impl Default for Hash{Map,Set} iterators that don't already have it

library/std/src/collections/hash/map.rs

@@ -1404,6 +1404,14 @@ impl<K, V> Clone for Iter<'_, K, V> {
     }
 }
 
+#[stable(feature = "default_iters_hash", since = "CURRENT_RUSTC_VERSION")]
+impl<K, V> Default for Iter<'_, K, V> {
+    #[inline]
+    fn default() -> Self {
+        Iter { base: Default::default() }
+    }
+}
+
 #[stable(feature = "std_debug", since = "1.16.0")]
 impl<K: Debug, V: Debug> fmt::Debug for Iter<'_, K, V> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
@@ -1441,6 +1449,14 @@ impl<'a, K, V> IterMut<'a, K, V> {
     }
 }
 
+#[stable(feature = "default_iters_hash", since = "CURRENT_RUSTC_VERSION")]
+impl<K, V> Default for IterMut<'_, K, V> {
+    #[inline]
+    fn default() -> Self {
+        IterMut { base: Default::default() }
+    }
+}
+
 /// An owning iterator over the entries of a `HashMap`.
 ///
 /// This `struct` is created by the [`into_iter`] method on [`HashMap`]
@@ -1471,6 +1487,14 @@ impl<K, V> IntoIter<K, V> {
     }
 }
 
+#[stable(feature = "default_iters_hash", since = "CURRENT_RUSTC_VERSION")]
+impl<K, V> Default for IntoIter<K, V> {
+    #[inline]
+    fn default() -> Self {
+        IntoIter { base: Default::default() }
+    }
+}
+
 /// An iterator over the keys of a `HashMap`.
 ///
 /// This `struct` is created by the [`keys`] method on [`HashMap`]. See its
@@ -1502,6 +1526,14 @@ impl<K, V> Clone for Keys<'_, K, V> {
     }
 }
 
+#[stable(feature = "default_iters_hash", since = "CURRENT_RUSTC_VERSION")]
+impl<K, V> Default for Keys<'_, K, V> {
+    #[inline]
+    fn default() -> Self {
+        Keys { inner: Default::default() }
+    }
+}
+
 #[stable(feature = "std_debug", since = "1.16.0")]
 impl<K: Debug, V> fmt::Debug for Keys<'_, K, V> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
@@ -1540,6 +1572,14 @@ impl<K, V> Clone for Values<'_, K, V> {
     }
 }
 
+#[stable(feature = "default_iters_hash", since = "CURRENT_RUSTC_VERSION")]
+impl<K, V> Default for Values<'_, K, V> {
+    #[inline]
+    fn default() -> Self {
+        Values { inner: Default::default() }
+    }
+}
+
 #[stable(feature = "std_debug", since = "1.16.0")]
 impl<K, V: Debug> fmt::Debug for Values<'_, K, V> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
@@ -1626,6 +1666,14 @@ pub struct ValuesMut<'a, K: 'a, V: 'a> {
     inner: IterMut<'a, K, V>,
 }
 
+#[stable(feature = "default_iters_hash", since = "CURRENT_RUSTC_VERSION")]
+impl<K, V> Default for ValuesMut<'_, K, V> {
+    #[inline]
+    fn default() -> Self {
+        ValuesMut { inner: Default::default() }
+    }
+}
+
 /// An owning iterator over the keys of a `HashMap`.
 ///
 /// This `struct` is created by the [`into_keys`] method on [`HashMap`].
@@ -1648,6 +1696,14 @@ pub struct IntoKeys<K, V> {
     inner: IntoIter<K, V>,
 }
 
+#[stable(feature = "default_iters_hash", since = "CURRENT_RUSTC_VERSION")]
+impl<K, V> Default for IntoKeys<K, V> {
+    #[inline]
+    fn default() -> Self {
+        IntoKeys { inner: Default::default() }
+    }
+}
+
 /// An owning iterator over the values of a `HashMap`.
 ///
 /// This `struct` is created by the [`into_values`] method on [`HashMap`].
@@ -1670,6 +1726,14 @@ pub struct IntoValues<K, V> {
     inner: IntoIter<K, V>,
 }
 
+#[stable(feature = "default_iters_hash", since = "CURRENT_RUSTC_VERSION")]
+impl<K, V> Default for IntoValues<K, V> {
+    #[inline]
+    fn default() -> Self {
+        IntoValues { inner: Default::default() }
+    }
+}
+
 /// A builder for computing where in a HashMap a key-value pair would be stored.
 ///
 /// See the [`HashMap::raw_entry_mut`] docs for usage examples.

library/std/src/collections/hash/set.rs

@@ -1274,6 +1274,14 @@ pub struct Iter<'a, K: 'a> {
     base: base::Iter<'a, K>,
 }
 
+#[stable(feature = "default_iters_hash", since = "CURRENT_RUSTC_VERSION")]
+impl<K> Default for Iter<'_, K> {
+    #[inline]
+    fn default() -> Self {
+        Iter { base: Default::default() }
+    }
+}
+
 /// An owning iterator over the items of a `HashSet`.
 ///
 /// This `struct` is created by the [`into_iter`] method on [`HashSet`]
@@ -1295,6 +1303,14 @@ pub struct IntoIter<K> {
     base: base::IntoIter<K>,
 }
 
+#[stable(feature = "default_iters_hash", since = "CURRENT_RUSTC_VERSION")]
+impl<K> Default for IntoIter<K> {
+    #[inline]
+    fn default() -> Self {
+        IntoIter { base: Default::default() }
+    }
+}
+
 /// A draining iterator over the items of a `HashSet`.
 ///
 /// This `struct` is created by the [`drain`] method on [`HashSet`].