From 1c2dee18d09c383bce51e9821f0f18656e71bb76 Mon Sep 17 00:00:00 2001
From: Araq <rumpf_a@web.de>
Date: Wed, 13 Dec 2017 13:48:48 +0100
Subject: [PATCH] attempt to get the stack trace logic right; fix boundaries

---
 lib/pure/asyncfutures.nim | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/pure/asyncfutures.nim b/lib/pure/asyncfutures.nim
index ea7a798fc..f3b4234cc 100644
--- a/lib/pure/asyncfutures.nim
+++ b/lib/pure/asyncfutures.nim
@@ -237,10 +237,10 @@ proc mergeEntries(entries: seq[StackTraceEntry]): seq[StackTraceEntry] =
 
       # either the nested block is new, then we insert it, or we discard it
       # completely. 'diff' is the wrong idea here.
-      var last = result.len
+      var last = result.len-1
       var e = reRaiseEnd-1
       var newBlock = true
-      while last > 0 and e > i+1:
+      while last >= 0 and e >= i+1:
         if result[last] != entries[e]:
           newBlock = false
           break