fixes #13240

tests/arc/tconst_to_sink.nim

@@ -0,0 +1,25 @@
+discard """
+  output: '''@[(s1: "333", s2: ""), (s1: "abc", s2: "def"), (s1: "3x", s2: ""), (s1: "3x", s2: ""), (s1: "3x", s2: ""), (s1: "3x", s2: ""), (s1: "lastone", s2: "")]'''
+  cmd: "nim c --gc:arc $file"
+"""
+
+# bug #13240
+
+type
+  Thing = object
+    s1: string
+    s2: string
+
+var box: seq[Thing]
+
+const c = [Thing(s1: "333"), Thing(s1: "abc", s2: "def")]
+
+for i in 0..high(c):
+  box.add c[i]
+
+for i in 0..3:
+  box.add Thing(s1: "3x")
+
+box.add Thing(s1: "lastone")
+
+echo box