From 29cd083e127f29c8af9b95ed9d22ce9e6cd39a33 Mon Sep 17 00:00:00 2001
From: flywind <43030857+xflywind@users.noreply.github.com>
Date: Mon, 2 Nov 2020 17:27:48 +0800
Subject: [PATCH] fixes #15717

(cherry picked from commit 558115fa2906abeda11e6fd128ac139e9aac1838)
---
 compiler/vmgen.nim        |  2 ++
 tests/vm/tnewseqofcap.nim | 19 +++++++++++++++++++
 2 files changed, 21 insertions(+)
 create mode 100644 tests/vm/tnewseqofcap.nim

diff --git a/compiler/vmgen.nim b/compiler/vmgen.nim
index 2969aed51c..aa8cd43477 100644
--- a/compiler/vmgen.nim
+++ b/compiler/vmgen.nim
@@ -683,6 +683,8 @@ proc genNewSeq(c: PCtx; n: PNode) =
 
 proc genNewSeqOfCap(c: PCtx; n: PNode; dest: var TDest) =
   let t = n.typ
+  if dest < 0:
+    dest = c.getTemp(n.typ)
   let tmp = c.getTemp(n[1].typ)
   c.gABx(n, opcLdNull, dest, c.genType(t))
   c.gABx(n, opcLdImmInt, tmp, 0)
diff --git a/tests/vm/tnewseqofcap.nim b/tests/vm/tnewseqofcap.nim
new file mode 100644
index 0000000000..c61c3c485f
--- /dev/null
+++ b/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
\ No newline at end of file