Merge pull request JuliaCollections#871 from Sinfaen/ll-fix-append

Fix for MutableLinkedList append!

Author: oxinabox

src/mutable_list.jl

@@ -153,7 +153,13 @@ end
 function Base.append!(l1::MutableLinkedList{T}, l2::MutableLinkedList{T}) where T
     l1.node.prev.next = l2.node.next # l1's last's next is now l2's first
     l2.node.prev.next = l1.node # l2's last's next is now l1.node
+    l2.node.next.prev = l1.node.prev # l2's first's prev is now l1's last
+    l1.node.prev      = l2.node.prev # l1's first's prev is now l2's last
     l1.len += length(l2)
+    # make l2 empty
+    l2.node.prev = l2.node
+    l2.node.next = l2.node
+    l2.len = 0
     return l1
 end
 

test/test_mutable_list.jl

@@ -97,7 +97,8 @@
                 @testset "append" begin
                     l2 = MutableLinkedList{Int}(n+1:2n...)
                     append!(l, l2)
-                    @test l == MutableLinkedList{Int}(1:2n...)
+                    @test l  == MutableLinkedList{Int}(1:2n...)
+                    @test l2 == MutableLinkedList{Int}()
                     @test collect(l) == collect(MutableLinkedList{Int}(1:2n...))
                     l3 = MutableLinkedList{Int}(1:n...)
                     append!(l3, n+1:2n...)