From 2d9af2bd559d03c4f6b2a5f89be316f2465a091b Mon Sep 17 00:00:00 2001
From: ringabout <43030857+ringabout@users.noreply.github.com>
Date: Mon, 6 Mar 2023 17:34:41 +0800
Subject: [PATCH] closes #20704; add a test case (#21480)

---
 tests/stdlib/tsugar.nim | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/tests/stdlib/tsugar.nim b/tests/stdlib/tsugar.nim
index 6ef3ae51981e6..1b629165a4ae2 100644
--- a/tests/stdlib/tsugar.nim
+++ b/tests/stdlib/tsugar.nim
@@ -3,7 +3,7 @@ discard """
 x + y = 30
 '''
 """
-import std/[sugar, algorithm, random, sets, tables, strutils]
+import std/[sugar, algorithm, random, sets, tables, strutils, sequtils]
 import std/[syncio, assertions]
 
 type # for capture test, ref #20679
@@ -287,6 +287,17 @@ proc mainProc() =
       doAssertRaises(AssertionDefect): doAssert false
     doAssert "except AssertionDefect" in s2
 
+  block: # bug #20704
+    proc test() =
+      var xs, ys: seq[int]
+      for i in 0..5:
+        xs.add(i)
+
+      xs.apply(d => ys.add(d))
+      doAssert ys == @[0, 1, 2, 3, 4, 5]
+
+    test()
+
 static:
   main()
   mainProc()