diff --git a/compiler/rustc_ty_utils/src/errors.rs b/compiler/rustc_ty_utils/src/errors.rs
index 42ecaaeafa9..5497d7d0bd2 100644
--- a/compiler/rustc_ty_utils/src/errors.rs
+++ b/compiler/rustc_ty_utils/src/errors.rs
@@ -7,14 +7,14 @@ use rustc_span::Span;
 
 #[derive(Diagnostic)]
 #[diag(ty_utils_needs_drop_overflow)]
-pub struct NeedsDropOverflow<'tcx> {
+pub(crate) struct NeedsDropOverflow<'tcx> {
     pub query_ty: Ty<'tcx>,
 }
 
 #[derive(Diagnostic)]
 #[diag(ty_utils_generic_constant_too_complex)]
 #[help]
-pub struct GenericConstantTooComplex {
+pub(crate) struct GenericConstantTooComplex {
     #[primary_span]
     pub span: Span,
     #[note(ty_utils_maybe_supported)]
@@ -24,7 +24,7 @@ pub struct GenericConstantTooComplex {
 }
 
 #[derive(Subdiagnostic)]
-pub enum GenericConstantTooComplexSub {
+pub(crate) enum GenericConstantTooComplexSub {
     #[label(ty_utils_borrow_not_supported)]
     BorrowNotSupported(#[primary_span] Span),
     #[label(ty_utils_address_and_deref_not_supported)]
@@ -71,40 +71,40 @@ pub enum GenericConstantTooComplexSub {
 
 #[derive(Diagnostic)]
 #[diag(ty_utils_unexpected_fnptr_associated_item)]
-pub struct UnexpectedFnPtrAssociatedItem {
+pub(crate) struct UnexpectedFnPtrAssociatedItem {
     #[primary_span]
     pub span: Span,
 }
 
 #[derive(Diagnostic)]
 #[diag(ty_utils_zero_length_simd_type)]
-pub struct ZeroLengthSimdType<'tcx> {
+pub(crate) struct ZeroLengthSimdType<'tcx> {
     pub ty: Ty<'tcx>,
 }
 
 #[derive(Diagnostic)]
 #[diag(ty_utils_multiple_array_fields_simd_type)]
-pub struct MultipleArrayFieldsSimdType<'tcx> {
+pub(crate) struct MultipleArrayFieldsSimdType<'tcx> {
     pub ty: Ty<'tcx>,
 }
 
 #[derive(Diagnostic)]
 #[diag(ty_utils_oversized_simd_type)]
-pub struct OversizedSimdType<'tcx> {
+pub(crate) struct OversizedSimdType<'tcx> {
     pub ty: Ty<'tcx>,
     pub max_lanes: u64,
 }
 
 #[derive(Diagnostic)]
 #[diag(ty_utils_non_primitive_simd_type)]
-pub struct NonPrimitiveSimdType<'tcx> {
+pub(crate) struct NonPrimitiveSimdType<'tcx> {
     pub ty: Ty<'tcx>,
     pub e_ty: Ty<'tcx>,
 }
 
 #[derive(Diagnostic)]
 #[diag(ty_utils_impl_trait_duplicate_arg)]
-pub struct DuplicateArg<'tcx> {
+pub(crate) struct DuplicateArg<'tcx> {
     pub arg: GenericArg<'tcx>,
     #[primary_span]
     #[label]
@@ -115,7 +115,7 @@ pub struct DuplicateArg<'tcx> {
 
 #[derive(Diagnostic)]
 #[diag(ty_utils_impl_trait_not_param, code = E0792)]
-pub struct NotParam<'tcx> {
+pub(crate) struct NotParam<'tcx> {
     pub arg: GenericArg<'tcx>,
     #[primary_span]
     #[label]
diff --git a/compiler/rustc_ty_utils/src/lib.rs b/compiler/rustc_ty_utils/src/lib.rs
index ad0bcbfbbc2..dc5303317a8 100644
--- a/compiler/rustc_ty_utils/src/lib.rs
+++ b/compiler/rustc_ty_utils/src/lib.rs
@@ -16,6 +16,7 @@
 #![feature(let_chains)]
 #![feature(never_type)]
 #![feature(rustdoc_internals)]
+#![warn(unreachable_pub)]
 // tidy-alphabetical-end
 
 use rustc_middle::query::Providers;