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Fix #19314 - fixing broken DoublyLinkedList after adding empty `Dou…
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…blyLinkedList` (#19315) [backport]

* Update lists.nim

* Update tlists.nim
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rockcavera authored Jan 3, 2022
1 parent 19bcb43 commit 526a32e
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Showing 2 changed files with 18 additions and 6 deletions.
12 changes: 6 additions & 6 deletions lib/pure/collections/lists.nim
Original file line number Diff line number Diff line change
Expand Up @@ -675,12 +675,12 @@ proc addMoved*[T](a, b: var DoublyLinkedList[T]) {.since: (1, 5, 1).} =
assert s == [0, 1, 0, 1, 0, 1]

if b.head != nil:
b.head.prev = a.tail
if a.tail != nil:
a.tail.next = b.head
a.tail = b.tail
if a.head == nil:
a.head = b.head
if a.head == nil:
a.head = b.head
else:
b.head.prev = a.tail
a.tail.next = b.head
a.tail = b.tail
if a.addr != b.addr:
b.head = nil
b.tail = nil
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12 changes: 12 additions & 0 deletions tests/stdlib/tlists.nim
Original file line number Diff line number Diff line change
Expand Up @@ -245,6 +245,18 @@ template main =
doAssert a.toSeq == @[1]
a.add(2)
doAssert a.toSeq == @[1, 2]

block issue19314: # add (appends a shallow copy)
var a: DoublyLinkedList[int]
var b: DoublyLinkedList[int]

doAssert a.toSeq == @[]
a.add(1)
doAssert a.toSeq == @[1]
a.add(b)
doAssert a.toSeq == @[1]
a.add(2)
doAssert a.toSeq == @[1, 2]

static: main()
main()

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