gistfile1.txt

pub struct Node<'a> {
    node_type: NodeType,
    parent:    RefCell<Option<Weak<Node<'a>>>>, // cell for interior mutability; optional; weak ref to parent
    children:  Vec<Rc<Node<'a>>>,   // strong references to children
    state:     *mut RsvgState,
    node_impl: &'a NodeTrait
}

impl<'a> Node<'a> {
    // ...
    
    pub fn add_child (&mut self, child: &Rc<Node<'a>>) {
        self.children.push (child.clone ());
    }
}

type RsvgRcNode<'a> = Rc<Node<'a>>;

#[no_mangle]
pub extern fn rsvg_node_add_child<'a> (raw_node: *mut RsvgRcNode<'a>, raw_child: *const RsvgRcNode<'a>) {
    assert! (!raw_node.is_null ());
    let rc_node: &mut RsvgRcNode<'a> = unsafe { &mut *raw_node };
    let rc_child: &RsvgRcNode<'a> = unsafe { & *raw_child };

    rc_node.add_child (rc_child);
}


error: cannot borrow immutable borrowed content as mutable
   --> node.rs:160:5
    |
160 |     rc_node.add_child (rc_child);
    |     ^^^^^^^