AssocItem {
                     }
                 }
 
-                if let ty::TraitContainer(_) = self.container {
+                if let ty::TraitContainer = self.container {
                     let bounds = tcx.explicit_item_bounds(self.def_id);
                     let predicates = ty::GenericPredicates { parent: None, predicates: bounds };
                     let mut generics =
@@ -1232,7 +1232,7 @@ impl<'tcx> Clean<'tcx, Item> for ty::AssocItem {
                                 if assoc.name != my_name {
                                     return false;
                                 }
-                                if trait_.def_id() != self.container.id() {
+                                if trait_.def_id() != self.container_id(tcx) {
                                     return false;
                                 }
                                 match **self_type {
@@ -1356,7 +1356,7 @@ fn clean_qpath<'tcx>(hir_ty: &hir::Ty<'tcx>, cx: &mut DocContext<'tcx>) -> Type
             }
 
             let trait_segments = &p.segments[..p.segments.len() - 1];
-            let trait_def = cx.tcx.associated_item(p.res.def_id()).container.id();
+            let trait_def = cx.tcx.associated_item(p.res.def_id()).container_id(cx.tcx);
             let trait_ = self::Path {
                 res: Res::Def(DefKind::Trait, trait_def),
                 segments: trait_segments.iter().map(|x| x.clean(cx)).collect(),
diff --git a/src/tools/clippy/clippy_lints/src/eta_reduction.rs b/src/tools/clippy/clippy_lints/src/eta_reduction.rs
index 80c84014bfd..4f9ff97f1fd 100644
--- a/src/tools/clippy/clippy_lints/src/eta_reduction.rs
+++ b/src/tools/clippy/clippy_lints/src/eta_reduction.rs
@@ -220,9 +220,11 @@ fn check_sig<'tcx>(cx: &LateContext<'tcx>, closure_ty: Ty<'tcx>, call_ty: Ty<'tc
 }
 
 fn get_ufcs_type_name(cx: &LateContext<'_>, method_def_id: DefId) -> String {
-    match cx.tcx.associated_item(method_def_id).container {
-        ty::TraitContainer(def_id) => cx.tcx.def_path_str(def_id),
-        ty::ImplContainer(def_id) => {
+    let assoc_item = cx.tcx.associated_item(method_def_id);
+    let def_id = assoc_item.container_id(cx.tcx);
+    match assoc_item.container {
+        ty::TraitContainer => cx.tcx.def_path_str(def_id),
+        ty::ImplContainer => {
             let ty = cx.tcx.type_of(def_id);
             match ty.kind() {
                 ty::Adt(adt, _) => cx.tcx.def_path_str(adt.did()),
diff --git a/src/tools/clippy/clippy_lints/src/missing_doc.rs b/src/tools/clippy/clippy_lints/src/missing_doc.rs
index a20377f320b..88ba002927a 100644
--- a/src/tools/clippy/clippy_lints/src/missing_doc.rs
+++ b/src/tools/clippy/clippy_lints/src/missing_doc.rs
@@ -10,7 +10,7 @@ use clippy_utils::diagnostics::span_lint;
 use rustc_ast::ast;
 use rustc_hir as hir;
 use rustc_lint::{LateContext, LateLintPass, LintContext};
-use rustc_middle::ty::{self, DefIdTree};
+use rustc_middle::ty::DefIdTree;
 use rustc_session::{declare_tool_lint, impl_lint_pass};
 use rustc_span::def_id::CRATE_DEF_ID;
 use rustc_span::source_map::Span;
@@ -153,13 +153,12 @@ impl<'tcx> LateLintPass<'tcx> for MissingDoc {
 
     fn check_impl_item(&mut self, cx: &LateContext<'tcx>, impl_item: &'tcx hir::ImplItem<'_>) {
         // If the method is an impl for a trait, don't doc.
-        match cx.tcx.associated_item(impl_item.def_id).container {
-            ty::TraitContainer(_) => return,
-            ty::ImplContainer(cid) => {
-                if cx.tcx.impl_trait_ref(cid).is_some() {
-                    return;
-                }
-            },
+        if let Some(cid) = cx.tcx.associated_item(impl_item.def_id).impl_container(cx.tcx) {
+            if cx.tcx.impl_trait_ref(cid).is_some() {
+                return;
+            }
+        } else {
+            return;
         }
 
         let (article, desc) = cx.tcx.article_and_description(impl_item.def_id.to_def_id());
diff --git a/src/tools/clippy/clippy_lints/src/missing_inline.rs b/src/tools/clippy/clippy_lints/src/missing_inline.rs
index 9e14ccd3433..07bc2ca5d3c 100644
--- a/src/tools/clippy/clippy_lints/src/missing_inline.rs
+++ b/src/tools/clippy/clippy_lints/src/missing_inline.rs
@@ -151,9 +151,11 @@ impl<'tcx> LateLintPass<'tcx> for MissingInline {
             hir::ImplItemKind::Const(..) | hir::ImplItemKind::TyAlias(_) => return,
         };
 
-        let trait_def_id = match cx.tcx.associated_item(impl_item.def_id).container {
-            TraitContainer(cid) => Some(cid),
-            ImplContainer(cid) => cx.tcx.impl_trait_ref(cid).map(|t| t.def_id),
+        let assoc_item = cx.tcx.associated_item(impl_item.def_id);
+        let container_id = assoc_item.container_id(cx.tcx);
+        let trait_def_id = match assoc_item.container {
+            TraitContainer => Some(container_id),
+            ImplContainer => cx.tcx.impl_trait_ref(container_id).map(|t| t.def_id),
         };
 
         if let Some(trait_def_id) = trait_def_id {