diff --git a/compiler/rustc_borrowck/src/lib.rs b/compiler/rustc_borrowck/src/lib.rs
index 4c380ddcf7084..268cb47fd1261 100644
--- a/compiler/rustc_borrowck/src/lib.rs
+++ b/compiler/rustc_borrowck/src/lib.rs
@@ -119,7 +119,7 @@ pub fn provide(providers: &mut Providers) {
 fn mir_borrowck(
     tcx: TyCtxt<'_>,
     def: LocalDefId,
-) -> Result<&ConcreteOpaqueTypes<'_>, ErrorGuaranteed> {
+) -> Result<&DefinitionSiteHiddenTypes<'_>, ErrorGuaranteed> {
     assert!(!tcx.is_typeck_child(def.to_def_id()));
     let (input_body, _) = tcx.mir_promoted(def);
     debug!("run query mir_borrowck: {}", tcx.def_path_str(def));
@@ -130,7 +130,7 @@ fn mir_borrowck(
         Err(guar)
     } else if input_body.should_skip() {
         debug!("Skipping borrowck because of injected body");
-        let opaque_types = ConcreteOpaqueTypes(Default::default());
+        let opaque_types = DefinitionSiteHiddenTypes(Default::default());
         Ok(tcx.arena.alloc(opaque_types))
     } else {
         let mut root_cx = BorrowCheckRootCtxt::new(tcx, def, None);
diff --git a/compiler/rustc_borrowck/src/region_infer/mod.rs b/compiler/rustc_borrowck/src/region_infer/mod.rs
index 0910e8ef4b37b..e98c60e633805 100644
--- a/compiler/rustc_borrowck/src/region_infer/mod.rs
+++ b/compiler/rustc_borrowck/src/region_infer/mod.rs
@@ -1382,10 +1382,10 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     }
 
     /// The constraints we get from equating the hidden type of each use of an opaque
-    /// with its final concrete type may end up getting preferred over other, potentially
+    /// with its final hidden type may end up getting preferred over other, potentially
     /// longer constraint paths.
     ///
-    /// Given that we compute the final concrete type by relying on this existing constraint
+    /// Given that we compute the final hidden type by relying on this existing constraint
     /// path, this can easily end up hiding the actual reason for why we require these regions
     /// to be equal.
     ///
diff --git a/compiler/rustc_borrowck/src/region_infer/opaque_types/mod.rs b/compiler/rustc_borrowck/src/region_infer/opaque_types/mod.rs
index 0af636aa734ca..8d89f3e0d8700 100644
--- a/compiler/rustc_borrowck/src/region_infer/opaque_types/mod.rs
+++ b/compiler/rustc_borrowck/src/region_infer/opaque_types/mod.rs
@@ -8,7 +8,7 @@ use rustc_infer::infer::outlives::env::RegionBoundPairs;
 use rustc_infer::infer::{InferCtxt, NllRegionVariableOrigin, OpaqueTypeStorageEntries};
 use rustc_infer::traits::ObligationCause;
 use rustc_macros::extension;
-use rustc_middle::mir::{Body, ConcreteOpaqueTypes, ConstraintCategory};
+use rustc_middle::mir::{Body, ConstraintCategory, DefinitionSiteHiddenTypes};
 use rustc_middle::ty::{
     self, DefiningScopeKind, EarlyBinder, FallibleTypeFolder, GenericArg, GenericArgsRef,
     OpaqueHiddenType, OpaqueTypeKey, Region, RegionVid, Ty, TyCtxt, TypeFoldable,
@@ -129,9 +129,9 @@ fn nll_var_to_universal_region<'tcx>(
 /// Collect all defining uses of opaque types inside of this typeck root. This
 /// expects the hidden type to be mapped to the definition parameters of the opaque
 /// and errors if we end up with distinct hidden types.
-fn add_concrete_opaque_type<'tcx>(
+fn add_hidden_type<'tcx>(
     tcx: TyCtxt<'tcx>,
-    concrete_opaque_types: &mut ConcreteOpaqueTypes<'tcx>,
+    hidden_types: &mut DefinitionSiteHiddenTypes<'tcx>,
     def_id: LocalDefId,
     hidden_ty: OpaqueHiddenType<'tcx>,
 ) {
@@ -139,7 +139,7 @@ fn add_concrete_opaque_type<'tcx>(
     // back to the opaque type definition. E.g. we may have `OpaqueType<X, Y>` mapped to
     // `(X, Y)` and `OpaqueType<Y, X>` mapped to `(Y, X)`, and those are the same, but we
     // only know that once we convert the generic parameters to those of the opaque type.
-    if let Some(prev) = concrete_opaque_types.0.get_mut(&def_id) {
+    if let Some(prev) = hidden_types.0.get_mut(&def_id) {
         if prev.ty != hidden_ty.ty {
             let guar = hidden_ty.ty.error_reported().err().unwrap_or_else(|| {
                 let (Ok(e) | Err(e)) = prev.build_mismatch_error(&hidden_ty, tcx).map(|d| d.emit());
@@ -151,15 +151,15 @@ fn add_concrete_opaque_type<'tcx>(
         // FIXME(oli-obk): collect multiple spans for better diagnostics down the road.
         prev.span = prev.span.substitute_dummy(hidden_ty.span);
     } else {
-        concrete_opaque_types.0.insert(def_id, hidden_ty);
+        hidden_types.0.insert(def_id, hidden_ty);
     }
 }
 
-fn get_concrete_opaque_type<'tcx>(
-    concrete_opaque_types: &ConcreteOpaqueTypes<'tcx>,
+fn get_hidden_type<'tcx>(
+    hidden_types: &DefinitionSiteHiddenTypes<'tcx>,
     def_id: LocalDefId,
 ) -> Option<EarlyBinder<'tcx, OpaqueHiddenType<'tcx>>> {
-    concrete_opaque_types.0.get(&def_id).map(|ty| EarlyBinder::bind(*ty))
+    hidden_types.0.get(&def_id).map(|ty| EarlyBinder::bind(*ty))
 }
 
 #[derive(Debug)]
@@ -173,22 +173,22 @@ struct DefiningUse<'tcx> {
 }
 
 /// This computes the actual hidden types of the opaque types and maps them to their
-/// definition sites. Outside of registering the computed concrete types this function
+/// definition sites. Outside of registering the computed hidden types this function
 /// does not mutate the current borrowck state.
 ///
 /// While it may fail to infer the hidden type and return errors, we always apply
-/// the computed concrete hidden type to all opaque type uses to check whether they
+/// the computed hidden type to all opaque type uses to check whether they
 /// are correct. This is necessary to support non-defining uses of opaques in their
 /// defining scope.
 ///
 /// It also means that this whole function is not really soundness critical as we
 /// recheck all uses of the opaques regardless.
-pub(crate) fn compute_concrete_opaque_types<'tcx>(
+pub(crate) fn compute_definition_site_hidden_types<'tcx>(
     infcx: &BorrowckInferCtxt<'tcx>,
     universal_region_relations: &Frozen<UniversalRegionRelations<'tcx>>,
     constraints: &MirTypeckRegionConstraints<'tcx>,
     location_map: Rc<DenseLocationMap>,
-    concrete_opaque_types: &mut ConcreteOpaqueTypes<'tcx>,
+    hidden_types: &mut DefinitionSiteHiddenTypes<'tcx>,
     opaque_types: &[(OpaqueTypeKey<'tcx>, OpaqueHiddenType<'tcx>)],
 ) -> Vec<DeferredOpaqueTypeError<'tcx>> {
     let mut errors = Vec::new();
@@ -201,8 +201,7 @@ pub(crate) fn compute_concrete_opaque_types<'tcx>(
     // We start by checking each use of an opaque type during type check and
     // check whether the generic arguments of the opaque type are fully
     // universal, if so, it's a defining use.
-    let defining_uses =
-        collect_defining_uses(&mut rcx, concrete_opaque_types, opaque_types, &mut errors);
+    let defining_uses = collect_defining_uses(&mut rcx, hidden_types, opaque_types, &mut errors);
 
     // We now compute and apply member constraints for all regions in the hidden
     // types of each defining use. This mutates the region values of the `rcx` which
@@ -210,11 +209,11 @@ pub(crate) fn compute_concrete_opaque_types<'tcx>(
     apply_member_constraints(&mut rcx, &defining_uses);
 
     // After applying member constraints, we now check whether all member regions ended
-    // up equal to one of their choice regions and compute the actual concrete type of
+    // up equal to one of their choice regions and compute the actual hidden type of
     // the opaque type definition. This is stored in the `root_cx`.
-    compute_concrete_types_from_defining_uses(
+    compute_definition_site_hidden_types_from_defining_uses(
         &rcx,
-        concrete_opaque_types,
+        hidden_types,
         &defining_uses,
         &mut errors,
     );
@@ -224,7 +223,7 @@ pub(crate) fn compute_concrete_opaque_types<'tcx>(
 #[instrument(level = "debug", skip_all, ret)]
 fn collect_defining_uses<'tcx>(
     rcx: &mut RegionCtxt<'_, 'tcx>,
-    concrete_opaque_types: &mut ConcreteOpaqueTypes<'tcx>,
+    hidden_types: &mut DefinitionSiteHiddenTypes<'tcx>,
     opaque_types: &[(OpaqueTypeKey<'tcx>, OpaqueHiddenType<'tcx>)],
     errors: &mut Vec<DeferredOpaqueTypeError<'tcx>>,
 ) -> Vec<DefiningUse<'tcx>> {
@@ -244,9 +243,9 @@ fn collect_defining_uses<'tcx>(
             // with `TypingMode::Borrowck`.
             if infcx.tcx.use_typing_mode_borrowck() {
                 match err {
-                    NonDefiningUseReason::Tainted(guar) => add_concrete_opaque_type(
+                    NonDefiningUseReason::Tainted(guar) => add_hidden_type(
                         infcx.tcx,
-                        concrete_opaque_types,
+                        hidden_types,
                         opaque_type_key.def_id,
                         OpaqueHiddenType::new_error(infcx.tcx, guar),
                     ),
@@ -277,9 +276,9 @@ fn collect_defining_uses<'tcx>(
     defining_uses
 }
 
-fn compute_concrete_types_from_defining_uses<'tcx>(
+fn compute_definition_site_hidden_types_from_defining_uses<'tcx>(
     rcx: &RegionCtxt<'_, 'tcx>,
-    concrete_opaque_types: &mut ConcreteOpaqueTypes<'tcx>,
+    hidden_types: &mut DefinitionSiteHiddenTypes<'tcx>,
     defining_uses: &[DefiningUse<'tcx>],
     errors: &mut Vec<DeferredOpaqueTypeError<'tcx>>,
 ) {
@@ -358,9 +357,9 @@ fn compute_concrete_types_from_defining_uses<'tcx>(
                 },
             ));
         }
-        add_concrete_opaque_type(
+        add_hidden_type(
             tcx,
-            concrete_opaque_types,
+            hidden_types,
             opaque_type_key.def_id,
             OpaqueHiddenType { span: hidden_type.span, ty },
         );
@@ -489,20 +488,20 @@ impl<'tcx> FallibleTypeFolder<TyCtxt<'tcx>> for ToArgRegionsFolder<'_, 'tcx> {
 ///
 /// It does this by equating the hidden type of each use with the instantiated final
 /// hidden type of the opaque.
-pub(crate) fn apply_computed_concrete_opaque_types<'tcx>(
+pub(crate) fn apply_definition_site_hidden_types<'tcx>(
     infcx: &BorrowckInferCtxt<'tcx>,
     body: &Body<'tcx>,
     universal_regions: &UniversalRegions<'tcx>,
     region_bound_pairs: &RegionBoundPairs<'tcx>,
     known_type_outlives_obligations: &[ty::PolyTypeOutlivesPredicate<'tcx>],
     constraints: &mut MirTypeckRegionConstraints<'tcx>,
-    concrete_opaque_types: &mut ConcreteOpaqueTypes<'tcx>,
+    hidden_types: &mut DefinitionSiteHiddenTypes<'tcx>,
     opaque_types: &[(OpaqueTypeKey<'tcx>, OpaqueHiddenType<'tcx>)],
 ) -> Vec<DeferredOpaqueTypeError<'tcx>> {
     let tcx = infcx.tcx;
     let mut errors = Vec::new();
     for &(key, hidden_type) in opaque_types {
-        let Some(expected) = get_concrete_opaque_type(concrete_opaque_types, key.def_id) else {
+        let Some(expected) = get_hidden_type(hidden_types, key.def_id) else {
             if !tcx.use_typing_mode_borrowck() {
                 if let ty::Alias(ty::Opaque, alias_ty) = hidden_type.ty.kind()
                     && alias_ty.def_id == key.def_id.to_def_id()
@@ -521,12 +520,7 @@ pub(crate) fn apply_computed_concrete_opaque_types<'tcx>(
                 hidden_type.span,
                 "non-defining use in the defining scope with no defining uses",
             );
-            add_concrete_opaque_type(
-                tcx,
-                concrete_opaque_types,
-                key.def_id,
-                OpaqueHiddenType::new_error(tcx, guar),
-            );
+            add_hidden_type(tcx, hidden_types, key.def_id, OpaqueHiddenType::new_error(tcx, guar));
             continue;
         };
 
@@ -566,18 +560,13 @@ pub(crate) fn apply_computed_concrete_opaque_types<'tcx>(
                 "equating opaque types",
             ),
         ) {
-            add_concrete_opaque_type(
-                tcx,
-                concrete_opaque_types,
-                key.def_id,
-                OpaqueHiddenType::new_error(tcx, guar),
-            );
+            add_hidden_type(tcx, hidden_types, key.def_id, OpaqueHiddenType::new_error(tcx, guar));
         }
     }
     errors
 }
 
-/// In theory `apply_concrete_opaque_types` could introduce new uses of opaque types.
+/// In theory `apply_definition_site_hidden_types` could introduce new uses of opaque types.
 /// We do not check these new uses so this could be unsound.
 ///
 /// We detect any new uses and simply delay a bug if they occur. If this results in
@@ -682,13 +671,6 @@ impl<'tcx> InferCtxt<'tcx> {
     ///
     /// (*) C1 and C2 were introduced in the comments on
     /// `register_member_constraints`. Read that comment for more context.
-    ///
-    /// # Parameters
-    ///
-    /// - `def_id`, the `impl Trait` type
-    /// - `args`, the args used to instantiate this opaque type
-    /// - `instantiated_ty`, the inferred type C1 -- fully resolved, lifted version of
-    ///   `opaque_defn.concrete_ty`
     #[instrument(level = "debug", skip(self))]
     fn infer_opaque_definition_from_instantiation(
         &self,
diff --git a/compiler/rustc_borrowck/src/root_cx.rs b/compiler/rustc_borrowck/src/root_cx.rs
index cd4e9683f2d87..21c11e1287353 100644
--- a/compiler/rustc_borrowck/src/root_cx.rs
+++ b/compiler/rustc_borrowck/src/root_cx.rs
@@ -12,12 +12,12 @@ use smallvec::SmallVec;
 use crate::consumers::BorrowckConsumer;
 use crate::nll::compute_closure_requirements_modulo_opaques;
 use crate::region_infer::opaque_types::{
-    apply_computed_concrete_opaque_types, clone_and_resolve_opaque_types,
-    compute_concrete_opaque_types, detect_opaque_types_added_while_handling_opaque_types,
+    apply_definition_site_hidden_types, clone_and_resolve_opaque_types,
+    compute_definition_site_hidden_types, detect_opaque_types_added_while_handling_opaque_types,
 };
 use crate::type_check::{Locations, constraint_conversion};
 use crate::{
-    ClosureRegionRequirements, CollectRegionConstraintsResult, ConcreteOpaqueTypes,
+    ClosureRegionRequirements, CollectRegionConstraintsResult, DefinitionSiteHiddenTypes,
     PropagatedBorrowCheckResults, borrowck_check_region_constraints,
     borrowck_collect_region_constraints,
 };
@@ -27,7 +27,7 @@ use crate::{
 pub(super) struct BorrowCheckRootCtxt<'tcx> {
     pub tcx: TyCtxt<'tcx>,
     root_def_id: LocalDefId,
-    concrete_opaque_types: ConcreteOpaqueTypes<'tcx>,
+    hidden_types: DefinitionSiteHiddenTypes<'tcx>,
     /// The region constraints computed by [borrowck_collect_region_constraints]. This uses
     /// an [FxIndexMap] to guarantee that iterating over it visits nested bodies before
     /// their parents.
@@ -49,7 +49,7 @@ impl<'tcx> BorrowCheckRootCtxt<'tcx> {
         BorrowCheckRootCtxt {
             tcx,
             root_def_id,
-            concrete_opaque_types: Default::default(),
+            hidden_types: Default::default(),
             collect_region_constraints_results: Default::default(),
             propagated_borrowck_results: Default::default(),
             tainted_by_errors: None,
@@ -72,11 +72,11 @@ impl<'tcx> BorrowCheckRootCtxt<'tcx> {
         &self.propagated_borrowck_results[&nested_body_def_id].used_mut_upvars
     }
 
-    pub(super) fn finalize(self) -> Result<&'tcx ConcreteOpaqueTypes<'tcx>, ErrorGuaranteed> {
+    pub(super) fn finalize(self) -> Result<&'tcx DefinitionSiteHiddenTypes<'tcx>, ErrorGuaranteed> {
         if let Some(guar) = self.tainted_by_errors {
             Err(guar)
         } else {
-            Ok(self.tcx.arena.alloc(self.concrete_opaque_types))
+            Ok(self.tcx.arena.alloc(self.hidden_types))
         }
     }
 
@@ -88,12 +88,12 @@ impl<'tcx> BorrowCheckRootCtxt<'tcx> {
                 &input.universal_region_relations,
                 &mut input.constraints,
             );
-            input.deferred_opaque_type_errors = compute_concrete_opaque_types(
+            input.deferred_opaque_type_errors = compute_definition_site_hidden_types(
                 &input.infcx,
                 &input.universal_region_relations,
                 &input.constraints,
                 Rc::clone(&input.location_map),
-                &mut self.concrete_opaque_types,
+                &mut self.hidden_types,
                 &opaque_types,
             );
             per_body_info.push((num_entries, opaque_types));
@@ -103,14 +103,14 @@ impl<'tcx> BorrowCheckRootCtxt<'tcx> {
             self.collect_region_constraints_results.values_mut().zip(per_body_info)
         {
             if input.deferred_opaque_type_errors.is_empty() {
-                input.deferred_opaque_type_errors = apply_computed_concrete_opaque_types(
+                input.deferred_opaque_type_errors = apply_definition_site_hidden_types(
                     &input.infcx,
                     &input.body_owned,
                     &input.universal_region_relations.universal_regions,
                     &input.region_bound_pairs,
                     &input.known_type_outlives_obligations,
                     &mut input.constraints,
-                    &mut self.concrete_opaque_types,
+                    &mut self.hidden_types,
                     &opaque_types,
                 );
             }
diff --git a/compiler/rustc_hir_analysis/src/check/check.rs b/compiler/rustc_hir_analysis/src/check/check.rs
index 886ebddc75c97..e1e6860e43004 100644
--- a/compiler/rustc_hir_analysis/src/check/check.rs
+++ b/compiler/rustc_hir_analysis/src/check/check.rs
@@ -219,7 +219,7 @@ fn check_opaque(tcx: TyCtxt<'_>, def_id: LocalDefId) {
 
     // HACK(jynelson): trying to infer the type of `impl trait` breaks documenting
     // `async-std` (and `pub async fn` in general).
-    // Since rustdoc doesn't care about the concrete type behind `impl Trait`, just don't look at it!
+    // Since rustdoc doesn't care about the hidden type behind `impl Trait`, just don't look at it!
     // See https://github.com/rust-lang/rust/issues/75100
     if tcx.sess.opts.actually_rustdoc {
         return;
@@ -252,7 +252,7 @@ pub(super) fn check_opaque_for_cycles<'tcx>(
     Ok(())
 }
 
-/// Check that the concrete type behind `impl Trait` actually implements `Trait`.
+/// Check that the hidden type behind `impl Trait` actually implements `Trait`.
 ///
 /// This is mostly checked at the places that specify the opaque type, but we
 /// check those cases in the `param_env` of that function, which may have
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 b6d898886ac4d..a02990fe4abaf 100644
--- a/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs
+++ b/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs
@@ -177,7 +177,7 @@ impl<'tcx> TaitConstraintLocator<'tcx> {
                 let tables = tcx.typeck(item_def_id);
                 if let Some(guar) = tables.tainted_by_errors {
                     self.insert_found(ty::OpaqueHiddenType::new_error(tcx, guar));
-                } else if let Some(&hidden_type) = tables.concrete_opaque_types.get(&self.def_id) {
+                } else if let Some(&hidden_type) = tables.hidden_types.get(&self.def_id) {
                     self.insert_found(hidden_type);
                 } else {
                     self.non_defining_use_in_defining_scope(item_def_id);
@@ -185,8 +185,8 @@ impl<'tcx> TaitConstraintLocator<'tcx> {
             }
             DefiningScopeKind::MirBorrowck => match tcx.mir_borrowck(item_def_id) {
                 Err(guar) => self.insert_found(ty::OpaqueHiddenType::new_error(tcx, guar)),
-                Ok(concrete_opaque_types) => {
-                    if let Some(&hidden_type) = concrete_opaque_types.0.get(&self.def_id) {
+                Ok(hidden_types) => {
+                    if let Some(&hidden_type) = hidden_types.0.get(&self.def_id) {
                         debug!(?hidden_type, "found constraint");
                         self.insert_found(hidden_type);
                     } else if let Err(guar) = tcx
@@ -247,7 +247,7 @@ pub(super) fn find_opaque_ty_constraints_for_rpit<'tcx>(
             let tables = tcx.typeck(owner_def_id);
             if let Some(guar) = tables.tainted_by_errors {
                 Ty::new_error(tcx, guar)
-            } else if let Some(hidden_ty) = tables.concrete_opaque_types.get(&def_id) {
+            } else if let Some(hidden_ty) = tables.hidden_types.get(&def_id) {
                 hidden_ty.ty
             } else {
                 assert!(!tcx.next_trait_solver_globally());
@@ -261,8 +261,8 @@ pub(super) fn find_opaque_ty_constraints_for_rpit<'tcx>(
             }
         }
         DefiningScopeKind::MirBorrowck => match tcx.mir_borrowck(owner_def_id) {
-            Ok(concrete_opaque_types) => {
-                if let Some(hidden_ty) = concrete_opaque_types.0.get(&def_id) {
+            Ok(hidden_types) => {
+                if let Some(hidden_ty) = hidden_types.0.get(&def_id) {
                     hidden_ty.ty
                 } else {
                     let hir_ty = tcx.type_of_opaque_hir_typeck(def_id).instantiate_identity();
diff --git a/compiler/rustc_hir_typeck/src/opaque_types.rs b/compiler/rustc_hir_typeck/src/opaque_types.rs
index 5cefa506b5a06..4c1fe69405e91 100644
--- a/compiler/rustc_hir_typeck/src/opaque_types.rs
+++ b/compiler/rustc_hir_typeck/src/opaque_types.rs
@@ -15,7 +15,7 @@ use crate::FnCtxt;
 
 impl<'tcx> FnCtxt<'_, 'tcx> {
     /// This takes all the opaque type uses during HIR typeck. It first computes
-    /// the concrete hidden type by iterating over all defining uses.
+    /// the hidden type by iterating over all defining uses.
     ///
     /// A use during HIR typeck is defining if all non-lifetime arguments are
     /// unique generic parameters and the hidden type does not reference any
@@ -35,8 +35,8 @@ impl<'tcx> FnCtxt<'_, 'tcx> {
         }
         debug!(?opaque_types);
 
-        self.compute_concrete_opaque_types(&opaque_types);
-        self.apply_computed_concrete_opaque_types(&opaque_types);
+        self.compute_definition_site_hidden_types(&opaque_types);
+        self.apply_definition_site_hidden_types(&opaque_types);
     }
 }
 
@@ -71,7 +71,7 @@ impl<'tcx> UsageKind<'tcx> {
 }
 
 impl<'tcx> FnCtxt<'_, 'tcx> {
-    fn compute_concrete_opaque_types(
+    fn compute_definition_site_hidden_types(
         &mut self,
         opaque_types: &[(OpaqueTypeKey<'tcx>, OpaqueHiddenType<'tcx>)],
     ) {
@@ -142,7 +142,7 @@ impl<'tcx> FnCtxt<'_, 'tcx> {
 
             self.typeck_results
                 .borrow_mut()
-                .concrete_opaque_types
+                .hidden_types
                 .insert(def_id, OpaqueHiddenType::new_error(tcx, guar));
             self.set_tainted_by_errors(guar);
         }
@@ -161,7 +161,7 @@ impl<'tcx> FnCtxt<'_, 'tcx> {
         ) {
             match err {
                 NonDefiningUseReason::Tainted(guar) => {
-                    self.typeck_results.borrow_mut().concrete_opaque_types.insert(
+                    self.typeck_results.borrow_mut().hidden_types.insert(
                         opaque_type_key.def_id,
                         OpaqueHiddenType::new_error(self.tcx, guar),
                     );
@@ -197,20 +197,19 @@ impl<'tcx> FnCtxt<'_, 'tcx> {
         let prev = self
             .typeck_results
             .borrow_mut()
-            .concrete_opaque_types
+            .hidden_types
             .insert(opaque_type_key.def_id, hidden_type);
         assert!(prev.is_none());
         UsageKind::HasDefiningUse
     }
 
-    fn apply_computed_concrete_opaque_types(
+    fn apply_definition_site_hidden_types(
         &mut self,
         opaque_types: &[(OpaqueTypeKey<'tcx>, OpaqueHiddenType<'tcx>)],
     ) {
         let tcx = self.tcx;
         for &(key, hidden_type) in opaque_types {
-            let expected =
-                *self.typeck_results.borrow_mut().concrete_opaque_types.get(&key.def_id).unwrap();
+            let expected = *self.typeck_results.borrow_mut().hidden_types.get(&key.def_id).unwrap();
 
             let expected = EarlyBinder::bind(expected.ty).instantiate(tcx, key.args);
             self.demand_eqtype(hidden_type.span, expected, hidden_type.ty);
diff --git a/compiler/rustc_hir_typeck/src/writeback.rs b/compiler/rustc_hir_typeck/src/writeback.rs
index d01eeb9a4b691..697029e55f7cb 100644
--- a/compiler/rustc_hir_typeck/src/writeback.rs
+++ b/compiler/rustc_hir_typeck/src/writeback.rs
@@ -550,13 +550,12 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
     fn visit_opaque_types_next(&mut self) {
         let mut fcx_typeck_results = self.fcx.typeck_results.borrow_mut();
         assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner);
-        for hidden_ty in fcx_typeck_results.concrete_opaque_types.values() {
+        for hidden_ty in fcx_typeck_results.hidden_types.values() {
             assert!(!hidden_ty.has_infer());
         }
 
-        assert_eq!(self.typeck_results.concrete_opaque_types.len(), 0);
-        self.typeck_results.concrete_opaque_types =
-            mem::take(&mut fcx_typeck_results.concrete_opaque_types);
+        assert_eq!(self.typeck_results.hidden_types.len(), 0);
+        self.typeck_results.hidden_types = mem::take(&mut fcx_typeck_results.hidden_types);
     }
 
     #[instrument(skip(self), level = "debug")]
@@ -588,7 +587,7 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
                 hidden_type.span,
                 DefiningScopeKind::HirTypeck,
             ) {
-                self.typeck_results.concrete_opaque_types.insert(
+                self.typeck_results.hidden_types.insert(
                     opaque_type_key.def_id,
                     ty::OpaqueHiddenType::new_error(tcx, err.report(self.fcx)),
                 );
@@ -600,16 +599,11 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
                 DefiningScopeKind::HirTypeck,
             );
 
-            if let Some(prev) = self
-                .typeck_results
-                .concrete_opaque_types
-                .insert(opaque_type_key.def_id, hidden_type)
+            if let Some(prev) =
+                self.typeck_results.hidden_types.insert(opaque_type_key.def_id, hidden_type)
             {
-                let entry = &mut self
-                    .typeck_results
-                    .concrete_opaque_types
-                    .get_mut(&opaque_type_key.def_id)
-                    .unwrap();
+                let entry =
+                    &mut self.typeck_results.hidden_types.get_mut(&opaque_type_key.def_id).unwrap();
                 if prev.ty != hidden_type.ty {
                     if let Some(guar) = self.typeck_results.tainted_by_errors {
                         entry.ty = Ty::new_error(tcx, guar);
@@ -628,7 +622,7 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
 
         let recursive_opaques: Vec<_> = self
             .typeck_results
-            .concrete_opaque_types
+            .hidden_types
             .iter()
             .filter(|&(&def_id, hidden_ty)| {
                 hidden_ty
@@ -636,7 +630,7 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
                     .visit_with(&mut HasRecursiveOpaque {
                         def_id,
                         seen: Default::default(),
-                        opaques: &self.typeck_results.concrete_opaque_types,
+                        opaques: &self.typeck_results.hidden_types,
                         tcx,
                     })
                     .is_break()
@@ -651,7 +645,7 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
                 .with_code(E0720)
                 .emit();
             self.typeck_results
-                .concrete_opaque_types
+                .hidden_types
                 .insert(def_id, OpaqueHiddenType { span, ty: Ty::new_error(tcx, guar) });
         }
     }
diff --git a/compiler/rustc_middle/src/arena.rs b/compiler/rustc_middle/src/arena.rs
index fa6a2db38ef9c..feaad5bb96eb9 100644
--- a/compiler/rustc_middle/src/arena.rs
+++ b/compiler/rustc_middle/src/arena.rs
@@ -27,7 +27,7 @@ macro_rules! arena_types {
                     rustc_middle::mir::Body<'tcx>
                 >,
             [decode] typeck_results: rustc_middle::ty::TypeckResults<'tcx>,
-            [decode] borrowck_result: rustc_middle::mir::ConcreteOpaqueTypes<'tcx>,
+            [decode] borrowck_result: rustc_middle::mir::DefinitionSiteHiddenTypes<'tcx>,
             [] resolver: rustc_data_structures::steal::Steal<(
                 rustc_middle::ty::ResolverAstLowering,
                 std::sync::Arc<rustc_ast::Crate>,
diff --git a/compiler/rustc_middle/src/mir/query.rs b/compiler/rustc_middle/src/mir/query.rs
index a509c40c89cd6..2e6c9f207e26b 100644
--- a/compiler/rustc_middle/src/mir/query.rs
+++ b/compiler/rustc_middle/src/mir/query.rs
@@ -84,11 +84,10 @@ impl Debug for CoroutineLayout<'_> {
     }
 }
 
-/// All the opaque types that are restricted to concrete types
-/// by this function. Unlike the value in `TypeckResults`, this has
-/// unerased regions.
+/// All the opaque types that have had their hidden type fully computed.
+/// Unlike the value in `TypeckResults`, this has unerased regions.
 #[derive(Default, Debug, TyEncodable, TyDecodable, HashStable)]
-pub struct ConcreteOpaqueTypes<'tcx>(pub FxIndexMap<LocalDefId, OpaqueHiddenType<'tcx>>);
+pub struct DefinitionSiteHiddenTypes<'tcx>(pub FxIndexMap<LocalDefId, OpaqueHiddenType<'tcx>>);
 
 /// The result of the `mir_const_qualif` query.
 ///
diff --git a/compiler/rustc_middle/src/query/mod.rs b/compiler/rustc_middle/src/query/mod.rs
index 326df9239aa08..895c8c0295a04 100644
--- a/compiler/rustc_middle/src/query/mod.rs
+++ b/compiler/rustc_middle/src/query/mod.rs
@@ -1244,7 +1244,7 @@ rustc_queries! {
 
     /// Borrow-checks the given typeck root, e.g. functions, const/static items,
     /// and its children, e.g. closures, inline consts.
-    query mir_borrowck(key: LocalDefId) -> Result<&'tcx mir::ConcreteOpaqueTypes<'tcx>, ErrorGuaranteed> {
+    query mir_borrowck(key: LocalDefId) -> Result<&'tcx mir::DefinitionSiteHiddenTypes<'tcx>, ErrorGuaranteed> {
         desc { |tcx| "borrow-checking `{}`", tcx.def_path_str(key) }
     }
 
diff --git a/compiler/rustc_middle/src/ty/typeck_results.rs b/compiler/rustc_middle/src/ty/typeck_results.rs
index 8dd80aab946d4..944bd9756a957 100644
--- a/compiler/rustc_middle/src/ty/typeck_results.rs
+++ b/compiler/rustc_middle/src/ty/typeck_results.rs
@@ -167,7 +167,7 @@ pub struct TypeckResults<'tcx> {
     /// We also store the type here, so that the compiler can use it as a hint
     /// for figuring out hidden types, even if they are only set in dead code
     /// (which doesn't show up in MIR).
-    pub concrete_opaque_types: FxIndexMap<LocalDefId, ty::OpaqueHiddenType<'tcx>>,
+    pub hidden_types: FxIndexMap<LocalDefId, ty::OpaqueHiddenType<'tcx>>,
 
     /// Tracks the minimum captures required for a closure;
     /// see `MinCaptureInformationMap` for more details.
@@ -250,7 +250,7 @@ impl<'tcx> TypeckResults<'tcx> {
             coercion_casts: Default::default(),
             used_trait_imports: Default::default(),
             tainted_by_errors: None,
-            concrete_opaque_types: Default::default(),
+            hidden_types: Default::default(),
             closure_min_captures: Default::default(),
             closure_fake_reads: Default::default(),
             rvalue_scopes: Default::default(),
diff --git a/compiler/rustc_pattern_analysis/src/rustc.rs b/compiler/rustc_pattern_analysis/src/rustc.rs
index d9f8085083ebd..0652461e97501 100644
--- a/compiler/rustc_pattern_analysis/src/rustc.rs
+++ b/compiler/rustc_pattern_analysis/src/rustc.rs
@@ -120,7 +120,7 @@ impl<'p, 'tcx: 'p> fmt::Debug for RustcPatCtxt<'p, 'tcx> {
 impl<'p, 'tcx: 'p> RustcPatCtxt<'p, 'tcx> {
     /// Type inference occasionally gives us opaque types in places where corresponding patterns
     /// have more specific types. To avoid inconsistencies as well as detect opaque uninhabited
-    /// types, we use the corresponding concrete type if possible.
+    /// types, we use the corresponding hidden type if possible.
     // FIXME(#132279): This will be unnecessary once we have a TypingMode which supports revealing
     // opaque types defined in a body.
     #[inline]
@@ -146,7 +146,7 @@ impl<'p, 'tcx: 'p> RustcPatCtxt<'p, 'tcx> {
     /// know it.
     fn reveal_opaque_key(&self, key: OpaqueTypeKey<'tcx>) -> Option<Ty<'tcx>> {
         self.typeck_results
-            .concrete_opaque_types
+            .hidden_types
             .get(&key.def_id)
             .map(|x| ty::EarlyBinder::bind(x.ty).instantiate(self.tcx, key.args))
     }
diff --git a/compiler/rustc_trait_selection/src/traits/select/mod.rs b/compiler/rustc_trait_selection/src/traits/select/mod.rs
index 1dd31990ab73e..fb4f28412d428 100644
--- a/compiler/rustc_trait_selection/src/traits/select/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/mod.rs
@@ -2359,7 +2359,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
                 if self.infcx.can_define_opaque_ty(def_id) {
                     unreachable!()
                 } else {
-                    // We can resolve the `impl Trait` to its concrete type,
+                    // We can resolve the opaque type to its hidden type,
                     // which enforces a DAG between the functions requiring
                     // the auto trait bounds in question.
                     match self.tcx().type_of_opaque(def_id) {
diff --git a/compiler/rustc_type_ir/src/infer_ctxt.rs b/compiler/rustc_type_ir/src/infer_ctxt.rs
index f743b84bce689..feafcee7bad9e 100644
--- a/compiler/rustc_type_ir/src/infer_ctxt.rs
+++ b/compiler/rustc_type_ir/src/infer_ctxt.rs
@@ -80,7 +80,7 @@ pub enum TypingMode<I: Interner> {
     /// the old solver as well.
     PostBorrowckAnalysis { defined_opaque_types: I::LocalDefIds },
     /// After analysis, mostly during codegen and MIR optimizations, we're able to
-    /// reveal all opaque types. As the concrete type should *never* be observable
+    /// reveal all opaque types. As the hidden type should *never* be observable
     /// directly by the user, this should not be used by checks which may expose
     /// such details to the user.
     ///