fixes #15717

tests/vm/tnewseqofcap.nim

@@ -0,0 +1,19 @@
+discard """
+  output: '''@["aaa", "bbb", "ccc"]'''
+"""
+
+
+const
+  foo = @["aaa", "bbb", "ccc"]
+
+proc myTuple: tuple[n: int, bar: seq[string]] =
+  result.n = 42
+  result.bar = newSeqOfCap[string](foo.len)
+  for f in foo:
+    result.bar.add(f)
+
+# It works if you change the below `const` to `let`
+const
+  (n, bar) = myTuple()
+
+echo bar