Rollup of 17 pull requests

src/doc/unstable-book/src/language-features/on-unimplemented.md

@@ -138,3 +138,16 @@ error[E0277]: `&str` is not an iterator
   = help: the trait `std::iter::Iterator` is not implemented for `&str`
   = note: required by `std::iter::IntoIterator::into_iter`
 ```
+
+If you need to filter on multiple attributes, you can use `all`, `any` or
+`not` in the following way:
+
+```rust,compile_fail
+#[rustc_on_unimplemented(
+    on(
+        all(_Self="&str", T="std::string::String"),
+        note="you can coerce a `{T}` into a `{Self}` by writing `&*variable`"
+    )
+)]
+pub trait From<T>: Sized { /* ... */ }
+```

src/liballoc/collections/btree/node.rs

@@ -109,7 +109,7 @@ impl<K, V> LeafNode<K, V> {
             keys: uninitialized_array![_; CAPACITY],
             vals: uninitialized_array![_; CAPACITY],
             parent: ptr::null(),
-            parent_idx: MaybeUninit::uninitialized(),
+            parent_idx: MaybeUninit::uninit(),
             len: 0
         }
     }
@@ -129,7 +129,7 @@ unsafe impl Sync for NodeHeader<(), ()> {}
 // ever take a pointer past the first key.
 static EMPTY_ROOT_NODE: NodeHeader<(), ()> = NodeHeader {
     parent: ptr::null(),
-    parent_idx: MaybeUninit::uninitialized(),
+    parent_idx: MaybeUninit::uninit(),
     len: 0,
     keys_start: [],
 };
@@ -261,7 +261,7 @@ impl<K, V> Root<K, V> {
             -> NodeRef<marker::Mut<'_>, K, V, marker::Internal> {
         debug_assert!(!self.is_shared_root());
         let mut new_node = Box::new(unsafe { InternalNode::new() });
-        new_node.edges[0].set(unsafe { BoxedNode::from_ptr(self.node.as_ptr()) });
+        new_node.edges[0].write(unsafe { BoxedNode::from_ptr(self.node.as_ptr()) });
 
         self.node = BoxedNode::from_internal(new_node);
         self.height += 1;
@@ -737,7 +737,7 @@ impl<'a, K, V> NodeRef<marker::Mut<'a>, K, V, marker::Internal> {
         unsafe {
             ptr::write(self.keys_mut().get_unchecked_mut(idx), key);
             ptr::write(self.vals_mut().get_unchecked_mut(idx), val);
-            self.as_internal_mut().edges.get_unchecked_mut(idx + 1).set(edge.node);
+            self.as_internal_mut().edges.get_unchecked_mut(idx + 1).write(edge.node);
 
             (*self.as_leaf_mut()).len += 1;
 
@@ -1080,7 +1080,7 @@ impl<'a, K, V> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Internal>, marker::
         let mut child = self.descend();
         unsafe {
             (*child.as_leaf_mut()).parent = ptr;
-            (*child.as_leaf_mut()).parent_idx.set(idx);
+            (*child.as_leaf_mut()).parent_idx.write(idx);
         }
     }