container/list element.Next() panics and should return nil #6349
Description
Not that there is a good reason to call Next() on an element removed from a list, but
the element removed should still return nil for Next() to satisfy the API.
// remove removes e from its list, decrements l.len, and returns e.
func (l *List) remove(e *Element) *Element {
e.prev.next = e.next
e.next.prev = e.prev
e.next = nil // avoid memory leaks
e.prev = nil // avoid memory leaks
e.list = nil
l.len--
return e
}
When e.next is nil then calling e.Next() will panic
// Next returns the next list element or nil.
func (e *Element) Next() *Element {
if p := e.next; p != &e.list.root {
return p
}
return nil
}
Here e.list is nil, and so e.list.root will panic. Prior to this CL
https://golang.org/cl/6569072
e.list was not set to nil when the element was removed from a list. There is a
discussion of the problem here:
https://groups.google.com/forum/#!topic/golang-nuts/HGCY7IanlvU