From d6d7653f250bac41ddfbfbb3b1c45f0b4409e07f Mon Sep 17 00:00:00 2001
From: ringabout <43030857+ringabout@users.noreply.github.com>
Date: Sat, 29 Aug 2026 20:41:36 +0800
Subject: [PATCH] =?UTF-8?q?fixes=20#26134;=20del(seq)=20performs=20self-as?=
 =?UTF-8?q?signment=20and=20=3Ddestroy=20for=20del(=E2=80=A6=20(#26138)?=
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…0) of 1-length seq

fixes #26134

(cherry picked from commit dcec8e1cd1a33b3dfa6a9fa38784d0c9195b6aca)
---
 lib/system.nim          |  4 +++-
 tests/stdlib/t26134.nim | 24 ++++++++++++++++++++++++
 2 files changed, 27 insertions(+), 1 deletion(-)
 create mode 100644 tests/stdlib/t26134.nim

diff --git a/lib/system.nim b/lib/system.nim
index ef241136b4..e053b2d67e 100644
--- a/lib/system.nim
+++ b/lib/system.nim
@@ -1257,7 +1257,9 @@ proc del*[T](x: var seq[T], i: Natural) {.noSideEffect.} =
     a.del(2)
     assert a == @[10, 11, 14, 13]
   let xl = x.len - 1
-  movingCopy(x[i], x[xl])
+  # Avoid moving the element onto itself when deleting the last item.
+  if i != xl:
+    movingCopy(x[i], x[xl])
   setLen(x, xl)
 
 proc insert*[T](x: var seq[T], item: sink T, i = 0.Natural) {.noSideEffect.} =
diff --git a/tests/stdlib/t26134.nim b/tests/stdlib/t26134.nim
new file mode 100644
index 0000000000..2d2d916665
--- /dev/null
+++ b/tests/stdlib/t26134.nim
@@ -0,0 +1,24 @@
+discard """
+  matrix: "--mm:orc --undef:nimPreviewNonVarDestructor"
+  output: "hello"
+"""
+
+# bug #26134
+
+type MyObject = object
+
+proc `=destroy`(v: var MyObject) =
+  echo "hello"
+
+proc remove(v: var seq[MyObject]) =
+  v.del(0)
+
+proc aaa(v: var seq[MyObject], i: sink MyObject) =
+  v.add(i)
+
+proc main =
+  var v: seq[MyObject]
+  v.aaa(MyObject())
+  v.remove()
+
+main()