1 files changed, 16 insertions, 0 deletions
diff --git a/library/std/src/sync/once.rs b/library/std/src/sync/once.rs
index 0f25417d6..1b17c3108 100644
--- a/library/std/src/sync/once.rs
+++ b/library/std/src/sync/once.rs
@@ -43,6 +43,12 @@ pub struct OnceState {
     pub(crate) inner: sys::OnceState,
 }
 
+pub(crate) enum ExclusiveState {
+    Incomplete,
+    Poisoned,
+    Complete,
+}
+
 /// Initialization value for static [`Once`] values.
 ///
 /// # Examples
@@ -248,6 +254,16 @@ impl Once {
     pub fn is_completed(&self) -> bool {
         self.inner.is_completed()
     }
+
+    /// Returns the current state of the `Once` instance.
+    ///
+    /// Since this takes a mutable reference, no initialization can currently
+    /// be running, so the state must be either "incomplete", "poisoned" or
+    /// "complete".
+    #[inline]
+    pub(crate) fn state(&mut self) -> ExclusiveState {
+        self.inner.state()
+    }
 }
 
 #[stable(feature = "std_debug", since = "1.16.0")]