lib/date.rb: Backport #2707 [ruby-core:28011]; backport r27014 to fix problem with Date#>> and very small numbers.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_1_8_6@28233 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 5 insertions, 1 deletions

diff --git a/lib/date.rb b/lib/date.rb
index ea557313f7..d562fd12b1 100644
--- a/lib/date.rb
+++ b/lib/date.rb
@@ -1273,7 +1273,11 @@ class Date
     y, m = (year * 12 + (mon - 1) + n).divmod(12)
     m,   = (m + 1)                    .divmod(1)
     d = mday
-    d -= 1 until jd2 = self.class.valid_civil?(y, m, d, fix_style)
+    until jd2 = self.class.valid_civil?(y, m, d, fix_style)
+      d -= 1
+      raise ArgumentError, 'invalid date' unless d > 0
+    end
+
     self + (jd2 - jd)
   end