Fix variance for IterMut

Amanieu · Amanieu · commit 17ab35dc3b9c · 2018-12-11T20:50:34.000Z
diff --git a/src/map.rs b/src/map.rs
@@ -1128,7 +1128,8 @@ impl<'a, K: Debug, V: Debug> fmt::Debug for Iter<'a, K, V> {
 /// [`HashMap`]: struct.HashMap.html
 pub struct IterMut<'a, K: 'a, V: 'a> {
     inner: RawIter<(K, V)>,
-    _marker: PhantomData<&'a mut HashMap<K, V>>,
+    // To ensure invariance with respect to V
+    _marker: PhantomData<&'a mut V>,
 }
 
 impl<'a, K, V> IterMut<'a, K, V> {

Original file line number	Diff line number	Diff line change
`@@ -1128,7 +1128,8 @@ impl<'a, K: Debug, V: Debug> fmt::Debug for Iter<'a, K, V> {`
`1128`	`1128`	/// [`HashMap`]: struct.HashMap.html
`1129`	`1129`	`pub struct IterMut<'a, K: 'a, V: 'a> {`
`1130`	`1130`	`inner: RawIter<(K, V)>,`
`1131`		`- _marker: PhantomData<&'a mut HashMap<K, V>>,`
	`1131`	`+ // To ensure invariance with respect to V`
	`1132`	`+ _marker: PhantomData<&'a mut V>,`
`1132`	`1133`	`}`
`1133`	`1134`
`1134`	`1135`	`impl<'a, K, V> IterMut<'a, K, V> {`