diff --git a/compiler/rustc_transmute/src/layout/tree.rs b/compiler/rustc_transmute/src/layout/tree.rs
index 2c67e7d4847..c3fd771b797 100644
--- a/compiler/rustc_transmute/src/layout/tree.rs
+++ b/compiler/rustc_transmute/src/layout/tree.rs
@@ -204,7 +204,7 @@ fn from(err: &LayoutError<'tcx>) -> Self {
     }
 
     impl<'tcx> Tree<Def<'tcx>, Ref<'tcx>> {
-        pub fn from_ty(ty: Ty<'tcx>, cx: LayoutCx<'tcx, TyCtxt<'tcx>>) -> Result<Self, Err> {
+        pub(crate) fn from_ty(ty: Ty<'tcx>, cx: LayoutCx<'tcx, TyCtxt<'tcx>>) -> Result<Self, Err> {
             use rustc_target::abi::HasDataLayout;
             let layout = layout_of(cx, ty)?;
 
diff --git a/compiler/rustc_transmute/src/layout/tree/tests.rs b/compiler/rustc_transmute/src/layout/tree/tests.rs
index 3cb47517c21..44f50a25c93 100644
--- a/compiler/rustc_transmute/src/layout/tree/tests.rs
+++ b/compiler/rustc_transmute/src/layout/tree/tests.rs
@@ -1,7 +1,7 @@
 use super::Tree;
 
 #[derive(Debug, Hash, Eq, PartialEq, Clone, Copy)]
-pub enum Def {
+enum Def {
     NoSafetyInvariants,
     HasSafetyInvariants,
 }
diff --git a/compiler/rustc_transmute/src/lib.rs b/compiler/rustc_transmute/src/lib.rs
index bdc98bcea5e..c1d0b704ab2 100644
--- a/compiler/rustc_transmute/src/lib.rs
+++ b/compiler/rustc_transmute/src/lib.rs
@@ -2,6 +2,7 @@
 #![allow(unused_variables)]
 #![feature(alloc_layout_extra)]
 #![feature(never_type)]
+#![warn(unreachable_pub)]
 // tidy-alphabetical-end
 
 pub(crate) use rustc_data_structures::fx::{FxIndexMap as Map, FxIndexSet as Set};
diff --git a/compiler/rustc_transmute/src/maybe_transmutable/mod.rs b/compiler/rustc_transmute/src/maybe_transmutable/mod.rs
index 2762b4e6384..b3e1bb31e58 100644
--- a/compiler/rustc_transmute/src/maybe_transmutable/mod.rs
+++ b/compiler/rustc_transmute/src/maybe_transmutable/mod.rs
@@ -366,13 +366,13 @@ fn or<R>(lhs: Answer<R>, rhs: Answer<R>) -> Answer<R>
     }
 }
 
-pub enum Quantifier {
+enum Quantifier {
     ThereExists,
     ForAll,
 }
 
 impl Quantifier {
-    pub fn apply<R, I>(&self, iter: I) -> Answer<R>
+    fn apply<R, I>(&self, iter: I) -> Answer<R>
     where
         R: layout::Ref,
         I: IntoIterator<Item = Answer<R>>,