From 841d9d59755f805245d862456d53e4fd8a426813 Mon Sep 17 00:00:00 2001
From: ringabout <43030857+ringabout@users.noreply.github.com>
Date: Wed, 2 Nov 2022 12:01:36 +0800
Subject: [PATCH] closes #16331; add testcase (#20730)

---
 tests/tuples/ttuples_issues.nim | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/tests/tuples/ttuples_issues.nim b/tests/tuples/ttuples_issues.nim
index 0cc505d28..70defdfce 100644
--- a/tests/tuples/ttuples_issues.nim
+++ b/tests/tuples/ttuples_issues.nim
@@ -107,6 +107,18 @@ template main() =
         return (x,y)
     doAssert bar() == (10, (11,))
 
+  block: # bug #16331
+    type T1 = tuple[a, b: int]
+
+    proc p(b: bool): T1 =
+      var x: T1 = (10, 20)
+      x = if b: (x.b, x.a) else: (-x.b, -x.a)
+      x
+
+    doAssert p(false) == (-20, -10)
+    doAssert p(true) == (20, 10)
+
+
 proc mainProc() =
   # other tests should be in `main`
   block: