From 282128ab66b6391c4ab9bc76cd19a63a5bce16f8 Mon Sep 17 00:00:00 2001
From: Clyybber <darkmine956@gmail.com>
Date: Wed, 15 Jul 2020 23:33:58 +0200
Subject: [PATCH] Fix #14994 (#14996)

* Fix #14994

* Revert misplaced "optimization"

* Typo
---
 lib/pure/collections/sequtils.nim |  3 ++-
 lib/system/seqs_v2.nim            |  1 +
 tests/arc/tarcmisc.nim            | 14 ++++++++++++++
 3 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/lib/pure/collections/sequtils.nim b/lib/pure/collections/sequtils.nim
index f101d508e7..51d8ade85d 100644
--- a/lib/pure/collections/sequtils.nim
+++ b/lib/pure/collections/sequtils.nim
@@ -527,7 +527,8 @@ proc insert*[T](dest: var seq[T], src: openArray[T], pos = 0) =
     assert dest == outcome
 
   var j = len(dest) - 1
-  var i = len(dest) + len(src) - 1
+  var i = j + len(src)
+  if i == j: return
   dest.setLen(i + 1)
 
   # Move items after `pos` to the end of the sequence.
diff --git a/lib/system/seqs_v2.nim b/lib/system/seqs_v2.nim
index 4001e97c31..3c94a03f94 100644
--- a/lib/system/seqs_v2.nim
+++ b/lib/system/seqs_v2.nim
@@ -82,6 +82,7 @@ proc shrink*[T](x: var seq[T]; newLen: Natural) =
 
 proc grow*[T](x: var seq[T]; newLen: Natural; value: T) =
   let oldLen = x.len
+  #sysAssert newLen >= x.len, "invalid newLen parameter for 'grow'"
   if newLen <= oldLen: return
   var xu = cast[ptr NimSeqV2[T]](addr x)
   if xu.p == nil or xu.p.cap < newLen:
diff --git a/tests/arc/tarcmisc.nim b/tests/arc/tarcmisc.nim
index 2d7e6b455e..56aa3ec3b3 100644
--- a/tests/arc/tarcmisc.nim
+++ b/tests/arc/tarcmisc.nim
@@ -21,6 +21,8 @@ whiley ends :(
 (x: "9")
 (x: "10")
 0
+new line before - @['a']
+new line after - @['a']
 closed
 destroying variable: 20
 destroying variable: 10
@@ -243,3 +245,15 @@ l.setParent(l)
 # bug #14968
 import times
 let currentTime = now().utc
+
+
+# bug #14994
+import sequtils
+var newLine = @['a']
+let indent = newSeq[char]()
+
+echo "new line before - ", newline
+
+newline.insert(indent, 0)
+
+echo "new line after - ", newline