message: Mark VecMap iterator functions inline
  Summary: Safer.
diff: @@ -28,6 +28,7 @@ pub(crate) struct Keys<'a, K: 'a, V: 'a> {
  }
  impl<'a, K: 'a, V: 'a> Keys<'a, K, V> {
  + #[inline]
  fn map(b: &'a Bucket<K, V>) -> <Self as Iterator>::Item {
  &b.key
  }
  @@ -44,6 +45,7 @@ impl<'a, K: 'a, V: 'a> DoubleEndedIterator for Keys<'a, K, V> {
  }
  impl<'a, K: 'a, V: 'a> ExactSizeIterator for Keys<'a, K, V> {
  + #[inline]
  fn len(&self) -> usize {
  self.iter.len()
  }
  @@ -55,6 +57,7 @@ pub(crate) struct Values<'a, K: 'a, V: 'a> {
  }
  impl<'a, K: 'a, V: 'a> Values<'a, K, V> {
  + #[inline]
  fn map(b: &'a Bucket<K, V>) -> <Self as Iterator>::Item {
  &b.value
  }
  @@ -71,6 +74,7 @@ impl<'a, K: 'a, V: 'a> DoubleEndedIterator for Values<'a, K, V> {
  }
  impl<'a, K: 'a, V: 'a> ExactSizeIterator for Values<'a, K, V> {
  + #[inline]
  fn len(&self) -> usize {
  self.iter.len()
  }
  @@ -81,6 +85,7 @@ pub(crate) struct ValuesMut<'a, K: 'a, V: 'a> {
  }
  impl<'a, K: 'a, V: 'a> ValuesMut<'a, K, V> {
  + #[inline]
  fn map(b: &'a mut Bucket<K, V>) -> <Self as Iterator>::Item {
  &mut b.value
  }
  