From 7674df0dffc8746a9377ed9680b179118f14a0cd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Oscar=20Nihlg=C3=A5rd?= <oscarnihlgard@gmail.com>
Date: Fri, 29 Jun 2018 14:53:09 +0200
Subject: [PATCH] Fixes #8100 (#8101)

---
 lib/pure/strformat.nim | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/lib/pure/strformat.nim b/lib/pure/strformat.nim
index 36404cdf7c..247b9ec5cb 100644
--- a/lib/pure/strformat.nim
+++ b/lib/pure/strformat.nim
@@ -258,7 +258,9 @@ template callFormat(res, arg) {.dirty.} =
     # workaround in order to circumvent 'strutils.format' which matches
     # too but doesn't adhere to our protocol.
     res.add arg
-  elif compiles(format(arg, res)):
+  elif compiles(format(arg, res)) and
+      # Check if format returns void
+      not (compiles do: discard format(arg, res)):
     format(arg, res)
   elif compiles(format(arg)):
     res.add format(arg)
@@ -684,6 +686,9 @@ when isMainModule:
   var nullTime: DateTime
   check &"{nullTime:yyyy-mm-dd}", "0000-00-00"
 
+  var tm = fromUnix(0)
+  discard &"{tm}"
+
   # Unicode string tests
   check &"""{"αβγ"}""", "αβγ"
   check &"""{"αβγ":>5}""", "  αβγ"