From a64d0d4774db30bd37ec2ede87e966dcdd33dfc2 Mon Sep 17 00:00:00 2001
From: Yoshua Wuyts <yoshuawuyts@gmail.com>
Date: Fri, 20 Nov 2020 01:42:43 +0100
Subject: [PATCH] Add `core::slice::fill_with`

---
 library/core/src/slice/mod.rs | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/library/core/src/slice/mod.rs b/library/core/src/slice/mod.rs
index 79ae1d5829a24..a8f199e17a804 100644
--- a/library/core/src/slice/mod.rs
+++ b/library/core/src/slice/mod.rs
@@ -2599,6 +2599,34 @@ impl<T> [T] {
         }
     }
 
+    /// Fills `self` with elements returned by calling a closure repeatedly.
+    ///
+    /// This method uses a closure to create new values. If you'd rather
+    /// [`Clone`] a given value, use [`fill`]. If you want to use the [`Default`]
+    /// trait to generate values, you can pass [`Default::default`] as the
+    /// argument.
+    ///
+    /// [`fill`]: #method.fill
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(slice_fill_with)]
+    ///
+    /// let mut buf = vec![1; 10];
+    /// buf.fill_with(Default::default);
+    /// assert_eq!(buf, vec![0; 10]);
+    /// ```
+    #[unstable(feature = "slice_fill_with", issue = "79221")]
+    pub fn fill_with<F>(&mut self, mut f: F)
+    where
+        F: FnMut() -> T,
+    {
+        for el in self {
+            *el = f();
+        }
+    }
+
     /// Copies the elements from `src` into `self`.
     ///
     /// The length of `src` must be the same as `self`.