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Signed-off-by: tison <[email protected]>

Author: tisonkun

library/core/src/cell/once.rs

@@ -164,6 +164,30 @@ impl<T> OnceCell<T> {
         }
     }
 
+    /// Gets the mutable reference of the contents of the cell,
+    /// initializing it with `f` if the cell was empty.
+    ///
+    /// # Panics
+    ///
+    /// If `f` panics, the panic is propagated to the caller, and the cell
+    /// remains uninitialized.
+    ///
+    /// It is an error to reentrantly initialize the cell from `f`. Doing
+    /// so results in a panic.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::cell::OnceCell;
+    ///
+    /// let mut cell = OnceCell::new();
+    /// let value = cell.get_mut_or_init(|| 92);
+    /// assert_eq!(value, &92);
+    /// *value += 2;
+    /// assert_eq!(value, &94);
+    /// let value = cell.get_mut_or_init(|| unreachable!());
+    /// assert_eq!(value, &94);
+    /// ```
     #[inline]
     #[stable(feature = "once_cell", since = "1.70.0")]
     pub fn get_mut_or_init<F>(&mut self, f: F) -> &mut T
@@ -214,6 +238,35 @@ impl<T> OnceCell<T> {
         self.try_init(f)
     }
 
+    /// Gets the mutable reference of the contents of the cell, initializing
+    /// it with `f` if the cell was empty. If the cell was empty and `f` failed,
+    /// an error is returned.
+    ///
+    /// # Panics
+    ///
+    /// If `f` panics, the panic is propagated to the caller, and the cell
+    /// remains uninitialized.
+    ///
+    /// It is an error to reentrantly initialize the cell from `f`. Doing
+    /// so results in a panic.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(once_cell_try)]
+    ///
+    /// use std::cell::OnceCell;
+    ///
+    /// let mut cell = OnceCell::new();
+    /// assert_eq!(cell.get_mut_or_try_init(|| Err(())), Err(()));
+    /// assert!(cell.get().is_none());
+    /// let value = cell.get_mut_or_try_init(|| -> Result<i32, ()> {
+    ///     Ok(92)
+    /// });
+    /// assert_eq!(value, Ok(&mut 92));
+    /// *value.unwrap() += 2;
+    /// assert_eq!(cell.get(), Some(&94))
+    /// ```
     #[unstable(feature = "once_cell_try", issue = "109737")]
     pub fn get_mut_or_try_init<F, E>(&mut self, f: F) -> Result<&mut T, E>
     where