From 075ee26b6884514a65b0822b8745a6f5f35e8720 Mon Sep 17 00:00:00 2001
From: Jules Bertholet <julesbertholet@quoi.xyz>
Date: Sat, 22 Oct 2022 12:13:03 -0400
Subject: [PATCH] Loosen `From<&[T]> for Box<[T]>` bound to T: Clone

---
 library/alloc/src/boxed.rs | 38 ++++++++++++++++++++++++++++++--------
 1 file changed, 30 insertions(+), 8 deletions(-)

diff --git a/library/alloc/src/boxed.rs b/library/alloc/src/boxed.rs
index ad86c19309831..2a26661cab4a7 100644
--- a/library/alloc/src/boxed.rs
+++ b/library/alloc/src/boxed.rs
@@ -1455,9 +1455,35 @@ where
     }
 }
 
+/// Specialization trait used for `From<&[T]>`.
+trait BoxFromSlice<T> {
+    fn from_slice(slice: &[T]) -> Self;
+}
+
+#[cfg(not(no_global_oom_handling))]
+impl<T: Clone> BoxFromSlice<T> for Box<[T]> {
+    #[inline]
+    default fn from_slice(slice: &[T]) -> Self {
+        slice.to_vec().into_boxed_slice()
+    }
+}
+
+#[cfg(not(no_global_oom_handling))]
+impl<T: Copy> BoxFromSlice<T> for Box<[T]> {
+    #[inline]
+    fn from_slice(slice: &[T]) -> Self {
+        let len = slice.len();
+        let buf = RawVec::with_capacity(len);
+        unsafe {
+            ptr::copy_nonoverlapping(slice.as_ptr(), buf.ptr(), len);
+            buf.into_box(slice.len()).assume_init()
+        }
+    }
+}
+
 #[cfg(not(no_global_oom_handling))]
 #[stable(feature = "box_from_slice", since = "1.17.0")]
-impl<T: Copy> From<&[T]> for Box<[T]> {
+impl<T: Clone> From<&[T]> for Box<[T]> {
     /// Converts a `&[T]` into a `Box<[T]>`
     ///
     /// This conversion allocates on the heap
@@ -1471,19 +1497,15 @@ impl<T: Copy> From<&[T]> for Box<[T]> {
     ///
     /// println!("{boxed_slice:?}");
     /// ```
+    #[inline]
     fn from(slice: &[T]) -> Box<[T]> {
-        let len = slice.len();
-        let buf = RawVec::with_capacity(len);
-        unsafe {
-            ptr::copy_nonoverlapping(slice.as_ptr(), buf.ptr(), len);
-            buf.into_box(slice.len()).assume_init()
-        }
+        <Self as BoxFromSlice<T>>::from_slice(slice)
     }
 }
 
 #[cfg(not(no_global_oom_handling))]
 #[stable(feature = "box_from_cow", since = "1.45.0")]
-impl<T: Copy> From<Cow<'_, [T]>> for Box<[T]> {
+impl<T: Clone> From<Cow<'_, [T]>> for Box<[T]> {
     /// Converts a `Cow<'_, [T]>` into a `Box<[T]>`
     ///
     /// When `cow` is the `Cow::Borrowed` variant, this