From cac44def0b0f0fdcd1aa8cf610e16a5506d2726b Mon Sep 17 00:00:00 2001
From: Koichi Sasada <ko1@atdot.net>
Date: Wed, 31 Jul 2019 15:01:19 +0900
Subject: backtrace can be nil.

Surprisingly, on SystemStackError#backtrace can return nil.
---
 tool/lib/minitest/unit.rb | 3 +++
 1 file changed, 3 insertions(+)

(limited to 'tool/lib')

diff --git a/tool/lib/minitest/unit.rb b/tool/lib/minitest/unit.rb
index d922a5fc41..a384ddc17c 100644
--- a/tool/lib/minitest/unit.rb
+++ b/tool/lib/minitest/unit.rb
@@ -984,6 +984,9 @@ module MiniTest
 
     def location e # :nodoc:
       last_before_assertion = ""
+
+      return '<empty>' unless e.backtrace # SystemStackError can return nil.
+
       e.backtrace.reverse_each do |s|
         break if s =~ /in .(assert|refute|flunk|pass|fail|raise|must|wont)/
         last_before_assertion = s
-- 
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