diff --git a/compiler/rustc_data_structures/src/marker.rs b/compiler/rustc_data_structures/src/marker.rs
index e2193a97a0f4..997077ac4402 100644
--- a/compiler/rustc_data_structures/src/marker.rs
+++ b/compiler/rustc_data_structures/src/marker.rs
@@ -188,53 +188,6 @@ pub fn assert_dyn_send<T: ?Sized + PointeeSized + DynSend>() {}
 pub fn assert_dyn_send_val<T: ?Sized + PointeeSized + DynSend>(_t: &T) {}
 pub fn assert_dyn_send_sync_val<T: ?Sized + PointeeSized + DynSync + DynSend>(_t: &T) {}
 
-#[derive(Copy, Clone)]
-pub struct FromDyn<T>(T);
-
-impl<T> FromDyn<T> {
-    #[inline(always)]
-    pub fn from(val: T) -> Self {
-        // Check that `sync::is_dyn_thread_safe()` is true on creation so we can
-        // implement `Send` and `Sync` for this structure when `T`
-        // implements `DynSend` and `DynSync` respectively.
-        assert!(crate::sync::is_dyn_thread_safe());
-        FromDyn(val)
-    }
-
-    #[inline(always)]
-    pub fn derive<O>(&self, val: O) -> FromDyn<O> {
-        // We already did the check for `sync::is_dyn_thread_safe()` when creating `Self`
-        FromDyn(val)
-    }
-
-    #[inline(always)]
-    pub fn into_inner(self) -> T {
-        self.0
-    }
-}
-
-// `FromDyn` is `Send` if `T` is `DynSend`, since it ensures that sync::is_dyn_thread_safe() is true.
-unsafe impl<T: DynSend> Send for FromDyn<T> {}
-
-// `FromDyn` is `Sync` if `T` is `DynSync`, since it ensures that sync::is_dyn_thread_safe() is true.
-unsafe impl<T: DynSync> Sync for FromDyn<T> {}
-
-impl<T> std::ops::Deref for FromDyn<T> {
-    type Target = T;
-
-    #[inline(always)]
-    fn deref(&self) -> &Self::Target {
-        &self.0
-    }
-}
-
-impl<T> std::ops::DerefMut for FromDyn<T> {
-    #[inline(always)]
-    fn deref_mut(&mut self) -> &mut Self::Target {
-        &mut self.0
-    }
-}
-
 // A wrapper to convert a struct that is already a `Send` or `Sync` into
 // an instance of `DynSend` and `DynSync`, since the compiler cannot infer
 // it automatically in some cases. (e.g. Box<dyn Send / Sync>)
diff --git a/compiler/rustc_data_structures/src/sync.rs b/compiler/rustc_data_structures/src/sync.rs
index 327c28fd1389..7967b8c9a452 100644
--- a/compiler/rustc_data_structures/src/sync.rs
+++ b/compiler/rustc_data_structures/src/sync.rs
@@ -34,7 +34,7 @@
 pub use self::freeze::{FreezeLock, FreezeReadGuard, FreezeWriteGuard};
 #[doc(no_inline)]
 pub use self::lock::{Lock, LockGuard, Mode};
-pub use self::mode::{is_dyn_thread_safe, set_dyn_thread_safe_mode};
+pub use self::mode::{is_dyn_thread_safe, FromDyn, set_dyn_thread_safe_mode};
 pub use self::parallel::{
     broadcast, par_fns, par_for_each_in, par_join, par_map, parallel_guard, spawn,
     try_par_for_each_in,
@@ -64,6 +64,8 @@ mod atomic {
 mod mode {
     use std::sync::atomic::{AtomicU8, Ordering};
 
+    use crate::sync::{DynSend, DynSync};
+
     const UNINITIALIZED: u8 = 0;
     const DYN_NOT_THREAD_SAFE: u8 = 1;
     const DYN_THREAD_SAFE: u8 = 2;
@@ -99,6 +101,53 @@ pub fn set_dyn_thread_safe_mode(mode: bool) {
         // Check that the mode was either uninitialized or was already set to the requested mode.
         assert!(previous.is_ok() || previous == Err(set));
     }
+
+    #[derive(Copy, Clone)]
+    pub struct FromDyn<T>(T);
+
+    impl<T> FromDyn<T> {
+        #[inline(always)]
+        pub fn from(val: T) -> Self {
+            // Check that `sync::is_dyn_thread_safe()` is true on creation so we can
+            // implement `Send` and `Sync` for this structure when `T`
+            // implements `DynSend` and `DynSync` respectively.
+            assert!(crate::sync::is_dyn_thread_safe());
+            FromDyn(val)
+        }
+
+        #[inline(always)]
+        pub fn derive<O>(&self, val: O) -> FromDyn<O> {
+            // We already did the check for `sync::is_dyn_thread_safe()` when creating `Self`
+            FromDyn(val)
+        }
+
+        #[inline(always)]
+        pub fn into_inner(self) -> T {
+            self.0
+        }
+    }
+
+    // `FromDyn` is `Send` if `T` is `DynSend`, since it ensures that sync::is_dyn_thread_safe() is true.
+    unsafe impl<T: DynSend> Send for FromDyn<T> {}
+
+    // `FromDyn` is `Sync` if `T` is `DynSync`, since it ensures that sync::is_dyn_thread_safe() is true.
+    unsafe impl<T: DynSync> Sync for FromDyn<T> {}
+
+    impl<T> std::ops::Deref for FromDyn<T> {
+        type Target = T;
+
+        #[inline(always)]
+        fn deref(&self) -> &Self::Target {
+            &self.0
+        }
+    }
+
+    impl<T> std::ops::DerefMut for FromDyn<T> {
+        #[inline(always)]
+        fn deref_mut(&mut self) -> &mut Self::Target {
+            &mut self.0
+        }
+    }
 }
 
 /// This makes locks panic if they are already held.