From 3379d26629f30e6be8d303a36e220d1039eb4551 Mon Sep 17 00:00:00 2001
From: ringabout <43030857+ringabout@users.noreply.github.com>
Date: Thu, 18 Jan 2024 21:20:54 +0800
Subject: [PATCH] fixes #23223; prevents `insert` self-assignment (#23225)

fixes #23223
---
 lib/system.nim                | 2 ++
 tests/system/tsystem_misc.nim | 7 +++++++
 2 files changed, 9 insertions(+)

diff --git a/lib/system.nim b/lib/system.nim
index 0602d8fa42..8aa1cc34c2 100644
--- a/lib/system.nim
+++ b/lib/system.nim
@@ -2520,6 +2520,8 @@ when hasAlloc or defined(nimscript):
     ##   var a = "abc"
     ##   a.insert("zz", 0) # a <- "zzabc"
     ##   ```
+    if item.len == 0: # prevents self-assignment
+      return
     var xl = x.len
     setLen(x, xl+item.len)
     var j = xl-1
diff --git a/tests/system/tsystem_misc.nim b/tests/system/tsystem_misc.nim
index 7f59147254..c8e2b2a9df 100644
--- a/tests/system/tsystem_misc.nim
+++ b/tests/system/tsystem_misc.nim
@@ -212,3 +212,10 @@ block:
   doAssert not compiles(echo p.rawProc.repr)
   doAssert not compiles(echo p.rawEnv.repr)
   doAssert not compiles(echo p.finished)
+
+proc bug23223 = # bug #23223
+  var stuff = "hello"
+  stuff.insert ""
+  doAssert stuff == "hello"
+
+bug23223()