Remove call to clone, and explain why

James Munns · James Munns · commit 67bcac6665d2 · 2018-11-01T13:18:14.000+01:00
diff --git a/src/libcore/cell.rs b/src/libcore/cell.rs
@@ -1515,7 +1515,10 @@ impl<T: ?Sized> UnsafeCell<T> {
 #[stable(feature = "unsafe_cell_copy_clone_conservative", since = "1.31.0")]
 impl<T: Clone + Copy> Clone for UnsafeCell<T> {
     fn clone(&self) -> UnsafeCell<T> {
-        UnsafeCell::new(self.value.clone())
+        // NOTE: we are explicitly not calling `.clone()` here, to enforce the
+        // use of Copy, rather than relying on what could be a custom impl
+        // of Clone
+        UnsafeCell::new(self.value)
     }
 }
 

Original file line number	Diff line number	Diff line change
`@@ -1515,7 +1515,10 @@ impl<T: ?Sized> UnsafeCell<T> {`
`1515`	`1515`	`#[stable(feature = "unsafe_cell_copy_clone_conservative", since = "1.31.0")]`
`1516`	`1516`	`impl<T: Clone + Copy> Clone for UnsafeCell<T> {`
`1517`	`1517`	`fn clone(&self) -> UnsafeCell<T> {`
`1518`		`- UnsafeCell::new(self.value.clone())`
	`1518`	+ // NOTE: we are explicitly not calling `.clone()` here, to enforce the
	`1519`	`+ // use of Copy, rather than relying on what could be a custom impl`
	`1520`	`+ // of Clone`
	`1521`	`+ UnsafeCell::new(self.value)`
`1519`	`1522`	`}`
`1520`	`1523`	`}`
`1521`	`1524`